Fluid Mechanics - Dec 2015
Mechanical Engineering (Semester 4)
TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1 (a) Define a fluid and distinguish between ideal and real fluids.(5 marks) 1 (b) A stone weights 2KN in air and 168N in water. Calculate the volume and specific gravity.(5 marks) 1 (c) Explain Hydrostatic law.(5 marks) 1 (d) Define steam lines, path lines and streak lines.(5 marks) 1 (e) Define Mach number, stagnation density and stagnation temperature.(5 marks) 2 (a) The velocity components in two dimensional flow fields are as follows
i) whether the flow is possible
ii) obtain an expression for steam function
iii) obtain an expression for potential function.(10 marks) 2 (b) A sliding gate 3m and 1.5m high situated in a vertical plane has a coefficient of friction between itself and guide of 0.18. If the gate weight is 19n and its upper edge is at a depth of 9m, what vertical force is required to raise it? Neglect buoyancy force on gate.(10 marks) 3 (a) Starting from the Navier Stokes equation for an incompressible Newtonian fluid derive Bernoulli's equation starting the assumptions.(10 marks) 3 (b) Derive the expression for stagnation density and stagnation temperature.(10 marks) 4 (a) A pipeline of length 2400m is used for power transmission. If 115KW power is to be transmitted through the pipe in which water having a pressure of 500 N/cm2 at inlet is flowing? Find the diameter of the pipe and efficiency of transmission if the pressure drop over the length of pipe is 100 N/cm2. Take f=0.026 also find diameter if pipe corresponding to maximum efficiency of transmission.(10 marks)
Write short note on.
4 (b) (i) Moody's diagram(5 marks)
4 (b) (ii) Major and minor losses.(5 marks)
5 (a) A normal shock wave occurs in a duct in which air is flowing at a Mach number of 1.5. The static pressure and temperature upstream of the shock wave is 1.5 bar and 270°C. Determine pressure, temperature and mach number downstream of the shock. Also calculate strength of shock.(10 marks)
5 (b) Explain Prandtl's mixing length theory.(10 marks)
6 (a) The velocity profile within a laminar boundary layer over a flat plate is given by the equation.
u/U =2(y/δ) - (y/δ)2
Where U is the mean stream velocity and δ is the boundary layer thickness. Determine the displacement thickness and momentum thickness.(10 marks)
6 (b) (i) Aerofoil theory(5 marks) 6 (b) (ii) Reynolds Transportation theorem.(5 marks)