32 Commits

Include renames

Author	SHA1	Message	Date
Omar SobhandClaude Fable 5.1	02c855b9c4	rtx-cfd: overset Schwarz stall rule guarded (fires only within 10× the tolerance) — unguarded it cut CFD1's transient at round 3 every step and the coupled march diverged at ny=62 (pressure 4e4 → 1e140 by step 450); CFD1 harness knobs (stall, step cap, trace) ... Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-05 21:01:57 -07:00
Omar SobhandClaude Fable 5.1	45ff34da8f	rtx-cfd: overset P4-0 — the O-grid around the Turek–Hron rigid body (cylinder + flag), gated ... patch_gen::{cylinder_flag_outline, cylinder_flag_patch, winslow_smooth, respace_rays} (+ convex_hull, offset_convex_polygon, nearest_on_polyline): the outline CCW then reversed to clockwise (tip semicircle 16 cells, junction fillets of a FIXED radius with 3 cells, straights graded 0.3 h → h, cylinder arc at h); the outer ring the 6 h normal offset of the body's convex hull; initial pairing by the inner point's normal offset projected onto the hull offset (an arclength-proportional pairing folded the transfinite grid at the tip: rays crossed where the curvatures differ); Winslow (TTM) smoothing of the interior with the outer nodes SLIDING along the hull offset (each re-placed at the nearest point to the extrapolated ray), then re-spacing along the smoothed rays to the across stretch. Gates (tests/patch_cylinder_flag.rs): ny = 41/62/82 → 143×12 / 183×12 / 225×12 cells, positive, wall row 0.23 h (fillet max 0.37 / 0.43 / 0.50 h), worst non-orthogonality 76.6 / 69.1 / 63.3° at the concave fillets (structural: a concave arc's normals converge at its centre), classification of the benchmark background with both donor invariants. P0 MMS on these meshes (tests/cylinder_flag_mms.rs, exact acceptors, line-implicit): Stokes orders 2.17 / 2.13, upwind 2.00 / 1.86 (cell Péclet ≈ 0.1), divergence ≤ 9e-14 — the fillet skew costs nothing measurable. Rule: a refinement ladder's geometry must be fixed in physical units — with fillet = h/2 the Stokes orders read 1.74 → 1.31, the O(h) boundary perturbation masquerading as a scheme defect; the fillet is a parameter (5 mm across the ladder). Also: the P3b knock-outs H1/H2 on the balanced default (no effect), the P3 §5.10 record in the falsifier's header. Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-05 19:50:14 -07:00
Omar SobhandClaude Fable 5.1	62df6bd628	rtx-cfd: overset P3b — the reclassification impulse located (the fringe ring is a staircase of the interpolated velocities' mass defect) and removed by a converged fringe flux balance (default on): falsifier max spike 594 → 5.50 N/m at the FSI2 step (staircase 6490), 10.95 / 16.79 at dt/2 / dt/4 (12600 / 25600), rms spike 0.07% of the force, far probe 6 (7900), KE per event 4.9e-3 J/m falling with Δt (2.6 fixed) ... OverlapMap::balance_fringe_fluxes: Gauss–Seidel through the prescribed faces of every fringe cell to 1e-12 of the prescribed flux scale (≤ 50 sweeps), after every fringe stamping (3 fixed sweeps 101 N/m, 10 sweeps 5.5 — converged is the rule). OversetParameters: fringe_flux_balance (default on, RTX_OVERSET_NO_BALANCE off), fringe_balance_tolerance, refill_turned_active (measured no effect: 593.7 → 593.8; kept as the record), stall_rounds opt-in. P3b locating trace RTX_OVERSET_TRACE_SP (continuity source by class change in cell volumes/step, stored-pressure jump of turned-active cells): the flipped cells' mass source ≤ 6e-3 cell volumes/step, their stored pressure 5–10% of the range off their neighbours (4.4% on the static MMS — the meshes' discretization disagreement). Knock-outs refuted (RTX_OVERSET_H1 keep own face velocities, H4 no warm start, pressure refill): 593–597 N/m each. S4 MMS with the balance: velocity errors within 0.1% of the pinned values, the background's overlap mass defect 1e-13 by construction, pressure errors unchanged. overset_mms prints pressure diagnostics; overset_falsifier records the balanced ladder (regression guard 20 N/m at dt; RTX_OVERSET_FALSIFIER_STRICT asserts the registered gates — (ii) holds at dt, misses at dt/2, dt/4; (iv) fails: residual ∝ 1/Δt^0.8). Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-05 19:16:16 -07:00
Omar SobhandClaude Fable 5.1	6b8837301f	rtx-cfd: overset Schwarz stall detection is opt-in (stall_rounds, default 0): right for a steady march (n=64: 2.26 rounds mean, no cap hits, L2 identical), wrong for a transient (falsifier max spike 594 → 4044 N/m when on); the MMS harness sets 2 ... Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-05 18:35:06 -07:00
Omar SobhandClaude Fable 5.1	e2edff9b1d	rtx-cfd: overset A-P3 — the falsifier plate on the overset (FAILS the registered gates by one order less than the staircase); wall force; composite pressure-level pin; Schwarz stall detection ... patch_gen::{stadium, graded_fractions}: the falsifier plate as a stadium O-grid (semicircular ends r = half-thickness; 16 cells per end arc, straights graded 0.30 h -> h at 1.15, offset 6 h, 12 rows stretched 4x; 148x12 cells, every ray a normal, worst non-orthogonality 4 deg). CurvilinearPisoSolver::surface_force (+ PatchLoad): F = sum(-p_f S_f + mu (grad u + grad u^T)_f . S_f) on the wall faces with the wall cell's LSQ gradients (wall Dirichlet in the velocity fit); HELD on the phantom circle against the exact stress integral: 1.3e-2 / 6.3e-3 / 3.6e-3 at n = 32/64/128 (orders 1.05 / 0.81), 22x the staircase's accuracy. OversetPisoSolver: the composite p' level pinned to zero mean over the active cells every round (the coupled problem is pure Neumann; the temporal warm start handed each step's level to the next — background pressure 1e7 growing 5e4 per step on the falsifier; an unpinned level also inflated the relative Schwarz stop); stall detection (no progress over three rounds = the inner solvers' noise floor; 6560 of 150k steps burned the 20-round cap at n = 64, a 7.5 h n = 128 march); schwarz_stalled in the result. tests/overset_falsifier.rs (records; RTX_OVERSET_FALSIFIER_STRICT asserts the registered gates, _LADDER runs dt/2 and dt/4, _TRACE the top-12 spike steps): max spike 594 / 981 / 1720 N/m at dt / dt/2 / dt/4 (staircase 6490 / 12600 / 25600), rms spike 61-89 (810), far probe 502-1509 (7900), KE injection 0.16-0.21 J/m per event on the common cell set (2.6) — every large spike a ~104-cell full-row reclassification; exponent -0.77 (-1.0). The registered 5% gate (8.75 N/m) is missed 68x: the overset's own reclassification impulse is the finding (omni-cortex overset_metal_campaign.md §5.10); P3b = locate per cell, then the fringe flux balance. tests/patch_stadium.rs, curvilinear_loads.rs, overset_common::plate_patch. Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-05 04:32:43 -07:00
Omar SobhandClaude Fable 5.1	afd1bff6ee	rtx-cfd: overset A-P2 — the patch overlaps the background (OversetPisoSolver), gated S1–S5 ... Background = the embedded solver with a mask from the overlap classification (embedded/{mod,projection}.rs: module split, projection's solve/apply halves, set_overlap, fringe p' Dirichlet by elimination into extra_diag/rhs, anchor dropped, set_inner_stop_factor, phase API begin_step/solve_correction/ apply_correction/end_step; advance rebuilt on the phases — every suite digit- identical, FSI2 default line-for-line). Patch = the curvilinear solver with an acceptor ring (set_side_velocity; set_acceptor_ring/stamp_acceptors/ set_acceptor_correction; acceptor Dirichlet by elimination into PressureSystem.links so the BiCGSTAB stop stays in flux units — identity rows measured unconverged at 2431 iterations; same phase API). overset/overlap.rs: OverlapMap — hole/fringe/active from the patch's own indices (hole = body or k <= nn-1-overlap_rows, DEFAULT_OVERLAP_ROWS = 4 from the 2.9 h depth budget), dual-quad inverse-bilinear donors patch→fringe, lattice donors →acceptors, both invariants asserted, mass-defect measures. overset/mod.rs: OversetPisoSolver — advance (exchange rebuilt BEFORE the predictors from the previous corrected field), alternating Schwarz on the acceptor p' vector with Anderson(3) (plain Schwarz measured 0.82/round: floating patch, Neumann wall) and the previous step's vector as warm start (1 round/corrector at steady state), stop relative to the STEP's p' scale (the MG absolute stop is 1e-9/dt² in pressure — the whole second correction), set_patch_mesh, snapshot/restore carrying the warm-start vector. Gates: overlap linear-exact 1e-13, quadratic orders 1.96/1.99 (acceptors), 1.40/1.91 (fringe); half-couplings: patch with exact acceptors Stokes 2.07/1.98 + 2.08/1.98, upwind 0.84/0.84, background with exact fringe 7.86e-3/2.90e-3/ 1.09e-3 (1.44/1.41); two-mesh MMS n=32/64: background 8.717e-3/4.207e-3 (1.03x/ 0.97x the embedded circle), patch 1.322e-2/6.904e-3 (1.5-1.6x), orders 1.05/ 0.94, patch div <= 5e-13, overlap mass defect 3.6e-3 -> 8.2e-4 of the overlap flux (under the registered 1e-3 from n=64; disclosed at 32); motion: stationary patch through set_patch_mesh bit-identical, snapshot/restore with a pending mesh bit-identical, translating phantom circle 1.22x/1.19x the static level over 4.5 cells. Inherited, disclosed: poisson_equivalence's no-body multigrid pin fails by 3.9e-9 at d46fb0b (M1's commit; verified in a clean worktree). Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-04 19:24:13 -07:00
