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-   -   Formula for velocity in buffer layer of turbulent boundary layer (http://www.cfd-online.com/Forums/main/96880-formula-velocity-buffer-layer-turbulent-boundary-layer.html)

nickvinn February 3, 2012 12:57

Formula for velocity in buffer layer of turbulent boundary layer
 
Hello!
I was calculating turbulent viscosity according to Baldwin-Lomax model for the fixed velocity field of flat plate turbulent boundary layer and had problems with too low viscosity in the outer layer of the model. Now I realize that the velocity profile by Reihardt u^+=ln(1+\kappa y^+)/\kappa+7.8*(1-exp(-y^+/11)-y^+*exp(-y^+/3)/11), which I was using, yields bad F-function with peak located too close to the wall. I changed for piecewise u^+=piecewise(y^+<5, y^+, y^+<30, 5*ln(y^+)-3.05, ln(y^+)/\kappa+5.5). It yields F-function with correct global maximum. However, du^+/dy^+ is discontinuous, so another local maximum exists closer to the wall. I'm afraid that for some values of parameters I can take it for the right one. Is there any analytical expression for velocity profile with correct description of buffer layer (5<y^+<30) and continuous derivative?


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