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Research Papers: Flows in Complex Systems

Computational Towing Tank Procedures for Single Run Curves of Resistance and Propulsion

[+] Author and Article Information
Tao Xing

IIHR-Hydroscience and Engineering, C. Maxwell Stanley Hydraulics Laboratory, The University of Iowa, Iowa City, IA 52242-1585tao-xing@uiowa.edu

Pablo Carrica

IIHR-Hydroscience and Engineering, C. Maxwell Stanley Hydraulics Laboratory, The University of Iowa, Iowa City, IA 52242-1585pablo-carrica@uiowa.edu

Frederick Stern

IIHR-Hydroscience and Engineering, C. Maxwell Stanley Hydraulics Laboratory, The University of Iowa, Iowa City, IA 52242-1585frederick-stern@uiowa.edu

J. Fluids Eng 130(10), 101102 (Sep 08, 2008) (14 pages) doi:10.1115/1.2969649 History: Received January 22, 2008; Revised June 08, 2008; Published September 08, 2008

A procedure is proposed to perform ship hydrodynamics computations for a wide range of velocities in a single run, herein called the computational towing tank. The method is based on solving the fluid flow equations using an inertial earth-fixed reference frame, and ramping up the ship speed slowly such that the time derivatives become negligible and the local solution corresponds to a quasi steady-state. The procedure is used for the computation of resistance and propulsion curves, in both cases allowing for dynamic calculation of the sinkage and trim. Computational tests are performed for the Athena R/V model DTMB 5365, in both bare hull with skeg and fully appended configurations, including two speed ramps and extensive comparison with experimental data. Comparison is also performed against steady-state points, demonstrating that the quasisteady solutions obtained match well the single-velocity computations. A verification study using seven systematically refined grids was performed for one Froude number, and grid convergence for resistance coefficient, sinkage, and trim were analyzed. The verification study concluded that finer grids are needed to reach the asymptotic range, though validation was achieved for resistance coefficient and sinkage but not for trim. Overall results prove that for medium and high Froude numbers the computational towing tank is an efficient and accurate tool to predict curves of resistance and propulsion for ship flows using a single run. The procedure is not possible or highly difficult using a physical towing tank suggesting a potential of using the computational towing tank to aid the design process.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Definition of absolute inertial earth-fixed coordinates (X,Y,Z) and noninertial ship-fixed coordinates (x,y,z)

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Figure 2

Solution strategy using absolute inertial earth-fixed coordinates

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Figure 3

The change of Fr to cover one ship length as a function of Fr

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Figure 4

Simulation domain, grids, and boundary conditions for Athena bare hull with skeg

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Figure 5

Grid design for a fully appended Athena

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Figure 6

Verification for resistance coefficients and motions for Athena bare hull with skeg (Fr=0.48): (a) resistance coefficients, (b) relative change εN=∣(SN−SN+1)∕S1∣×100 and iterative errors for resistance coefficients, (c) sinkage and trim, and (d) relative change εN and iterative errors for sinkage and trim

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Figure 7

Resistance coefficient, sinkage, and trim for a slow acceleration of Athena bare hull with skeg (grid 5). Solid circles: experimental data; open triangles: resistance coefficient predictions for fixed experimental sinkage and trim (24); open squares: steady-state computation of resistance coefficient, sinkage, and trim; lines: predictions.

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Figure 8

Validation of Athena bare hull with skeg: (a) resistance coefficient, (b) sinkage, and (c) trim

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Figure 9

Free surface wave fields for Athena bare hull with skeg at Fr=0.43

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Figure 10

Whole powering curve for a slow acceleration of a fully appended Athena as a function of RPS. Solid circles: experimental data; open squares: steady-state computation of resistance coefficient, sinkage, and trim; lines: predicted quantities.

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