Question

Encircle the correct answer for the following questions: • What is the hydraulic diameter of a rectangular air ventilation duet whose cross section is 1 m by 25 cm? (a) 25 cm (b) 40 cm (c) 100 cm (d) 75 cm (e) 50 cm Oil = 0.1kg/ms, specific gravity= 0.9] flows through a 50-m-long smooth 8-cm-diameter pipe. The maximum pressure drop for which laminar flow is expected is approximately • • (a) 40 kPa (b) 50 kPa (c) 60 kPa (d) 70 kPa (e) 80 kPa Water at 4°C flows at 0.01 m'Is through a pipe 150 m long and 8 cm in diameter. If the friction head loss is 12 m, the Moody friction factor is most nearly equal to (a) 0.010 (b) 0.015 (C) 0.022 (d) 0.025 (e) 0.032 A fluid flows in a 25-cm-diameter pipe at a velocity of 4.5 ms. If the pressure drop along the pipe is estimated to be 6400 Pa, the required pumping power to overcome this pressure drop is most nearly (a) 314 W (b) 640 W (c) 1415 W (d) 1235 W (e) 5655 W Consider a pipe that branches out into three parallel pipes and then rejoins at a junction downstream. All three pipes have the same diameters (D-3 cm) and friction factors (-0.015). The lengths of pipe 1 pipe 2 are 5 m and 12 m, respectively while the velocities of the fluid in pipe 2 and pipe 3 are 2 m/s and 4 m/s, respectively. The length of pipe 3 is most nearly (a) 8 m (6) 5m () 4 m (d) 3 m (e)2 m The primary dimensions of kinematic viscosity are (a) M L (b) M/L (c) L (d) LMt (e) LM- Which similarity condition is related to force-scale equivalence? (a) Geometrie (b) Kinematic (c) Dynamic (d) Kinematic and dynamic (e) Geometric and kinematic A one-third scale model of a car is to be tested in a wind tunnel. The conditions of the actual car are - 75 km/h and T-20°C. The air temperature in the wind tunnel is 0°C. The air viscosity is 1.338x10m/s at 0 °C and 1.516x10m/s at 20 °C. In order to achieve similarity between the model and the prototype, the wind tunnel velocity should be (most nearly): • . (a) 250 km/h (b) 225 kmh (c) 200 kmh (d) 150 kmh (e) 25 kmh The problem of unsteady fully developed flow between two infinitely wide parallel plates involves the following parameters: velocity componentu, distance between the plates h, vertical distance y, top plate speed V, fluid density , fluid viscosity, and time 1. The number of expected nondimensional parameters (Ts) for this problem is (a) 6 (b) (c) 4 (d)3 (e)2 Consider an airplane cruising at 850 kmh to the right. If the velocity of exhaust gases is 700 kmh to the left relative to the ground, the velocity of the exhaust gases relative to the nozzle exit is most nearly (a) 1350 kmh (b) 850 km/h (c) 700 kmh (d) 350 kmh (e) 150 km/h

Answer 1

7 Hydraulic diameter = 4x Area Wetted perimeter 4 X 1 X 0.25 2 (1+0.25 ) 0.4 m or 40 cm = Arus - Option (b) 2% Presure drop - 321 VL D2 & Laminar flow, Re < 2000 2000 = 3 Va 900 X VX0-08 ve 2-778 m/s. , P, P2 32X01 X 2.777 X SO (0.08) - 69.444 kpo = 70 cpa. Ans - Option (d) 31 Head loss, 72gos hf = 87182 ;f hf x 7729 DS 8X LX 82 12x772x9.81x10.09,5 8X 150 X 10-002 = 0.032 • Ans - option e) 0.032 Discharge, B: A XV - 2x 10.25)2X4.5 = 0.220 7 ml Prerure drops $400 kPa. . power required - Presu x discharge - 6900 8 0 2 20 % - 1413.7 W Aron option (c)

5) Kinematic w's cosity olimension : 64 (c) L²/t . Perce -scole equivalence ( Dynamic