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January 31, 2017, 09:03 |
Y plus Calculation
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Alejo
Join Date: Mar 2014
Posts: 1
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Hello everyone,
I would like to know how Fluent calculates de Y+ parameter from the velocity field ? I know the definition of this parameter: Y+ = U_tau * Y_node / Kinematic_Viscosity With Y_node the distance from the center of the volumen to the wall; ans U_tau the friction velocity. This velocity is calculated as: U_tau = (T_tau / Fluid density)^(1/2) With T_Tau the wall shear stress. This value is deficed as: T_Tau = Dynamic_Viscosity * (du/dy)_(y=0) With (du/dy)_(y=0) the slope of the parallel velocity in the normal direction to the wall. What I do not understand is how I could determine this derivate value at the wall if I only have the velocity field at the center of the control volume closet to the wall? Besides, when I am using a wall function I am far from the wall, so how can I obtain the value of the friction velocity? Does Fluent use the log-velocity profile to define if the cell is in the sub-viscous layer or the turbulent layer ? Best, Alejandro |
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friction velocity, log. velocity-profile, wall shear stress, yplus |
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