clean up old cache differently

bfps/NavierStokes.py

@@ -612,8 +612,11 @@ class NavierStokes(_fluid_particle_base):
                     for k in ['t', 'vel_max(t)', 'renergy(t)',
                               'energy(t)', 'enstrophy(t)',
                               'energy(k)', 'enstrophy(k)',
+                              'energy(t, k)',
+                              'enstrophy(t, k)',
                               'R_ij(t)',
                               'ii0', 'ii1', 'iter0', 'iter1']:
+                        if k in pp_file.keys():
                             del pp_file[k]
             if computation_needed:
                 pp_file['iter0'] = iter0