The 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.

The 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.

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 5.13P: 5.13 The torque due to the frictional resistance of the oil film between a rotating shaft and its...

See similar textbooks

Similar questions

When a sphere falls freely through a homogeneous fluid, it reaches a terminal velocity at which the weight of the sphere is balanced by the buoyant force and the frictional resistance of the fluid. Make a dimensional analysis of this problem and indicate how experimental data for this problem could be correlated. Neglect compressibility effects and the influence of surface roughness.
We want to predict the drag force on a remote-control airplane as it flies through air having a density of 1.21 kg/m³ and a viscosity of 1.76x10- Pa-s. The airplane's fuselage has a diameter of 200 mm and the airplane will fly through air at a speed of 32 m/s. A model of the airplane's fuselage will be tested in a pressurized wind tunnel. The diameter of the model is 75 mm and the density and viscosity of the air in the wind tunnel are 3.00 kg/m³ and 1.82× 10-5 Pa-s, respectively. a) The diameter of the airplane's fuselage will be used to define the Reynolds number Re, for the flow around the fuselage. Compute the Reynolds number for the flow around the airplane's fuselage (answer: Re, = 4.40x 10'). b) Find the speed of the air that should be used to test a model of the fuselage in the wind tunnel to correctly model dynamic conditions (answer: 35.6 m/s). c) The model is tested in the wind tunnel at four speeds that bracket the speed computed above. The measured drag forces on the…
The drag force acting on a model torpedo, 1/20 the size of the prototype, is measured at 80 N in water with density of 988 kg/m³, and kinematic viscosity of 0.56 × 10-6 m² /s. The prototype's speed is 15 m/s in sea water with density of is 1010 kg/m³, and kinematic viscosity of 1.3 x 10-6 m² /s. Determine the drag force acting on the prototype. 2
By dimensional analysis, obtain an expression for the drag force (F) on a partially submerged body moving with a relative velocity (u) in a fluid; the other variables being the linear dimension (L), surface roughness (e), fluid density (p), and gravitational acceleration (g).
A student needs to measure the drag on a prototype of characteristic length d, moving at velocity U, in air at sea-level conditions. She constructs a model of characteristic length dm such that the ratio d,/dm drag under dynamically similar conditions in sea-level air. The student claims that the drag force on the prototype will be = a factor f. She then measures the model identical to that of the model. Is her claim correct? Explain, showing your work (no credit for just guessing).
A fighter aircraft is to operate at 200 m/s in air at standard conditions ( = 1.2 kg/m3). Amodel is constructed to 1/20 scale (length ratio) and tested in a wind tunnel at the sameair temperature (same air viscosity) to determine the drag force. The drag force FD is afunction of the air density  and viscosity , the velocity V and the cross section length ofthe airplane D.
Ex. The force required to tow a 1:30scale model of a motor boat in a lake at a speed of 2m/s is 0.5 N, Assuming that the viscosity resistance due to water and air is negligible in comparison with the wave resistance, calculate the corresponding speed of the prototype for dynamically similar conditions. What would be the force required to propel the prptype at that velocity in the same lake? Ans.: 10.95m/s, 13500N
using 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 prototype
A liquid of density ? and viscosity ? flows by gravity through a hole of diameter d in the bottom of a tank of diameter DFig. . At the start of the experiment, the liquid surface is at height h above the bottom of the tank, as sketched. The liquid exits the tank as a jet with average velocity V straight down as also sketched. Using dimensional analysis, generate a dimensionless relationship for V as a function of the other parameters in the problem. Identify any established nondimensional parameters that appear in your result. (Hint: There are three length scales in this problem. For consistency, choose h as your length scale.) except for a different dependent parameter, namely, the time required to empty the tank tempty. Generate a dimensionless relationship for tempty as a function of the following independent parameters: hole diameter d, tank diameter D, density ? , viscosity ? , initial liquid surface height h, and gravitational acceleration g.
Mott ." cometer, which we can analyze later in Chap. 7. A small ball of diameter D and density p, falls through a tube of test liquid (p. µ). The fall velocity V is calculated by the time to fall a measured distance. The formula for calculating the viscosity of the fluid is discusses a simple falling-ball vis- (Po – p)gD² 18 V This result is limited by the requirement that the Reynolds number (pVD/u) be less than 1.0. Suppose a steel ball (SG = 7.87) of diameter 2.2 mm falls in SAE 25W oil (SG = 0.88) at 20°C. The measured fall velocity is 8.4 cm/s. (a) What is the viscosity of the oil, in kg/m-s? (b) Is the Reynolds num- ber small enough for a valid estimate?
The drag of a sonar transducer is to be predicted, based on wind (Air) tunnel test data. The prototype is 1.5 m diameter sphere, is to be towed at 4.3 m/s in seawater. The model is 0.2 m diameter. Take: Air density = 1.2 kg/m, Air dynamic viscosity = 1.81 x 10$ Pa. s, seawater density = 1000 kg/m, seawater dynamic viscosity 1.813x 10 Pa s, If the drag of the model at these test conditions is 9.5 N, estimate the drag of the prototype in (N).
A ship 350 m long moves in sea water whose density is 1030 kg/m3 . A 1:120 model of this ship is to be tested in a wind tunnel. The velocity of the wind tunnel around the model is 35 m/s and the resistance of the model is 65 N. Determine the velocity and also the resistance of the ship in sea water. The density of air is given as 1.24 kg/m3 . Take the kinematic viscosity of air and sea water as 0.012 stokes and 0.018 stokes respectively.