Omar SobhandClaude Fable 5.1	d46fb0b7a7	rtx-cfd: overset A-P1 GATED — the curvilinear patch moves and deforms under an exact 2-D DGCL ... StepGeometry (motion.rs): time-averaged face vectors S̄_f = ½(S^n + S^{n+1}) and swept volumes δV_f = S̄_f·δc_f — exact for linear node motion on any quad, so Σ sign δV_f = V^{n+1} − V^n is algebra (1.8e-14 measured; the EndOfStep control 2.1e-3). CurvilinearPisoSolver::set_mesh(next) names the end-of-step geometry; advance swaps it in, rebuilds operators + pressure matrix on it (L_f, LSQ gradients, no mesh-velocity term in the projection), keeps the old mesh for V^n and the explicit boundary data; predictor in the conservative ALE form V^{n+1} û = V^n u^n + dt(−Σ sign (F − δV/dt) u_f + ν D + f V^n), written as u·(V^n/V^{n+1}) + … so a stationary mesh is bitwise the static path; fluxes on S̄_f; snapshot carries both meshes; swept_face_rule knob (Trapezoidal default, EndOfStep = negative control). Stokes limit keeps the mesh flux (was dropped with convection) and centres it (upwinding it cost an order: 1.06/1.00). Gates (tests/curvilinear_ale.rs, 11 tests, 83 s): uniform flow on a wiggling AND bending annulus 4.44e-15 over 400 steps, p exactly 0, 0 pressure iterations; control deviates 4.9e-5; stationary mesh through the moving path bit-identical (both diffusion variants); snapshot/restore on the moving mesh bit-identical; Taylor–Green orders unchanged — upwind 0.995/0.976 vs fixed 0.987/0.975 at 1.05× error, Stokes 1.92/1.97 vs 1.94/1.99 at 2.4×, moving annulus 2.11/2.02; linear-field falsifier 1.95/1.92 (annulus), 1.91/1.43 (square, sliding wall nodes). P0 ladders re-run identical to every digit. Rule from the diagnosis: start a moving run ON the t = 0 mesh and sweep less than a cell per step — a first step that jumped 2–4 cells imprinted an O(displacement) error no refinement removed (dt- and motion-independent). Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-04 17:00:04 -07:00
Omar SobhandClaude Fable 5.1	c63d79c300	rtx-cfd/rtx-fsi: overset A-P0 GATED + M1 precision probe — curvilinear collocated PISO: relative-reduction pressure stop (the absolute stop floored |du/dt| at 2e-4 on 64²), line-implicit-n sign fix, adjustPhi; gates: Cartesian reduction 1.37–1.40x the staggered error at orders 0.83/0.90; skewed stretched periodic annulus Stokes orders 2.30/2.06 (explicit and line-implicit), upwind 1.08/0.80; Poiseuille exact to 1e-9 on Cartesian and affine-sheared periodic channels (both diffusion variants), varying-skew channel order 2.02 (v 1.9), cell mass 1e-14; divergence ≤ 1e-11 relative every step; snapshot/restore bit-identical. M1: poisson.rs multigrid hierarchy generic over MgScalar (f32/f64), f64 CG keeps its own fine level; MgPrecision on MultigridParameters/EmbeddedParameters/PisoParameters, set_poisson_precision, harness RTX_FSI2_POISSON_F32 (march + noise probe, printed marker); f64 arm bit-identical in vivo (FSI2 default line-for-line with 08-31), f32 arm holds the noise floor and stall pins and the FSI2 band; poisson_equivalence f32 arm ... Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-04 12:40:43 -07:00
Omar SobhandClaude Fable 5.1	52da75a3a9	rtx-cfd: curvilinear collocated PISO on a structured patch (overset A-P0, WIP) — PatchMesh (right-handed s,n; periodic seam with shift; face metrics), patch generators (TFI, skewed annulus, sheared/varying-skew channels), CSR + Jacobi-BiCGSTAB, the Zang–Street–Koseff incremental step with the node-based 9-point L_f, LSQ gradients, explicit and line-implicit-n predictors, adjustPhi; tests: mesh metrics (5 green), operators exact on linear fields incl. the seam (green), sparse (2 green), MMS ladder (Cartesian 16/32: 1.37–1.39x the staggered error, order 0.83; n=64 stalls at a |du/dt| floor 2e-4 — open, tolerance-scaling hypothesis), annulus/Poiseuille not yet run ... Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-04 05:00:08 -07:00
Omar SobhandClaude Fable 5.1	c9492d3e1e	test(rtx-cfd): fresh-cell falsifier extended (circle body, far-field probe, kinetic energy, speed knob) + print-only divergence trace; two candidate fixes REFUTED on it (swept-volume source 40x worse at either sign; fresh-face field extension no effect), both kept default-off with their verdicts ... Phase 1 of omni-cortex docs/fresh_cell_gcl_campaign.md. The mechanism of the moving-body force spikes is measured from four directions: per-flip force amplitude ∝ 1/dt, kinetic energy injected per flipped cell 0.048 J/m independent of dt and body shape (plate row vs circle), felt at a far-field pressure probe, and ∝ U^2 (2.60 / 0.64 / 0.15 J/m at U = 1 / 0.5 / 0.25). A binary mask's wall position jumps by one cell at every flip and the fluid answers with a fixed impulse. Neither the swept-volume source (the wall faces already carry the swept volume — the source double-counts it) nor the fresh-face velocity is where it lives. Next: the virtual cut cell in the projection (apertures + the wall-relative divergence), registered in the campaign doc. Co-Authored-By: Claude Fable 5.1 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-09-03 11:40:28 -07:00
Omar SobhandClaude Fable 5	4d2cede7bc	rtx-cfd: warm-start the first corrector's pressure-correction solve — measured 2.5x fewer PCG iterations where it counts ... The MG smoother (neighbour_sum + PCG, 34-40% of the fluid) was the remaining fluid cost. Measured in vivo (FSI2 default, temporary iteration counters): 2.7-3.0 PCG iterations/solve from a zero initial guess. The correction field is temporally correlated step to step, so project() now seeds the FIRST corrector's solve from the previous step's p' (current fluid cells only — the p'=0 invariant on non-fluid cells survives the copy-back); later correctors and the SOR fallback start from zero exactly as before. The corrector restriction is measured, not guessed: the all-correctors draft cut the rigid phase 2.8 -> 1.27 iters/solve but cost 3.9/solve in the coupled phase (baseline 2.56) — corrector 2 solves for a much smaller correction and corrector 1's full-magnitude p' is a WORSE guess than zero there. First-corrector-only: rigid 2.8 -> ~1.1 (best of the three variants), coupled 2.62 ~= baseline. Total PCG iterations on the FSI2 default: 55,088 -> 32,836 (1.68x fewer). Wall: FSI2 default 225 -> 172 s, FSI3 default 343 -> 249 s. Session cumulative (banded LU + indexed SDF + warm start): FSI2 524 -> 172 s (3.0x), FSI3 944 -> 249 s (3.8x). This is a TOLERANCE-LEVEL solver-path change (each projection reaches the same true-residual stop from a different start), and the FSI3 release-window pins fired for the third and fourth time across the drafts — completing the picture: EVERY windowed observable of the [4.0, 4.2] release transient is branch-sensitive (four measured branches now recorded in the test: uy mid 10.77/6.02/2.91/8.88, amp 23.6/25.2/24.6/19.9, ux mid -2.90/-2.91/-2.56/-1.82, retries 2/0/1/1). The release bands are re-pinned as gross-physics tripwires around the measured scatter; the load-bearing regression pins for solver changes are the settled-cycle study bands, whose re-verification under this change is launched (verdicts to solver_status.md). Protocol: FSI2 default green (uy 3.4921 in-band), FSI3 default green under the re-pinned release bands (deterministic across two runs), FSI1 green, noise-probe floors identical, rtx-cfd suite + rtx-fsi quick tests green. Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-08-30 08:54:27 -05:00
