# CFX calculates wrong secondary flows

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February 22, 2010, 04:19
CFX calculates wrong secondary flows
#1
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moein
Join Date: Dec 2009
Posts: 132
Rep Power: 9
i'm modeling free surface flow in a rectangular channel by CFX 12. CFX calculates secondary flows inverse. this false calculation result in false velocity field (my last thread). dose anybody know waht's the reason of this wrong result? i attached a pic.
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 February 22, 2010, 13:50 #2 Senior Member     moein Join Date: Dec 2009 Posts: 132 Rep Power: 9 please help

 February 25, 2010, 02:53 #3 New Member   Join Date: Jan 2010 Posts: 27 Rep Power: 9 Salam I dont have this idea! Beacause in my simulation, it is correct. But the number of it is incorrect(Instead of 3 in half of section,it is only 2). Perhaps your bundary condition is incorrect.

 February 25, 2010, 06:42 #4 Senior Member     moein Join Date: Dec 2009 Posts: 132 Rep Power: 9 what kind of boundry condition are you using?

 February 25, 2010, 10:14 #5 New Member   Join Date: Jan 2010 Posts: 27 Rep Power: 9 I use static pressure in inlet stead Normal speed.

February 25, 2010, 10:28
#6
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Join Date: Jan 2010
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Quote:
 Originally Posted by feizaghaee i'm modeling free surface flow in a rectangular channel by CFX 12. CFX calculates secondary flows inverse. this false calculation result in false velocity field (my last thread). dose anybody know waht's the reason of this wrong result? i attached a pic.
Salam
You must see Tominaga's Paper. I think yours is incorret, Both of direction and location of them,base on this paper I tell it.

 February 27, 2010, 08:56 #7 Senior Member     moein Join Date: Dec 2009 Posts: 132 Rep Power: 9 i found that CFX calculates secondary currents like close channels (ducts). i dont know why!!!!!!!!!!!!

 February 28, 2010, 18:54 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 14,098 Rep Power: 109 ? What are you saying? If the Navier Stokes equations say secondary flows exist then if CFX is running well it will predict secondary flows. So what are you asking?

 March 1, 2010, 04:40 #9 Senior Member     moein Join Date: Dec 2009 Posts: 132 Rep Power: 9 directions of secondary currents in ducts (close channel) and open channel are different. this different is related to free surfce effect. the direction of ducts' secondary currents are in contrast with open channel and CFX dosen't calculate the free surface effect.

March 1, 2010, 15:01
#10
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Fatema Zandi Goharrizi
Join Date: Mar 2009
Posts: 156
Rep Power: 10
Quote:
 Originally Posted by feizaghaee i found that CFX calculates secondary currents like close channels (ducts). i dont know why!!!!!!!!!!!!
salam
if we can not get a right answer to our problem that doesn't mean cfx is in a wrong way! (if it happens we can challenge with ANSYS cfx team) of course there is something with our modeling (or ghoflshekastegi barname bekhatere aberu finglish neveshtam!!!).
check all things with a sample that exists (catched from someone who had good answers) or change the conditions and data and test them in a simple run to catch right answer then use conditions.
good luck

Last edited by zandi; March 1, 2010 at 15:20.

 March 1, 2010, 15:35 #11 Senior Member     moein Join Date: Dec 2009 Posts: 132 Rep Power: 9 hi miss. doctor bonakdary said that he has worked with a version of CFX before version 10. and it wasn't able to calculate the channel and roughness of the channel. he reported that problem to Ansys and they sent him version 10 beta to be examined by him. no one has obtained such answer i need. why do you think these software always give right answers

 March 1, 2010, 18:01 #12 Senior Member     Fatema Zandi Goharrizi Join Date: Mar 2009 Posts: 156 Rep Power: 10 ok you know miss Tajnesaie. she has the similar project, if i'm right. did you test the static pressure in the inlet instead of normal velocity? if you insist on wrong answering of cfx why don't you share it with ansys, too? anyway I’m looking forward and will be glad to hear from your solution Last edited by zandi; March 1, 2010 at 18:29.

 March 3, 2010, 02:01 #13 Senior Member     moein Join Date: Dec 2009 Posts: 132 Rep Power: 9 yes i know her. she used static pressure at inlet and outlet. what about flow's velocity. in that way we can't control velocity of inflow or outflow. i investigating an experimental research and i need to put a certain velocity at inlet or outlet. and about reporting to ANSYS, it's reason is exactly ghofl shekastegi. regards

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