Problems

1. Describe the principle of operation of a hotwire anemometer (HWA). List the components used and explain their functions. Separately discuss 1-, 2-, and 3-component velocity measurement. Also refer the text given in module 2.

3. Consider a two-wire probe used for two component measurement of fluid velocity. Develop data analysis techniques for converting voltage outputs from each wire into time-averaged velocity, velocity fluctuations, and Reynolds stresses. Consider the wires to be (a) equal sensitivity and (b) unequal sensitivity. Reference texts separately listed will be useful in this regard.

4. Study data analysis for a three-wire probe; the article by Chew and Simpson (1988) may be useful in this context.

5. Write computer programs to fit suitable curves through the calibration data using a least square procedure.

6. Discuss using a hotwire anemometer in a nonisothermal flow field. Temperature compensation may be achieved by developing calibration curves as a function of the wire temperature. Other alternatives can also be pursued.

7. Discuss the use of a hotwire anemometer when the fluid speed is quite small, for example, creeping flows.

8. Describe the principle of operation of a laser Doppler velocimeter. List the components used and explain their functions. Separately discuss 1-, 2-, and 3-component velocity measurement. The review articles by Adrian as well as the chapter in the book by Goldstein (1997) will be useful.

9. Discuss specific advantages of LDV over HWA as well as possible disadvantages. Comment on spatial resolution, speed of response, linearity, and sensitivity to room temperature fluctuation.

10. What is the role of coherence of the light source in the operation of the LDV.