Question

If you measured a pressure difference of 50 mm of mercury across a pitot tube placed in a wind tunnel with 200 mm diameter, what is the velocity of air in the wind tunnel? What is the Reynolds number of the air flowing in the wind tunnel? Is the flow laminar or turbulent? Assume air temperature is 25°C.

Answer 1

Answer:

V=33.66 m/s

$Re=448.8\times 10^6$

Re>4000, The flow is turbulent flow.

Explanation:

Given that

Pressure difference  = 50 mm of Hg

We know that density of Hg=136000$Kg/m^3$

ΔP= 13.6 x 1000 x 0.05 Pa

ΔP=680 Pa

Diameter of tunnel = 200 mm

Property of air at 25°C

ρ=1.2$Kg/m^3$

Dynamic viscosity

$\mu =1.8\times 10^{-8}\ Pa.s$

Velocity of fluid given as

$V=\sqrt{\dfrac{2\Delta P}{\rho_{air}}}$

$V=\sqrt{\dfrac{2\times 680}{1.2}}$

V=33.66 m/s

Reynolds number

$Re=\dfrac{\rho _{air}Vd}{\mu }$

$Re=\dfrac{1.2\times 33.66\times 0.2}{1.8\times 10^{-8}}$

$Re=448.8\times 10^6$

Re>4000,So the flow is turbulent flow.