Added timestep limiter for maximal u change

src/hydro/PressureEnergy/hydro.h

@@ -283,7 +283,12 @@ __attribute__((always_inline)) INLINE static float hydro_compute_timestep(
   const float dt_cfl = 2.f * kernel_gamma * CFL_condition * cosmo->a * p->h /
                        (cosmo->a_factor_sound_speed * p->force.v_sig);
 
-  return dt_cfl;
+  /* Limit maximum change in u */
+  const float dt_u_change = 
+      (p->u_dt != 0.0f) ? fabsf(const_max_u_change * p->u / p->u_dt)
+                        : FLT_MAX;
+
+  return fminf(dt_cfl, dt_u_change);
 }
 
 /**