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

Ton · April 28, 2009, 04:00

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?

Tristan · April 28, 2009, 13:50

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

Ton · May 3, 2009, 22:12

Hi Tristan,

Thanks for your details reply!

Ton

mysterious_man · August 22, 2011, 15:13

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.

ghorrocks · August 22, 2011, 22:39

This is easy to do with a CEL expression.

mysterious_man · August 23, 2011, 09:35

Hey ghorrocks,

Are there any tutorials on how to create the CEL expression for sinusoidal inlet mass flow rate ?

Thanks for your reply !

ghorrocks · August 23, 2011, 20:05

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.

mysterious_man · August 24, 2011, 11:12

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

Lance · August 25, 2011, 02:55

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

amoon · March 22, 2012, 11:44

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?

ghorrocks · March 22, 2012, 17:57

Again, this is a routine CEL expression. Lance's link gives some further details. Do the tutorials and they demonstrate using CEL expressions.

April 28, 2009, 04:00	How to set pulsating inlet boundary conditions with a very high frequency	#1
Ton New Member Join Date: Apr 2009 Posts: 7 Rep Power: 17	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?

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April 28, 2009, 13:50		#2
Tristan Member Tristan Burton Join Date: Mar 2009 Posts: 43 Rep Power: 17	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, 22:12		#3
Ton New Member Join Date: Apr 2009 Posts: 7 Rep Power: 17	Hi Tristan, Thanks for your details reply! Ton

August 22, 2011, 15:13		#4
mysterious_man New Member Join Date: Aug 2011 Posts: 11 Rep Power: 15	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, 22:39		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	This is easy to do with a CEL expression.

August 23, 2011, 09:35		#6
mysterious_man New Member Join Date: Aug 2011 Posts: 11 Rep Power: 15	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, 20:05		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	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, 11:12		#8
mysterious_man New Member Join Date: Aug 2011 Posts: 11 Rep Power: 15	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

March 22, 2012, 17:57		#11
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Again, this is a routine CEL expression. Lance's link gives some further details. Do the tutorials and they demonstrate using CEL expressions.