# torque converter simulation

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 January 30, 2013, 18:11 torque converter simulation #1 New Member   steve Join Date: Apr 2011 Posts: 2 Rep Power: 0 Hello all. Now, I'm trying to simulate torque converter. I already set up model but I have no idea how to set up boundary conditions in CFX. usually, boundary set up in CFX, I have to set up inlet and outlet but in torque converter, it's closed and rotating. if you have any exemples or hints, please let me know. thank you in advance.

 January 31, 2013, 17:06 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,929 Rep Power: 85 CFX handles closed domains just fine. You need something to drive the flow, in the torque converter this is impellers whizzing around. But you should not run a incompressible flow in a closed domain. You will have convergence difficulties. You should add a small port with a pressure control to allow the simulation to "breathe" and control pressure. The torque converter will have a pressure port to do just this - so this is physically realistic.

 May 10, 2013, 05:11 #3 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 155 Rep Power: 11 Might be late reply. But I have question about convergence. How convergence issue could happen in closed domain simulations with in-compressible flows. In general, oil is used as fluid in torque converter and that is in-compressible in nature. Could you please explain the reason. Thanks in advance. __________________ With regards, JSM

May 10, 2013, 05:35
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Mr CFD
Join Date: Jun 2012
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Quote:
 Originally Posted by jsm Might be late reply. But I have question about convergence. How convergence issue could happen in closed domain simulations with in-compressible flows.
I'm going to take a stab in the dark with this so don't take my answer as the correct solution! My guess is CFX is a pressure-based coupled solver where pressure and velocity is strongly coupled. If you have high velocities and low pressure the solver may not be able to calculate the small pressure differences inside your fluid domain without a "port with a pressure control" as this might allow your domain imbalances to equalise.

 May 10, 2013, 23:51 #5 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,929 Rep Power: 85 There are two main ways of asse3ssing convergence. The residual tolerance is calculated per unit cell as an estimate of how accurately the equations are solved in that unit cell. It does not matter if the simulation has inlets and outlets or not, the units cells do not know that anyway. The second method is imbalances. This checks the flow in equals the flow out. In closed domains this can be a problem as any imbalance is divided by zero, so even tiny numerical noise becomes a large imbalance. That is why this imbalance tolerance is optional, it is not appropriate for all fows.

 May 11, 2013, 06:58 #6 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 155 Rep Power: 11 Thank you for your replies - Glenn Horrocks & RicochetJ __________________ With regards, JSM

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