Limit the time-step size such that the smoothing length does not change by...

Limit the time-step size such that the smoothing length does not change by more than a pre-defined constant.

src/hydro/Default/hydro.h

@@ -28,12 +28,7 @@ __attribute__((always_inline)) INLINE static float hydro_compute_timestep(
     struct part* p, struct xpart* xp) {
 
   /* CFL condition */
-  float dt_cfl = const_cfl * p->h / p->force.v_sig;
-
-  /* Limit change in h */
-  float dt_h_change = (p->h_dt != 0.0f)
-                          ? fabsf(const_ln_max_h_change * p->h / p->h_dt)
-                          : FLT_MAX;
+  float dt_cfl = 2.f * const_cfl * kernel_gamma * p->h / p->force.v_sig;
 
   /* Limit change in u */
   float dt_u_change = (p->force.u_dt != 0.0f)

src/runner.c

@@ -871,7 +871,14 @@ void runner_dokick(struct runner *r, struct cell *c, int timer) {
           const float new_dt_grav = gravity_compute_timestep(p, xp);
 
           new_dt = fminf(new_dt_hydro, new_dt_grav);
-
+	  
+	  /* Limit change in h */
+	  const float dt_h_change = (p->h_dt != 0.0f)
+	    ? fabsf(const_ln_max_h_change * p->h / p->h_dt)
+	    : FLT_MAX;
+
+	  new_dt = fminf(new_dt, dt_h_change);
+	  
           /* Recover the current timestep */
           const float current_dt = p->t_end - p->t_begin;