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Old   September 18, 2016, 23:53
Default About Newtons law of viscosity
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krishna Atreyapurapu
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can anyone brief me, whether newton's law of viscosity works in laminar sub layers zone of Turbulent Boundary Layer ? if it is so why we are going to wall function in that layer.
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Old   September 19, 2016, 03:19
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Filippo Maria Denaro
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Originally Posted by krishnaA View Post
can anyone brief me, whether newton's law of viscosity works in laminar sub layers zone of Turbulent Boundary Layer ? if it is so why we are going to wall function in that layer.

the law is valid everywhere in the fluid and the wall function are used when you do not have a enough grid resolution to describe the boundary layer:


http://www.cfd-online.com/Wiki/Wall_functions
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Old   September 19, 2016, 04:28
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krishna Atreyapurapu
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Originally Posted by FMDenaro View Post
the law is valid everywhere in the fluid and the wall function are used when you do not have a enough grid resolution to describe the boundary layer:


http://www.cfd-online.com/Wiki/Wall_functions
Thank you for your replay, is it right idea to calculate the shear stress in laminar sub layers using liner relationship of newton law of viscosity, and compare for the results what i get from CFD.

My 2nd query is, if i have enough grid resolution near wall (keep the high accept ratio in maid) what make the sense to calculate wall shear stress using the wall function and acting it to the source term in momentum equation with out solve them directly.
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Old   September 19, 2016, 05:06
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I suggest to study the topics in this book

https://www.scribd.com/doc/50191605/...ing-CFD-Wilcox
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turbulence models, viscosity model, wall functions, wall y+

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