# How to set pulsating inlet boundary conditions with a very high frequency

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 April 28, 2009, 03:00 How to set pulsating inlet boundary conditions with a very high frequency #1 New Member   Join Date: Apr 2009 Posts: 7 Rep Power: 10 Hi, I have a problem about how to set boundary conditions with a very high frequency. I want to simulate a transient flow in a pipe. The inlet of pipe is mass flow rate (amplitude of sinusoidal flow) of 0.2 kg/s with frequecy 60Hz. The outlet of pipe is total pressure . If the inlet of pipe is set mass flow rate, ANSYS CFX-Solver enforces inflow by erecting artificial walls on those faces where the flow attempts to exit the domain. The flow direction @inlet or outlet should change with time. So i set the inlet as velocity and outlet as openning. Is it OK?

 April 28, 2009, 12:50 #2 Member   Tristan Burton Join Date: Mar 2009 Posts: 43 Rep Power: 10 Ton, You can turn off the artificial wall using Expert Parameters: Discretisation: Miscellaneous: build artificial wall: f. I've never tried it with a sinusoidal mass flow rate at my inlet, I've only done a sinusoidal total pressure at my inlet. Tristan

 May 3, 2009, 21:12 #3 New Member   Join Date: Apr 2009 Posts: 7 Rep Power: 10 Hi Tristan, Thanks for your details reply! Ton

 August 22, 2011, 14:13 #4 New Member   Join Date: Aug 2011 Posts: 11 Rep Power: 8 Hey Ton, I am also trying to do a transient simulation with sinusoidal inlet flow. But i haven't got any idea on how i can change the boundary conditions to incorporate the sinusoidal inlet flow.

 August 22, 2011, 21:39 #5 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,205 Rep Power: 110 This is easy to do with a CEL expression.

 August 23, 2011, 08:35 #6 New Member   Join Date: Aug 2011 Posts: 11 Rep Power: 8 Hey ghorrocks, Are there any tutorials on how to create the CEL expression for sinusoidal inlet mass flow rate ? Thanks for your reply !

 August 23, 2011, 19:05 #7 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,205 Rep Power: 110 No, but it the CEL expession language is quite straight forward and once you have seen how the tutorials do it you will work it out. Have a look at the CFX tutorials.

 August 24, 2011, 10:12 #8 New Member   Join Date: Aug 2011 Posts: 11 Rep Power: 8 Hey ghorrocks, Thanks for your reply ! I am still having difficulty on understanding how i can incorporate CEL expression for Sinusoidal Inlet Flow Boundary Conditions ? Thanks

August 25, 2011, 01:55
#9
Senior Member

Lance
Join Date: Mar 2009
Posts: 622
Rep Power: 15
Quote:
 Originally Posted by mysterious_man Hey ghorrocks, Thanks for your reply ! I am still having difficulty on understanding how i can incorporate CEL expression for Sinusoidal Inlet Flow Boundary Conditions ? Thanks
Have you tried the search function on the forum?
http://www.cfd-online.com/Forums/cfx...ne-funtin.html

March 22, 2012, 11:44
i need help plzzzzz
#10
New Member

kamar
Join Date: Mar 2012
Posts: 3
Rep Power: 7
Dear all,
I am using Ansys to simulate how sinusoidal pressure at the inlet of a tube propagates and arrives to the output.
I am going to record the pressure at both inlet and outlet on the same time.
Please can anyone tell me how i can do that.
many thanks
amoon
Quote:
 Originally Posted by Ton Hi, I have a problem about how to set boundary conditions with a very high frequency. I want to simulate a transient flow in a pipe. The inlet of pipe is mass flow rate (amplitude of sinusoidal flow) of 0.2 kg/s with frequecy 60Hz. The outlet of pipe is total pressure . If the inlet of pipe is set mass flow rate, ANSYS CFX-Solver enforces inflow by erecting artificial walls on those faces where the flow attempts to exit the domain. The flow direction @inlet or outlet should change with time. So i set the inlet as velocity and outlet as openning. Is it OK?

 March 22, 2012, 17:57 #11 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,205 Rep Power: 110 Again, this is a routine CEL expression. Lance's link gives some further details. Do the tutorials and they demonstrate using CEL expressions.

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