A massless, circular disk of radius a is initially separated from a flat surface by a thin layer of a viscous fluid by a gap of h, h<< a. Both surfaces are highly polished and smooth. (a) Calculate the pressure distribution and the force required to lift the disk off of the solid surface at a constant velocity V, in terms of µ, V, h, and a. (b) E. 11.. if

Elements Of Electromagnetics
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Author:Sadiku, Matthew N. O.
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A massless, circular disk of radius a is initially separated from a flat surface by a thin layer of a
viscous fluid by a gap of h, h<< a. Both surfaces are highly polished and smooth.
(a) Calculate the pressure distribution and the force required to lift the disk off of the solid
surface at a constant velocity V, in terms of u, V, h, and a.
(b) Evaluate the force numerically if a = 3 cm, V 5 m/s, h 1 mm, and the fluid is water.
(Not for credit) What would happen if the gap height were smaller, say 10 um?
(c) How would the required force change if the disk were no longer flat, but (i) concave downward
or (ii) concave upward? You do not need to provide exact expressions, just give qualitative
answers (but justify them!).
Transcribed Image Text:A massless, circular disk of radius a is initially separated from a flat surface by a thin layer of a viscous fluid by a gap of h, h<< a. Both surfaces are highly polished and smooth. (a) Calculate the pressure distribution and the force required to lift the disk off of the solid surface at a constant velocity V, in terms of u, V, h, and a. (b) Evaluate the force numerically if a = 3 cm, V 5 m/s, h 1 mm, and the fluid is water. (Not for credit) What would happen if the gap height were smaller, say 10 um? (c) How would the required force change if the disk were no longer flat, but (i) concave downward or (ii) concave upward? You do not need to provide exact expressions, just give qualitative answers (but justify them!).
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