Air at 90 degree C and 1 atm flows over a flat plate at a ve

Air at 90 degree C and 1 atm flows over a flat plate at a velocity of 30 m/s. How thick is the boundary layer at a distance of 2.5 cm from the leading edge of the plate?

Solution

Reynold\'s number is

Re = pvd/u

Re = 0.972 x 30 x 0.025 / 21.48 x 10^-6

Re = 33938.55

as Re < 5 x 10^5 so the flow is laminar

h = hydrodynamic boundary layer

h = 5 x d x Re ^-.5

h = 5 x 0.025 x 33938.55 ^-.5

h = 6.78 x 10^-4 m (answer)