Omar SobhandClaude Fable 5	6c48e53998	rtx-cfd: indexed polygon SDF — bit-identical queries, the fluid's measured hot function cut ... The 2026-08-30 fluid profile (symbolized samples, rigid AND coupled phases of the FSI3 default) attributed the fluid step to the function: polygon_signed_distance 51% rigid / 35% coupled — the embedded mask rebuild and its ghost reconstruction walk every edge of the ~150-vertex interface polygon for every cell-centre and face query, every step. (Also measured, refuting the parked consolidation: Level::new — the MG hierarchy build — is 0.5-0.7% in BOTH phases; caching it would buy nothing. The MG smoother at 34-40% is the honest remaining fluid cost.) PolygonSdf (solvers/incompressible/polygon_sdf.rs): a binned edge index whose query is BIT-IDENTICAL to polygon_signed_distance by construction — per-edge distances use the same float ops, the ring search provably visits a superset of the argmin (convex-projection lower bound sqrt(d_out^2 + ((r-1)b)^2)), and parity XORs the same ray tests over exactly the straddling edges (y-binned). Equality is ASSERTED, not assumed: tests compare to_bits against the brute force over ~40k adversarial points (flag-like walks, random polygons with degenerate zero-length edges, horizontal-edge/vertex-y rays). Wired into EmbeddedBody::polygon and the FSI harness's shared geometry (rebuilt per set_geometry, ~microseconds for 150 edges). Verification — the bar for a bit-exact change is digit identity, and it holds: FSI2 and FSI3 committed defaults reproduce EVERY printed digit of the banded-LU baseline logs (uy 3.7732±3.7920 / 6.0229± 25.2190 mm, conservation 8.26e-12 / 1.49e-12, rigid drags 121.4 / 426.9); rtx-cfd full suite 0 failures; rtx-fsi lib/piston/transfer/ FSI1 green. The study pins need no re-run: the trajectories are unchanged by construction and confirmed by measurement. Wall clock: FSI2 rigid 323 -> 167 s (1.93x), whole default 400 -> 225 s; FSI3 rigid 420 -> 250 s (1.68x), whole default 539 -> 343 s. Cumulative with the banded LU this session: FSI3 default 944 -> 343 s (2.75x), FSI2 524 -> 225 s (2.33x). Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-08-30 07:47:42 -05:00
Omar SobhandClaude Fable 5	9fe9d7f74a	rtx-cfd + rtx-fsi: ECSW campaign phase 1 — snapshot dump + FlowField save/load ... FlowField::save/load serialize the complete field state bit-exact (all twelve matrices including *_old, predictors and sources, so a load is a true restart state), with a roundtrip test asserting to_bits equality on every value and rejection of truncated/corrupt files. The march gains an ECSW snapshot knob (RTX_FSI{2,3}_SNAP path, SNAPEVERY, default off): every N committed steps it appends an FSNP record — t, full-DOF displacement/velocity/acceleration (what rtx_fea::mor's pod_basis/train_ecsw consume, plus what the phase-4 dynamic reduction will need) and the committed sparse nodal load for the offline full-vs-reduced replay. Reporting-only: reads committed state after acceptance, no float ops on the solver path. Verified: smoke run's FSNP parsed by an independent reader (570 DOFs, correct record count, physical values); FSI2 committed default digit-identical with the knob off. Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-08-28 21:56:37 -05:00
Omar SobhandClaude Fable 5	bff84ccdcc	rtx-cfd: mask hysteresis — sticky cell classification against a reference mask ... The measured FSI3 killer is the bistable mask: one geometry (|d| identical to 4 digits) samples two load branches (60 vs 120 kN), and the traced s=1 death is the secant walking a 20x load cliff (68,886 -> 1,307,938 N over a 1e-3 candidate change). A sticky band makes the load map single-valued at the crossing: formerly-fluid cells flip only at phi < -band, formerly-solid at phi > band, classified against the mask held at rebuild time — in a coupling loop, the restored committed step-start mask. Band 0 is structurally bit-identical (phi > -0.0 <=> phi > 0.0) and verified digit-for-digit on both committed defaults (FSI2 and FSI3, every physics digit). Measured cost on the translating-circle MMS at band 0.25h: +0.5% field error (u/p ratios 1.17/2.12 vs the no-hysteresis moving levels 1.16/2.11); flip delay = band/(v dt), deterministic. Exposed as RTX_FSI{2,3}_HYST in multiples of h_min. Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2	2026-08-26 15:27:09 -05:00
Omar SobhandClaude Fable 5	4534d90684	rtx-fea + rtx-cfd: the single-step seams FSI2 stands on ... rtx-fea: NonlinearDynamicAnalysis refactored onto a NonlinearDynamicStepper - set_nodal_forces on both (the interface load of a coupling subiteration, replaceable between steps and between subiterations of one step); - step(&DynamicState) is a pure function of the start-of-step state and the current forces - commits nothing, so a partitioned coupling re-runs one Newmark step to the interface fixed point (the piston semantics); - run() marches through the same stepper: one code path, pinned from both ends (linear limit, CSM3, and a new manual-drive == run() assertion); - new test: a nodal step load oscillates about the *static* nonlinear analysis's deflection (cross-code-path, mean within 3%, amplitude 6%), with re-run determinism and force-swap sensitivity asserted mid-march (a one-step response to a force change is ~ beta dt^2 - the first assertion draft demanded 10% and was corrected against the physics). rtx-cfd: the subiteration seam and the moving no-slip closure - EmbeddedPisoSolver::snapshot()/restore() (mask + time + init flag; the mask is now Clone): re-running a fluid step within a subiteration is bit-identical to never having diverted - proven on a moving body with cells flipping in the re-run window; - polygon_interface_velocity: nearest-edge linear interpolation of per-vertex velocities, exact for the linear-along-edge boundary data a finite-element interface hands over - the no-slip closure that replaces FSI1's zero-velocity polygon. Suites: rtx-fea 567, rtx-cfd 325, rtx-fsi piston+transfer - all green. Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01Lnyrw33Lu6rUhW42E9KHwq	2026-08-20 20:00:49 -07:00
Omar SobhandClaude Fable 5	c0f5a86f03	rtx-cfd: the embedded-body pieces FSI1 stands on (belongs with b82f307) ... EmbeddedMask::traction_at (the per-sample traction factored out of surface_force, so a coupling loop can load a structure at its own quadrature points), EmbeddedBody::polygon and the public polygon_signed_distance (a deformable interface as a vertex list, usable behind a lock through EmbeddedBody::from_sdf). Left unstaged by mistake in b82f307 — that commit's FSI1 test needs these to compile. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 17:22:44 -07:00
Omar SobhandClaude Fable 5	0ad31abb6b	rtx-cfd: F2 — the moving embedded body, and falsifier 3 measured ... EmbeddedPisoSolver::set_moving_body: the mask is rebuilt at the end-of-step geometry every step, and the new mask's ghost values are reconstructed FROM THE PREVIOUS CORRECTED FIELD (EmbeddedMask:: impose_from — the boundary-history principle extended to a moving wall), so a stationary body run through the moving path is bit-identical to the static path, which is the first test. A velocity face that flips solid -> fluid enters the new interval holding exactly the ghost reconstruction the previous step left on it — a consistent near-wall value, not garbage; a fresh pressure cell is refilled from its fluid neighbours before the predictor's gradient can read the value it kept while inside the body. The body must move under a cell per step (the convective dt limit already enforces this for bodies slower than the local peak velocity). EmbeddedResult reports fresh_cells. tests/embedded_moving.rs: - a stationary body through the moving path: 0.0 difference over 100 steps (and zero fresh cells, identical ghost corrections); - a circle (r = 0.2) translating through the steady manufactured field with the exact field as its surface velocity — the solution must hold still while the mask sweeps 84 cells fresh over 300 steps at n = 32: max L2 velocity error 9.85e-3 = 1.16x the static steady level (8.489e-3), max L2 pressure error 4.67e-2 = 2.11x the static level (2.22e-2), bulk |div u| 1.6e-7, projection residual 5.9e-9 every step. That pressure ratio is the geometry decision's falsifier 3 (omni-cortex docs/turek_hron_geometry_decision.md): fresh-cell transients sit at ~2x the static discretisation error, not orders above it — the falsifier does not fire and no cut cells are needed. Measurement note, recorded in the test: the divergence of body-adjacent cells read after the end-of-step ghost re-imposition is a one-step lag by design (the next projection honours the re-imposed prescribed fluxes — the same lag the static path has); the continuity claims are the projection residual and the bulk divergence over all-fluid-faced cells. Deferred: an oscillating-cylinder benchmark against published force histories (Duetsch et al. 1998) when the FSI rungs need it. rtx-cfd 321 -> 323 green. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 13:07:28 -07:00
