Measurement of hydrodynamic forces and moments and flow field mapping of a model in coning motion
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Authors
Eccles, Thomas John
Subjects
Advisors
Date of Issue
1990
Date
Jun-90
Publisher
Monterey California. Naval Postgraduate School
Language
en_US
Abstract
A method of captive model testing using an axisymmetric marine vehicle model in steady motion with constant roll and yaw rates has been used experimentally to obtain functional relationships between certain motion parameters and the resultant hydrodynamic forces and moments on the body. Specifically, cross coupling terms in roll rate and yaw rate have been investigated for non-planar cross-flow. An instrumented slender body of revolution with length/diameter of 9.5 was tested at Reynolds number of about 5 million, based ol length. The tests were conducted at free streani velocity of 25 ft/s for coning angles between zero and -20j in 2Zincrements, at rotation rates of up to 200 rpm in 12.5 rpm increments in both rotational directions. The character of force and moment terms varying with rotation rate and coning angle was determined. The results may be translated to functional relationships between the hydrodynamic coefficients and the angular velocities in roll and yaw. The data showed a transition in the forms of the sway force and the pitch moment after the coning angle exceeded -10*, due to body lift in the cross flow. A method for measuring the velocity field about the model using laser doppler velocimetry has been developed. The flow field was mapped for two model coning angles at one moderate rotation rate. The flow field representation portrays perturbations in cross flow velocity at five sections in a body-fixed reference frame. This method is useful in understanding the vortex mechanisms at work to influence body forces and moments. The data showed formation of asynnetric body vortices after the coning angle exceeded -10".
Type
Thesis
Description
CIVINS (Civilian Institutions) Thesis document
Series/Report No
Department
Mechanical Engineering
Organization
Identifiers
NPS Report Number
Sponsors
Funder
U.S. Naval Postgraduate School, CIVINS program
Format
Citation
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.