ME2204 Fluid Mechanics and Machinery April/May 2011 Question Paper - Anna University B.E Mech Question Papers

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2011

Third Semester

Mechanical Engineering

ME 2204 — FLUID MECHANICS AND MACHINERY

(Common to Automobile Engineering, Production Engineering and

Aeronautical Engineering)

(Regulation 2008)

Time : Three hours Maximum : 100 marks

Answer ALL questions

PART A — (10 × 2 = 20 marks)

1. Define surface tension and expression its unit.

2. What is Darey's equation? Identify various terms in the equation.

3. What is viscosity and give its units?

4. Distinguish between a control and differential control volume.

5. Check whether the following equation is dimensionally homogeneous.

6. Distinguish between Rayleigh's method and Buckingham's Π- theorem.

7. Write the Euler's equation.

8. A shaft transmits 150 Kw at 600 rpm. What is the torque in Newton –metres?

9. Why is the reciprocating pump called a positive displacement pump?

10. What is a rotary pump? Give its classification.

PART B — (5 × 16 = 80 marks)

11. (a) Explain in detail the Newton's law of viscosity. Briefly classify the fluids based on the density and viscosity. Give the limitations of applicability of Newton's law of viscosity. (16)

(b) State the law of conservation of man and derive the equation of continuity in Cartesian coordinates for an incompressible fluid. Would it alter if the flow were unsteady, highly viscous and compressible?

12. (a) A lubricating oil flows in a 10 cm diameter pipe at 1 m/s. Determine whether the flow is laminar or turbulent. For the lubricating oil μ = 0.1Ns² /m and ρ = 930 kg/m³. Calculate also transition and

turbulent velocities.

(b) A smooth flat plate with a sharp leading edge is placed along a free stream of water flowing at 3m/s. Calculate the distance from the leading edge and the boundary thickness where the transition from

laminar to turbulent- flow may commence. Assume the density of water as 1000 kg/m³ and viscosity as 1 centipoise.

13. (a) What is the significance and the role of the following parameters?

(i) Reynolds number

(ii) Froude number

(iii) Mach number

(iv) Weber number. (16)

(b) An agitator of diameter D rotates at a speed N in a liquid of density ρ and viscosity μ . Show that the power required to mix the liquid is expressed by a functional form

14. (a) A gas turbine operates between 1000k and 650 k temperature limits taking in air 20 kg/s at 125 m/s and discharging at 300 m³/s. Estimate the power developed by the turbine. Given C p =995 J / Kg.K .

(b) Explain in detail about the performance curves for pumps and turbines.

(16)

15. (a) A single acting reciprocatory pump has a plunger of diameter 30 cm and stroke of 20 cm. If the speed of the pumps is 30 rpm and it delivers to 6.5 lit/s of water, find the coefficient of discharge and the percentage slip of the pump.

(b) Write briefly on the following.

(i) Rotary pumps and their classifications. (8)

(ii) Indicator diagram for reciprocating pump. (8)

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