Omar SobhandClaude Fable 5	35b2b2cdf4	rtx-cfd: TVD convection in the embedded predictor — the wake sheds — and Turek–Hron CFD2/CFD3 ... First-order upwind's numerical viscosity |u| h / 2 is ~10x the physical viscosity on the Turek–Hron grids: the effective Reynolds number lands near 20 and CFD3 (Re 200) produced NO vortex shedding at all — one lift zero-crossing in three seconds at h = 10 mm. The physics, not a bug. EmbeddedParameters gains `convection_scheme` (default Upwind, bit- identical — the no-body degeneracy test still reads 0.0): the TVD branch adds SIMPLE's limited face corrections (van Albada / van Leer, `face_correction` now pub(crate)) directly in the explicit predictor — no deferred iteration needed in an explicit step. Domain-side faces and faces whose far-upwind node is outside fall back to upwind exactly as in SIMPLE; near the body the stencil reads ghost values, which encode the wall. Verified: the embedded-circle MMS error drops 10–16x below upwind (8.16e-4 vs 8.49e-3 at n = 32) at observed order 1.56 (SIMPLE's TVD measured 1.59–1.84). tests/turek_hron_cfd23.rs — CFD2 (Re 100, steady) and CFD3 (Re 200, periodic), both with the benchmark's inflow ramp, both measured as time statistics over a window (never a snapshot), surface route primary and the control volume printed as the diagnostic (its central-difference evaluation truncation grows with the convective flux: the routes agree to 0.6% at Re 20 and differ 15–25% at Re 100–200 on these grids). Measured across h = 10 / 6.6 / 5 mm: - CFD3 shedding frequency 4.2746 / 4.3400 / 4.3939 Hz vs the reference 4.3956 — converging −2.8% -> −1.3% -> −0.04%; - CFD3 lift mean −184 / +160 / −2.6 vs −11.9 — lands on the reference; lift amplitude ±438 / ±556 / ±557 vs ±437.8 — +27% at the finer grids, unconverged (the flag is 2/3/4 cells thick); - CFD2 control-volume drag 152.4 / 143.3 / 139.4 vs 136.700 — +2.0% at 5 mm; CFD2 surface drag sits ~−10% (the boundary layer is ~one cell); CFD2 lift −3.4 / +30.2 / +8.4 vs 10.53. Suite defaults run CFD2 at ny = 62 and CFD3 at ny = 41 (cost); the asserted bands are the measured ones (frequency 10%, mean drag 15%, amplitude 35%), not accuracy claims; RTX_CFD2_NY / RTX_CFD3_NY run the studies. Also recorded: the CFD1 refinement study extended to h = 3.3 mm (RTX_CFD1_NY): control-volume drag 14.8996 (+4.25%), apparent order ~0.70 sustained over four grids, control-volume lift 1.1332 vs 1.11905 (+1.3%). rtx-cfd 318 -> 321 green (full suite 321 passed / 0 failed). Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 11:37:04 -07:00
Omar SobhandClaude Fable 5	327da7ff47	rtx-cfd: multigrid-PCG projection — 30x faster, same answers — and the CFD1 refinement study ... Falsifier 4 of the Turek–Hron geometry decision fired (the SOR projection cost 0.09 s/step at 250x41 and an hour per run at 5 mm); this answers it. solvers::incompressible::poisson: PoissonProblem (cell-centred five-point SPD operator as per-cell face coefficients + Dirichlet diagonal extra + active mask) and solve_multigrid_pcg — conjugate gradient preconditioned by one V-cycle of geometric multigrid: aggregation by 2 per direction (odd sizes absorbed, coarse cell active iff any child is), the Galerkin coarse operator for piecewise-constant prolongation / summation restriction, symmetric Gauss–Seidel smoothing, coarse correction scaled by 2 (Braess's under-correction of unsmoothed aggregation; scalar, so the preconditioner stays symmetric and positive on range(A)), L1 TRUE-residual stop with a stagnation guard. Singular systems are handled per connected component of the active cells (mean projection and level per pure-Neumann component; the anchor's component to p[anchor] = 0). PoissonSolverKind::{Sor, Multigrid} on PisoParameters / EmbeddedParameters; Sor is the default and its code is byte-for-byte untouched; an unconverged multigrid solve falls back to the SOR sweeps for that projection. Verified (poisson/tests.rs, tests/poisson_equivalence.rs): - PCG iterations to cut the residual 1e-8 on the closed Neumann box at 32^2..256^2: 4, 4, 4, 4; ragged masked domains 8/8/8; - manufactured recoveries to ~1e-14; Galerkin identity A_c v = R A P v to 7e-15 on every level (masked, outlet column, non-uniform conductances); V-cycle symmetric to 1e-14; NaN-poisoned inactive cells untouched; - two Neumann components with opposite imbalances, and a Dirichlet component beside an imbalanced Neumann one (review scenarios): converge, each component right up to its own constant; - speed vs plain SOR at the same stop: 22.7x (128^2), 41x (256^2); - same answers as SOR: PISO MMS 4.6e-8 relative, Taylor–Green divergence 1.4e-9 every step, embedded-circle MMS 7e-8, no-body bit-identity with MG on both solvers, channel+outlet+circle 1.4e-10; CFD1 loads identical to four digits at 0.003 s/step vs 0.094 (30x). CFD1 refinement study (tests/turek_hron_cfd.rs, three grids, 257 s): h = 10 / 6.6 / 5 mm -> control-volume drag 15.6156 / 15.2829 / 15.0988 vs 14.2929 (+9.25 / +6.93 / +5.64%), apparent order 0.71, Richardson extrapolate 14.04; surface route and lift not monotone (flag 2/3/4 cells thick) — the test asserts the measured band at the finest grid. Built with a 4-agent workflow (core, integration, refinement study, adversarial review); the review found no defects and four risks, three fixed here (per-component projection, one symmetric smoother-sweep parameter, acting on `converged` with an SOR fallback) and one recorded (isotropic aggregation loses grid-independence on anisotropic cells). rtx-cfd 301 -> 318 green. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 10:20:25 -07:00
Omar SobhandClaude Fable 5	c25f15b3c4	rtx-cfd + rtx-fea: embedded-boundary PISO and total-Lagrangian SVK — the first two Turek–Hron rungs ... The Turek–Hron geometry decision (omni-cortex docs/turek_hron_geometry_decision.md) chose an embedded boundary on the fixed Cartesian MAC grid over body-fitted unstructured ALE; this commit builds the first rung on each side of the ladder, verified MMS-first. rtx-cfd — solvers::incompressible::{embedded, embedded_body}: EmbeddedPisoSolver is the fixed-grid PISO predictor/projection with per-side domain boundaries (ALE's SideBoundary semantics, so the channel has an outlet), a (x, y, t) boundary-velocity function, and an optional EmbeddedBody (signed distance + surface velocity; circle / rectangle / union). EmbeddedMask classifies cells (fluid iff phi > 0 at the centre) and faces (fluid iff both cells fluid; ghost within 1.5 h; solid deeper); the predictor updates fluid faces only, the projection enforces continuity on fluid cells with zero coefficient across prescribed faces, ghost faces are re-imposed after each projection from a boundary-intercept least-squares linear fit (exact for linear fields), the net ghost mass flux is removed uniformly so a Neumann projection stays compatible, and loads come by two routes: surface-stress reconstruction (full viscous traction) and a control-volume momentum balance. Verified (tests/embedded_mms.rs, tests/turek_hron_cfd.rs): - no body, closed box: bit-identical to PisoSolver over 200 steps; - embedded off-centre circle MMS 16/32/64: velocity orders 0.92, 0.97 (plain PISO 0.85, 0.91), pressure 0.96, 0.90, max |div u| <= 9e-8 on every fluid cell, compatibility correction 6e-4 -> 3e-5; force on the circle vs the exact surface integral: surface route 0.52 -> 0.29 -> 0.15, control-volume route 0.61 -> 0.30 -> 0.15 (both first order, two unrelated readings of the same solution); - Turek–Hron CFD1 (Re 20, h = 10 mm, flag two cells thick), settled to four digits: surface drag 15.71 / lift 0.94, control-volume drag 15.62 / lift 1.08 vs reference 14.29 / 1.119 — the drag routes agree to 0.6%, both +9.5%. A coarse first number; the refinement study waits on a multigrid projection (SOR: 0.1 s/step at 250x41 in the test profile). Fourteenth defect of the campaign: the fixed-grid PISO predictor zeroes the transverse convective face velocity on its domain sides (exact for walls); carried into a solver with an outlet it dropped the OUTGOING momentum flux through the outlet side of the v control volumes, the last column accumulated, and CFD1 went NaN at t ~ 4 s. Found by printing where max |u| lived (x = 2.5) after halving dt changed nothing. Fluxes now come from the stored boundary faces on every side. rtx-fea — elements::total_lagrangian + NonlinearStaticAnalysis:: with_total_lagrangian(): Green–Lagrange strain, second Piola–Kirchhoff stress from a St. Venant–Kirchhoff law on the material's Lamé parameters (plane strain in 2-D), B_L of the current deformation, material plus geometric tangent; dead-load body force per reference volume. Verified (tests/total_lagrangian_svk.rs): - zero displacement: the plane-strain stiffness to 1e-13; - tangent = d f_int/du by central differences at 20% random displacement (Quad4, Quad8, Hex8): relative < 1e-7, symmetric to 1e-12; - a 34-degree rigid rotation produces no internal force; the small-strain routine does (negative control); - manufactured finite-strain solution, body force by FD of the exact P = F S: Quad4 orders 1.95, 1.98; Quad8 2.93, 3.03, 3.02 (an 8% amplitude, Green–Lagrange strain to -0.25 near SVK's compressive limit E = -1/3, broke Newton on fine meshes — the material, not the code; 3% is clean); - Turek–Hron CSM1 at 70x4 Quad8: u(A) = (-7.060, -65.43) mm vs (-7.188, -66.10), 1.0% / 1.8%, converging from below (35x2: -65.14); CSM2: (-0.4604, -16.79) vs (-0.4690, -16.97), 1.1% / 1.8%. rtx-cfd 293 -> 301 green (5 unit + 3 integration), rtx-fea 559 -> 564. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 08:51:32 -07:00
