[Springroove]

Dear,

I am trying to model a train moving through a tunnel and as such I'm trying to impose a 'moving wall' boundary condition, e.g. the train is moving with 100 m/s so I try to let the walls move with that speed.
However, in the solver configuration I can't seem to find this option?

Can someone help me out please, many thanks!

[ghorrocks]

If the wall moves tangentially such that the fluid domain does not change shape then you can use a tangential wall velocity boundary condition. This can be found in the wall boundary condition settings.

If the wall moves with a normal component such that the fluid domain changes shape then you will need to use moving mesh to model it. Have a look at the moving mesh tutorial examples for CFX for details on how to do this.

[Springroove]

Thank you, got it!

[shreyashbalpande]

I am trying to do the same thing, but i am not getting it....please help me with it.

Thanks

[ghorrocks]

We can help you. But my post #2 is pretty clear, so if you do not understand it you need to say what you don't understand.

[shreyashbalpande]

What type of mesh, I should go for the problem and what all parts should be considered for moving bouandary.

[ghorrocks]

The type of mesh does not matter. The boundary conditions are applied to all mesh types.

What parts for moving boundary? I would have thought that would be the ones which move. Or am I missing something here?

[shreyashbalpande]

If I am trying to simulate train moving inside a tunnel, then what would be the moving bouandary train or tunnel.

[ghorrocks]

As always, we need more information to answer your question.

Are you looking for the steady state result (ie, an infinitely long tunnel), or a transient result? If transient then please describe what you are looking for (tunnel length, how long you want, entry or exit).

Is the train simplified, so just a box or cylinder, or are you modelling the real train shape?

Is the tunnel simplified, so just a box or cylindrical shape, or are you modelling the real tunnel profile?

How fast is the train going? Will there be compressible flow effects?

Are you looking for pressure wave results? Or drag on the train? Or stability? Or acoustic effects?

[shreyashbalpande]

Train dimensions 160mm*120mm*4metre, Tunnel lenght 12 metre... looking for transient results, the pressure changes inside the tunnel, compression of air inside tunnel..... speed of train 70km/hr, I am looking for pressure wave results, tunnel is a simple box geometry. I am trying to simulate ice2 train in the following paper. I have made the geometry,generated mesh in icem but facing issues regarding solver settings,procedure. I am trying to use both fluent and CFX but not getting through.please help me with that

https://www.researchgate.net/publica...ins_in_tunnels

[ghorrocks]

The two main options I can think of are:

1) Model the train as a Moving mesh, and the tunnel as a stationary mesh. Use a sliding GGI to connect the two.

2) Model the train as an immersed solid. Then everything is in the stationary frame with no moving mesh.

2 is simpler but won't give you detailed flows for the boundary layer over the train. Whether that is important or not is up to you. Option 1 can model the train boundary layer well, but will be much more difficult to implement and much slower to run.