Which of these does not result in two or more flows being dynamically similar?

Length of the body is same

The shape of the blunt body is same

Streamlines are geometrically similar

Non dimensional parameters remain same

Correct Answer : Length of the body is same

Explanation : Two or more flows are considered to be geometrically similar when the flow over the bodies remains identical. This happens when the shape of the bodies is identical and the variation in non – dimensional parameters remain same for the flows.

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Why is hypersonic similarity parameter essential?

Hypersonic flow over cone

Supersonic flow over wedges

Hypersonic flow over slender bodies

Hypersonic flow over flat plate

Correct Answer : Option (C) : Hypersonic flow over slender bodies

Explanation : Hypersonic similarity parameter K is an important governing parameter in order to study the hypersonic flow i.e. flow with Mach number greater than 5 over slender bodies. It is given by the product of free stream Mach number and flow deflection angle.

For two bodies with same shape but different scales, which of these parameters must be equal for the flow to be same in hypersonic regime?

Mach number

Normal flow velocity

Tangential flow velocity

Product of Mach number and slenderness ratio

Correct Answer : Option (D) : Product of Mach number and slenderness ratio

Explaination : The product of Mach number and slenderness ratio along with gamma are the two parameters which appear in the non – dimensional equations. For a body that has same shape but have different scale ratio, if these parameters are same, the flow over them at hypersonic regime remain same. This is the physical meaning of the hypersonic similarity parameter.