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-   -   Total pressure boundary condition at inlet:how to sustain inlet pressure in cfx (https://www.cfd-online.com/Forums/cfx/131145-total-pressure-boundary-condition-inlet-how-sustain-inlet-pressure-cfx.html)

faizan March 10, 2014 06:59

Total pressure boundary condition at inlet:how to sustain inlet pressure in cfx
 
Hi All,

I have selected Total pressure of 1.4MPa at Inlet in ANSYS CFX software. I am modeling a Nitrogen gas flow through convergent-divergent DeLaval Nozzle. I set a areaAve(Pressure) monitor at inlet in solver control monitors. After 3 4 iterations the inlet monitor shows drastic drop of pressure form 1.4e6 Pa to 2e5Pa. How can I imposed a constant total pressure boundary condition at Inlet? Please help...

ghorrocks March 10, 2014 17:18

You imposed constant total pressure. You are monitoring pressure. The difference is the dynamic head. If your monitor on total pressure it should be your boundary value setting.

faizan March 10, 2014 23:52

Thanks ghorrock for your response.

Can you suggest me about the expression of total pressure monitor?

ghorrocks March 11, 2014 07:29

areaAve(Total Pressure)@inlet

Look in the CFX reference manual for a full list of available variables and their names.

faizan March 15, 2014 23:28

1 Attachment(s)
Thanks ghorrock,

I have solved the total pressure issue. But another problem occurred with total temperature. When I set the total temperature expression at inlet it is just showing a flat line at 0 value. The total temp at inlet is set to 550 deg C. Please see the attached picture and reply.

Thanks in advance.

ghorrocks March 16, 2014 05:37

Have you seen the y scale size? Maybe you should put the temperature curve on another plot with more appropriate scaling.....

faizan March 17, 2014 21:53

Thanks ghorrocks- I have separated the plots and now it is better.

Can you suggest that how can I put the pressure monitors on different locations over the length of nozzle. At the moment I put the monitor on inlet and it is showing. I need to check the pressure on throat section which is at 81.2 mm linear distance from inlet. Also one pressure monitor at exit of nozzle which is at 151.2 mm distance form the inlet.

How can I set the pressure monitor at these distances ? please suggest.I am CONFUSED...

ghorrocks March 17, 2014 23:44

Try a monitor point set at a specific XYZ location.

faizan March 18, 2014 05:06

This is the problem. I am unable to find from where and how can I set specific location at nozzle length.

I tried the option imprint but it is not showing and inactive in my model because my model geometry have frozen bodies.

Please suggest?

chiragsvnit March 18, 2014 07:27

Have you created monitoring points using XYZ values at CFX Pre during job set-up along with monitoring variables? The option is available in Monitoring Tab CFX Pre.

ghorrocks March 18, 2014 17:47

You do not set up monitor points in the meshing. You set it up in CFX-Pre.


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