On the Added Mass of a Sphere in a Circular Cylinder Considering Real Fluid Effects

Author: Mellsen, Stanley Brun

Year: 1966

Degree: Engineer's thesis

Advisors: Ellis, Albert T.; Acosta, Allan J.

Committee Member: Unknown, Unknown

Option: Mechanical Engineering

DOI: 10.7907/63N8-1N50

Abstract

An experimental method combined with boundary layer theory is given for evaluating the added mass of a sphere moving along the axis of a circular cylinder filled with water or oil. The real fluid effects are separated from ideal fluid effects.

The experimental method consists essentially of a magnetic steel sphere propelled from rest by an electromagnetic coil in which the current is accurately controlled so that it only supplies force for a short time interval which is within the laminar flow regime of the fluid. The motion of the sphere as a function of time is recorded on single frame photographs using a short-arc multiple flash lamp with accurately controlled time intervals between flashes.

A concept of the effect of boundary layer displacement on the fluid flow around a sphere is introduced to evaluate the real fluid effects on the added mass. Surprisingly accurate agreement between experiment and theory is achieved.

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