1. 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
Explanation: 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.
2. 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
Explanation: When a uniform of velocity U combines with a source flow of strength q, the resultant flow is a flow over a half body.
3. The circles with their centre on the X axis _____________
a) eccentric circles
b) concentric circles
c) potential lines
d) equal circles
Explanation: 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.
4. Centre of pressure can be calculated using __________
a) Principle of moments
b) Principle of energy
c) Mass conservation
d) Rayleigh’s principle
Explanation: 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.
5. 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
Explanation: 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.
6. Why the circular cylinder will create more drag?
a) The pressure difference between upstream and downstream direction of flow
b) The pressure difference between relative wind and downstream direction of flow
c) The pressure difference between upstream and direction of flow
d) The pressure difference between downstream of flow
Explanation: A circular cylinder produces large drag due to the pressure difference between upstream and downstream of the flow. The difference in pressure is causes by the periodic separation of flow over the surface of the cylinder. This will increase the drag in the cylinder.
7. How the cylinder will vibrate in the wind tunnel test?
a) Due to high pressure
b) Due to low pressure
c) Due to relative pressure
d) Due to fluctuations in the flow
Explanation: The difference in pressure is caused by the periodic separation of flow over the surface of the cylinder. Periodic separation induces fluctuations in the flow and makes cylinder vibrate in the wind tunnel.
8. What is passive flow control method used to reduce the drag co-efficient over a cylinder?
a) Surface framing
b) Flow visualization
c) Roughened surfaces
d) Wiring surfaces
Explanation: To reduce the amount of drag on a cylinder various active and passive flow control method have been employed and tested successfully.T hese method include dimpled surfaces, trip wires, roughened surfaces.
9. What is the reduction of drag by installing the small cylinder?
a) 48%
b) 55%
c) 30%
d) 75%
Explanation: A 48% drag reduction of a cylinder by installing a much smaller cylinder in the upstream direction of flow. The shear layer coming from the smaller cylinder changes the pressure distribution around the layer cylinder in such a way that the drag is dramatically altered
10. What are the quantitative flow visualization techniques?
a) Smoke flow visualization
b) Surface framing
c) Shadow projecting
d) Shadow graphic technique
Explanation: The visualization technique such as smoke flow visualization, surface oil film technique, particle image velocimetry have been employed to locate the position of transition and separation of a boundary layer.