JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II LOW SPEED AERODYNAMICS Previous Question Paper (May - 2019 - R16)
Part A is compulsory. Answer all questions. Part B consists of 5 Units. Answer any one full question from each unit.
PART A
What is the reason to non-dimensionalise the aerodynamic performance quantities?
Answer
Non-dimensionalisation allows aerodynamic data to be generalized, making performance quantities independent of the specific size of the model, the fluid density, or the flow velocity. This enables the comparison of results between different scales and flow conditions through similarity parameters.
Define Reynolds number. What is physical significance of it in classifying the flows?
Answer
The Reynolds number (Re) is defined as the ratio of inertial forces to viscous forces in a fluid flow, expressed as:
Its physical significance lies in its ability to classify flows; low Reynolds numbers indicate laminar flow where viscous forces dominate, while high Reynolds numbers indicate turbulent flow where inertial forces dominate.
What is a starting vortex?
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Define Vorticity and Circulation.
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Draw a typical velocity variation in a turbulent boundary layer.
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Write the Blasius expression for calculating displacement thickness over a flat plate.
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What is induced drag?
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State Biot-Savart’s law.
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Write an expression for Froude efficiency of the propulsive system.
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What are the advantages of slats?
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PART B
Derive the momentum equation in differential form for an incompressible flow.
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Derive the expressions for aerodynamic center and centre of pressure. What is use of knowing these?
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Derive the stream function for a lifting flow over a circular cylinder.
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Derive the potential function of a uniform flow, Source flow and Sink flow.
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Define a boundary layer and its thickness. Derive Von Karman’s momentum equation.
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Explain the characteristics of a boundary layer over a flat plate using the necessary equations and diagrams.
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An aeroplane weighing 73.6 kN has elliptic wings 15.23 m in span. For a speed of 90 m/s in straight and level flight at low altitude find (a) the induced drag; (b) the circulation around sections halfway along the wings.
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An aeroplane weighing 100 kN has a span of 19.5 m and a wing-loading of 1.925 kN/m2. The wings are rather sharply tapered having around the centre of span a circulation 10% greater than that for elliptic wings of the same span and lift. Determine the downwash angle one-quarter of the span behind the centre of pressure, which is located at the quarter-chord point. The air speed is 67 m/s. Assume the trailing vorticity to be completely rolled up just behind the wings.
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Explain the concept of actuator disk theory.
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Discuss about various lift augmentation methods.
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