[dyson]

Hello
in cfx, rigid body:
how can i define local coordinate frame (axis of rotation) that in transient run, moves in a straight line too.

I would like to rotate my subdomain with deforming mesh. This is OK. But this domain moves in a straight line too. Rotation of the body is based on the original X-Y-Z coordinate frame but of course it should move with the body together.
Can i define moving coordinate frame that is local and attached to the my rigid body ?

Regards
Dyson ilia.

[dyson]

in cfx-pre coordinate frame setting, how i define local coordinate frame on boat surface that moves with my boat?

[ghorrocks]

I don't think the motion you describe is supported, so you will have to use moving mesh to do it.

But why do you need to do this at all? Why can't the helicopter body be stationary, the blades simply rotate, and the surrounding air can flow past it with an inlet/outlet?

[dyson]

thanks a lot.

- problem : simulation of "self propulsion test of boat".
- two domain : main and trs(transient rotor domain-with 3 blade propeller)
- boat is defined as a rigid body.freedom: vertically and rotate about axis normal to plan axis) {attached pic}
- shaft and trs interfaces , wall motions setting: rigid body
- flow from inlet to outlet (horz)
- in transient run,boat move up by hydrodynamcis effect of hull, then axis of rotation of propeller must be move with boat vertically, is it possible ?

- in my runs shaft and propeller moves with rigid body but axis of rotation is the same stationary axis that define in cfx-pre setting, as a result the gap occur between propeller and boat. because propeller axis rotation isnot correct axis.
***- in cfx-pre coordinate frame setting, how i define local coordinate frame on boat surface that moves with my boat.

[ghorrocks]

This is going to be a very hard simulation to do.

It is MUCH easier if you separate the simulation into two:
* One simulation where you do the propeller by itself and get its performance curve. This is just a standard rotating frames of reference turbo machine simulation.
* A second simulation where you do the rigid body simulation of the boat, but you model the propeller as a force acting on the hull and a momentum source to generate the flow - but you do not actually model the prop, just its performance curve from the first simulation.

[dyson]

thanks a lot 4 your reply Glenn.


in general, in cfx-pre coordinate frame setting, how i define local coordinate frame on(rigid body) boat surface that moves with my boat?

[ghorrocks]

I do not know, I am not familiar with that area of the software. I don't even know if it can be done.

[dyson]

OK Glenn, thanks


no any body 4 reply?

[dyson]

friends; any one for reply?!

[ghorrocks]

Why don't you just try it and see if it can be done?

[armin najarian]

i have the same problem.
i dont know how to define a coord that move with a rigid body.
but i think there is a way with using expressions.
i am working on it.
if i can move the coordinate with the rigid body so we can rotate the coordinate frame with a constant angular vel.
u can send me an email to share our informations faster.
armin.najarian@gmail.com