Evaluating effect of secondary flows in a bend pipe
Hello everyone!
I am a relative novice in turbulence modelling. I have made and simulated the flow of air in a pipe with a 90-degree bend using a k-omega SST model on ANSYS Fluent Academic. Through this, it is easy to visualize the formation of Dean's flows at the outlet of the pipe section. Now, I want to divide the total pressure drop and total friction losses into its components coming from the primary and secondary flow. I looked at the literature but until now, I have been unable to find some CFD analyses or even some theoretical models that might allow me to do this. So I needed your expert guidance on the topic. Specifically, I would like to ask the following:
I would greatly appreciate if you could help me with the same and please do let me know if I was not clear enough or can provide some additional information. Thank you for your time! Kind Regards! |
Maybe you can give more information why you want two values. An idea that comes to my mind would be to make a second simulation with slip-walls (zero wall friction) as comparison. I would be interested in the results.
Karman-Prandtl friction factor for straight pipes is not valid for curved conduits. For large curvature ratios there is a friction factor by Ito: Ito, H. Flow in curved pipes. Jap. Sch. Mech. Eng. Int. J., 1987, 30, 543–552. |
Usually we simulate a case without the secondary flows by inserting some slip walls to break them up and then compare the pressure drop.
You could integrate the wall shear stress along the pipe axis but this is not that trivial. You'd have use the components of the wall shear stress and then project it onto the local coordinate system and local surface normals of each cell. I don't think you'll find any answers over there but a similar issue occurs in trying to break down contributions of form drag and pressure drag. |
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I will definitely try this and post the results here. Quote:
Thank you both again! :) |
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