Forces, moment, and wave pattern for surface combatant in regular head waves

Gui, Lichuan; Longo, Joseph; Metcalf, Bryson; Shao, Jun Peng; Stern, Frederick

doi:10.1007/s003480100321

“…The test case chosen has been experimentally studied extensively for a DTMB 5512 model and unsteady free surface elevation, resistance, heave force and pitch moments [39,40] and velocities [41] In order to simulate the boundary layer turbulence using the model, a fine near wall discretization is necessary, with spacing around . This makes the design of the computational grid difficult, since an orthogonal grid is convenient in the far field to avoid deformation of the incoming wave.…”

Section: Forward Speed Diffraction In a Surface Shipmentioning

confidence: 99%

An unsteady single‐phase level set method for viscous free surface flows

Carrica

¹

,

Wilson

²

,

Stern

³

2006

Numerical Methods in Fluids

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Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. ABSTRACTThe single-phase level set method for unsteady viscous free surface flows is presented. In contrast to the standard level set method for incompressible flows, the single-phase level set method is concerned with the solution of the flow field in the water (or the denser) phase only. Some of the advantages of such an approach are that the interface remains sharp, the computation is performed within a fluid with uniform properties and that only minor computations are needed in the air. The location of the interface is determined using a signed distance function, and appropriate interpolations at the fluid/fluid interface are used to enforce the jump conditions. A reinitialization procedure has been developed for non-orthogonal grids with large aspect ratios. A convective extension is used to obtain the velocities at previous time-steps for the grid points in air, which allows a good estimation of the total derivatives. In this report we discuss the details of such implementations. The method was applied to three unsteady tests: a plane progressive wave, sloshing in a two-dimensional tank, and the wave diffraction problem in a surface ship, and the results compared against analytical solutions or experimental data. The method can in principle be applied to any problem in which the standard level-set method works, as long as the stress on the second phase can be specified (or neglected) and no bubbles appear in the flow during the computation.

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“…In particular, with regard to the prediction and data for the unsteady diffraction wave field and data for the unsteady boundary layer and wake. The present work was useful in this regard both in guiding future code development efforts [47] and experimental towing tests for validation data [48].…”

Section: Discussionmentioning

confidence: 99%

Unsteady RANS method for surface ship boundary layer and wake and wave field

Rhee

¹

,

Stern

²

2001

Numerical Methods in Fluids

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SUMMARYResults are reported of an unsteady Reynolds-averaged Navier -Stokes (RANS) method for simulation of the boundary layer and wake and wave field for a surface ship advancing in regular head waves, but restrained from body motions. Second-order finite differences are used for both spatial and temporal discretization and a Poisson equation projection method is used for velocity -pressure coupling. The exact kinematic free-surface boundary condition is solved for the free-surface elevation using a body-fitted/freesurface conforming grid updated in each time step. The simulations are for the model problem of a Wigley hull advancing in calm water and in regular head waves. Verification and validation procedures are followed, which include careful consideration of both simulation and experimental uncertainties. The steady flow results are comparable to other steady RANS methods in predicting resistance, boundary layer and wake, and free-surface effects. The unsteady flow results cover a wide range of Froude number, wavelength, and amplitude for which first harmonic amplitude and phase force and moment experimental data are available for validation along with frequency domain, linear potential flow results for comparisons. The present results, which include the effects of turbulent flow and non-linear interactions, are in good agreement with the data and overall show better capability than the potential flow results. The physics of the unsteady boundary layer and wake and wave field response are explained with regard to frequency of encounter and seakeeping theory. The results of the present study suggest applicability for additional complexities such as practical ship geometry, ship motion, and maneuvering in arbitrary ambient waves.

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“…Since the behavior at the experimental conditions is linear, the free surface elevations were reconstructed and reported in terms of the zero and first Fourier harmonic amplitudes and first Fourier phase [38,39]. We chose to compare against quarter periods at and 3/4.…”

Section: Forward Speed Diffraction In a Surface Shipmentioning

confidence: 99%

An Unsteady Single-Phase Level Set Method for Viscous Free Surface Flows

Carrica¹,

Wilson²,

Stern³

2005

Self Cite

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Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. ABSTRACTThe single-phase level set method for unsteady viscous free surface flows is presented. In contrast to the standard level set method for incompressible flows, the single-phase level set method is concerned with the solution of the flow field in the water (or the denser) phase only. Some of the advantages of such an approach are that the interface remains sharp, the computation is performed within a fluid with uniform properties and that only minor computations are needed in the air. The location of the interface is determined using a signed distance function, and appropriate interpolations at the fluid/fluid interface are used to enforce the jump conditions. A reinitialization procedure has been developed for non-orthogonal grids with large aspect ratios. A convective extension is used to obtain the velocities at previous time-steps for the grid points in air, which allows a good estimation of the total derivatives. In this report we discuss the details of such implementations. The method was applied to three unsteady tests: a plane progressive wave, sloshing in a two-dimensional tank, and the wave diffraction problem in a surface ship, and the results compared against analytical solutions or experimental data. The method can in principle be applied to any problem in which the standard level-set method works, as long as the stress on the second phase can be specified (or neglected) and no bubbles appear in the flow during the computation.

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Forces, moment, and wave pattern for surface combatant in regular head waves

Cited by 21 publications

References 0 publications

An unsteady single‐phase level set method for viscous free surface flows

An unsteady single‐phase level set method for viscous free surface flows

Unsteady RANS method for surface ship boundary layer and wake and wave field

An Unsteady Single-Phase Level Set Method for Viscous Free Surface Flows

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