Questions and Answers of Engineering Fluid Mechanics

Th e pump shown is supplied with 1.5 kW from the shaft of a motor, to provide a mass flow rate of 20 kg/s. If the pump operates at 70% efficiency, what is the increase in the EGL? EGL HGL Pump
In the figure shown, the magnitude of the EGL changes from 14 m to 22 m. What is the pump head, h? EGL HGL Pump
Th e HGL and the EGL for a pipeline are shown in the figure.a. Indicate which is the HGL and which is the EGL.b. Are all pipes the same size? If not, which is the smallest?c. Is there any region in
Sketch the HGL and the EGL for this conduit, which tapers uniformly from the left end to the right end. Water Uniformly tapered pipe
Th e HGL and the EGL are as shown for a certain flow system.a. Is flow from A to E or from E to A?b. Does it appear that a reservoir exists in the system?c. Does the pipe at E have a uniform or a
For the system shown:a. What is the flow direction?b. What kind of machine is at A?c. Do you think both pipes, AB and CA, are the same diameter?d. Sketch in the EGL for the system.e. Is there a
If the pipe shown has constant diameter, is this type of HGL possible? If so, under what additional conditions? If not, why not? HGL Datum
The energy grade line for steady flow in a uniform-diameter pipe is shown. Which of the following could be in the “black box”? (a) A pump, (b) A partially closed valve, (c) An
Using Section 7.8 and other resources, answer the following questions. Strive for depth, clarity, and accuracy while also combining sketches, words, and equations in ways that enhance the
In a local water treatment plant, water flows in this bend at a rate of 7 m3/s, and the pressure at the inlet is 800 kPa. If the head loss in the bend is 13 m, what will the pressure be at the outlet
Water flows in this bend at a rate of 5 m3/s, and the pressure at the inlet is 650 kPa. If the head loss in the bend is 10 m, what will the pressure be at the outlet of the bend? Also estimate the
This rough aluminum pipe is 6 in. in diameter. It weighs 1.5 lb per foot of length, and the length L is 50 ft. If the discharge of water is 6 cfs and the head loss due to friction from section 1 to
This abrupt expansion is to be used to dissipate the high energy flow of water in the 5 ft diameter penstock. Assume α = 1.0 at all locations.a. What power (in horsepower) is lost through the
Water (γ = 62.4 lbf/ft 3) flows through a horizontal constant diameter pipe with a cross-sectional area of 9 in.2. The velocity in the pipe is 15 ft/s, and the water discharges to the atmosphere.
A 40 cm pipe abruptly expands to a 60 cm size. Th ese pipes are horizontal, and the discharge of water from the smaller size to the larger is 1.0 m3/s. What horizontal force is required to hold the
Water is draining from tank A to tank B. The elevation difference between the two tanks is 10 m. The pipe connecting the two tanks has a sudden-expansion section as shown. The cross-sectional area of
A 6 in. pipe abruptly expands to a 12 in. size. If the discharge of water in the pipes is 5 cfs, what is the head loss due to abrupt expansion?
A 7 cm pipe carries water with a mean velocity of 2 m/s. If this pipe abruptly expands to a 15 cm pipe, what will be the head loss due to the abrupt expansion?
What is the head loss at the outlet of the pipe that discharges water into the reservoir at a rate of 0.8 m3/s if the diameter of the pipe is 53 cm?
What is the head loss at the outlet of the pipe that discharges water into the reservoir at a rate of 14 cfs if the diameter of the pipe is 18 in.?
