|January 31, 2017, 09:03||
Y plus Calculation
Join Date: Mar 2014
Posts: 1Rep Power: 0
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 ?
|friction velocity, log. velocity-profile, wall shear stress, yplus|
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