Fluid Mechanics

391.Power number is the ratio of

1. Drag stress to inertial stress
2. Inertial stress to drag stress
3. Inertial stress to gravitational stress
4. Gravitational stress to drag stress

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392.Power required by a centrifugal pump is proportional to (where, D = diameter, N = r.p.m)

1. N²D³
2. Nd²
3. N²D
4. N³D⁵

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393.Power required for mixing Newtonian fluids is a function of the

1. Speed of impeller, diameter of impeller & viscosity
2. Density & viscosity of fluid only
3. Density of fluid, viscosity of fluid & impeller dia only
4. None of these

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394.Power requirement of fans having constant wheel diameter varies _________ fan speed.

1. As square of
2. Directly as
3. As cube of
4. None of these

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395.Prandtl mixing length is

1. Applicable to laminar flow problems
2. A universal constant
3. Zero at the pipe wall
4. None of these

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396.Prandtl number is a measure of the

1. Heat conduction to viscosity of a fluid
2. C_p/C_v of a fluid
3. Elastic force to pressure force in the fluid flow
4. Inertial force to elastic force in the fluid flow

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397.Pressure co-efficient is the ratio of pressure forces to _________ forces.

1. Gravity
2. Inertial
3. Viscous
4. None of these

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398.Pressure difference between two points in vessels, pipelines or in two different pipelines can be measured by a differential manometer. The pressure difference measured as the mm of water column in case of mercury-water, differential manometer is equal to (where, H = difference in height of mercury column in mm).

1. H
2. 12.6 H
3. 13.6 H
4. 14.6 H

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399.Pressure drag does not depend upon the

1. Roughness of surface of the body
2. Pressure of main flow only
3. Length of the body in flow direction
4. All (A), (B) and (C)

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400.Pressure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as

1. V^1.8
2. V^-0.2
3. V^2.7
4. V²

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