How is the energy equation (7.29) in §7.3 similar to the Bernoulli equation? How is it different? Give two important similarities and three important differences. (7.29) P2 + a2 + z2 2g + h, + h P1
A pumping system is to be designed to pump crude oil a distance of 1 mile in a 1 foot-diameter pipe at a rate of 3860 gpm. The pressures at the entrance and exit of the pipe are atmospheric, and the
The pump shown draws water (20°C) through a 20 cm suction pipe and discharges it through a 11 cm pipe in which the velocity is 3 m/s. The 10 cm pipe discharges horizontally into air at point C. To
The pump shown draws water through an 8 in. suction pipe and discharges it through a 3 in. pipe in which the velocity is 12 ft/s. The 6 in. pipe discharges horizontally into air at C. To what height
An engineer is making an estimate for a home owner. This owner has a small stream (Q = 1.4 cfs, T = 40°F) that is located at an elevation H = 34 ft above the owner’s residence. The owner is
A fan produces a pressure rise of 6 mm of water to move air through a hair dryer. The mean velocity of the air at the exit is 10 m/s, and the exit diameter is 44 mm. Estimate the electrical power in
A small-scale hydraulic power system is shown. The elevation difference between the reservoir water surface and the pond water surface downstream of the reservoir, H, is 24 m. The velocity of the
If the discharge is 480 cfs, what power output may be expected from the turbine? Assume that the turbine efficiency is 85% and that the overall head loss is 1.3 V2/ 2g, where V is the velocity in the
In the pump test shown, the rate of flow is 6 cfs of oil (SG = 0.88). Calculate the horsepower that the pump supplies to the oil if there is a differential reading of 46 in. of mercury in the U-tube
Water (10°C) is flowing at a rate of 0.35 m3/s, and it is assumed that hL = 2V2/2g from the reservoir to the gage, where V is the velocity in the 30 cm pipe. What power must the pump supply? Assume
Neglecting head losses, determine what power the pump must deliver to produce the flow as shown. Here, the elevations at points A, B, C, and D are 40 m, 64 m, 35 m, and 30 m, respectively. The nozzle
Neglecting head losses, determine what horsepower the pump must deliver to produce the flow as shown. Here, the elevations at points A, B, C, and D are 124 ft, 161 ft, 110 ft, and 90 ft,
An engineer is designing a subsonic wind tunnel. The test section is to have a cross-sectional area of 4 m2 and an airspeed of 60 m/s. Th e air density is 1.2 kg/m3. The area of the tunnel exit is 10
A water discharge of 8 m3/s is to flow through this horizontal pipe, which is 1 m in diameter. If the head loss is given as 7 V 2/2g (V is velocity in the pipe), how much power will have to be
The pump shown in the figure supplies energy to the flow such that the upstream pressure (12 in. pipe) is 5 psi and the downstream pressure (6 in. pipe) is 59 psi when the flow of water is 7 cfs.
As shown, water at 15°C is flowing in a 15 cm diameter by 60 m long run of pipe that is situated horizontally. The mean velocity is 2 m/s, and the head loss is 2 m. Determine the pressure drop and
A pump is used to transfer SAE-30 oil from tank A to tank B as shown. The tanks have a diameter of 12 m. The initial depth of the oil in tank A is 20 m, and in tank B the depth is 1 m. The pump
A pump is used to fill a tank 5 m in diameter from a river as shown. The water surface in the river is 2 m below the bottom of the tank. The pipe diameter is 5 cm, and the head loss in the pipe is
In this system, d = 15 cm, D = 35 cm, and the head loss from the venturi meter to the end of the pipe is given by hL = 1.5 V 2/2g, where V is the velocity in the pipe. Neglecting all other head
In this system, d = 6 in., D = 12 in., Δz1 = 6 ft , and Δz2 = 12 ft . The discharge of water in the system is 10 cfs. Is the machine a pump or a turbine? What are the pressures at points A and B?
For this system, point B is 10 m above the bottom of the upper reservoir. The head loss from A to B is 1.1V 2/2g, and the pipe area is 8 × 10–4 m2. Assume a constant discharge of 8 × 10–4 m3/s.
For this siphon the elevations at A, B, C, and D are 30 m, 32 m, 27 m, and 26 m, respectively. The head loss between the inlet and point B is three-quarters of the velocity head, and the head loss in
The discharge in the siphon is 2.5 cfs, D = 7 in., L1 = 4 ft , and L2 = 5 ft. Determine the head loss between the reservoir surface and point C. Determine the pressure at point B if three quarters of
The application of the Reynolds transport theorem to the first law of thermodynamics (select all that are correct)a. Refers to the increase of energy stored in a closed systemb. Extends the
Solve Prob. 6.56, and answer the following questions:a. Do the two pressure forces from the inlet and exit act in the same direction, or in opposite directions?b. For the data given, which term has
Th e expansion section of a rocket nozzle is often conical in shape, and because the flow diverges, the thrust derived from the nozzle is less than it would be if the exit velocity were everywhere
