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Structures and Safety Reliability

Experimental Investigation of the Hydrodynamic Coefficients of a Remotely Operated Vehicle Using a Planar Motion Mechanism

[+] Author and Article Information
Juan Julca Avila1

 Federal University of ABC, Rua Santa Adélia, 166, 09210-170, Santo André, SP, Braziljuan.avila@ufabc.edu.br

Kazuo Nishimoto

Department of Naval Architecture and Ocean Engineering,  University of São Paulo, Av. Prof. Mello Moraes, 2231, 05508-900, São Paulo, SP, Brazilknishimo@usp.br

Claudio Mueller Sampaio

Department of Naval Architecture and Ocean Engineering,  University of São Paulo, Av. Prof. Mello Moraes, 2231, 05508-900, São Paulo, SP, Brazilclasamp@usp.br

Julio C. Adamowski

Department of Mechatronics Engineering,  University of São Paulo, Av. Prof. Mello Moraes, 2231, 05508-900 São Paulo, SP, Braziljcadamow@usp.br

1

Corresponding author.

J. Offshore Mech. Arct. Eng 134(2), 021601 (Dec 02, 2011) (6 pages) doi:10.1115/1.4004952 History: Received July 02, 2009; Revised April 18, 2010; Published December 02, 2011; Online December 02, 2011

The determination of hydrodynamic coefficients of full scale underwater vehicles using system identification (SI) is an extremely powerful technique. The procedure is based on experimental runs and on the analysis of on-board sensors and thrusters signals. The technique is cost effective and it has high repeatability; however, for open-frame underwater vehicles, it lacks accuracy due to the sensors’ noise and the poor modeling of thruster-hull and thruster-thruster interaction effects. In this work, forced oscillation tests were undertaken with a full scale open-frame underwater vehicle. These conducted tests are unique in the sense that there are not many examples in the literature taking advantage of a PMM installation for testing a prototype and; consequently, allowing the comparison between the experimental results and the ones estimated by parameter identification. The Morison’s equation inertia and drag coefficients were estimated with two parameter identification methods, that is, the weighted and the ordinary least-squares procedures. It was verified that the in-line force estimated from Morison’s equation agrees well with the measured one except in the region around the motion inversion points. On the other hand, the error analysis showed that the ordinary least-squares provided better accuracy and, therefore, was used to evaluate the ratio between inertia and drag forces for a range of Keulegan–Carpenter and Reynolds numbers. It was concluded that, although both experimental and estimation techniques proved to be powerful tools for evaluation of an open-frame underwater vehicle’s hydrodynamic coefficients, the research provided a rich amount of reference data for comparison with reduced models as well as for dynamic motion simulation of ROVs.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

LAURS general layout

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Figure 2

The planar motion mechanism and the experimental setup. The picture shows the LAURS during the tests in sway.

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Figure 3

Forced oscillation experimental results for amplitude of 400 mm and period of 8 s: (a) force and (b) position

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Figure 4

Forced oscillation test: experimental measured force (filtered) and in-line force

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Figure 5

Comparison of the measured and the Morison’s equation calculated in-line forces for the 400 mm amplitude and 8 s period test condition

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Figure 6

Drag, inertia and Morison’s equation forces for the 400 mm and 8 s test case

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Figure 7

(Top) Variation of the drag to inertia force ratio and (bottom) prediction error of the peaks of force

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Figure 8

Mean absolute error obtained by fitting the Morison’s equation to the experimental data

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Figure 9

Drag coefficient for the LAURS in different Keulegan–Carpenter and Reynolds numbers. Motion direction: surge.

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Figure 10

Inertia coefficient for the LAURS in different Keulegan–Carpenter and Reynolds numbers. Motion direction: surge

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