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Spying from below

The periscope of a submarine is mounted on a vertical, cylindrical tube, with a diameter of 120 mm and a height of 4 m. The submarine is moving horizontally with a constant speed of 10 km/hr. Assume the salt water specific gravity to be 1.03 and its kinematic viscosity to be 1.25×10-6 m2/s.
a) Determine the total force and the total moment on the tube, when the tube is i) fully submerged, ii) fully exposed to the air, and iii) partly submerged; plot the force and moment vs. the submersion depth.
b) For the cases i) and ii) only above, determine the frequency of vortex shedding from the tube.


Contributed by Stavros Tavoularis, Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada. U.S. Navy imagery used in illustration without endorsement expressed or implied.

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