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# MCQs on Vortex Flow

1 - Question

The free vortex flow forms _________

a) straight lines

b) concentric circles

c) parabola

d) hyperbola

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bExplanation: The free vortex flow is a circulatory flow of the fluid such that its stream lines are concentric circles. The velocity components for a free vortex flow are Ur and Uθ and is equal to Ur=0 and Uθ=circulation/ 2*pi*r.

2 - Question

The following figure is an example of ____________

Free vortex flow diagram along with streamlines

a) source flow

b) sink flow

c) doublet

d) free vortex flow

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dExplanation: The above figure shows the concentric circles along with streamlines. Here, the stream function is a function of radius and it is constant value and hence the streamlines are concentric.

3 - Question

Except at the origin where r=0, the vortex flow is ___________

a) rotational

b) laminar

c) irrotational

d) turbulent

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cExplanation: Vortex flow is irrotational everywhere except at the point r=0, where the vorticity is infinite. Therefore, the origin, r=0, is a singular point in the flow field. Here, the origin point represents the singularity point.

4 - Question

The strength of the vortex flow can be given by ______________

a) Γ=2*pi*C

b) Γ=2*pi

c) Γ=-2*pi*C

d) Γ=0

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cExplanation: The circulation for vortex flow can be given by – Γ=2*pi*C where, C – constant and Γ is the strength of the vortex flow. When Γ is positive, it means that vortex of positive strength rotates in the clockwise direction and vice versa.

5 - Question

The combination of uniform flow and source flow gives ___________

a) flow past a cylinder

b) flow past a half body

c) flow past a full body

d) flow past a wedge

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bExplanation: When a uniform of velocity U combines with a source flow of strength q, the resultant flow is a flow over a half body. Uniform flow diagram of velocity U

6 - Question

The circles with their centre on the X axis _____________

a) eccentric circles

b) concentric circles

c) potential lines

d) equal circles

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cExplanation: Potential lines are eccentric non-intersecting circles with their centres on x-axis. The potential lines for source pair will be eccentric non-intersecting circles. Non-intersecting circles on x-axis

7 - Question

Centre of pressure can be calculated using __________

a) Principle of moments

b) Principle of energy

c) Mass conservation

d) Rayleigh’s principle

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aExplanation: The centre of pressure can be calculated using a principle of moments which states that the moment of the resultant force about an axis is equal to the sum of moments of the components about the same axis.

8 - Question

A body floats on the surface when ____________

a) metacenter is above gravity

b) metacenter is below gravity

c) metacenter is equal to gravity

d) gravity is above metacenter

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aExplanation: In case of a floating object, the metacenter should always be above gravity. Metacentre is the point about which a body starts oscillating when the body is tilted by a small angle. In the case of a floating body, the weight of an object is equal to the amount of fluid displaced.