1.

According to Newton’s theory, what happens to the lift to drag value with decreasing angle of attack of a flat plate?(a) Remains same(b) Increase monotonically(c) Decreases parabolically(d) Becomes zero with maximum angle of attackI had been asked this question at a job interview.My enquiry is from Time-Marching Technique in section Time-Marching Technique of Aerodynamics

Answer»

Correct answer is (b) Increase monotonically

To elaborate: The lift/drag ratio for inviscid hypersonic flow over a flat plate is given by:

\(\FRAC {L}{D}\) = cotα

On plotting the curve, as the angle of attack decreases, L/D ratio monotonically INCREASES. Obviously this is a HYPOTHETICAL condition as SKIN friction drag is not incorporated in this.



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