embedded3 A3-i: the advancing-wall friction closure (RTX_E3_WALL_ADVANCING=1, host + device, per-face normal-velocity table; f(0) = 1 exactly) — REFUTED as built on the slab ladder (flag shear 34.2 / 33.6 / 31.1 vs 28.9 / 32.3 / 30.1: spread 3.4 -> 3.1, now from above; worst mass residual 1e-8 -> 1e-4); knob stays off, default digit-identical

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

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

@@ -216,6 +216,7 @@ impl Mask {
             wall_distance_oblique: false,
             diffusion_transverse: false,
             distance_floor_fine: false,
+            wall_advancing: false,
             wall_exchange_axis: false,
             grad_weights: None,
             diffusion_centroid: false,
@@ -658,8 +659,15 @@ impl Mask {
                         if a_w == 0.0 {
                             continue;
                         }
-                        let ub = self.surface_velocity_at(body, lat.face_position(c, p), c, t);
-                        let (c1, c2, nb) = self.wall_gradient(c, p, &cv);
+                        let x = lat.face_position(c, p);
+                        let ub = self.surface_velocity_at(body, x, c, t);
+                        let xi = if self.wall_advancing {
+                            self.surface_normal_velocity_at(body, x, t) * cv.distance * self.density
+                                / mu
+                        } else {
+                            0.0
+                        };
+                        let (c1, c2, nb) = self.wall_gradient(c, p, &cv, xi);
                         let un = nb.map_or(ub, |f| values[c][f]);
                         force[c] += mu * a_w * (c1 * (values[c][idx] - ub) + c2 * (un - ub));
                     }