Is Fluent capable of handling mesh movement? For example, a wall moving normal to the flow. Thanks.

Yes it is. You can set a wall boundary condition from stationary to moving. You can do the same for a Fluid zone also.

The ultimate goal of my research is to obtain the topology due to bed deformation, for the interaction of water and sediment. Whether it could be solved using this tips or not?

I am not sure this is the feature I am looking for. I need a changing mesh; for example, unsteady flow in a reciprocating engine.

There is no general mesh movement in Fluent. Just use StarCD for that.

This feature is reported to be available in Fluent 6 around September (who knows for sure). I also understand this feature is the main reason for the delay in Fluent 6, so it may not be very robust initially. Star-CD and CFX both have this to my knowledge....

Greg

I'm not sure if this will work but you can try it if you need to: Set the cylinder walls as stationary and the piston as a moving wall. When you hit TDC or BDC change the direction of wall motion. For inlet or outlet valves, use pressure outlets or inlets. Do you think this might provide a temporary solution or am I just blowing smoke?

You can not specify the normal component via bc. Only the tangetial component.

Why do you say that we cannot specify the normal component of flow with the boundary condition? I'm not sure I understand your comment.

You can specify the normal component of a boundary, but then it is not a wall.

Try the following: take a box and move one wall inside in normal direction. After some time the volume of the box goes to zero. Now try to run this case with your sort of "normal wall bc". It will not work. In order to simulate this case you have to move your mesh points.

Thanks. I believe this is correct. I did not realize this at first. What I need to obtain are the forces on the moving wall. You cannot do this by specifying a wall velocity in the bc. One can try this by placing a cylinder in a cross flow and instead of specifying a cross flow, specify a wall velocity on the cylinder. You can't get the drag forces on the cylinder. However, you can get the drag forces by running a transient case and a moving cylinder mesh.