embedded3 S2-6: the oblique-wall instrument (tests/embedded3_wall_position_oblique.rs: z-flow / in-plane Poiseuille + Couette linear exactness; gate oblique_wall_position_is_second_order) and the closures it found, host + device, default OFF — the transverse centroid correction (RTX_E3_DIFFUSION_TRANSVERSE=1, wall_order bit 7), the fine distance floor (RTX_E3_DISTANCE_FLOOR=fine, bit 8); kernel geometry factored into cut_cv; DFG 2D-1 x-shift knob (RTX_E3_DFG_SHIFT_X); FLAG_X0 0.6 -> 0.25 in the three flag tests (the flag of every record was detached)

Co-Authored-By: Claude Fable 5.1 <[email protected]>

crates/specialized/rtx-cfd/src/solvers/incompressible/embedded3/cutwall.rs

@@ -25,6 +25,8 @@ use super::wall::{FaceKind, Mask};
 pub(super) const INERTIA_FLOOR: f64 = 0.1;
 /// The wall-distance floor of a face, in units of the smallest spacing.
 pub(super) const DISTANCE_FLOOR: f64 = 0.05;
+/// The fine floor (S2-6, `Parameters::distance_floor_fine`).
+pub(super) const DISTANCE_FLOOR_FINE: f64 = 0.01;
 /// Virtual merging: a cell whose fluid fraction (at either end of the
 /// step) stays below this shares its pressure unknown with a neighbour.
 pub(super) const MERGE_FRACTION: f64 = 0.1;
@@ -211,6 +213,8 @@ impl Mask {
             density: 1.0,
             wall_order: 1,
             wall_distance_oblique: false,
+            diffusion_transverse: false,
+            distance_floor_fine: false,
             wall_exchange_axis: false,
             grad_weights: None,
             diffusion_centroid: false,
@@ -398,7 +402,8 @@ impl Mask {
         } else {
             1.0
         };
-        let distance = (phi_face + 0.5 * h[c] * (1.0 - alpha) * n_t).max(DISTANCE_FLOOR * h_min);
+        let distance =
+            (phi_face + 0.5 * h[c] * (1.0 - alpha) * n_t).max(self.distance_floor() * h_min);
         CvGeometry {
             alpha,
             ap,