## GATE ME solved Questions on Turbomachinery and Dimensional Analysis(Fluid Mechanics)

Question #1

For a Pelton wheel with a given water jet velocity, the maximum output power from the Pelton wheel is obtained when the ratio of the bucket speed to the water jet speed is _______ (correct to two decimal places).

[GATE 2018 Set 1, 1 mark]

Question #2

Which of the following is NOT a rotating machine

(A) centrifugal pump

(B)Gear pump

(C)Jet pump

(D)vane pump

[GATE 2017 Set 1, 1 mark]

Question #3

Which one of the following statement is TRUE?
(A) Both Pelton and Francis turbines are impulse turbines.
(B) Francis turbine is a reaction turbine but Kaplan turbine is an impulse turbine.
(C) Francis turbine is an axial – flow reaction turbine.
(D) Kaplan turbine is an axial – flow reaction turbine.

[GATE 2017 Set 2, 1 mark]

Question #4

For the laminar flow of water over a sphere, the drag coefficient C is defined as $C_f=F/\rho U^2d^2$, where F is the drag force, ρ is the fluid density, U is the fluid velocity and D is the diameter of the sphere. The density of water is 1000 kg/m . When the diameter of the sphere is 100mm and the fluid velocity is 2m/s, the drag coefficient is 0.5. If water now flows over another sphere of diameter 200mm under dynamically similar conditions, the drag force (in N) on this sphere is
_____________

[GATE 2017 Set 2, 2 marks]

Question #5

Consider two hydraulic turbines having identical specific speed and effective head at the inlet. If the speed ratio (N1/N2) of the two turbines is 2, then the respective power ratio P1/P2 is _____________

[GATE 2016 Set 1, 1 mark]

Question #6

Oil (kinematic viscosity, $\nu _{oil}$ = 1.0 × 10−5 m 2/s) flows through a pipe of 0.5 m diameter with a velocity of 10 m/s. Water (kinematic viscosity, $\nu _{water}$ = 0.89 × 10−6 m 2 /s) is flowing through a model pipe of diameter 20 mm. For satisfying the dynamic similarity, the velocity of water (in m/s) is __________

[GATE 2016 Set 1, 2 marks]

Question #7

The blade and fluid velocities for an axial turbine are as shown in the figure. The magnitude of absolute velocity at entry is 300 m/s at an angle of 65 o to the axial direction, while the magnitude of the absolute velocity at exit is 150 m/s. The exit velocity vector has a component in the downward direction. Given that the axial (horizontal) velocity is the same at entry and exit, the specific work (in kJ/kg) is__________

[GATE 2016 Set 3, 1 mark]

Question #8

Kaplan water turbine is commonly used when the flow through its runner is
(A) axial and the head available is more than 100 m
(B) axial and the head available is less than 10 m
(C) radial and the head available is more than 100 m
(D) mixed and the head available is about 50 m

[GATE 2014 Set 4, 1 mark]

Question #9

In order to have maximum power from Pelton turbine, the bucket speed must be

(A)equal to the jet speed

(B)equal to half the jet speed

(C)equal to twice the jet speed

(D)independent of the jet speed

[GATE 2013, 1 mark]

Question #10

A phenomenon is modeled using n dimensional variable with k primary dimensions. The number of non-dimensional variables is

(A) k

(B) n

(C) n-k

(D) n+k

[GATE 2010, 1 mark]

Question #11

A hydraulic turbine develops 1000 kW power for a head of 40 m. If the head is reduced to20 m the power developed (in kW) is

(A) 177

(B) 354

(C) 500

(D) 707

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