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I I I I I I I I D MFouth Semester B. E. Deg ree Examina tion,
Dec. 07 I Jan. 08
Fluid Mechanicsrime: 3 Ius. Max. Marks:
I
Note :1. Answer any FIVEfull questions.2. Missing data i fany
can be suitably assumed.
a Define the following and mention their S.l. tmits:i)
Density.ii) O y n ~ m i c viscosity.iii) Surface tension.iv) Vapour
pressurev) Bulk modulus.
b. Derive lln expression for capillary rise of liquid in a
tube.c. The surface t e n ~ i o n ' of water droplet in contact
with air at 20 C is 0.071diameter ofdroplet is 1.45 mm. calculate
the pressure within the droplet.
(10 Ma(05 MaN/m. If(05 M
2 a. Dcriw an expression lor hydrostatic force on an inclined
submerged plane surface depth ofcentre of pressure. (10 Mab. A
circular plate of 2 m diameter is immersed in an oil of specific
gravity of 0.8, suchits surface is 30" to the free surJace. Its top
cdgo: 2.5 m bel ow the lrcc surface. Findforce and center of
pressure. (05 Mac. Measurements of pressure at l11e base and top of
a mountain are 74 em and 60 emmercury respectively. Calculate tlte
h.:ight of the mountain if air has a specific weigh
1.22 kg/m1. (05 Ma3 a. Define the (()Jiowing:i) Buoyancy.ii)
Absolute pressure.iii} Mctaccntrc.iv) Gauge p r e ~ s u r e . v)
Centre of pressure 00 Mab. /\ bloc!-. of wood of s p e c i f i ~
gravity 0.8 l l o a t ~ in watl'r. Determine the mctacentrie he
of block 1f its size is 3 m long, 2 111 wide and I m height.
State whether cquilil>riumstable or unstable. {05 :1-1ac. fhe
left limb of a mert.llf)' Utubc manometer is open to atmospheric
and the riglu limconnected to a pipe carrying water under pressure.
The c.cntrc of the pipe is at the levethe free surface of mercury.
Find the di1ference in level of mncury limbs of lilllbc ifabsolute
pressure of water in the pipe is 14.5 m of water, atmospheric
pressure is 760
of mercury. (OS ~ ' l-1 a. Derive the general three-dimensional
continuity equation and then reduce it to continequation for
steady. two dimensional in compressible llow. (tO Ma
b. Explain:i) Vel
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5 a. Using Buckingham's n theorem, show that the velocity
through a circuhn orificegi\en hy V - J2KilJ D l. here H 1s the
hcad causing flow. D is the d1amete1_ H piD Jthe urilice. Jl the
coefficient of viscosity, p is the mass density arC)-\\'clsbach
formula to calculate the frictional head loss tn pipe I l l
lcnnsfriction factor. (tO M a r
a. rxphun:i) Mach number1i) Suhsomc !lowiii) Supersonic llow.1v)
l.aminar flow\ ) I urbulcnt !low.
b. Water at 15 C fl,msUctemune
t i l l '1arbetween to larg.: parallel plates at a dbt.tncc of
1.6 mm api) 'I he maxunum velocityti) lh e pressure drop per unit
length andiii) Ihe shear stress at the walls of the plates iftht:
a\'cragc velocity is 0.2 mls.The \IScosity ofwater at 1sc is given
as 0.0 I poise. ( 0 ~ Maric. l;inJ thc velocny of bullet fir.:d in
standard air if the Mach angle is 30". Ta.kc R 287J/kg K and K -
1.4 fclr air. Assume temperature at IS"C. (OS Mar
!I a. Definei) Drag.ii) I iii.iu I lloundary layer
thickness.i\'l Displac.:mcnt thickness.v) Momentum thid.ness. (10
l\1ar
b. A circular disc 3 m in diamder is beld n o r m : ~ ] to a
26.4 m/s wmd of Jcnsity ()0011 gmlcW h : ~ t force is rl!l(Uircd to
hold it at rest? Assume co-ci11cknt of drag of disc 1.1.
(05 Marc. FmJ the displaccmcnt thickness and the momentum
tlnckness li'r tl;, velocll}' distributiin the boundary layer given
by 2( ( f )2where 11 is the v ~ : l n c 1 t y at a