Omar SobhandClaude Fable 5	4bd98b5264	rtx-cfd + rtx-fsi: the added-mass piston — partitioned FSI on the real ALE fluid ... The first coupled fluid-structure computation in the workspace, verified against a closed form, and the first time rtx-fsi's added-mass claims run against a real discretised fluid rather than a linear model map. ALE extensions: per-side boundaries (Velocity / SlipWall / PressureOutlet) and moving boundary lines. A moving Velocity side is a material wall whose prescribed normal velocity must equal the line's own motion; a pressure outlet takes Dirichlet p' = 0 in the projection (replacing the Neumann anchor) with a zero-gradient predictor on its faces. Fluid half verified alone (tests/ale_piston_channel.rs): prescribed piston motion, slip walls, outlet. The incompressible rigid column is exact DISCRETELY - continuity forces every u to the wall's discrete velocity (8e-12) and the projected pressure is exactly linear with gradient rho times the wall's backward-difference acceleration (2.5e-9). Coupled benchmark (rtx-fsi/tests/piston_added_mass.rs): elastic piston (Newmark average acceleration) against added mass rho*L*H at mass ratio 6.25, rtx-fsi's Subiterated driving a real fluid/structure pass per step: - plain staggered diverges in 7 subiterations (Causin-Gerbeau-Nobile on a real solver); - Aitken converges at 3.0 subiterations/step onto T = 1.07009 vs the closed form 1.06999 - 9.8e-5 relative, halving with dt; - outlet flux matches the piston sweep to ~1e-9 every step. Discrete-analysis finding: Newmark beta scales the staggered added-mass threshold - the iteration gain is beta*m_a/(M + K*beta*dt^2), so the continuous ratio 2.5 CONVERGES at beta = 1/4 (gain 0.625, measured ~17 passes/step) and the benchmark needs ratio 6.25 (gain 1.56). Two real defects found and fixed, twelfth and thirteenth of the campaign: 1. rtx-cfd ale::advance re-stamped boundary faces at t_old from the current boundary function, which in a coupling loop carries the NEW interval's wall velocity - the predictor's old state had interior u = w0 but wall face u = w1, leaving an O(dt) pressure artifact confined to the wall-adjacent cells (p exact to 6e-11 everywhere except the wall cell at 4.7e-5). The start-of-step boundary faces are whatever the previous step's end-of-step application left there. 2. rtx-fsi aitken_factor guarded its denominator - a SQUARED residual- difference norm - against a bare f64::EPSILON, silently disabling Aitken below residual ~1e-8 and degrading to unit relaxation exactly in the well-converged regime; the repulsive fixed point then amplified 1e-9 residuals back up and the coupling diverged. Third instance of the absolute-threshold species (NNLS, ECSW). The guard is relative now; aitken_is_scale_invariant pins it at initial residual 1e-9. rtx-cfd 293 green (+1), rtx-fsi 29 green (+3). rtx-fsi's lib gains only the relative guard; the coupling layer still depends on no solver (rtx-cfd is a dev-dependency of its tests). Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 06:10:13 -07:00
Omar SobhandClaude Fable 5	259c5baa63	rtx-cfd: ALE on a moving tensor-product grid, DGCL-exact by construction ... The first brick of the Turek-Hron frontier: PISO (explicit conservative predictor + SOR projection) generalised to a staggered grid whose x- and y-lines move arbitrarily each step while the domain boundary stays fixed. The discretisation choice that carries everything: time-averaged face areas (A^n + A^{n+1})/2 in both the fluid fluxes and the face-swept volumes. For tensor-product motion the discrete geometric conservation law then holds as an algebraic identity, so uniform flow is a machine-precision fixed point, not a truncation-order one: - DGCL test: uniform (0.7, -0.4) on a 16x12 grid with interior lines wiggling out of phase, 400 steps: max deviation 7.9e-15 (~35 ulp). Negative control with end-of-step areas (per-step cell error exactly dw*dh/V, the cross term the identity absorbs): 1.5e-2 - a 1e12 separation, so the test can fail. - Degeneracy: zero motion on a uniform grid vs fixed-grid PISO over Taylor-Green steps: max difference 2.2e-16 - one ulp - pinning every geometric generalisation to the verified implementation. - Physics under motion: Taylor-Green on the wiggling mesh, L2 error 2.42e-2 -> 1.07e-2 (n=16 -> 32, order 1.17); moving-mesh error at n=32 sits below the fixed-mesh 1.1532e-2 (PISO's published value to four digits); energy decay unchanged by the motion. One trap documented in the test: the projection's inner-stop floor (0.1 * tolerance * reference_flux) at an engineering tolerance lets a one-sweep partial p' accumulate into p, whose gradient perturbs the velocities at ~1e-11 with the geometry blameless. The DGCL run must use a rounding-level tolerance because machine-precision preservation is the claim under test. Measured: 3.6e-11 at tol 1e-9, 7.9e-15 at 1e-13. Incompressibility needs no mesh-velocity term: subtracting the GCL from moving-cell mass conservation leaves plain div(u) = 0 on the current geometry, so the projection is the fixed-grid one with non-uniform coefficients. 292 rtx-cfd tests green (288 + 4). Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 05:31:12 -07:00
Omar SobhandClaude Fable 5	b321a9aba7	rtx-cfd: Taylor-Green validates PISO's transient path — and fixes the projection's inner solve ... With k = pi the decaying Taylor-Green vortex has zero normal velocity on the unit box for all time, so it fits the closed staggered domain exactly, with ZERO body force: convection is balanced identically by the true TG pressure and the decay comes from viscosity alone. This exercises exactly what the steady MMS harness cannot see — the time derivative, the unsteady pressure coupling and the projection's splitting error. The time-decaying tangential wall velocity enters by re-setting the wall hook each step. Measured (16/32/64, dt ~ h^2): L2 velocity 2.267e-2, 1.153e-2, 5.841e-3 — orders 0.97 and 0.98, first-order upwind's rate — and the kinetic-energy deficit against the exact e^(-4 nu pi^2 T) halves per refinement (0.0690, 0.0360, 0.0185; ratios 1.92, 1.95), within 2.3% on the finest mesh. Every step divergence-free to ~1e-7. Its first run caught two defects in the projection's inner solver: - The inner Gauss-Seidel stop summed the per-sweep iterate CHANGE — the same movement-not-residual pseudo-criterion the SIMPLE census flagged: slow modes move little per sweep while their residual is still large. - Plain GS contracts smooth modes by only 1 - O(h^2) per sweep, so the 400-sweep cap left max |div u| ~ 1e-2, GROWING with mesh size (8e-3 at 16^2 to 2e-2 at 64^2). The inner stop now measures the true equation residual, the sweep is SOR at the optimal Poisson factor omega = 2/(1 + sin(pi h)), and it converges relative to each projection's own source with a floor tied to the outer mass tolerance — so a long steady march no longer burns a hundred sweeps per step polishing negligible corrections. The steady MMS harness had masked all of this: a march to steady state iterates the projection to death regardless, which is why its divergence read 1e-9 while a 205-step transient left 1e-2. mms_piso's steady-state criterion is 1e-6 (was 1e-7): per-step projection noise at the mass tolerance floors |du/dt| just below 1e-6, and the L2 errors under measurement are 1e-2 to 1e-3. Its results are unchanged to six figures and still match SIMPLE's. 288 rtx-cfd tests, 0 failing. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-20 00:35:06 -07:00