The semicircular nozzle sprays a sheet of liquid through 180° of arc as shown. The velocity is V at the efflux section where the sheet thickness is t. Derive a formula for the external force F (in
A design contest features a submarine that will travel at a steady speed of Vsub = 1 m/s in 15°C water. Th e sub is powered by a water jet. Th is jet is created by drawing water from an inlet of
For Example 6.2 in §6.4, the situation diagram shows concrete being “shot” at an angle into a cart that is tethered by a cable, and sitting on a scale. Determine whether the following two
When making a force diagram (FD) and its partner momentum diagram (MD) to set up the equations for a momentum equation problem (see Fig. 6.10), which of the following elements should be in the FD and
When the hydrofoil shown was tested, the minimum pressure on the surface of the foil was found to be 2.7 psi vacuum when the foil was submerged 3.1 ft. and towed at a speed of 20 ft /s. At the same
Oxygen leaks slowly through a small orifice in an oxygen bottle. The volume of the bottle is 0.1 m3, and the diameter of the orifice is 0.12 mm. Th e temperature in the tank remains constant at
A compressor supplies gas to a 8 m3 tank. The inlet mass flow rate is given by m· = 0.5 ρ0/ρ (kg/s), where ρ is the density in the tank and ρ0 is the initial density. Find the time it would take
In Fig. 5.11, isa. The CV passing through the system?b. The system passing through the CV? Control surface ABout B1) B(t + At) -Control volume- ABin (fixed volume) Flow Flow System at time t (dark
A tank of liquid (SG = 0.80) that is 1 ft in diameter and 1.0 ft high (h = 1.0 ft) is rigidly fixed (as shown) to a rotating arm having a 2 ft radius. The arm rotates such that the speed at point A
A fluid is flowing around a cylinder as shown in Fig. 4.37. A favorable pressure gradient can be found.Fig. 4.37.a. Upstream of the stagnation pointb. At the stagnation pointc. Between the stagnation
When the Bernoulli Equation applies to a venture, such as in Fig. 4.27, which of the following are true? (Select all that apply.)a. If the velocity head and elevation head increase, then the pressure
Which of these assumptions and/or limitations must be known when using Eq. (3.33) for a submerged surface or panel to calculate the distance between the centroid of the panel and the center of
Propose three new rows for Table 1.1, and fill them in. Attribute Solid Liquid Gas Typical Visualization Solids hold their shape; no need for a container Liquids take the shape of the container and
Using the first two sections in this chapter and using other resources, answer the questions that follow. Strive for depth, clarity, and accuracy. Also, strive for effective use of sketches, words,
A sphere is immersed in a flowing fluid. The velocity V is doubled. Also, the sphere diameter D is doubled. Figure out how much the drag force increases. Only V and D are changed; all other relevant
Flow over a rectangular plate produces an average wall shear stress of 1.2 pascals. Calculate the friction drag in units of N. The plate dimensions are 1.5 m by 2.0 m. The plate is inclined at 20
Use information in §11.2 and 11.3 to find the coefficient of drag for each case described.a. A sphere is falling through water, and ReD = 10,000.b. Air is blowing normal to a very long circular
Determine whether the following statement is true or false:When an automobile moves through still air, the power to overcome fluid dynamic drag varies as the speed of the automobile cubed.
Water is flowing over a sphere. The Reynolds number based on sphere diameter is 20. The flow is steady. Calculate the coefficient of drag. Choose the closest answer: (a) 0.4 or less, (b)
A cooling tower, used for cooling recirculating water in a modern steam power plant, is 350 ft high and 200 ft average diameter. Estimate the drag on the cooling tower in a 150 mph wind (T = 60°F).
What is the moment at the bottom of a flagpole 20 m high and 20 cm in diameter in a 15 m/s wind? The atmospheric pressure is 100 kPa, and the temperature is 20°C.
Windstorms sometimes blow empty boxcars off their tracks. The dimensions of one type of boxcar are shown. What minimum wind velocity normal to the side of the car would be required to blow the car
Estimate the wind force on a billboard 12 ft high and 36 ft wide when a 60 mph wind (T = 60°F) is blowing normal to it.
If Stokes’s law is considered valid below a Reynolds number of 0.5, what is the largest raindrop that will fall in accordance with Stokes’s law?
What drag is produced when a disk 0.75 m in diameter is submerged in water at 10°C and towed behind a boat at a speed of 4 m/s? Assume orientation of the disk so that maximum drag is produced.
A Ping-Pong ball of mass 2.6 g and diameter 38 mm is supported by an air jet. The air is at a temperature of 18°C and a pressure of 27 in.-Hg. What is the minimum speed of the air jet? Nozzle Air
A semiautomatic popcorn popper is shown. After the unpopped corn is placed in screen S, the fan F blows air past the heating coils C and then past the popcorn. When the corn pops, its projected area
How much power is required to move a spherical-shaped submarine of diameter 1.5 m through seawater at a speed of 10 knots? Assume the submarine is fully submerged.
