Question

The thickness of the laminar boundary layer over a flat plate at two different sections P and Q are 0.8 cm and 2.4 cm respectively. If the section Q is 3.6 m downstream of P, the distance of section P from the leading edge of the plate is

• A. 0.32 m
• B. 0.22 m
• C. 0.40 m
• D. 0.53 m

Answer 1

The correct option is C 0.40 m


For laminar boundary layer
Over a flat plate
$\frac{\delta }{x}=\frac{5}{\sqrt{R{e}_x}}\delta \alpha \sqrt{x}So,\frac{0.8}{2.4}=\sqrt{\frac{x}{x+3.6}}x=0.45m$
Since no any option is given.
So nearest answer is 0.4 m.