fsi2 harness: RTX_FSI2O_BG_CONVECTION knob (tvd default / upwind) on the background, printed in both headers beside the patch's — the patch scheme was excluded as the h-term's carrier (upwind ladder +1.52 vs TVD +1.73 W/m from ny 41 to 62), the background's wake dissipation is the registered next probe

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LzcjQX7tvgn87CQCyg9Cfr

crates/specialized/rtx-fsi/tests/turek_hron_fsi2_overset.rs

@@ -413,10 +413,11 @@ fn fsi2_overset_prescribed_motion() {
     let dt = fluid.dt_fluid;
     let (d_rigid, l_rigid) = fluid.measure_force();
     println!(
-        "  PRESCRIBED ny = {ny}: dt {dt:.3e}, rigid drag {d_rigid:.2} lift {l_rigid:.2}, replay from t = {t0} (ramp {ramp_w} s) to {t_end}; patch offset {} h × {} rows, patch convection {:?}",
+        "  PRESCRIBED ny = {ny}: dt {dt:.3e}, rigid drag {d_rigid:.2} lift {l_rigid:.2}, replay from t = {t0} (ramp {ramp_w} s) to {t_end}; patch offset {} h × {} rows, patch convection {:?}, bg convection {:?}",
         std::env::var("RTX_FSI2O_PATCH_OFFSET").unwrap_or_else(|_| "6".into()),
         std::env::var("RTX_FSI2O_PATCH_ROWS").unwrap_or_else(|_| "12".into()),
         fsi2_harness::overset::patch_convection(),
+        fsi2_harness::overset::bg_convection(),
     );
     let mut csv = std::env::var("RTX_FSI2O_CSV").ok().map(|p| {
         use std::io::Write as _;