Show that the kinematic viscosity has the primary dimensions of L2T-1.
Solution:
The kinematic viscosity is defined as the ratio of the dynamic
... [Show More] viscosity by the density of the fluid.
The density has units of mass (kg) divided by volume (m3); whereas the dynamic viscosity has the units
of mass (kg) per meter (m) per time (s).
Hence:
1.2 In a fluid the velocity measured at a distance of 75mm from the boundary is 1.125m/s. The fluid
has absolute viscosity 0.048 Pa s and relative density 0.913. What is the velocity gradient and
shear stress at the boundary assuming a linear velocity distribution? Determine its kinematic
viscosity.
[Ans: 15 s-1, 0.72Pa.s; 5.257x10-5 m2/s]
Solution:
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Engineering Fluid Mechanics Solution Manual
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Chapter One Tutorial Problems
1.3 A dead-weight tester is used to calibrate a pressure transducer by the use of known weights
placed on a piston hence pressurizing the hydraulic oil contained. If the diameter of the piston
is 10 mm, determine the required weight to create a pressure of 2 bars.
[Ans: 1.6 kg]
Solution:
(a) P = F/A
Hence the weight = P x A / g
= 2 x 105 x7.854x10-5 / 9.81
= 1.60 kg
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Engineering Fluid Mechanics Solution Manual
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Chapter One Tutorial Problems
1.4 How deep can a diver descend in ocean water without damaging his watch, which will withstand
an absolute pressure of 5.5 bar?
Take the density of ocean water, r = 1025 kg/m3.
[Ans: 44.75 m]
Solution:
Use the static equation:
Hence the depth can be calculated as:
1.5 The U-tube manometer shown below, prove that the difference in pressure is given by:
−
=
+
2
1 2 2 . . 1
D
P P ρ g z d
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Engineering Fluid Mechanics Solution Manual
9
Chapter One Tutorial Problems
Solution:
The relationship between liquid columns and the area of cross section is based on the conservation of
matter, ie continuity equation, hence:
volume 1 = volume 2
For the “U” tube manometer that the height different in the two columns gives the pressure difference,
therefore:
hence
Clearly if D is very much larger than d then (d/D)2 is very small so
1.6 A flat circular plate, 1.25 m diameter is immersed in sewage water (density 1200 kg/m3) such
that its greatest and least depths are 1.50 m and 0.60 m respectively. Determine the force exerted
on one face by the water pressure [Show Less]