Aerodynamics Questions and Answers – Hypersonic Similarity

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Hypersonic Similarity”.

1. Which of these does not result in two or more flows being dynamically similar?
a) Streamlines are geometrically similar
b) The shape of the blunt body is same
c) Length of the body is same
d) Non dimensional parameters remain same
View Answer

Answer: c
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.

2. Why is hypersonic similarity parameter essential?
a) Supersonic flow over wedges
b) Hypersonic flow over slender bodies
c) Hypersonic flow over cone
d) Hypersonic flow over flat plate
View Answer

Answer: b
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.

3. 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?
a) Mach number
b) Product of Mach number and slenderness ratio
c) Tangential flow velocity
d) Normal flow velocity
View Answer

Answer: b
Explanation: 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.
advertisement
advertisement

4. Two bodies holding hypersonic similarity at small angle of attack need the values of γ and Mτ to be same.
a) True
b) False
View Answer

Answer: b
Explanation: For two bodies at hypersonic regime at very small angle of attack, apart from product of Mach number and slenderness ratio Mτ and the value of gamma γ, there is one more condition to be met to have similar dynamic flow. That condition is that the ratio of angle of attack to slenderness ratio (α/τ) should be same.

5. The ratio \(\frac {C_p}{τ^{2}}\) behind a shock wave is a function of which of these parameters?
a) Hypersonic similarity parameter K and γ
b) Angle of attack and wedge angle
c) Coefficient of lift and wedge angle
d) Hypersonic similarity parameter and angle of attack
View Answer

Answer: a
Explanation: For the flow over a wedge having slenderness ratio τ has formation of oblique shock waves. The relation is given by:
\(\frac {C_p}{τ^{2}}\) = f(K,γ)
According to this, \(\frac {C_p}{τ^{2}}\) is a function of only gamma and the hypersonic similarity parameter.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

6. On which of this parameter is the coefficient of lift over a two – dimensional body at hypersonic flow dependent?
a) γ.\(\frac {α}{τ}\)
b) γ, K, M
c) MT, \(\frac {α}{τ}\), γ
d) MT, K, γ
View Answer

Answer: c
Explanation: The lift coefficient over the body at hypersonic flow is obtained by integrating the pressure coefficient over the surface.
cl = \(\frac {1}{l} \int _0^{l}\)(Cpl – Cpu)dx
Where, Cpl – Cpu are coefficient of pressure over the upper and lower surface
l is the length of body
The above equation in terms of x is
cl = \(\int _0^{1}\)(Cpl – Cpu)dx
Diving this equation with the square of slenderness ratio, we get
\(\frac {c_l}{τ^{2}} = \int _0^{1}\)(Cpl – Cpu)dx = f(MT, \(\frac {α}{τ}\), γ)
Thus, coefficient of lift is a function of MT, \(\frac {α}{τ}\) and γ.

7. Hypersonic similarity is applicable for only irrotational flow.
a) True
b) False
View Answer

Answer: b
Explanation: While deriving for hypersonic similarity using the governing equations for hypersonic flow, there is no assumption made for rotational or irrotational flow. Thus, when the graph is plotted for both rotational and irrotational flow for different values of freestream velocity and slenderness ratio, both the graphs are same.
advertisement

8. For which range of values is the hypersonic similarity rule valid for very slender bodies?
a) K = 0.5 to infinity
b) K > 1.5
c) 0.5 < K < 1.5
d) 2 < K < 1000
View Answer

Answer: a
Explanation: Hypersonic similarity condition does not hold true for all values of K. For bodies which are very slender such as the cone having half angle of 3 degrees, the similarity stays valid only when the value of K ranges from 0.5 to infinity.

Sanfoundry Global Education & Learning Series – Aerodynamics.

advertisement

To practice all areas of Aerodynamics, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.