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Skin Friction Coefficient in the Turbulent flow over a backward-facing step.

Posted Feb 21, 2011, 7:24 a.m. EST Fluid & Heat, Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.0 2 Replies

Yerko Luppi
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Hi!

My name is Yerko Luppi, i live in Chile and i'm studying mechanical engineering. This is my last year.
I'm learning about CFD and i started with the 2D Backstep Model www.comsol.com/showroom/documentation/model/228/

My teacher wants validate the model by the Skin friction coefficient (using the Wilcox's graphics).
The problem is that i don't know how to get to this coefficient in comsol.
The Skin friction coefficient is www.cfd-online.com/Wiki/Skin_friction_coefficient

How can i do it?

I hope someone can help me, I'll be very grateful.

Best Regards from Chile :)
2 Replies Last Post Jan 10, 2012, 1:13 a.m. EST
COMSOL Moderator

Hello Yerko Luppi

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Dan Forsström
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Posted: 1 decade ago Jan 9, 2012, 5:01 p.m. EST
HI,

I read your request on cfd and skin-surface problem. I have a similar problem but no solution.
Did you solve the problem?

Regards,
Dan Forsström
Polymira AB
Sweden
HI, I read your request on cfd and skin-surface problem. I have a similar problem but no solution. Did you solve the problem? Regards, Dan Forsström Polymira AB Sweden
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 10, 2012, 1:13 a.m. EST
Hola Chile

Well I haven't studied that part of Physics recently, I would have to dig into the books again, but there are a few things you can easily do to get some clues:

1) you can plot the local stress tensor i.e. normal and tangential to your surface, even double your solid volume by a second fluid volume slightly greater than the solid such that you get the shear forces somewhat above the no-slip contact region

2) for the standard FSI it's not that interesting, but for a sphere or cylinder, or ellipsoid, or a "wing" in a fluid flow you can use the polar plot to get a 360° view (add a polar plot, add a line graph and use atan2(y,x) as equation per line graph, then select variables like spf.K_stressx, or spf.T_stressx

3) use the data set cut line to see how these components change with separation distance from the FSI boundary

greetings from the north
--
Have fun Comsoling
Ivar
Hola Chile Well I haven't studied that part of Physics recently, I would have to dig into the books again, but there are a few things you can easily do to get some clues: 1) you can plot the local stress tensor i.e. normal and tangential to your surface, even double your solid volume by a second fluid volume slightly greater than the solid such that you get the shear forces somewhat above the no-slip contact region 2) for the standard FSI it's not that interesting, but for a sphere or cylinder, or ellipsoid, or a "wing" in a fluid flow you can use the polar plot to get a 360° view (add a polar plot, add a line graph and use atan2(y,x) as equation per line graph, then select variables like spf.K_stressx, or spf.T_stressx 3) use the data set cut line to see how these components change with separation distance from the FSI boundary greetings from the north -- Have fun Comsoling Ivar

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