rtx-cfd: overset_cfd1 prints five CV boxes (all outside the fringe ring), the wall pressure/viscous split and the fringe extents at the settled state

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01X2GmJXeQ2njUecEKiJZ1G2

crates/specialized/rtx-cfd/tests/overset_cfd1.rs

@@ -285,6 +285,65 @@ async fn run_cfd1(ny: usize) -> CfdResult<Cfd1> {
         100.0 * (ring.0 - hole.0) / wall[0],
         100.0 * (hole.0 - wall[0]) / wall[0],
     );
+    // The wall load split and the fringe ring's extent (the tight box in
+    // the sensitivity list must stay outside it).
+    let (mut jmin, mut jmax, mut imin, mut imax) = (usize::MAX, 0, usize::MAX, 0);
+    for e in &solver.overlap().fringe_cells {
+        jmin = jmin.min(e.j);
+        jmax = jmax.max(e.j);
+        imin = imin.min(e.i);
+        imax = imax.max(e.i);
+    }
+    println!(
+        "    wall load split: pressure ({:.4}, {:.4}) viscous ({:.4}, {:.4}); fringe ring cells i {imin}–{imax} (x {:.3}–{:.3}) j {jmin}–{jmax} (y {:.3}–{:.3})",
+        load.pressure[0],
+        load.pressure[1],
+        load.viscous[0],
+        load.viscous[1],
+        imin as f64 * h,
+        (imax + 1) as f64 * h,
+        jmin as f64 * h,
+        (jmax + 1) as f64 * h
+    );
+    // Box sensitivity of the control-volume route: the same balance on
+    // other rectangles, all outside the fringe ring (x 0.110–0.640, y
+    // 0.110–0.290 at ny = 41 — a first list had a box at x0 = 0.12 cutting
+    // through it and read −21 %). A route that moves with the box by more
+    // than its own formula error cannot arbitrate the gap.
+    for (x0, x1, y0, y1) in [
+        (0.10, 0.75, 0.05, 0.36),
+        (0.09, 0.70, 0.07, 0.34),
+        (0.08, 1.00, 0.03, 0.38),
+        (0.10, 1.50, 0.05, 0.36),
+        (0.10, 0.75, 0.02, 0.39),
+    ] {
+        let boxc = (
+            (x0 / h).round() as usize,
+            (x1 / h).round() as usize,
+            (y0 / h).round() as usize,
+            (y1 / h).round() as usize,
+        );
+        let (bx, by) = solver
+            .background()
+            .mask()
+            .expect("mask")
+            .control_volume_force(
+                &field.background.u,
+                &field.background.v,
+                &field.background.p,
+                &field.background.u_old,
+                &field.background.v_old,
+                dt,
+                RHO,
+                mu,
+                None,
+                boxc,
+            );
+        println!(
+            "    CV box x {x0:.2}–{x1:.2} y {y0:.2}–{y1:.2}: drag {bx:.4} ({:+.2}% vs wall) lift {by:.4}",
+            100.0 * (bx - wall[0]) / wall[0]
+        );
+    }
     Ok(Cfd1 {
         drag_surface: load.total()[0],
         lift_surface: load.total()[1],