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 1.76x 10-5 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 1.82x 10- 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 10³). 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 fuselage's model at these four speeds are (1) 1.62 N at 27.2 m/s, (2) 2.29 N at 32.4 m/s, and (3) 3.08 N at 37.5 m/s, and (4) 3.97 N at 42.7 m/s. The frontal area of the airplane's fuselage will be used to define the drag coefficient C, for the fuselage. Compute Re, and C, for the fuselage at each tested flow condition.
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 1.76x 10-5 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 1.82x 10- 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 10³). 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 fuselage's model at these four speeds are (1) 1.62 N at 27.2 m/s, (2) 2.29 N at 32.4 m/s, and (3) 3.08 N at 37.5 m/s, and (4) 3.97 N at 42.7 m/s. The frontal area of the airplane's fuselage will be used to define the drag coefficient C, for the fuselage. Compute Re, and C, for the fuselage at each tested flow condition.
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
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Chapter5: Analysis Of Convection Heat Transfer
Section: Chapter Questions
Problem 5.9P: When a sphere falls freely through a homogeneous fluid, it reaches a terminal velocity at which the...
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Transcribed Image Text: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 fuselage's model at these four
speeds are (1) 1.62 N at 27.2 m/s, (2) 2.29 N at 32.4 m/s, and (3) 3.08 N at 37.5
m/s, and (4) 3.97 N at 42.7 m/s. The frontal area of the airplane's fuselage will be
used to define the drag coefficient C, for the fuselage. Compute Re, and C, for
D
the fuselage at each tested flow condition.
d) The Reynolds number range in part (c) spans the range where the remote-control
airplane's fuselage will be operated. Use the results of (c) to predict a value for
the fuselage's C, in the Reynolds number region where the remote-control
airplane will be operated.
e) Find the expected drag force on the 200-mm diameter remote-control airplane's
fuselage as it flies through the 1.21 kg/m³ air at 32 m/s (answer: 6.42 N).
D= 200 mm
V= 32 m/s
p= 1.21 kg/m³
µ = 1.76×10-5 Pa-s
FDRAG = ?
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