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Old   October 11, 2012, 07:36
Default Boundary Condition
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Prashant Kumar Singh
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I have to give BC for compressor inlet & outlet

......in which velocity profile at inlet is mandatory to give n aslo

i need mass flow rate as my BC(inlet/outlet) for comparison for different results based on mass flow

@inlet plane BC velocity profile & any pressure(Total/static) both r not taking together
(i want to give both so that i can give mass flow rate at outlet....plz suggest me some method to give Both BC)

@outlet plane BC mass flow rate & any pressure(Total/static) ......both are not taking.....


when i give run without Pas BC then cfx is telling atleast one P should be as BC
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Old   October 11, 2012, 07:55
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Christoph
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Quote:
Originally Posted by pks126 View Post
I have to give BC for compressor inlet & outlet

......in which velocity profile at inlet is mandatory to give n aslo

i need mass flow rate as my BC(inlet/outlet) for comparison for different results based on mass flow

@inlet plane BC velocity profile & any pressure(Total/static) both r not taking together
(i want to give both so that i can give mass flow rate at outlet....plz suggest me some method to give Both BC)

@outlet plane BC mass flow rate & any pressure(Total/static) ......both are not taking.....


when i give run without Pas BC then cfx is telling atleast one P should be as BC
http://www1.ansys.com/customer/conte...30/cfx_mod.pdf

chapter 2.2
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Old   October 11, 2012, 09:54
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Chris DeGroot
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There should be no need to specify mass flow at the outlet. You have specified it at the inlet and the code will conserve mass. Specifying it at the outlet is over constraining your problem which is why it won't let you do it. Did you try just giving an average static pressure condition at the outlet?
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Old   October 12, 2012, 00:31
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Prashant Kumar Singh
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thanks energy382 and cdgeroot for ur reply

currently i have given run on following BC

inlet BC velocity profile & outlet BC static P(101325Pa)
but in this case i m unable to draw compressor map
thats why i want to give mass flow at one BC so that i can vary it n plot a compressor map
velocity profile at inlet and mass flow at outlet BC is not taken by cfx it is asking one P as BC
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Old   October 12, 2012, 08:47
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Chris DeGroot
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Yes I understand. Since you are running compressible flow, specifying the velocity profile does not fix your mass flow rate. Is there a reason that you want to specify a profile rather than just give the mass flow rate? Using a mass flow inlet and static pressure outlet is a stable configuration that should give you what you want, apart from the desired inflow profile.
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Old   October 12, 2012, 13:08
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Prashant Kumar Singh
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Yes I want to simulation distortion by giving velocity profile at the inlet...that velocity profile is not uniform it have some specific circumferential velocity distribution by which i am trying to simulate distortion at the compressor inlet.

what you told is correct that is robust BC and it works.
here in this case i will obtained one mass flow for one particular velocity profile and when i will change velocity profile mass flow will also change accordingly.

and i have to obtained compressor map pressure ratio Vs mass flow rate for one velocity profile or distortion pattern so that i can compare how much this kind of distortion design deviates compressor performance from clean inlet compressor performance.

thanks a lot for your valuable reply
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