CIVIL ENGINEERING
Paper: Fluid Mechanics & Hydraulics IIPaper Code: ETCE205
Semester : IV Marks : 75
Note: Q.1 is compulsory. Attempt any one question from each unit.
Q.1.Attempt the following. (5x5=25)
a Define the following (1) Momentum thickness (2) Friction Drag (3) intensity of turbulence (4) hydraulic efficiency
b. Compare velocity distribution in laminar and turbulent flow in a pipe.
c. What is priming of siphons? Why is the limit of minimum pressure imposed in the case of siphons?
d. What is the function of surge tank in the case of turbines?
e. Draw a sketch of a hydropower plant and label its various components.
UNIT I
2. (a)Why is it necessary to control the growth of boundary layer on most of the body? Explain the methods for such a control. ( 7.5 )
(b)For a rotating cylinder viscometer, inner diameter= 100mm, outer diameter = 108mm, depth of immersion of inner cylinder=200mm, clearance at bottom=4mm N= 100rpm, total torque=0.393Nm.Determine the viscosity of liquid. (5)
3. (a)what are the semi-empirical theories of turbulence? Explain the concept of mixing length introduced by Prandtl and state the relationship that exists between the turbulent shearing stress and the mixing length. (5)
(b)oil of mass density 800kg/m3 and dynamic viscosity 0.02 poise flows through 50 mm diameter pipe of length 500 m at the rate of 0.19 l/s. Determine (1) Reynolds number of flow, (2) centerline velocity, (3) pressure gradient (4) loss of pressure in 500 m length, (5) wall shear stress and (6) power required to maintain the flow. (7.5)
UNIT 2
4. (a) Give reason for the following:-
1.Will it be easier to swim in fresh water or in sea water?
2.What type of drag predominates in (a) mist droplet falling in air? (b) Air bubble rising in honey (c) Airplane wing at a speed of 300km/hr. (5)
(b)Oil with a free stream velocity of 2m/s flows over a thin plate 2 m wide and 2 m long. Calculate the boundary layer thickness and the shear stress at the trailing end point and determine the total surface resistance of the plate. Take specific gravity as 0.86 and kinematic viscosity as 10-5 m2/s. (7.5)
5. (a)Two reservoirs with a difference in water level of 180 m are connected by a 64 km long pipe of 600 mm diameter and f of 0.015. Determine the discharge through the pipe. In order to increase this discharge by fifty per cent, another pipe of the same diameter is to belaid from the lower reservoir for part of the length and connected to the first pipe, Determine the length of additional pipe required. (5)
(b)
Determine the distribution of flow in the pipe network shown in the above figure. The head loss hL = KQ2. The value of K for each pipe is indicated in the figure. (7.5)
UNIT 3
6. (a)Compare method of controlling flow in the case of Pelton wheel, Francis turbine and Kaplan turbine. (6)
(b)An inward flow turbine has the following data.
Q = 0.60 m3/s. H = 18 m, power developed = 89 kW, N = 375 rpm,
D1 = 0.75 m, D2 = 0.50 m, exit velocity = 3.5m/s and is radial, b1 = b2. Determine overall efficiency, hydraulic efficiency and inlet angles of guide and runner blades. (6.5)
7. (A)what are the characteristic curves of a turbine? How are they obtained? What is its utility? (6.5)
(B)A model turbine constructed to a scale of 1/10 when tested under a head of 8 m at 400 r.p.m. gave efficiency of 77 per cent. Determine the r.p.m. of the prototype and the ratio of power developed by the model and prototype if the prototype works under a head of 100 m. What will be the efficiency of the prototype if scale effect is considered? (6)
UNIT 4
8 (a)A centrifugal pump having an impeller 30 cm outside diameter rotates at 1050 r.p.m. The vanes are radial at exit and are 7.5 cm wide. The velocity of radial flow through the impeller is 3 m/s. The velocities in the suction and delivery pipes are 2.5 m/s and 1.5 m/s respectively. Neglecting frictional losses, determine the height through which the pump lifts, and the horse power of the pump. Assume radial entry. (7.5) (b.1) which part of centrifugal pump is most susceptible to cavitations? What are the undesirable effects of cavitation?
(b.2) Explain the condition under which centrifugal pumps is connected in series and parallel. (5)
9(a)Following details of a single acting, single cylinder, reciprocating pump is given:-
L = 500 mmD = 125 mmHatm = 10.2 m
l s = 5.0 mDs = 100 mmHs = 3.0 m
ld = 15 mDd = 100 mmHd = 10.0 m
f = 0.02 for both suction and delivery pipes.
Safe minimum head = 2.4 m
Neglect slip and calculate (1) maximum permissible speed, and (2) energy required to drive the pump if an air vessel is provided on the delivery side very close to the cylinder. (7.5)
(b)Draw the indicator diagram for a single cylinder single acting reciprocating pump when air vessel is provided only on the suction side. (5)