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Yusoff January 11, 2001 18:05

simulating separated flow past the airfoil
Hi all, I am now trying to simulate a flow past an airfoil(NACA 2412) at high incidence angle(> 18 degrees). At this angle the flow should be separated from the airfoil and have an almost constant pressure past the quarter chord. However when I visualize the results using streamline ... there is no separated flow and the surface pressure plot also did not show contant pressure in the separated region. Have anyone tried this with some good results comparing with the experimental data. Could you advise me on the preparation and the turbulence model I have to use and any additional factor that I may have left out unknowingly..


Yusoff January 11, 2001 18:07

using CFX 5.4
I am using CFX 5.4 .

John C. Chien January 12, 2001 15:49

Re: simulating separated flow past the airfoil
(1). You are dealing with an extremely difficult problem of "turbulent, separated flow from a smooth curved surface", even though it is a simple flow over airfoil problem. (2). Do it from the other end, run a case with incidence angle=60 degree first, to see whether you can get the stalled case from the code.

Yusoff January 13, 2001 05:04

have some success
Phew .. finally I managed to get the flow separated at 17.9 degrees. The case with 60 degrees is still running though it was not able to converge several times. Hope that this time it will converge. Takes lots of reading the manual and tutorials to get things right.

Thanks for the suggestion anyway


John C. Chien January 13, 2001 21:23

Re: have some success
(1). Well, next time remember to open the parachute when sky diving from an airplane with the wing incidence angle equal to 17.9 degrees. (2). Don't forget about a strong heart too. A happy landing to you.

Yusoff January 14, 2001 14:59

:) thanks
thanks for your advice ... but probably the aircraft have flaps which help reattach the flow :)

Bart Prast January 16, 2001 04:10

Re: simulating separated flow past the airfoil
What turbulence model did you use in CFX 5.4?

Yusoff January 16, 2001 20:19

Re: simulating separated flow past the airfoil
I made two runs before obtaining the results. -first run : k-epsilon model -second run : Reynold Stress Model

however for the cfx to be able to solve compressible flow you have to use ideal gas as your fluid not air at stp and choose total energy model.

for more information you could refer to cfx5 manual :

CFX5-solver Physical Models,Fluid Properties and Boundary Conditions in Cfx-5

page 2-11

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