Unidirectional periodic flow about circular cylinders.
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Authors
Greenamyer, Richard Doyle
Subjects
Advisors
Date of Issue
1973-06
Date
June 1973
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
The instantaneous force acting on a circular cylinder
immersed in a unidirectional periodic flow characterized by
U = V + VA sin 2π ft was investigated. The total force was
divided into three components consisting of a steady-state
drag; an oscillating drag which is a function of the
frequency parameter λ = fd/V ; and an inertial force v;hich
is also a function of the frequency parameter. The three
resistance coefficients associated with the force components,
CD (0), CD(λ), and CM (λ) were calculated. It was found that the resistance coefficients are not
materially affected by the free-stream oscillations whenever
the frequency of the oscillation is lower than the natural
frequency of the vortex shedding. However, when λ approaches
the Strouhal frequency of vortex shedding, the inertia
coefficient CM is significantly reduced, and likewise when λ approaches the value of twice the Strouhal number, CD (λ) is markedly reduced. In regions below this range, the
inertial force becomes negligible and the total resistance
could be represented accurately by the coefficients DC (0) and CD (λ) with CM fixed at its theoretical unseparated-flow value, 2.0.
Type
Thesis
Description
Series/Report No
Department
Mechanical Engineering
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Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.