BENG1 INTRODUCTION to
THERMO-FLUIDS (THER 103)
TUTORIAL EXAMPLES in MOMENTUM
(SSL conditions are 101.325 kPa, and 15°C)
1.
A jet of water, 225 mm diameter, impinges
on a flat plate moving at 0.6 m/s in the same direction as the jet. If the
volume flow rate of the jet is 0.14 m3/s, find the force which the
fluid exerts on the plate and the power generated. [339 N ; 204 W]
2.
A jet of water, having a velocity
of 15 m/s, impinges tangentially onto a vane, which is in the form of a
circular arc with a subtended angle of 120o. Find the magnitude and direction of the force
on the vane when the flow rate is 0.45 m3/s, assuming that the
velocity of the fluid relative to the vane remains constant. If the vane is now
allowed to move with a velocity of 6 m/s in the direction of the jet, find the
power developed for the same flow rate.*
3.
A jet boat is propelled by a hydraulic
water jet. A pump takes in sea water at the rate of 2.832 m3/s
through a hole in the bow and ejects it through a nozzle in the stern.
Determine the thrust on the boat if the boat has a velocity of 4.49 m/s. The
area of the hole in the bow is 0.186 m2 and the area of the nozzle
outlet is 0.0465m2. Assume the density of sea water is 1026 kg/m3. [163.9 kN]
4.
A rocket, which is restrained from
moving, ejects gases at a velocity of 1525 m/s and a flow rate of 45.36 kg/s.
Calculate the thrust on the rocket. Would the thrust be different if the rocket
was moving? [69.17
kN]
5.
The nozzle of a fire hose produces a
jet of water having a diameter of 50 mm. if the discharge is 0.085 m3/s
and the velocity of the jet is 10 times the velocity in the hose, calculate the
reaction force of the jet. If the gauge pressure just upstream of the nozzle
reads 1.92 MPa(gauge) and the nozzle discharges to atmosphere, determine the
total force on the nozzle. Assume the water enters the hose at right angles to
the direction of the jet. [3680 N ; 38.25
kN]