Engineering Questions with Answers - Multiple Choice Questions

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# Aerodynamics – Circulation

1 - Question

The line integral of a closed curve around of a velocity field is defined as____________

a) Vorticity

b) Circulation

c) Dilatation

d) Streamline

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Answer: bExplanation: Circulation is the line integral of the velocity around a closed curve in the flow. It depends on the velocity field and the selection of the curve. It defines the movement of the flow inside the curve. It is given by- Γ=∮c V. ds where, Γ- circulation, ∮c – curve, V.ds – velocity field.

2 - Question

If the flow is irrotational everywhere within the contour of integration then the circulation is ____________

a) 1

b) positive

c) negative

d) zero

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Answer: dExplanation: In the case of irrotational flow, the circulation about a curve is equal to the vorticity integrated over any open surface bounded by the curve. This leads to the result that if the flow is irrotational everywhere, the circulation is zero.

3 - Question

The component of vorticity normal to dS is equal to __________

a) circulation per unit area

b) negative of circulation per unit area

c) zero

d) circulation

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Answer: bExplanation: The relation between circulation and vorticity can be given by- (∇*V).n = -dΓ/dS Where dS – infinitesimal area enclosed C – Infinitesimal curve.

4 - Question

Circulation is referred to as _____________

a) divergence of velocity

b) velocity field

c) flux of vorticity

d) velocity

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Answer: aExplanation: Using Stoke’s theorem, the line integral of velocity field along a closed curve is equal to the surface integral of velocity field along a closed path normal to the area covered by the path. But we know that curl of velocity is called vorticity and hence, the circulation is called a flux of vorticity.

5 - Question

Which of the following has more viscosity?

a) Water

b) Honey

c) Oil

d) Juice

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Answer: bExplanation: Honey has more viscosity. Viscosity is the measure of the resistance offered by the flow to the shear or tensile stress. The relative motion between the two surfaces moving with different velocities is given by viscosity.

6 - Question

The boundary layer is formed at the _____________

a) boundary of an object

b) surface of an object

c) at a point on an object

d) edges of an object

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Answer: aExplanation: The boundary layer is formed at the boundary of an object. The boundary layer divides the flow into two parts- Viscous and inviscid. The flow inside the boundary layer is highly viscous whereas, the flow outside the boundary is inviscid flow.

7 - Question

The nature of the boundary layer depends on _____________

a) Mach number

b) Inertia force

c) Reynold’s number

d) Viscosity

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Answer: cExplanation: The nature of the boundary layer depends on Reynold’s number which is the ratio of inertial force to viscous force. Depending on the value of Reynold’s number, the boundary layer may be laminar (the flow is continuous) or it may be turbulent ( the flow is discontinuous).

8 - Question

In microscopic view, Circulation is a __________ quantity.

a) vector

b) dimension less

c) scalar

d) non-measurable

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Answer: cExplanation: In a macroscopic view, circulation is a scalar quantity as it is defined as the line integral of velocity field over a closed region. In a microscopic view, circulation is a flux of vorticity, which makes it a vector quantity.