# Question Set 10

Question No. 1

What is the difference between streamline body and bluff body?

In streamline body the shape is such that separation in flow occurs past the near most part of the body so that wake formed is small and thus friction drag is much greater than pressure drag. In bluff body the flow gets separated much ahead of its rear resulting in large wake and thus pressure drag is much greater than the friction drag.

Question No. 2

Define hydraulically efficient channel cross section.

The shape of such section is that which produces minimum wetted perimeter for a given area of flow and carries maximum flow.

Question No. 3

What is the difference between Center of Mass and Centroid?

If the material composing a body is uniform or homogeneous, the density or specific weight will be constant throughout the body, and then the Centroid is the same as the center of gravity or center of mass.

Centroid: Centroid is the point, where the whole area of plane is going to be act. It is valid only for 2D problems like plane figures, square plate etc. The center of mass is a point that acts as if all the mass was centered there (the mass on one side of the point is equal to the mass on the opposite side). If supported at the center of mass, an object will be balanced under the influence of gravity.

Question No. 4

On what factors does the pressure at a point as a static mass of liquid depends upon?

Specific weight of liquid and the depth below the free liquid surface.

Question No. 5

When maximum discharge is obtained in nozzle?

At the critical pressure ratio.

Question No. 6

Under what condition the work done in reciprocating compressor will be least?

It is least when compression process approaches isothermal. For this purpose, attempts are made to cool the air during compression.

Question No. 7

What is the difference between stalling and surging in rotary compressions?

Stalling is a local phenomenon and it occurs when How breaks away from the blades. Surging causes complete breakdown of flow and as such it affects the whole machine.

Question No. 8

State Archimedes principle.

Any weight, floating or immersed in a liquid, is acted upon by a buoyant force equal to the weight of the liquid displaced. This force acts through the center of buoyancy, i.e. the e.g. of the displaced liquid.

Question No. 9

What do you understand by center of buoyancy?

Center of buoyancy is the center of gravity of the displaced liquid and buoyant force acts through it.

Question No. 10

Why the Centrifugal Pump is called High Discharge pump?

Centrifugal pump is a kinetic device. The centrifugal pump uses the centrifugal force to push out the fluid. So the liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the liquid. So it discharges the liquid in high rate. It is given in the following formula:

Centrifugal force F= (MV²)/R.