Time-averaged force in CFX

rjmcsherry · October 21, 2010, 05:10

Hello all,

I was wondering if anyone knows how to calculate a time averaged force in CFX please?

I've been trying to simulate 2D laminar flow past a square cylinder, for validation purposes. I expect vortex shedding to occur, so I'm performing a transient calculation, and would like to know how to obtain a time averaged drag force.

In the Ansys documentation and this website I've only been able to find information on the 'Force' funtion (Tools>Function Calculator>Force, and then select my 'cylinder' as the location, and 'y' as the direction, since this is my streamwise direction and I'm interested in the drag). According to the documentation, this will return the pressure force plus the viscous force; I have assumed that the force calculated here is an instantaneous force at the end of the run... Can anyone confirm this please? And if so, can anyone tell me how get the time averaged value?

Many thanks in advance for any help.

stumpy · October 21, 2010, 08:44

Look in the doc for the section on "Transient Statistics". They are under Output Control in CFX-Pre.

rjmcsherry · October 21, 2010, 10:34

OK thanks very much stumpy. I've had a look at that in the docs and set up a transient statistics output for the current run, hopefully that'll give me what I'm looking for.
Thanks again.

October 21, 2010, 05:10	Time-averaged force in CFX	#1
rjmcsherry New Member Join Date: Sep 2010 Posts: 6 Rep Power: 16	Hello all, I was wondering if anyone knows how to calculate a time averaged force in CFX please? I've been trying to simulate 2D laminar flow past a square cylinder, for validation purposes. I expect vortex shedding to occur, so I'm performing a transient calculation, and would like to know how to obtain a time averaged drag force. In the Ansys documentation and this website I've only been able to find information on the 'Force' funtion (Tools>Function Calculator>Force, and then select my 'cylinder' as the location, and 'y' as the direction, since this is my streamwise direction and I'm interested in the drag). According to the documentation, this will return the pressure force plus the viscous force; I have assumed that the force calculated here is an instantaneous force at the end of the run... Can anyone confirm this please? And if so, can anyone tell me how get the time averaged value? Many thanks in advance for any help.

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October 21, 2010, 08:44		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 22	Look in the doc for the section on "Transient Statistics". They are under Output Control in CFX-Pre.

October 21, 2010, 10:34		#3
rjmcsherry New Member Join Date: Sep 2010 Posts: 6 Rep Power: 16	OK thanks very much stumpy. I've had a look at that in the docs and set up a transient statistics output for the current run, hopefully that'll give me what I'm looking for. Thanks again.