cngf-pf

commit 491b69c62c0aa413975e5bd57df9289054d80d62
parent 254e00285ee8996710ca156a1cae30ac6c935779
Author: Anders Damsgaard <anders@adamsgaard.dk>
Date:   Thu, 15 Jan 2026 19:24:27 +0100

fix(simulation): fix transient mode velocity residual and mu_wall reset

- Use fmax(v_x_fix, v_x[top]) as reference for velocity residual to
  prevent division by near-zero when solver hasn't reached yield
- Reset mu_wall to original value after each timestep for v_x_fix
  (was only done for v_x_limit), preventing accumulation across timesteps
- Re-enable cngf_pf_dry_transient test now that basic transient works
- Update skip comments for trans_undercons/overcons (solver instability)

Diffstat:
M
simulation.c
 | 
7
++++---
M
test/Makefile
 | 
7
+++++--

2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/simulation.c b/simulation.c
@@ -837,8 +837,9 @@ int coupled_shear_solver(struct simulation *sim, const int max_iter,
         if (vel_res_norm > 0.0)
           vel_res_norm = 0.0;
       } else {
-        vel_res_norm = (sim->v_x_fix - sim->v_x[sim->nz - 1]) /
-                       (sim->v_x[sim->nz - 1] + 1e-12);
+        double v_ref =
+            fmax(fabs(sim->v_x_fix), fabs(sim->v_x[sim->nz - 1])) + 1e-12;
+        vel_res_norm = (sim->v_x_fix - sim->v_x[sim->nz - 1]) / v_ref;
       }
       sim->mu_wall *= 1.0 + (vel_res_norm * 1e-3);
     }
@@ -854,7 +855,7 @@ int coupled_shear_solver(struct simulation *sim, const int max_iter,
   } while ((!isnan(sim->v_x_fix) || !isnan(sim->v_x_limit)) &&
            fabs(vel_res_norm) > RTOL_VELOCITY);
 
-  if (!isnan(sim->v_x_limit))
+  if (!isnan(sim->v_x_limit) || !isnan(sim->v_x_fix))
     sim->mu_wall = mu_wall_orig;
 
   temporal_increment(sim);
diff --git a/test/Makefile b/test/Makefile
@@ -12,14 +12,17 @@ TESTS = cngf_pf_dry \
         cngf_pf_wet_vari_diff \
         cngf_pf_wet_vari_pulse \
         cngf_pf_wet_vari_pulse_vlim \
+		cngf_pf_dry_transient \
 		shear_flux_dry \
 		shear_flux_wet
 
 # Skipped tests:
-# - cngf_pf_dry_trans, cngf_pf_dry_trans_undercons, cngf_pf_dry_trans_overcons:
-#   Transient mode broken after inertia fix (commit 91d9022)
+# - cngf_pf_dry_trans_undercons, cngf_pf_dry_trans_overcons:
+#   Transient mode with fixed velocity and non-critical porosity has
+#   coupled solver instability (see walkthrough for details)
 # - max_depth_misc: test config uses removed -O option
 
+
 STANDARDS := $(TESTS:=.std)
 
 CNGF_PF_DRY_OPTS =          -o 0.03 -L 0.64 -n 40e3