particles can get out

fluid/fluid_problem.c

@@ -1819,7 +1819,7 @@ void fluid_problem_move_particles(FluidProblem *problem, int n, double *position
   compute_porosity(problem->mesh, problem->node_volume, particle_enter_porosity, problem->n_particles, position,
                    problem->particle_volume, problem->particle_element_id, problem->particle_uvw, particle_enter);
   compute_porosity(problem->mesh, problem->node_volume, particle_leave_porosity, problem->n_particles, problem->particle_position,
-                   problem->particle_volume, problem->particle_element_id, problem->particle_uvw, particle_leave);
+                   problem->particle_volume, old_element_id, problem->particle_uvw, particle_leave);
   compute_porosity(problem->mesh, problem->node_volume, problem->porosity, problem->n_particles, position, problem->particle_volume, problem->particle_element_id, problem->particle_uvw, NULL);
   for (int i = 0; i < problem->mesh->n_nodes; i++) {
     problem->oldporosity[i] += particle_enter_porosity[i]-particle_leave_porosity[i];
@@ -1827,7 +1827,7 @@ void fluid_problem_move_particles(FluidProblem *problem, int n, double *position
   int nf = fluid_problem_n_fields(problem);
   for (int i = 0; i < problem->mesh->n_nodes; i++) {
     for (int d = 0; d < DIMENSION; ++d) {
-      problem->solution[i*nf+U+d] *= problem->porosity[i]/(problem->porosity[i]-particle_enter_porosity[i]+particle_leave_porosity[i]);
+      problem->solution[i*nf+U+d] *= problem->porosity[i]/(problem->porosity[i] - particle_enter_porosity[i] + particle_leave_porosity[i]);
     }
   }
   free(particle_enter_porosity);