embedded3 S2-1: the traction sampler on the cut field (pressure fit excludes merged cells; sampler route in the sphere MMS and DFG drivers)

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

crates/specialized/rtx-cfd/tests/embedded3_dfg_2z.rs

@@ -75,7 +75,12 @@ fn dfg_3d_2z_on_the_device() {
             (0.0, 0.0, 0.0)
         }
     });
-    solver.set_body(Body::cylinder_z(CX, CY, 0.5 * D));
+    // The cylinder extruded across the width, with samples for the
+    // traction route (S2-1).
+    solver.set_body(Body::extruded(
+        rtx_cfd::solvers::incompressible::EmbeddedBody::circle(CX, CY, 0.5 * D),
+        H,
+    ));
     let g = Grid::cubic(nx, ny, nz, h);
     let mut field = Field::new(g);
     // Start from the inflow profile everywhere (a faster approach to steady).
@@ -99,13 +104,18 @@ fn dfg_3d_2z_on_the_device() {
     let coef = 2.0 / (RHO * U_BAR * U_BAR * D * H);
     let csv = std::env::var("RTX_E3_DFG_CSV").ok().map(|p| {
         let mut f = std::fs::File::create(p).expect("csv");
-        writeln!(f, "t,cd_wall,cl_wall,cd_cv,cl_cv,dp,residual,cg").unwrap();
+        writeln!(
+            f,
+            "t,cd_wall,cl_wall,cd_cv,cl_cv,dp,residual,cg,cd_sampler,cl_sampler"
+        )
+        .unwrap();
         f
     });
     let mut csv = csv;
     let sample_every = (steps / 100).max(1);
     let start = std::time::Instant::now();
     let mut last: Option<(f64, f64, f64, f64, f64)> = None;
+    let mut last_sampler = (f64::NAN, f64::NAN);
     let mut settled = false;
     for step in 0..steps {
         let r = device.advance(dt);
@@ -131,6 +141,8 @@ fn dfg_3d_2z_on_the_device() {
             );
             let fcv =
                 mask.control_volume_force_with_walls(&field, dt, RHO, RHO * NU, None, bx, true);
+            let fs = mask.surface_force(body, &field, RHO * NU, t, 0.5 * h);
+            let (cd_s, cl_s) = (coef * fs.f[0], coef * fs.f[1]);
             let zc = 0.5 * H;
             let p_front = mask
                 .pressure_at(&field.p, CX - 0.5 * D, CY, zc)
@@ -141,7 +153,8 @@ fn dfg_3d_2z_on_the_device() {
             let dp = p_front - p_back;
             let (cd, cl, cd_cv, cl_cv) = (coef * fw[0], coef * fw[1], coef * fcv[0], coef * fcv[1]);
             println!(
-                "  t {t:8.4}: c_D {cd:.4} (CV {cd_cv:.4})  c_L {cl:.5} (CV {cl_cv:.5})  Δp {dp:.4}  residual {:.1e} CG {}  [{:.0} s]",
+                "  t {t:8.4}: c_D {cd:.4} (CV {cd_cv:.4}, sampler {cd_s:.4} skipped {})  c_L {cl:.5} (CV {cl_cv:.5}, sampler {cl_s:.5})  Δp {dp:.4}  residual {:.1e} CG {}  [{:.0} s]",
+                fs.skipped,
                 r.final_residual,
                 r.poisson_iterations,
                 start.elapsed().as_secs_f64()
@@ -149,11 +162,12 @@ fn dfg_3d_2z_on_the_device() {
             if let Some(f) = csv.as_mut() {
                 writeln!(
                     f,
-                    "{t:.5},{cd:.6},{cl:.6},{cd_cv:.6},{cl_cv:.6},{dp:.6},{:.3e},{}",
+                    "{t:.5},{cd:.6},{cl:.6},{cd_cv:.6},{cl_cv:.6},{dp:.6},{:.3e},{},{cd_s:.6},{cl_s:.6}",
                     r.final_residual, r.poisson_iterations
                 )
                 .unwrap();
             }
+            last_sampler = (cd_s, cl_s);
             if let Some((pcd, pcl, _, _, pdp)) = last {
                 let rel = ((cd - pcd) / cd)
                     .abs()
@@ -180,8 +194,11 @@ fn dfg_3d_2z_on_the_device() {
     }
     let (cd, cl, cd_cv, cl_cv, dp) = last.expect("samples");
     println!(
-        "  FINAL ny {ny}: c_D {cd:.4} (CV {cd_cv:.4}, routes {:.2e} apart)  c_L {cl:.5} (CV {cl_cv:.5})  Δp {dp:.4}  — reference c_D 6.05–6.25, c_L 0.008–0.010, Δp 0.165–0.175; {:.0} s",
+        "  FINAL ny {ny}: c_D {cd:.4} (CV {cd_cv:.4}, routes {:.2e} apart; sampler {:.4}, {:.2e} from CV)  c_L {cl:.5} (CV {cl_cv:.5}, sampler {:.5})  Δp {dp:.4}  — reference c_D 6.05–6.25, c_L 0.008–0.010, Δp 0.165–0.175; {:.0} s",
         ((cd - cd_cv) / cd).abs(),
+        last_sampler.0,
+        ((last_sampler.0 - cd_cv) / cd_cv).abs(),
+        last_sampler.1,
         start.elapsed().as_secs_f64()
     );
     if let Some(t) = device.timers() {