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Problem
Consider a flat plate positioned inside a wind tunnel, and air at 1 atm and 20°C is flowing with a free stream velocity of 60 m/s. What is the minimum length of the plate necessary for the Reynolds number to reach 2 × 107? If the critical Reynolds number is 5 × 105, what type of flow regime would the airflow experience at 0.2 m from the leading edge?
Step-by-step solution
Step 1 of 2
From the table, ‘Properties of air at 1 atm pressure’ to obtain the value of kinematic viscosity at
for temperature.Kinematic viscosity,
Write the expression for the minimum length of the plate for the Reynolds number equal to
Here, x is the minimum length of the plate for the Reynolds number equal to
, Re is the Reynolds number, 
is the kinematic viscosity, and 
is the free stream velocity.Substitute
for Re, 
for V, and 
for 
.
Thus, the minimum length of the plate for the Reynolds number equal to
is 
.Comment Step 2 of 2
Write the expression for the Reynolds number to obtain the type of flow at a distance of
from the leading edge.
Here, x is the distance from the leading edge of the plate.
Substitute
for x, 
for V, and 
for 
.
The Reynolds number at 0.2 m from leading edge is equal to
which is greater than the critical Reynolds number
.Hence, the flow regime would be
.Comment
