Questions and answers for exam Preparation

MCQs

Total Questions : 47 | Page 2 of 5 pages

Question 11. For a particular engine, the underside of the crankcase can be idealized as a flat plate measuring 80 cm by 20 cm. The engine runs at 80 km/hr and the crankcase is cooled by the air flowing past it at the same speed. Find loss of the heat from the crank case surface (t S = 25 degree Celsius). Assume the boundary layer to be turbulent

465.04 W
565.04 W
665.04 W
765.04 W

Discuss Question

Answer: Option B. -> 565.04 W
Answer: (b).565.04 W

Question 12. A flat plate 1 m by 1 m is placed in a wind tunnel. The velocity and temperature of free stream air are 80 m/s and 10 degree Celsius. The flow over the whole length of the plate is made turbulent by turbulizing grid placed upstream of the plate. Find the heat flow from the surface of the plate

9424.5 W
8424.5 W
7424.5 W
6424.5 W

Discuss Question

Answer: Option C. -> 7424.5 W
Answer: (c).7424.5 W

Question 13. The concept of hydrodynamic boundary layer was first suggested by

Isaac Newton
Ludwig Prandtl
Rodridge
Fourier

Discuss Question

Answer: Option B. -> Ludwig Prandtl
Answer: (b).Ludwig Prandtl

Question 14. The pattern of flow in the boundary layer is judged by the

Reynolds number
Fourier number
Peclet number
Grashof number

Discuss Question

Answer: Option A. -> Reynolds number
Answer: (a).Reynolds number

Question 15. The conditions for flow beyond the boundary layer and its outer edge are

d u/d y = 0 and u = U 0
d u/d y = Infinity and u = U INFINITY
d u/d y = 1 and u = U 0
d u/d y = 0 and u = U INFINITY

Discuss Question

Answer: Option D. -> d u/d y = 0 and u = U INFINITY
Answer: (d).d u/d y = 0 and u = U INFINITY

Question 16. The free stream undisturbed flow has a uniform velocity U INFINITY in the

X-direction
Y-direction
Z-direction
Any direction

Discuss Question

Answer: Option A. -> X-direction
Answer: (a).X-direction

Question 17. The thin layer where velocity changes continuously is called

Differential layer
Thermal boundary layer
Hydrodynamic boundary layer
Velocity distribution layer

Discuss Question

Answer: Option C. -> Hydrodynamic boundary layer
Answer: (c).Hydrodynamic boundary layer

Question 18. A plate 0.3 m long is placed at zero angle of incidence in a stream of 15 degree Celsius water moving at 1 m/s. Find out the stream wise velocity component at the mid-point of the boundary layer. For water at 15 degree Celsius
p = 998.9 kg /m³
µ = 415.85 * 10¯² kg/hr m