Chemical Engineering Basics - Engineering

Q1:

The laminar boundary layer thickness in zero pressure gradient flow over a flat plate along the x-direction varies as x0.5 while the thickness of turbulent boundary layer varies as (where, x = distance from the leading edge)

A x1.5

B x0.8

C x-1.5

D x-0.8

ANS:B - x0.8

In zero-pressure gradient flow over a flat plate, the thickness of the laminar boundary layer (δ) varies with the distance from the leading edge (x) according to the Blasius solution, which is approximately proportional to 0.5x0.5. However, for the turbulent boundary layer, the thickness (δ_t) varies differently. It is typically proportional to 0.8x0.8 in the outer region of the turbulent boundary layer. Therefore, the correct statement for the variation of the turbulent boundary layer thickness (δ_t) with respect to distance (x) from the leading edge is: δ_t ∝ 0.8x0.8