2- The aerodynamic drag of a new sports truck is to be predicted at a speed of 50.0 km/h at an air temperature of 25°C. Automotive engineers build a one-sixth scale model of the car to test in a wind tunnel. It is winter and the wind tunnel is located in an unheated building; the temperature of the wind tunnel air is only about 10°C. Determine how fast the engineers should run the wind tunnel in order to achieve similarity between the model and the prototype, if the drag sensor read 80 N fine the drag force exerted on prototype. Properties for air at atmospheric pressure and T= 25 °C, p=1.184kg/cm3 and p=1.849*10^-5kg/m.s, similarity at T=10 °C, p=1.22 kg/cm3 and p=1.792*10^-5kg/m.s. Wind tunnel test section Model FD Moving belt Drag balance

2- The aerodynamic drag of a new sports truck is to be predicted at a speed of 50.0 km/h at an air temperature of 25°C. Automotive engineers build a one-sixth scale model of the car to test in a wind tunnel. It is winter and the wind tunnel is located in an unheated building; the temperature of the wind tunnel air is only about 10°C. Determine how fast the engineers should run the wind tunnel in order to achieve similarity between the model and the prototype, if the drag sensor read 80 N fine the drag force exerted on prototype. Properties for air at atmospheric pressure and T= 25 °C, p=1.184kg/cm3 and p=1.84910^-5kg/m.s, similarity at T=10 °C, p=1.22 kg/cm3 and p=1.79210^-5kg/m.s. Wind tunnel test section Model FD Moving belt Drag balance

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.70P

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A wind tunnel is being used to study the aerodynamics of a full-scale model rocket that is 30 cm long. Scaling for drag calculations are based on the Reynolds number. The rocket hasan expected maximum velocity of 190 km/h. What is the Reynolds number at this speed? Assume ambient air is at 20°C. The wind tunnel is capable of speeds up to 160 km/h; so an attempt is made to improve this top speed by varying the air temperature. Calculate the equivalent speed for the wind tunnel using air at 5°C and 65°C. Would replacing air with carbon dioxide provide higher equivalent speeds?
Problem 3: Let's say you want to predict the aerodynamic drag of a new car based on the use of a model that is one- fifth scale of the actual car/prototype car. We want to predict the drag of the car when it has wind velocity 75 miles/hour with an air temperature of 40°C. The model is placed in a wind tunnel at 10°C. Determine the wind tunnel velocity necessary to achieve similarity between the model and the prototype.
A student needs to measure the drag on a prototype of characteristicdimension d p moving at velocity U p in air at standardatmospheric conditions. He constructs a model ofcharacteristic dimension d m , such that the ratio d p / d m issome factor f . He then measures the drag on the model atdynamically similar conditions (also with air at standardatmospheric conditions). The student claims that the dragforce on the prototype will be identical to that measured onthe model. Is this claim correct? Explain.
(COLLAB) Simulate projectile motion with air resistance in PhysLab. A shuttlecock is launched from the ground with an initial speed of 36.9688 m/s at an angle of 6.8583 degrees with respect to the horizontal. The shuttlecock experiences air resistance with a drag coefficient of 0.1931 in an environment where the air density is 0.9453 kg/m3. If the shuttlecock has a radius of 3.4 cm and a mass of 5.2 grams, what is the maximum height reached by the shuttlecock? Assume that the experiment is done near the surface of the earth (initHeight = 0) .
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You are designing an airfoil for a new hobby RC plane. Because of your limited knowledge, you have mistakenly approximated your airfoil as an ellipse with a = 75mm and b = 12mm. Here, “a” is the depth of your wing and “b” is the thickness. Your plane travels through the air at approximately 20mph (8.9m/s). As it does so, skin friction produces a drag-induced heat of 800W on your wind, of length 1m. Properties of Air: k = 0.025 W/mK, Pr = 0.72, v = 1.847 x 10−5, u = 16.84 x 10−6, p = 1.2 kg/m3, B = 1/Tf (ideal gas), TInfinity = 25oC a) What is the Reynold’s number? Hint: “D” is taken to be the thickness for an elliptical crosssection. b) What is the Nusselt number? c) What is the convection coefficient? d) What is the average temperature of your wing? Assume an ellipse perimeter of approximately 200mm.
with the gravitational force is V - mgr12Rg. straight through the earth between points on the surface, trains travels from the North Pole to a point on the equator. Determine using magnetically levitated trains.) Suppose that such a train namic drag could be minimized by evacuating the tunnels and celeration and deceleration. (The effects of friction and aerody- 26.158 It has been pointed out that if tunnels could be drilled could travel between those points using gravitational force for ac- equator and (b) when it is halfway from the North Pole to the the magnitude of the velocity of the train (a) when it arrives at the equator. The radius of the earth is Re = 3960 mi. quator and (b) when it is halfway from the North Pole to the equator. The radius of the earth is RE 3960 mi.
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If a missile takes off vertically from sea level and leavesthe atmosphere, it has zero drag when it starts and zerodrag when it finishes. It follows that the drag must be amaximum somewhere in between. To simplify the analysis,assume a constant drag coefficient, CD, and constant verticalacceleration, a. Let the density variation be modeled by thetroposphere relation. Find an expression for thealtitude z* where the drag is a maximum. Comment onyour result.
A 1:20 scale down model of a hydrofoil is tested in a water channel, at velocity of 0.179 m/s. At this velocity, a drag force of 2.2 N is measured. Determine the drag force of the original hydrofoil, at velocity of 0.8 m/s.
A student wants to estimate drag force on a golf ball of diameter D moving in air at a speed of U at atmospheric conditions. The student has access to a wind-tunnel and develops a replica of the ball that is 5 times smaller in diameter sets the wind speed 5 times larger than the actual golf ball. Compared to the force on the replica, the estimated drag force on the actual golf ball will be