Omar SobhandClaude Fable 5	9b097fca0d	rtx-cfd: PISO validated by manufactured solution — after fixing the inverted projection ... PisoSolver was the only major solver in the workspace with no verification of any kind. Writing the MMS harness for it (tests/mms_piso.rs) and inspecting the implementation found the census's defect species again: - The pressure correction had its SIGN inverted: it solved -lap(p') = +rho div(u*)/dt and then corrected with u = u* - (dt/rho) grad(p'), so each projection DOUBLED the divergence instead of removing it. - The momentum sweeps froze the near-wall lines (1..ny-1) and the pressure correction skipped the outer ring of cells (1..nx-1) — both exactly the defects repaired in SIMPLE. - The "explicit" predictor read neighbours the same sweep had already overwritten, so the step depended on sweep order. - The pressure gradient was dropped entirely on the last interior face. Rewritten as a genuinely explicit predictor plus anchored-Neumann projection on the staggered grid, with the conventions SIMPLE now embodies: near-wall lines are unknowns with half-cell wall diffusion, continuity on every cell, boundary faces are prescribed data. Momentum-source and wall-velocity hooks added so the manufactured solution can reach it. Measured (16 -> 32 -> 64): L2 velocity 3.516214e-2, 1.953750e-2, 1.037512e-2 — orders 0.85 and 0.91, first-order upwind's rate — with max |div u| ~ 1e-9 in every cell. The errors agree with SIMPLE's on the same meshes to six or seven significant figures: an implicit under-relaxed outer iteration and an explicit time-marching projection land on the same discrete steady solution, which is what sharing a spatial discretisation must produce and is very hard for two independently wrong solvers to fake. 285 tests, 0 failing. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-19 19:28:39 -07:00
Omar SobhandClaude Fable 5	796cf173e6	rtx-cfd: second-order convection by deferred-correction TVD; MMS order 1.84, cavity closes on Ghia ... First-order upwind's O(h) numerical viscosity was the measured limit on the whole discretisation: MMS order ~0.9 at Re = 20 against 2.05 in the Stokes limit. This adds a ConvectionScheme parameter to SimPLE — Upwind (default, behaviour unchanged), TvdVanAlbada, TvdVanLeer — implemented by deferred correction: the upwind operator stays implicit, so a_p = sum(a_nb) and diagonal dominance survive unconditionally, and the limited high-order-minus-upwind flux difference enters the source explicitly at the current iterate. At a fixed point the two agree, so the converged answer is the TVD discretisation. Faces whose far-upwind node lies outside the domain fall back to pure upwind; wall faces pass no mass, so no correction enters. Measured by the manufactured solution (van Albada, 16 -> 32 -> 64): L2 velocity 1.325e-3 4.406e-4 1.232e-4 orders 1.59, 1.84 (upwind) 3.516e-2 1.954e-2 1.038e-2 orders 0.85, 0.91 The error is 27x to 84x below upwind's at equal resolution, the order climbs toward 2 (the shortfall is limiter clipping plus the boundary fallback, both of which shrink with h), the pressure error falls at the same rate, and continuity still holds to solver tolerance in every cell. On the Re = 100 lid-driven cavity at 65^2 the centreline minimum moves from -0.1932 (upwind) to -0.2036 against Ghia's -0.2109 — 59% of the remaining gap closed at equal resolution, converged in 790 iterations — and the vortex position moves from 0.5000 to 0.4844 toward Ghia's 0.4531. Both new cavity bounds exclude the upwind values, so falling back to first order fails them. 284 tests, 0 failing. Co-Authored-By: Claude Fable 5 <[email protected]>	2026-08-19 19:16:48 -07:00
Omar SobhandClaude Opus 5	698c844926	solvers: near-wall momentum, Newmark dynamics, QM6, and MMS across elements ... Four parallel work items plus two defects found while integrating them. 561 -> 592 tests, 0 failing, verified stable over repeated runs. ## rtx-cfd: solve the near-wall velocity lines Every u row sits at y = (j+0.5) dy and every v column at x = (i+0.5) dx -- strictly interior. The sweeps froze rows 0 and ny-1 and columns 0 and nx-1 and treated whatever was stored there as a boundary condition, which imposed wall values half a cell inside the domain. They are now unknowns, with the wall entering through the control volume's half-cell conductance (mu dx / (dy/2)), zero convective flux through the wall, and the wall's tangential velocity in the source. That in turn makes continuity enforceable on every cell, with a neighbour coefficient zero only for a genuine boundary face. Extending continuity had been tried before and broke convergence; it works now because the near-wall lines are no longer frozen. Order matters here. Manufactured solutions, which is how any of this is known: n L2 velocity order max |p - p_exact| 16 3.516212e-2 - 9.245576e-2 32 1.953751e-2 0.85 5.225739e-2 64 1.037523e-2 0.91 2.796415e-2 Velocity error is 7.4x smaller at n=16, and the observed order rises from 0.48 toward 1. The pressure error was 0.408 -> 0.624 -> 0.756, *growing* with refinement; it now falls. Divergence on the outer ring of cells goes from 1.0e1 to 2.5e-10. A separate defect found on the way: u_source_term was computed and never called, so the x-momentum equation carried no body force at all while the y-momentum one did. That is exactly the u-versus-v asymmetry the earlier diagnosis had flagged as an unexplained clue. Cavity at 65^2, against Ghia's u_min = -0.2109 at y = 0.4531: -0.1792 at 0.3906 before, -0.1932 at 0.5000 after, in 733 iterations rather than 971. The cavity test now sets FreeSlipWall on all four sides plus the lid through the new set_wall_velocity hook. That is not a weakened benchmark: on a staggered grid the only velocity component living *on* a boundary is the normal one, which is what FreeSlipWall prescribes, and the tangential no-slip arrives through the half-cell wall term with wall velocity zero on the three stationary walls. Prescribing whole u rows and v columns, as before, pins lines half a cell inside the domain and over-determines the cells beside them once every cell has a continuity equation. ## rtx-fea: DynamicAnalysis, previously a stub returning zeros Newmark-beta in acceleration form -- the displacement form divides by beta dt^2, singular at beta = 0 -- with Rayleigh damping, the effective matrix Cholesky-factorised once and reused. Initial acceleration is solved from M a0 = F0 - C v0 - K u0 rather than assumed zero, which would destroy the second-order rate. Verified two ways that cannot both be faked: against the closed-form single-degree-of-freedom response, undamped and damped, with the measured order of accuracy; and against the free-vibration period of the same bar whose modal frequencies are already validated. Time domain and frequency domain come from different code paths. ## rtx-fea: QM6 incompatible modes Wilson's Q6 with Taylor's correction, added alongside compute_stiffness_ matrix rather than replacing it -- the existing method is byte-identical, which matters because the manufactured-solution verification depends on it. Internal modes statically condensed; the incompatible strain block evaluated at the element centre, which is what makes the patch test pass on distorted elements. ## rtx-fea: manufactured solutions across the element library Quad4 order 2.00 Tri3 order 1.98 Quad8 order 3.00 Hex8 order 1.96 (new 3-D solution) Each element asserts its own theoretical rate. ## Two defects found while integrating Reverse Cuthill-McKee node ordering was nondeterministic. All three of its orderings -- seed selection, neighbour ordering, and the trailing sweep -- were decided by HashMap/HashSet iteration order, which std randomises per process. On a rectangular mesh every corner ties at minimum degree, so two calls to displacement_only on the same mesh in the same process returned different DOF indices for the same node, agreeing in only 5 of 20 measured runs. Ties now break by node id. This surfaced as a coin-flip test failure -- 12 in 25 runs -- and would have been dismissed as flaky rather than diagnosed had the integration pass not re-run it. Quadrature: triangle(3) weights summed to 0.25 against a reference area of 0.5, and tetrahedron(3) to 1/36 against a volume of 1/6. Both divided weights that were already tabulated for the reference measure by that measure again, so both rules integrated everything to a fraction of its value -- invisibly, since a scaled quadrature leaves the stiffness matrix symmetric, the mass matrix positive definite and the rigid-body modes exact. New test asserts every rule integrates 1 to its reference measure, across every family and order, plus Gauss-Legendre exactness to degree 2n-1. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>	2026-08-19 15:39:20 -07:00
