Fluid Mechanics: Fundamentals and Applications
4th Edition
ISBN: 9781259696534
Author: Yunus A. Cengel Dr., John M. Cimbala
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 11, Problem 31P
A submarine can be treated as an ellipsoid with a diameter of 5 m and a length of 25 m. Determine the power required for this submarine to cruise horizontally and steadily at 40 km/h in seawater whose density is 102$ kg/m3. Also determine the power required to tow this submarine in air whose density is 1.30 kg/m3. Assume the flow is turbulent in both cases.
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A submarine can be treated as an ellipsoid with a diameter of 5 m and a length of 25 m. Determine the power required for this submarine to cruise horizontally and steadily at 40 km/h in seawater whose density is 1025 kg/m3. Also determine the power required to tow this submarine in air whose density is 1.30 kg/m3. Assume the flow is turbulent in both cases.
Throughout, take the acceleration due to gravity to be 10 m/s? and water to have density of 1000 kg/m³.
Question 1
A large block of mass 1100 kg is towed at a constant speed UB up an inclined plane at 6° to the
horizontal, as shown in Fig. 1. The towing force applied on the block has magnitude 1165 N. The
block slides over an oil film with a constant thickness of 3 mm. The oil has density 900 kg/m and
dynamic viscosity 0.1 Pa.s. The area of the block in contact with the oil is 15 m2.
UB
F=1165 N
m=1100 kg
oil film
3 mm
contact area: 15 m²
6°
Figure 1
(i) Sketch, with appropriate labels, the forces acting on the block in the direction parallel to the
inclined plane.
(ii) Determine the magnitude of the drag force acting on the bottom surface of the block.
(iii) Assuming a laminar velocity profile in the oil film, determine the speed of the block Ug.
(iv) Verify that the flow of oil is laminar as assumed in (iii).
(v) Determine the power requirement to tow the block.
(vi) To reduce the…
A 3-m-long water taxi is floating in 1-m deep water on two lateral wings with the
velocity of 30 m/s. Determine the power, if the roughness height & of the wing
kg
surfaces is 0.1 mm. (F = 1000 =1.02 x10
m
Chapter 11 Solutions
Fluid Mechanics: Fundamentals and Applications
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