JNTU
JNTU B.Tech II AERODYNAMICS I Previous Question Paper (March - 2022 - R13)
Answer any Five Questions. All questions carry equal marks.
Main
With a neat sketch illustrate the typical aerodynamic characteristics at low speeds.
Answer
At low speeds, the aerodynamic characteristics of an airfoil are represented by plotting the lift coefficient (CL), drag coefficient (CD), and pitching moment coefficient (CM) against the angle of attack (α). The lift curve is linear up to the stall angle, where CL reaches its maximum value (CL,max). Beyond this point, flow separation occurs, leading to a sudden decrease in lift. The drag polar, which plots CD against CL, typically follows a parabolic shape, showing that drag is minimum at a specific lift coefficient and increases significantly near stall due to pressure drag. The pitching moment coefficient about the aerodynamic center remains relatively constant for symmetric airfoils or shows a small negative value for cambered airfoils.
Consider an airfoil in a flow with a free stream velocity of 45 m/s. The velocity at a given point on the airfoil is 70 m/s. Calculate the pressure co-efficient.
Answer
The pressure coefficient (Cp) is defined by the formula:
Given the free stream velocity V∞ = 45 m/s and the local velocity V = 70 m/s, the calculation is as follows:
- Substitute the given values into the formula: Cp = 1 - (70 / 45)2
- Calculate the ratio: 70 / 45 ≈ 1.5556
- Square the ratio: (1.5556)2 ≈ 2.42
- Calculate the final value: Cp = 1 - 2.42 = -1.42
The pressure coefficient at the given point is -1.42.
Calculate the velocity of bullet fire in standard air if the mach angle is 30°. Take R = 287.14 J/kg K and k = 1.4 for air. Assume temperature as 15 °C.
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Derive the continuity equation in differential form and explain the meaning of each term contained in it.
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Derive pressure coefficient using non-lifting flow over a circular cylinder, find the location on the surface of cylinder where the surface pressure equals the free stream pressure.
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In the ideal flow around a half body, the free stream velocity is 0.5 m/s and the strength of the source is 2 m2/s. Predict the fluid velocity and its direction at a point, r = 1.0 and θ = 120°.
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With a neat sketch explain the concept of circulation and discuss the importance in relevance to the aerodynamics.
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Explain about the boundary layer growth along a long thin plate and its characteristics.
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Derive the force expression of a complex body using Blasius theorem and discuss the salient points.
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Consider the flow over a small flat which is 8 cm long in the flow direction and 1 m wide. The free stream conditions correspond to standard sea level, and the flow velocity is 120 m/s. Assuming laminar flow, calculate the boundary layer thickness at the downstream edge and the drag force on the plate. For the same flow over the same plate, assume that the boundary layer is now completely turbulent. Calculate the boundary layer thickness at the trailing edge and the drag force on the plate.
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How is downwash produced on a finite wing? Explain its effect on the wing.
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Derive an expression for lift coefficient and induced drag coefficient in terms of circulation strength Γ(y) for a finite wing through Prandtl’s classical lifting line theory.
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Sketch and explain High Lift Devices. Discuss the advantages and disadvantages of high lift devices.
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Explain the following with neat sketches:
Drag-divergence Mach number and sound barrier
Transonic area rule
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