JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech IV EXPERIMENTAL AERODYNAMICS Previous Question Paper (January/February - 2023 - R18)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What is understood by dynamic similarity of wind tunnel models?
Answer
Dynamic similarity exists between a wind tunnel model and a full-scale prototype when the ratios of all corresponding forces (inertial, viscous, gravitational, etc.) acting on the fluid particles are identical. This requires the equality of relevant dimensionless parameters, such as the Reynolds number, Mach number, and Froude number, between the model and the prototype.
Explain the direct measurements.
Answer
Direct measurements involve the physical observation or sensing of a quantity by comparing it directly against a known standard or using a calibrated transducer that converts the physical property into a readable output. Examples include using a mercury manometer to measure pressure or a balance to measure force, where the output is directly proportional to the physical quantity being investigated without requiring complex intermediate mathematical transformations.
What are the power losses in a wind tunnel?
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What is the performance terms associated with measurement systems?
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What are the requirements of tracer particles used for flow visualization?
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Name some flow visualization techniques.
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Differentiate Schlieren, shadowgraph and interferometry methods.
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Why are hot wire anemometer preferred for measurement in the low velocity regimes?
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Define Rossby number. State its significance.
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Compare external estimate and internal estimate of errors.
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Part B
Explain the various terms used to describe the performance of measurement systems.
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What are the properties of fluids that are important for fluid mechanics measurement? Explain.
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Describe the wind tunnel balance, wire balance and balance calibration.
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An open-circuit subsonic wind tunnel of test-section area 1 m2 draws atmospheric air at 1 atm and 300C. (i) If a model of 4 percent blockage is tested at a test-section speed of 90 m/s, determine the change in mass flow rate per unit area, caused by the model blockage. (ii) If the model blockage is 5 percent, how much would be the change in the mass flow rate per unit area?
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A pitot probe has to be designed for measurement in a Mach 2 air stream.
If the probe blockage should not cause more than 1 percent error to the flow Mach number, what should be the ratio of the flow field area to the probe projected area?
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What will be the error in the flow Mach number measured, due to this probe blockage, in Mach 3, 1.5, and 1.2 flows of the same flow cross-Sectional area as the Mach 2 flow field?
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From these error estimates will it be possible to identify the probe blockage which will cause only acceptable error to the Mach number over the entire range of supersonic flow beginning from Mach 1.5?
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With a schematic diagram, explain the principle and operation of a smoke tunnel.
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Develop a flow visualization technique to visualize high-speed flows in the ranges of transonic and supersonic Mach numbers and explain.
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Explain constant current and constant temperature Hot-wire anemometer.
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The pressure and temperature of an air stream are measured as 650 mm of mercury and 320 C, respectively. If the fluctuation in the pressure is 2mm of mercury and error in the temperature measured is 0.10C, determine the uncertainty in the density calculated using thermal state equation.
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Calculate the dynamic pressure of a flow with free stream conditions of velocity 210 m/s, pressure 1 atm, and temperature 310 K. What will be the percentage error if the flow is treated as incompressible?
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A gas thermometer was calibrated by placing the bulb in melting ice at 00C and difference in height of the mercury column was 820mm. The bulb was then placed in steam at 1000 C and the mercury column was adjusted to be 1300 mm. The bulb was then placed in a fluid of unknown temperature and, after adjustment, the difference in height of the mercury column read was 97 cm. Determine the temperature of the fluid.
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Explain how do you carry out measurements in boundary layer.
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State and prove Taylor Proudman Theorem with aid of sketch the experimental setup.
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Explain about the estimation of measurement errors and uses of uncertainty analysis.
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