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# Aerodynamics – Region of Influence and Domain of Dependencies

1 - Question

Disturbances in the case of steady supersonic flow are felt in the entire flow field region.

a) True

c) False

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Answer: bExplanation: Unlike subsonic flow where the disturbances are felt in the entire flow field, this is not the case in supersonic flow. In steady supersonic linearized flow, the disturbances/perturbations are felt only in limited regions.

2 - Question

In which region will the disturbances be felt in a steady supersonic flow?

a) Point C only

c) Point A and B

b) Point C and D

d) Point A only

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Answer: bExplanation: When a conical body is placed in a supersonic flow, there is a formation of shock waves. When the points lie within the Mach waves, the disturbances introduce are felt otherwise it is not. Since point A and B lies inside the Mach wave, any perturbations will be felt at these two points.

3 - Question

What is the domain of dependence?

a) Area which does not lie within the characteristic lines

c) Area within the upstream characteristics

b) Area within the downstream characteristics

d) Area outside the left running wave

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Answer: bExplanation: If we consider a point A in the flow field through which two characteristic lines pass (C+ and C–) then area which is between the two upstream characteristics of both left and right running waves is known as domain of dependence.

4 - Question

What is the region of influence?

a) Area outside right running wave

c) Area within the upstream characteristics

b) Area within the downstream characteristics

d) Area outside the left running wave

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Answer: cExplanation: For a point A which is present in a flow field with incoming steady supersonic flow, there will be two characteristic lines passing through them. The area formed between these two characteristics in the downstream region is known as region of influence

5 - Question

For a point in the supersonic flow lying at the intersection of the characteristics, its flow field properties depend on change in which of these regions?

a) Domain of dependence

c) Intersection points of the characteristics

b) Region of influence

d) Region outside the characteristics

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Answer: aExplanation: If a point P lies at the intersection of the left and right running waves, the flow field properties at point P is dependent on the flow field information in the region upstream i.e. domain of dependence.

6 - Question

On which of these points does the properties of flow field at point A depend?

a) Point P

c) Point C

b) Point D

d) Point B

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Answer: a

Explanation: Point P lies at the intersection of the two characteristic lines. Point A lies in the region of influence thus its flow properties depend on the properties generated due to disturbances at point P which is the intersection point.