Define Dynamic Viscosity Determine The Centroid Pressure.

1. Compare liquids and gases with regard to their:

shape

volume occupied

density

viscosity

compressibility.

2. (a) (i) Define dynamic viscosity and give the mathematical formula for Newton`s law of viscosity.

(ii) How does kinematic viscosity differ from dynamic viscosity?

(b) Explain why viscosity is an important property in Fluid Mechanics.

(c) Name three classes of non-Newtonian fluids and explain how their viscosity is affected by factors other than temperature.
(d) What is the main difference between an ideal` fluid and a real` fluid?

3. (a) Often the mathematics of a problem in Fluid Mechanics is made easier if we assume the mass or area to be concentrated at a single point. What are these points known as for:

(i) mass

(ii) area?

11. (a) Distinguish, with the aid of simple sketches where appropriate, between the construction, operation and applications of the Pelton wheel, Francis turbine and Kaplan turbine.

(b) In a Francis turbine, the supply head (H) is 20 m of water (density 1000 kg m-3). The discharge rate to atmosphere is 600 kg s-1. The external radius of the runner (R1) is 0.43 m and the internal radius (R2) is 0.20 m. The runner blades are radial at inlet and they rotate at 300 revs min-1. The blades occupy 5% of the circumferential area and are shaped to ensure that the radial velocity (u1R) is kept constant and equal to If the shaft power is 80% of the water power, determine the:

(i) guide vane angle

(ii) blade exit angle

(iii) water power

(iv) diagram power

(v) shaft power

(vi) height of runner blade at inlet and outlet.

12. A process requires the precise control of the flow of a fluid to a reactor operating at 100 bar pressure (1 bar = 100 kPa). The flowrate may need to change to match the required reactor output. The flow should be relatively non-pulsating.

(i) Suggest a suitable pump for this duty. Give reasons for your choice.

(ii) Describe, with the aid of a suitable diagram, the construction and operation of your chosen pump.

13. It is proposed to pump 1500 m3 of a liquid (density 1100 kg m-3) each day through a total head of 10 m (including all losses) by using either a centrifugal pump or a reciprocating pump.

The centrifugal pump discharges 2.0 m3 min-1 when driven by an electric motor supplying a power of 5 kW.

The reciprocating pump has a discharge rate of 1.75 m3 min-1 when driven by an electric motor supplying 3.5 kW.

(a) Calculate the efficiency of each pump.

(b) If electricity costs 8p per kWh, select the most economical pump and determine the cost saving over 300 days of operation.

(c) State two other factors which should be considered before a final choice of pump is made.