A car is driving into a headwind. Calculate the power (in kW) that is required to overcome drag. A car is traveling due east at a steady speed of 30 m/s. The coefficient of drag for the car is 0.4
Estimate the additional power (in hp) required for the truck when it is carrying the rectangular sign at a speed of 30 m/s over that required when it is traveling at the same speed but is not
Estimate the added power (in hp) required for the car when the cartop carrier is used and the car is driven at 100 km/h in a 25 km/h headwind over that required when the carrier is not used in the
The resistance to motion of an automobile consists of rolling resistance and aerodynamic drag. The weight of an automobile is 3000 lbf, and it has a frontal area of 20 ft2. The drag coefficient is
A car coasts down a very long hill. The weight of the car is 2000 lbf, and the slope of the grade is 6%. The rolling friction coefficient is 0.01. The frontal area of the car is 18 ft2, and the drag
An automobile with a mass of 1000 kg is driven up a hill where the slope is 3° (5.2% grade). The automobile is moving at 30 m/s. The coefficient of rolling friction is 0.02, the drag coefficient is
A bicyclist is coasting down a hill with a slope of 4° into a headwind (measured with respect to the ground) of 7 m/s. The mass of the cyclist and bicycle is 80 kg, and the coefficient of rolling
A bicyclist is capable of delivering 275 W of power to the wheels. How fast can the bicyclist travel in a 3 m/s headwind if his or her projected area is 0.5 m2, the drag coefficient is 0.3, and the
One way to reduce the drag of a blunt object is to install vanes to suppress the amount of separation. Such a procedure was used on model trucks in a wind tunnel study. For tests on a van-type truck
Suppose you are designing an object to fall through seawater with a terminal velocity of exactly 1 m/s. What variables will have the most influence on the terminal velocity? List these variables and
A sphere is falling in a liquid. Calculate the terminal velocity in units of m/s. The projected area (i.e., reference area) is 10 cm2. The coefficient of drag is 0.4. The mass of the sphere is 70
A grain of pollen is falling at terminal velocity. The fluid is air. Calculate the coefficient of drag. Idealize the pollen grain as a smooth sphere with a diameter of 50 microns. The terminal
Determine the terminal velocity in water (T = 10°C) of an 8-cm ball that weighs 15 N in air.
This cube is weighted so that it will fall with one edge down as shown. The cube weighs 22.2 N in air. What will be its terminal velocity in water? 10 cm
As shown, a 35 cm diameter emergency medicine parachute supporting a mass of 20 g is falling through air (20°C). Assume a coefficient of drag of CD = 2.2, and estimate the terminal velocity V0. Use
Consider a small air bubble (approximately 4 mm diameter) rising in a very tall column of liquid. Will the bubble accelerate or decelerate as it moves upward in the liquid? Will the drag of the
A spherical rock weighs 30 N in air and 5 N in water. Estimate its terminal velocity as it falls in water (20°C).
A sphere 2 cm in diameter rises in oil at a velocity of 1.5 cm/s. What is the specific weight of the sphere if the oil density is 900 kg/m3 and the dynamic viscosity is 0.096 N∙s/m2?
Estimate the terminal velocity of a 1.5 mm plastic sphere in oil. The oil has a specific gravity of 0.95 and a kinematic viscosity of 10–4 m2/s. The plastic has a specific gravity of 1.07. The
What is the terminal velocity of a 0.5 cm hailstone in air that has an atmospheric pressure of 96 kPa absolute and a temperature of 0°C? Assume that the hailstone has a specific weight of 6 kN/m3.
A drag chute is used to decelerate an airplane after touchdown. The chute has a diameter of 12ft and is deployed when the aircraft is moving at 200 ft/s. The mass of the aircraft is 20,000 lbm, and
If a balloon weighs 0.10 N (empty) and is inflated with helium to a diameter of 60 cm, what will be its terminal velocity in air (standard atmospheric conditions)? The helium is at a pressure of 1
A 2 cm plastic ball with a specific gravity of 1.2 is released from rest in water at 20°C. Find the time and distance needed to achieve 99% of the terminal velocity. Write out the equation of motion
Using §11.8 and other resources, answer the following questions. Strive for depth, clarity, and accuracy. Also, use effective sketches, words, and equations.a. What is circulation? Why is it
The baseball is thrown from west to east with a spin about its vertical axis as shown. Under these conditions it will “break” toward the (a) North,(b) South, or (c) Neither. East Plan
A sphere of diameter 100 mm, rotating at a rate of 286 rpm, is situated in a stream of water (15°C) that has a velocity of 1.5 m/s. Determine the lift force (in newtons) on the rotating sphere.

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