Fluid Force Analysis and Accelerating Sphere Tests

by Wallis S. Hamilton, (M.ASCE), Prof.; Dept. of Civ. Engrg., Northwestern Univ., Evanston, IL,
James E. Lindell, Asst. Prof.; Dept. of Civ. Engrg., Univ. of Notre Dame, Notre Dame, IN,


Serial Information: Journal of the Hydraulics Division, 1971, Vol. 97, Issue 6, Pg. 805-817


Document Type: Journal Paper

Abstract: An adequate expression for the fluid force on an accelerating body depends on whether the history of motion is repetitive. The conventional form for periodic motion consists of the sum of a velocity and an acceleration term. When the motion is not repetitive, the equation in the paper is inadequate and some form of history term must be added. The history term is logically zero immediately after acceleration from rest or from constant velocity. In the latter case, Cv may be chosen as the steady-state resistance coefficient and CM evaluated experimentally. The writers towed spheres vertically in a tank of water, released them suddenly, and measured the acceleration with a telemetry system. The added mass coefficients 5 ms after release agreed substantially with the inviscid coefficient of 0.50. The Reynolds number at release varied from zero to 35,000.

Subject Headings: History | Motion (dynamics) | Spheres | Water tanks | Equations of motion | Steady states | Load and resistance factor design | Reynolds number

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