Mesh deformation

kimiaghalam · January 28, 2011, 15:40

I want to define a wall boundary condition which is moving and just the thing I know about its movement is the equation of motion which is y^2 + (a^2/h - h)y + x^2 + z^2 - a^2= 0 (a is a constant and h is changing with time), how can I do this ?

ghorrocks · January 28, 2011, 16:09

If the motion is tangential to the wall you can do it by applying a tangential velocity to the wall boundary condition. If the motion has any component normal to the wall (it the fluid domain gets bigger, smaller or moves) you need moving mesh.

There are examples of both types that come with CFX tutorials.

kimiaghalam · January 29, 2011, 18:40

Thanks for your consideration sir.

The wall boundary moves in normal direction but the problem is that the velocity in y direction changes with x and z (as you can see in the equation) so I can not give an specific value for V. Could you please let me know how can I input a different velocity for each r (x^2 + y^2). I am kinda lost in those tutorials. I dont know if I have to write a code in fortran or I can write an expression directly on cfx. Help me

ghorrocks · January 30, 2011, 05:43

If you are lost in the tutorials then do them again until you understand. You will never get anywhere until you understand the basics.

You should be able to do what you propose in CEL expressions in moving mesh. No need for fortran.

January 28, 2011, 15:40	Mesh deformation	#1
kimiaghalam New Member morteza Join Date: Jul 2009 Location: United States Posts: 12 Rep Power: 17	I want to define a wall boundary condition which is moving and just the thing I know about its movement is the equation of motion which is y^2 + (a^2/h - h)y + x^2 + z^2 - a^2= 0 (a is a constant and h is changing with time), how can I do this ?

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January 28, 2011, 16:09		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	If the motion is tangential to the wall you can do it by applying a tangential velocity to the wall boundary condition. If the motion has any component normal to the wall (it the fluid domain gets bigger, smaller or moves) you need moving mesh. There are examples of both types that come with CFX tutorials.

January 29, 2011, 18:40		#3
kimiaghalam New Member morteza Join Date: Jul 2009 Location: United States Posts: 12 Rep Power: 17	Thanks for your consideration sir. The wall boundary moves in normal direction but the problem is that the velocity in y direction changes with x and z (as you can see in the equation) so I can not give an specific value for V. Could you please let me know how can I input a different velocity for each r (x^2 + y^2). I am kinda lost in those tutorials. I dont know if I have to write a code in fortran or I can write an expression directly on cfx. Help me

January 30, 2011, 05:43		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	If you are lost in the tutorials then do them again until you understand. You will never get anywhere until you understand the basics. You should be able to do what you propose in CEL expressions in moving mesh. No need for fortran.