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modelling wall friction

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Old   May 6, 2015, 12:22
Default modelling wall friction
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Ronald Thompson
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Hi,
im currently trying to model the flow around an object in a tank using the K-epsilon solver, the object is attached to one of the concrete walls of the tank and i want to see what effect the friction of the concrete has on the acceleration of the flow around the object.

my question is how do I add in the friction coefficient of the concrete into my model?
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Old   May 6, 2015, 15:56
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Ethan Doan
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You should be able to specify a wall roughness in the boundary conditions. You cant use it with enhanced wall functions though. you can use a K-e with standard wall functions or a k-w model
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Old   May 6, 2015, 16:17
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do i simply put my value of friction coefficient in for the wall roughness boundary condition or is wall roughness a different scale, thanks
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Old   May 6, 2015, 16:53
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You cant use the friction coefficient for the wall roughness value you need to specify your wall roughness value in height like millimeters. im not really sure how to take a friction coefficient and turn it into a wall roughness. You could enter various values of wall roughness until your simulation gives you the correct skin friction drag corresponding to your friction coefficient.
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Old   April 4, 2016, 05:09
Default Wall roughness height
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I found moody chart useful in guessing the wall roughness from the friction coefficient. from the darcy weisbach factor and reynolds number, the chart gives you e/d ratio.
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flow around a wall, flow direction, fluent 14.5, friction coefficient, wall friction

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