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-   -   How to set pulsating inlet boundary conditions with a very high frequency (http://www.cfd-online.com/Forums/cfx/64050-how-set-pulsating-inlet-boundary-conditions-very-high-frequency.html)

 Ton April 28, 2009 03:00

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

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 12:50

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 21:12

Hi Tristan,

Ton

 mysterious_man August 22, 2011 14:13

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 21:39

This is easy to do with a CEL expression.

 mysterious_man August 23, 2011 08:35

Hey ghorrocks,

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

 ghorrocks August 23, 2011 19:05

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 10:12

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 01:55

Quote:
 Originally Posted by mysterious_man (Post 321404) 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

i need help plzzzzz

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 (Post 214424) 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.

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