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Indian Institute of Technology Madras (IIT-M) 2007 B.Tech Experimental Technique and Measurements, End Sem - Question Paper

Wednesday, 23 January 2013 03:00Web

OE 511 Experimental Techniques & Measurements
Semester exam
30-11-2007 three hrs
ans any 5 ques.. All ques. carry equal marks
(Properties of SS: E = two x 1011N/m2, µ = 0.3 and fatigue strength is 200 x 106 N/m2)

1.a Explain the working of piston kind wave maker to generate shallow water wave kinematics. (Marks 3)
b. How irregular waves simulating a mathematical spectrum is generated in a lab wave flume (Marks 3)
c. For a model test the scale factor used is 1:50. Tests have to be performed for an extreme wave of period 15 sec and height 12 m. Test facility has a flap kind wave maker with hinge at 1.2 m beneath the water surface in a water depth of two m. What stroke of the wave maker will simulate the prototype wave conditions? (Marks 4)

2.a Discuss a towing test facility and how are its dimensions decided? (Marks 3)
b. Discuss different passive wave absorbers used in test facilities. (Marks 4)
c. In a towing experiment using a 1:100 model, the total resistance measured was 50 N. at a velocity of two m/sec. What is the prototype force and velocity, if the test performed was as per Froude’s criteria? (Marks 3)

3.a Discuss the requirements of dynamic likeness in hydrodynamic issues. (Marks 3)
b. How do you achieve dynamic likeness in a issue involving free surface. (Marks 2)
c. A diaphragm kind pressure transducer with a diameter of 25 mm has to be designed to measure the depth of a submerged body operating at depths 200 m to 1000 m. Use a displacement transducer as the sensing element. What should be the range and the sensitivity of the displacement transducer, if the depth measurement requires a sensitivity of ±0.1 m. (Marks 5)

4.a Draw a block diagram of a Data Acquisition System to measure the data from all channels at the identical instant. discuss the working of every subsystem. (Marks 5)
b. How do you decide the sampling rate in a DAS? (Marks 2)
c. In an experiment, data have to be collected from four wave probes, two pressure transducers and forces and moments in all 3 directions. The tests are done in a random wave environment where the upper frequency limit is 32 rad/sec. What should be the sampling rate? (Marks 3)

5.a Explain the analytical basis for the design of a torque cell and the slip-ring method of data transmission from rotating components. (Marks 4)
b. A link kind force transducer is to be designed to measure mooring line forces. Maximum force expected is 106 N. Design the link element. four identical resistance strain gauges of resistance 120 ohms and K = 2.01 are to be used in a whetstone bridge on the element for maximum sensitivity. If SS is the material used, what will be its sensitivity in mV/V and output voltage when the force applied is the design value? The bridge excitation is five V. (Marks 6)

6.a Derive the theory of seismic mass. Under what conditions a seismic mass can be used for acceleration and displacement measurements? (Marks 4)
b. An accelerometer was calibrated on a turntable. When the turntable was rotated by 90 degrees the accelerometer output was five V. The natural frequency of the accelerometer is 15 Hz and the damping ratio is 0.5. This accelerometer was fixed on a structure vibrating at 10 Hz, recorded an output of 1.8 V. elaborate the maximum acceleration, velocity and displacement at the location? (Marks 6)

7. Write notes on any 4 of the following: ( (Marks 2.5 x 4)
a. Nondimensional parameters in coastal engineering issues
b. Shear beam force transducer
c. Vibrating wire strain gauges
d. Piezoelectric accelerometers
e. First order measuring instruments
f. Accuracy of measuring systems

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