Omar SobhandClaude Opus 5	b5814a304f	rtx-cfd: manufactured solution finds the diffusion conductances were 1/h too ... large Applies MMS to the SIMPLE solver. It found a major discretisation error on the first run, which is the point of the method. The diffusion conductances read `mu / dx` and `mu / dy`. Finite volume requires `Gamma * A / delta` — the face area over the distance between the nodes it separates — so they should be `mu * dy / dx` and `mu * dx / dy`. The face area was missing entirely, making viscosity too large by a factor of `1/h`: sixty-five times on a 65x65 mesh. Every other term in the equation was already a force (`dp * dy` for pressure, `rho u dy` for the convective flux), so the mismatch was confined to diffusion. The consequence was that the solver ran at an effective Reynolds number far below the one requested. Before the fix the manufactured-solution error did not reduce under refinement at all — observed order about -0.05, because the spurious viscosity grows with the mesh. After it, the error falls monotonically. This also explains an apparent regression that is really a correction. The cavity vortex position moved from y = 0.484 to y = 0.391 against Ghia's 0.4531, which reads as worse agreement. It is not: a strongly over-diffusive cavity approaches Stokes flow, whose vortex sits near mid-height, so the old number was closer to the reference than the scheme deserved. Correcting the viscosity exposed the discretisation's own error. The test now states that disagreement plainly rather than asserting a band around the reference. What MMS reports now, and it is not yet good enough: n = 16 L2 velocity error = 2.586104e-1 order - n = 32 L2 velocity error = 1.797373e-1 order 0.52 n = 64 L2 velocity error = 1.277188e-1 order 0.49 First-order upwind should give 1. It gives about 0.5, and the u component is markedly further from exact than v on the same mesh. Both say there is at least one more defect in the discretisation or its boundary treatment, and the asymmetry between the two momentum equations is the clue. The test asserts only monotone error reduction — what is established — and records the shortfall, because asserting a rate the solver does not achieve would either redden the suite or invite someone to weaken it later. This changes the plan: raising the observed order to 1 is now a precondition for the second-order convection work rather than a consequence of it. There is no value in adding a higher-order scheme to a discretisation that has not demonstrated first order. Supporting changes: - `SimpleSolver::set_momentum_source` applies a volumetric body force, which is what lets a manufactured solution be imposed at all. - Divergence is now detected by growth, not only by NaN. The 8x8 case at Reynolds 10^6 reached 1e149 before anything caught it, because `is_finite` stays true right up until it does not. - `test_simple_solver_workflow` specified water properties on a unit domain, which is Reynolds 10^6 on ten cells: no steady laminar solution exists and the solver diverges on it, correctly. It passed only while the excess diffusion stabilised it. Now set to Reynolds 100. 561 tests across the three crates, 0 failing. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>	2026-08-19 12:25:52 -07:00
Omar SobhandClaude Opus 5	10e5f9cb90	rtx-cfd: fix the cell-centre velocity interpolation, which was half a cell out ... `get_velocity_at` averaged u-faces `i - 1` and `i` to report the velocity at cell `i`. On this staggered layout `u` is `(ny, nx + 1)` and cell `i` is bounded by faces `i` and `i + 1` -- which is the convention `compute_mass_source` uses to form the divergence, and therefore the one that defines the grid. The two disagreed by one index. Consequences: every profile read through this function was shifted half a cell west of the field the solver actually computed, the first and last cells were special-cased to a single face, and the outermost face was never read at all. It is a diagnostic path rather than a solve path -- the residuals are byte-identical before and after -- but the cavity comparison against Ghia is taken through it, so the reported vortex position was affected. The corrected grid study, unchanged in the solve: n u_min y 17^2 -0.1257 0.4375 33^2 -0.1550 0.4688 65^2 -0.1743 0.4844 97^2 -0.1825 0.5000 Ghia -0.2109 0.4531 The shift matters most where the grid is coarse and washes out under refinement, which is what a half-cell offset should do. Found while establishing where each staggered variable physically sits, a prerequisite for applying the method of manufactured solutions to this solver. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>	2026-08-19 12:10:41 -07:00
Omar SobhandClaude Opus 5	03a9bdf41f	rtx-cfd: apply boundary conditions to u* before using its divergence ... Closes the relaxation-factor dependence. Converged solutions are now identical for velocity relaxation 0.3, 0.5, 0.7 and 0.9 -- bit for bit -- where they previously spread 18%. The cause was ordering, not formulation. Boundary conditions were applied only at the end of the iteration, so `copy_to_starred` snapshotted a predicted field whose boundary faces held whatever the momentum sweep had written there: values the wall overwrote with zero moments later. The divergence of that field is the pressure equation's source, so those un-constrained faces entered it as a spurious mass source, concentrated at the two lid corners where the moving lid meets a stationary wall. The swept value scales with the relaxation factor, so the spurious source did too -- and so did the answer. Diagnosis is worth recording because the symptom pointed away from the cause. At the stalled state the interior momentum equations were satisfied to machine precision at every relaxation factor: a fresh Gauss-Seidel sweep moved the interior by 1e-15, the pressure correction was 1e-14, and the momentum residual was 3.6e-16. The entire residual floor lived in the *mass* term, and only that term varied with alpha -- 3.7e-4 at 0.3 against 1.6e-4 at 0.9. Each relaxation factor was converging honestly, to the solution of a slightly different problem. The correction also moves the cavity substantially closer to the reference, because the spurious corner source had been suppressing the recirculation: grid before after Ghia (1982) 17^2 -0.068 -0.123 -0.2109 33^2 -0.109 -0.154 65^2 -0.142 -0.174 97^2 -0.157 -0.182 Richardson extrapolation on the two finest grids now gives about -0.199 against Ghia's -0.2109, within 6%, with the remaining gap consistent with first-order upwind's numerical viscosity. The residual floor falls roughly linearly with mesh size (1.6e-3, 5.2e-4, 1.6e-4, 7.8e-5), which is the signature of the corner singularity rather than of an unconverged solve -- the same one Botella & Peyret (1998) subtract analytically. Two further fixes fell out of it: - The solver returned NaN rather than reporting divergence. Asked for an 8x8 cavity at a Reynolds number of a million it now stops, says it did not converge, and reports the last finite residual, instead of handing back a field of NaN that poisons everything downstream. Previously the false transient's large diagonal damped that case into crawling rather than diverging, which hid it. - `apply_boundary_condition` used `start_index` where it meant `end_index` for the bottom wall. The other three arms are correct; with both indices unset the default masked it. 558 tests across the three crates, 0 failing. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>	2026-08-19 10:27:33 -07:00
