During major windstorms, high vehicles such as RVs and semis may be thrown off the road and boxcars off their tracks, especially when they are empty and in open areas. Consider a 6000-kg semi that is
10 m long, 2.5 m high, and 2 in wide. The distance between the bottom of the truck and the road is 0.8 in. Now the truck is exposed to winds from its side surface. Determine the wind velocity that will tip the truck over to its side. Take the air density to be 1.1 kg/m3 and assume the weight to be uniformly distributed.
The wind velocity that will tip the truck over to its side.
Answer to Problem 43P
The wind velocity that will tip the truck over to its side is
Explanation of Solution
Given information:
The mass of the truck is
Write the expression of weight of the truck.
Here, the mass of the truck is
Write the expression of frontal area.
Here, the length of the truck is
The below figure represent the forces acting on the truck.
Figure-(1)
Write the expression of equilibrium of momentum about point
Here, the width of the truck is
Refer table 11.2 "Representative drag coefficient
Write the expression of drag force acting on the truck.
Here, the density of the air is
Write the expression of characteristics length of the truck.
Here, the perimeter of the truck is
Write the expression of perimeter of the truck.
Write the expression of Reynolds number.
Here, the kinematic viscosity is
Calculation:
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Refer table A-9 "Properties of air" to find the value of kinematic viscosity of air as
Substitute
So, the Equation used for
Conclusion:
The wind velocity that will tip the truck over to its side is
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Chapter 11 Solutions
Fluid Mechanics: Fundamentals and Applications
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