fix: correct MTHINC normals on non-uniform grids by weighting by cell width

Author: sbryngelson

src/simulation/m_thinc.fpp

@@ -258,16 +258,19 @@ contains
                     ac = v_vf(eqn_idx%adv%beg)%sf(j, k, l)
 
                     if (ac >= ic_eps .and. ac <= 1._wp - ic_eps) then
-                        nr_x = (v_vf(eqn_idx%adv%beg)%sf(j + 1, k, l) - v_vf(eqn_idx%adv%beg)%sf(j - 1, k, l))*5e-1_wp
+                        nr_x = (v_vf(eqn_idx%adv%beg)%sf(j + 1, k, l) - v_vf(eqn_idx%adv%beg)%sf(j - 1, k, &
+                                & l))*(x_cb(j) - x_cb(j - 1))/(x_cc(j + 1) - x_cc(j - 1))
 
                         nr_y = 0._wp
                         if (n > 0) then
-                            nr_y = (v_vf(eqn_idx%adv%beg)%sf(j, k + 1, l) - v_vf(eqn_idx%adv%beg)%sf(j, k - 1, l))*5e-1_wp
+                            nr_y = (v_vf(eqn_idx%adv%beg)%sf(j, k + 1, l) - v_vf(eqn_idx%adv%beg)%sf(j, k - 1, &
+                                    & l))*(y_cb(k) - y_cb(k - 1))/(y_cc(k + 1) - y_cc(k - 1))
                         end if
 
                         nr_z = 0._wp
                         if (p > 0) then
-                            nr_z = (v_vf(eqn_idx%adv%beg)%sf(j, k, l + 1) - v_vf(eqn_idx%adv%beg)%sf(j, k, l - 1))*5e-1_wp
+                            nr_z = (v_vf(eqn_idx%adv%beg)%sf(j, k, l + 1) - v_vf(eqn_idx%adv%beg)%sf(j, k, &
+                                    & l - 1))*(z_cb(l) - z_cb(l - 1))/(z_cc(l + 1) - z_cc(l - 1))
                         end if
 
                         nmag = sqrt(nr_x*nr_x + nr_y*nr_y + nr_z*nr_z)