Omar SobhandClaude Opus 5	2db4e28760	rtx-cfd: make SIMPLE a steady solver; the converged answer no longer depends ... on the pseudo-time step Acting on a literature pass. Standard SIMPLE is a steady-state algorithm: it has no pseudo-time term, and stability comes from under-relaxation folded implicitly into the momentum coefficients. Ours had a false transient *and* an explicit post-hoc blend of the whole field, which is why the converged cavity solution varied with `time_step` -- something a steady state cannot legitimately do. Four changes, in the order they mattered: 1. The convergence measure was `|u - u_old|`, the change between successive iterates. That is not a residual: it reports how far the iteration moved, which depends on how heavily it is damped, and the damping was set by `dt`. Replaced with the imbalance of the discretised momentum equations, `|a_p u_P - sum a_nb u_nb - b|`, normalised by `sum |a_p u_P|` as CFD solvers conventionally report it. An unnormalised sum grows with the cell count and with `dt` through `a_p0`, so the same numeric tolerance meant a different thing on every grid. The residual is measured against the *unrelaxed* equation. Relaxation inflates the diagonal by 1/alpha and adds a matching source; reporting the relaxed system's residual makes one tolerance correspond to a different true error for each alpha. 2. Steady by default: `a_p0 = 0`, and Patankar's implicit under-relaxation -- `a_p / alpha` with `(1-alpha)/alpha * a_p * u_prev` added to the source. At a fixed point the two cancel exactly, so the converged solution is independent of alpha by construction. The explicit velocity blend is removed; it relaxed a second time and undid part of the continuity the pressure correction had just enforced. `steady: false` restores the transient term for genuinely time-dependent problems. Result: dt = 0.001, 0.01 and 0.05 now give bit-identical fields. 3. Dropped the net convective flux from `a_p`. It vanishes identically once continuity holds, but during the iteration it does not, and it can exceed the sum of the neighbour coefficients -- driving `a_p` through zero and the solve to NaN, which is what the workflow tests hit once `a_p0` was no longer there to mask it. Omitting it is what makes `a_p = sum a_nb` positive unconditionally. 4. Anchored one cell of the pressure correction. With velocity prescribed on every boundary the pressure equation is pure Neumann and singular; `p'` is fixed only up to a constant and Gauss-Seidel lets it drift. Enforcing solvability by subtracting the mean source is the textbook remedy and is wrong here -- this source is assembled from face fluxes that include the boundaries, so it need not sum to zero, and subtracting its mean injects a spurious source everywhere. Tried; it diverged. Anchoring a reference cell changes no pressure gradient, which is all the momentum equation uses. Also measured, and it settles the open question about Ghia: the under-prediction is numerical diffusion, not a defect. First-order upwind carries a numerical viscosity of about |u| dx / 2, which at 65^2 is 0.0078 against a physical 0.01 -- an effective Reynolds number near 56, not 100. Refinement moves the centreline minimum monotonically toward the reference: -0.068 at 17^2, -0.109 at 33^2, -0.142 at 65^2, -0.157 at 97^2, against Ghia's -0.2109, with the vortex position tracking 0.375 -> 0.406 -> 0.469 -> 0.490 against Ghia's 0.4531. The cavity test moves to 65^2 and asserts the vortex position tightly (0.40..0.52, Ghia 0.4531) while bounding the strength to the band first-order upwind can reach there. Its tolerance is 1e-4 rather than 1e-6: the two lid corners hold a velocity discontinuity whose discrete imbalance does not reduce with iteration, so the normalised residual floors near 7e-5. That is a property of the problem -- the same singularity Botella & Peyret (1998) subtract analytically -- and the physical assertions, not the stopping rule, are what establish correctness. Still open: converged solutions retain a dependence on the relaxation factor that the implicit formulation should have removed (-0.159 at alpha=0.3 against -0.134 at alpha=0.9 on 65^2, each stable to six decimals over 200k iterations). Recorded rather than papered over. 558 tests across the three crates, 0 failing. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>	2026-08-19 09:47:46 -07:00
Omar SobhandClaude Opus 5	bfd9f4dfd2	rtx-cfd: repair the pressure-velocity coupling, LBM walls and mesh quality ... Clears the rest of the quarantine. All three crates now run 558 tests with 0 failures and no `#[ignore]` markers. SIMPLE could not converge, and the reason was not slow convergence but wrong physics. The pressure correction equation used a bare Laplacian, 1/dx^2 and 1/dy^2, while the velocity correction divided by a_p = rho dx dy / dt. SIMPLE requires these to be each other's inverse: substituting the corrected velocities into continuity must reproduce the pressure equation, which fixes a_E = rho d dy/dx with d = dV/a_p. The two disagreed by roughly 1/(h^2 dt) -- about 2e4 on a 16x16 cavity -- so the pressure correction was that many times too weak to enforce continuity. The consequence was visible and specific. A lid-driven cavity at Re=100 produced a monotonic profile rising from 0 at the floor to 1 at the lid: Couette flow, with no recirculation anywhere, and a peak pressure of 1.6e-4 against the rho U^2 scale of 1. The return flow in a cavity is driven entirely by the pressure gradient, so with the pressure pinned near zero there was nothing to turn the flow around. With the coefficients made consistent the profile recirculates, the peak pressure is 2.9, and the solver converges. Also in SIMPLE: - `p'` was never reset between outer iterations. It is a correction that `pressure_update_step` folds into `p`, so carrying it forward applied the same correction twice. - The convergence measure was the inner Gauss-Seidel residual, which goes to zero whether or not the flow satisfies continuity. Now the mass imbalance. - The velocity correction used only the transient part of a_p, `rho dV/dt`, rather than the diagonal the momentum equation was actually solved with. - All four convective face fluxes were computed from a single cell-centred velocity, so `fe` and `fw` were the same number, as were `fn` and `fs`. Upwinding then picked the same direction on opposite faces of the control volume. Now interpolated per face on the staggered grid. Not claimed: agreement with Ghia, Ghia & Shin (1982). The vortex centre moves toward their y = 0.4531 under refinement (0.400 at 16^2, 0.419 at 32^2, 0.460 at 64^2) but the minimum centreline velocity reaches only -0.130 against their -0.2109, and the converged field still depends slightly on the pseudo-time step, which a true steady state cannot. The cavity test therefore asserts what is established -- convergence, recirculation, vortex position, and an O(1) pressure field -- and the remaining gap is recorded in omni-cortex/docs/solver_status.md rather than papered over with a loose tolerance. LBM bounce-back was doing neither of the things its name claims. It was written as assignment (`f[2] = f[4]`) rather than a swap, discarding the population being reflected -- bounce-back is a permutation and conserves mass exactly, so the domain leaked 0.013% of its mass every 100 steps and would have kept draining. And the pairs used were 5<->8 and 6<->7, which reverse only the wall-normal component: that is specular reflection, a free-slip wall, so the no-slip condition the walls were supposed to impose never held. Mesh quality: - Quadrilateral aspect ratio included the diagonals in the maximum but not the minimum, so it could never return 1: a unit square reported sqrt(2) and a 2:1 rectangle sqrt(5). - Triangle aspect ratio used longest-over-shortest edge, which does not detect the failure mode that matters. A sliver with vertices (0,0), (10,0), (5,0.1) scores 2.0 -- indistinguishable from a healthy 2:1 triangle -- while its area is a twentieth of what its edges suggest. Now the radius ratio R/2r, which is 1 for equilateral and 1250 for that sliver, and which also fixes the quality histogram. - StructuredMesh aspect ratio took bounding-box extents and guarded the z-extent with `.max(1e-10)`. On a 2-D mesh the depth is exactly zero, so the guard became the minimum and a unit square reported 2e10. Mesh refinement produced meshes that failed their own validation. `subdivide_triangle` reserved midpoint ids as `next_node_id + k`, then advanced the counter by 3, after which `refine_cells` called `add_node` and advanced it three more -- so every refined cell referenced vertices three ids away from the ones actually created. Separately, the position lookup selected by slot rather than by id ("This is simplified, should look up correct midpoint"), so three of four sub-triangles had their areas computed from the wrong points; the quadrilateral version mapped every new id to the cell centre. Fixtures corrected rather than tolerances loosened: a structured mesh test asserted 0.16 for the average cell volume while the comment beside it computed 0.25 from the node-count convention the code actually uses; the Zou-He pressure test built a *velocity* boundary at u = 1.2, far above the lattice speed of sound, making the density negative; and the cavity-setup test required the lid to influence the domain centre 16 rows away in 10 steps, which exceeds the lattice propagation speed. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>	2026-08-19 08:40:09 -07:00
redclawsystems	4d88dc0584	Initial commit	2026-03-04 00:08:42 +00:00