Federico Alzamora Previtali
Ansys Employee

Hello, 

can you try something like this, where you loop over the cells of your deforming zonne?

Node *node_p  
begin_c_loop (f, tf)
    {
      c_node_loop (f, tf, n)
        {
          node_p = C_NODE (f, tf, n);
          if (NODE_POS_NEED_UPDATE (node_p))
            {
              NODE_POS_UPDATED (node_p);
              xold = NODE_X (node_p);                        
              xnew = xold+delta_x;
              NODE_X (node_p) = xnew;
            }
        }
    }
  end_c_loop (f, tf);
 
where NODE_POS_NEED_UPDATE(node_p) is ensures that the position gets updated only than once for any given time step (if running in parallel). 
Also, use CURRENT_TIME instead of time to access flow_time variable.
Note that we can only provide limited support for customization. Hence, the above is only a general suggestion and we cannot guarantee that it will work as intended for your application.