Civil Engineering MCQAE Level Civil Engineering
In turbulent flow, the Prandtl mixing length theory gives the turbulent shear stress as:
Fluid MechanicsPrandtl Mixing LengthMEDIUM
Choose the correct answer
A
tau_t = rho x l^2 x (du/dy)^2
B
tau_t = mu x du/dy
C
tau_t = rho x nu x (du/dy)
D
tau_t = rho x l x du/dy
Correct Answer
A. tau_t = rho x l^2 x (du/dy)^2
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Prandtl mixing length: tau_t = rho x l^2 x |du/dy| x (du/dy), where l = mixing length (proportional to distance from wall: l = kappa x y, kappa = 0.41 von Karman constant). This leads to the logarithmic velocity profile in turbulent boundary layers.
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