Answer :
The wind tunnel speed that must be used to test the car 1 / 5 model of a car that normally runs at 30 mph is 150 mph
Re = u L / ν
Re = Reynold's number
u = Flow speed
L = Characteristic linear dimension
ν = Kinematic viscosity
ν[tex]_{p}[/tex] = 1.516 * [tex]10^{-5}[/tex] m² / s
ν[tex]_{p}[/tex] = ν[tex]_{m}[/tex] = 1.516 * [tex]10^{-5}[/tex] m² / s
L[tex]_{m}[/tex] = L[tex]_{p}[/tex] / 5
u[tex]_{p}[/tex] = 30 mph
Re[tex]_{m}[/tex] = u[tex]_{m}[/tex] L[tex]_{p}[/tex] / 5 * 1.516 * [tex]10^{-5}[/tex]
Re[tex]_{p}[/tex] = 30 L[tex]_{p}[/tex] / 1.516 * [tex]10^{-5}[/tex]
In tunnel,
Re[tex]_{m}[/tex] = Re[tex]_{p}[/tex]
u[tex]_{m}[/tex] L[tex]_{p}[/tex] / 5 * 1.516 * [tex]10^{-5}[/tex] = 30 L[tex]_{p}[/tex] / 5 * 1.516 * [tex]10^{-5}[/tex]
u[tex]_{m}[/tex] = 30 * 5
u[tex]_{m}[/tex] = 150 mph
Therefore, the wind tunnel speed that must be used to test the car is 150 mph
To know more about Reynold's number
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