Air at 25 degree C with a free stream velocity of 50 ms flow

Air at 25 degree C, with a free stream velocity of 50 m/s flows over a flat plate of length L. (For air at 25 degree C, v=15.71 times 10^-6 m^2/s.) If the Reynolds number at the trailing edge of the plate is 10^8, find the length of the plate, L. At what distance from the leading edge would the transition to turbulence occur? If the velocity boundary layer thickness is given by, delta=(5 x)/Re_x^1/2, what is the value of delta at mid-point of the plate, i.e., at L/2. What will be the thickness of thermal boundary layer at that point, L/2?

Solution

Given Re = 10pow8

(a).

Re= (V*L)/v

V= velocity of air.

L= Lengt of the plate.

v = kinematic viscocity.

10pow8= (50*L)/15,71* 10pow-6

L= 31.42m.

(c).

delta = (5*x)/sqrt Re_x

where x= L/2 in this case.

delta = (5*15.71)/sqrt((50*15.71)/15.71* 10pow-6)

delta = 0.011