Question

The velocity distribution for fluid flow over a flat plate is given by u=2y-6y2 in which u is the velocity in metre per second at a distance of y metre above the plate. Determine the shear stress at y=0.15m.Take dynamic viscosity of fluid as 8.6 poise.

(a) 0.172 N/m^2

(b) 0.344 N/m^2

(c) 0.086 N/m^2

(d) None of the mentioned

I have been asked this question in exam.

This interesting question is from Viscosity topic in chapter Properties of Fluids of Fluid Mechanics

Answer 1

The correct option is (a) 0.172 N/m^2

Best explanation: for y = 0.15m, velocity gradient = 0.2

                     viscosity= shear stress/velocity gradient

                     shear stress = 0.86*0.2 = 0.172N/m^2.