The flow about a 150 mm artillery projectile which travels at 600 m/s through still air at 30°C and absolute pressure 101.4 kPa is to be modeled in a high-speed wind tunnel with a 1:6 model. If the wind tunnel air has a temperature of −18°C and absolute pressure of 68.9 kPa, what velocity is required? If the drag force on the model is 35 N, what is the drag force on the prototype if skin friction may be neglected?
Want to see the full answer?
Check out a sample textbook solutionChapter 7 Solutions
Fox and McDonald's Introduction to Fluid Mechanics
Additional Engineering Textbook Solutions
Fundamentals Of Thermodynamics
Automotive Technology: Principles, Diagnosis, and Service (5th Edition)
Automotive Technology: Principles, Diagnosis, And Service (6th Edition) (halderman Automotive Series)
Heating Ventilating and Air Conditioning: Analysis and Design
INTERNATIONAL EDITION---Engineering Mechanics: Statics, 14th edition (SI unit)
Thinking Like an Engineer: An Active Learning Approach (3rd Edition)
- A wind tunnel is used to measure the pressure distribution in the airflow over an airplane model. The air speed in the wind tunnel is low enough that compressible effects are negligible. The Bernoulli equation approximation is valid in such a flow situation everywhere except very close to the body surface or wind tunnel wall surfaces and in the wake region behind the model. Far away from the model, the air flows at speed V∞ and pressure P∞, and the air density ? is approximately constant. Gravitational effects are generally negligible in airflows, so we write the Bernoulli equation asP + 1/2 ρV2 = P∞ + 1/2 ρV2∞ Nondimensionalize the equation, and generate an expression for the pressure coefficient Cp at any point in the flow where the Bernoulli equation is valid. Cp is defined as Cp = P−P∞/1/2ρV2arrow_forwardA 1:7 scale model simulates the operation of alarge turbine that is to generate 200 kW with a flowrate of 1.5 m3/s.What flow rate should be used inthe model, and what power output is expected?(a) Water at the same temperature is used in bothmodel and prototype.(b) The model water is at 25°C and the prototypewater is at 10°C.arrow_forwardThe drag force on a submarine, which is moving on the surface, is to be determined by a test on a model which is scaled down to one-twentieth of the prototype. The test is to be carried in a towing tank, where the model submarine is moved along a channel of liquid. The density and the kinematic viscosity of the seawater are 1010 kg/m³ and 1.3x10-6 m 2/s, respectively. The speed of the prototype is 2.6 m/s. Assume that F = f(V, L. g. p.), using pi-theorem and similarity principle to: a) Determine the speed at which the model should be moved in the towing tank. b) Determine the kinematic viscosity of the liquid that should be used in the towing tank.arrow_forward
- An airplane wing, with chord length of 1.5 m and span of 9 m, is designed to move through standard air (v= 1.51x105 m²/s) at a speed of 7.5 m/s. A 1/10-scale model of this wing is to be tested in a water tunnel (v= 1.00×106 m²/s). If viscous effects govern, what speed is necessary in the water tunnel to achieve dynamic similarity? a.11.33 m/s b.4.97 m/s c.1.51 m/s d.2.98 m/sarrow_forwardusing pure water at 20°C. The velocity of the prototype in seawater (p = A 1/18 scale model of the submarine is to be tested in the water tunnel 1015 kg/m³, v = 1.4x106 m²/s) is 3 m/s. Determine: a) the speed of the water in the water tunnel for dynamic similarity D) the ratio of the drag force on the model to the drag force on the prototypearrow_forwardi need the answer quicklyarrow_forward
- (a) A model low speed centrifugal compressor (a “blower") runs at 430 rpm and delivers 10 m/s of air against a pressure head of 60 mm of water. If the pump efficiency is estimated to be 80%, how much power is required to drive the compressor? (b) A geometrically similar compressor is made with a diameter 1.8 times the size of the model and is required to work against a pressure head of 80 mm of water. Determine the operating speed and the power needed to drive the compressor assuming dynamically similar condi- tions apply.arrow_forwardThe aerodynamic drag of a new sports car is to be predicted at a speed of 60.0 mi/h at an air temperature of 25°C. Automotive engineers build a one-third scale model of the car to test in a wind tunnel. The temperature of the wind tunnel air is also 25°C. The drag force is measured with a drag balance, and the moving belt is used to simulate the moving ground (from the car’s frame of reference). Determine how fast the engineers should run the wind tunnel to achieve similarity between the model and the prototype.arrow_forwardThe aerodynamic drag of a new sports car is to be predicted at a speed of 60.0 mi/h at an air temperature of 25°C. Automotive engineers build a one-third scale model of the car to test in a wind tunnel. The temperature of the wind tunnel air is also 25°C. The drag force is measured with a drag balance, and the moving belt is used to simulate the moving ground (from the car’s frame of reference). Determine how fast the engineers should run the wind tunnel to achieve similarity between the model and the prototype.arrow_forward
- An automobile has a characteristic length and area of 8 ft and 60 ft2, respectively. When tested in sea-level standard air, it has measured velocities of 20, 40, and 60 mi/h and drag forces of 31, 115, and 249 lbf, respectively. The same car travels in Colorado at 115 mi/h at an altitude of 3500 m. Using dimensional analysis, estimate its drag force (in lbf). Using dimensional analysis, estimate the horsepower required to overcome air drag (in hp)arrow_forwardA student team is to design a human-powered submarine for a design competition. The overall length of the prototype submarine is 95 (m), and its student designers hope that it can travel fully submerged through water at 0.440 m/s. The water is freshwater (a lake) at T = 15°C. The design team builds a one-fifth scale model to test in their university’s wind tunnel. A shield surrounds the drag balance strut so that the aerodynamic drag of the strut itself does not influence the measured drag. The air in the wind tunnel is at 25°C and at one standard atmosphere pressure. At what air speed do they need to run the wind tunnel in order to achievesimilarity?arrow_forwardA 1:30 scale model of a cavitating overflow structure is to be tested in a vacuum tank wherein the pressure is maintained at 140 kPa. The prototype liquid is water at 20°C. The barometric pressure on the prototype is 100 kPa. If the liquid to be used in the model has an absolute vapor pressure of 10.0 kPa, what values of density, viscosity, and surface tension must it have for complete dynamic similarity between model and prototype?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning