7/29/2019 2008 June.july ME45

1/2

USN I I I I I I I I I I IFourth Semester B.E. Degr ee Examination, June I July 08

Fluid Mechanics

M

Time: 3 hrs. Max. Marks: Note : A 11swer a11y FIVE full questio11s.

l a. State Newton's Jaw of viscosity and deduce the definition of absolute viscosity. (04 Mb. A capillary tube having an inside diameter of 4 mm is dipped in water at atmosphtemperature of 20. Dett:rminc Lhe height of water. which will rise in the tube. cr = 0.075 N/m and a = 60. for water. What will be the percentage increase in the valuheight, if the diameter of the tube is 2 mm? (06 M

c. The space between two square flat parallel plates is tilled with oil. Each side of the pla60 ems. The thickness of the oil film is 12.5 mm. The upper plate, which moves at 2.5requires a force of9.81 N to maintain the speed. Dctenninei) The dynamic viscosity of the nil in poise.ii) The kinematic viscosity of the oil, if its sp.gr. is 0.95.iii) Power absorbed in moving the plate. (tO M

2 a. Show that the centre of pressure. for a plane surface immersed in a s t a t i ~ nuid evertically or inclined, lies always below the centre of gravity. (08 M

h. A circular plate 4.5 m in diameter is submerged in water s1ach that its greatest anddepths below the water surface are J m and 1.5 m respectavely. Findi) Total pressure on the top face of the plate.ii) The position ofcentre of pressure. (08 Mc. State hydrostatic law and derive an e x p r e ~ s i o n li tr the same. (04 M

' a. Defino.: meta centre of a noating body. Describe the analytical method of detcm1ininmdacentric height. (tO Mb. Stnte the condition for stable equilibrium of a floating body and explain how this is tcare ul in the design ofa ship. (04 M

c. A wooden block of sp.gr 0.75 floats in water. If the size of the block is l m x 0.5 m x0.find its mctaccntric height for a roll on its longitudinal axis. (06 M4 a. Show that the continuity equation for a three dimensional steady incompressible flo

. liu Ol ' owgavenbv, - + -+ =0. (OS M. ox 1\y ozb. Define strean\ function and velocity potential !'unction and show how they are related.

(06 Mc. The \'clocity potential function for a two dimensional flow is = x(2y-l). At o p

P(4. 5) detcm1inc: i) The velocity ii) Value ofstream function. (06 M5 a. The pressure difference lbr viscous flow in a pipe depends upon the diameter opipe D, length of pipe L, the velocity V, viscosity fl and density p. Using Buckinghtheorem obtain an expression for ~ P . (08 M

b. State impulse momentum principle and mention its applications. (04 Mc. ln a 45" bend, a rectangular air duct of 1 m2 cross sectional area is gradually reduce0.5 m2 area. Find the magnitude and direction of the force required to hold the du

7/29/2019 2008 June.july ME45

2/2

() a. Derive an expression for the discharge through an IIICiined Ventunmeter for an upwtlow (08 M

b. A reservoir has been built 4 km away from a town having a population of5000. Waterl>c supplied from the n.--servoir to tbe t 0 \ ~ 1 1 The per capua consumption of "':ucr per da200 litres and half of this dally supply is to be pumped within 10 hrs . The loss of head to friction in the pipe line is 20 m and the co-efficient of friction lo r the pipe line is 0.0Calculate diameterof the supply main. Ne[!lcct minor losses. (08 Mac. Wntc a note on f nergy gradient line and hydraulic gradient. (04 Ma

7 a. Derive an expression for the loss of head due to friction for laminar flow through a ropipe. Sketch the ve loc ity prolile and shear stress proli le. (10 Mab. Derive an expression for the sonic vclocny in a compressible flow medium for.i) Isothermal processii) Adiabatic processJustify which o f these two is correct. (tO Ma

II a. On a tlat plate of 2 m length and I m \\idth. experiments were conducted in a wmd tunwnh .1 wind speed of 50 kmth.r The plate IS kept at such an angle that the co...:llicientsumg and lift arc 0.18 and 0.9 respectively. Determinei) Drag Ioreei1) L1fl forceiii) Resultant Ji1rcc andIV) Power exerted by air stream on the plate.Takcdcnsityofuir= 1.15 kg/m3 ( IOM"b. Ddlnc the following:i) Boundary la)'cr thickness.ii) Displacement thickness.iii) Momentum thickness. (01> \1a0c. A pn>jcctilc travels in air of pressure 10.1043 N/cm- at lO'C. at a speed of 1500 kmFind the Mach number and !Vlach angle. Take y = 1 l ,md R = 287 J/kg' K. (04 \1a