Investigation of the influence of tank geometry on a vessel’s stability under free surface effect when in coastal waters

The linearized potential flow resulting from a distribution of pressure that advances at constant speed along a straight path at the free surface of calm water, of effectively infinite depth and lateral extent, is considered. A practical method for evaluating the free-surface elevation caused by the moving free-surface pressure patch—which can be used to model steady flows of air-cushion vehicles, high-speed planing boats, surface-effect ships, and some types of hybrid ships—is given. The key ingredient of this method is a highly simplified analytical approximation to the local-flow component in the expression for the Green function associated with the classic Michell-Kelvin linearized free-surface boundary condition.

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An Analysis of Heave Added Mass and Damping of a Surface-Effect Ship

Journal of Ship Research ◽

10.5957/jsr.1981.25.1.44 ◽

1981 ◽

Vol 25 (01) ◽

pp. 44-61

Author(s):

C. H. Kim ◽

S. Tsakonas

Keyword(s):

Free Surface ◽

High Speed ◽

Surface Effect ◽

Practical Method ◽

Added Mass ◽

Damping Coefficients ◽

Calm Water ◽

Surface Effect Ship ◽

Long Time ◽

Computational Procedures

The analysis presents a practical method for evaluating the added-mass and damping coefficients of a heaving surface-effect ship in uniform translation. The theoretical added-mass and damping coefficients and the heave response show fair agreement with the corresponding experimental values. Comparisons of the coupled aero-hydrodynamic and uncoupled analytical results with the experimental data prove that the uncoupled theory, dominant for a long time, that neglects the free-surface effects is an oversimplified procedure. The analysis also provides means of estimating the wave elevation of the free surface, the escape area at the stern and the volume which are induced by a heaving surface-effect ship in uniform translation in otherwise calm water. Computational procedures have been programmed in the FORTRAN IV language and adapted to the PDP-10 high-speed digital computer.

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Radiation Hydrodynamics of a Surface Effect Ship

Volume 9: Odd M. Faltinsen Honoring Symposium on Marine Hydrodynamics ◽

10.1115/omae2013-10310 ◽

2013 ◽

Author(s):

Palaniswamy Ananthakrishnan

Keyword(s):

Free Surface ◽

Large Amplitude ◽

Small Amplitude ◽

Stokes Equations ◽

Surface Effect ◽

Wave Radiation ◽

Absolute Pressure ◽

Radiation Hydrodynamics ◽

Surface Effect Ship ◽

Air Cushion

The radiation hydrodynamics of a heaving surface effect ship (SES) is examined including the effect of air compressibility on the hydrodynamic forces and surface waves. Of particular focus of the study has been on determining the nonlinear viscous and air compressibility effects at natural frequencies corresponding to the piston and sloshing wave modes between the hulls and at the natural frequency corresponding to the heave motion of a surface effect ship with the restoring force dominated by the compressibility of the air cushion. In the present paper, the air cushion pressure is assumed to be uniform with its variation due to change of volume modeled using the adiabatic gas law pVγ = constant, where p denotes the absolute pressure of the air, V the air volume bounded by the side hulls, the free surface and the wet deck, and γ the ratio of specific heats Cp/Cv which is about 1.4 for air. The incompressible Navier-Stokes equations governing the nonlinear viscous wave-air-body interaction problem is solved in the time domain using a finite-difference method based on boundary fitted coordinates. New results presented in this paper show that air cushion compressibility affects the generation of waves and wave radiation forces significantly even at small amplitude of hull motion. As already well known, the free surface nonlinearity due to hull motion is significant for large amplitude of oscillation. At small amplitude of body oscillation, significant nonlinearity can be caused by air compressibility resulting in the generation of higher harmonic waves and forces. The results also highlight the significance of viscosity and flow separation, in conjunction with air compressibility, in the case of large amplitude hull motion with a small draft.

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Comparison of Single and Overset Grid Techniques for CFD Simulations of a Surface Effect Ship

Volume 2: CFD and VIV ◽

10.1115/omae2014-24207 ◽

2014 ◽

Cited By ~ 2

Author(s):

Colton G. Clark ◽

David G. Lyons ◽

Wayne L. Neu

Keyword(s):

Free Surface ◽

Surface Effect ◽

The Body ◽

Computational Domain ◽

Overset Grid ◽

Hexahedral Mesh ◽

Surface Effect Ship ◽

Mesh Resolution ◽

Refined Meshes ◽

Air Cushion

Overset, or Chimera meshes are used to discretize the governing equations within a computational domain using multiple meshes that overlap in an arbitrary manner. The overset mesh technique is most applicable to problems dealing with multiple or moving bodies. In order to extend existing full craft CFD (RANS) simulations of a surface effect ship (SES) into shallow water and maneuvering cases, an overset mesh is needed. Deep water simulations were carried out using both single and overset grid techniques for evaluation of the overset grid application. The single grid technique applies a hexahedral mesh to the fluid domain and SES geometry. An adequate mesh resolution was determined by performing a grid convergence study on a series of systematically refined meshes. An overset mesh of the same resolution was then constructed and was fixed to the body. Drag and pitch results are compared among the two simulations. Free surface elevations around the craft and under the air cushion for simulations with the single and overset meshes are compared. Steady-state simulations using the overset mesh and the single mesh show general similarities in drag, pitch, and free surface elevations.

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Multiscale modeling of free-surface effect on crack formation in unidirectional off-axis laminates

Composites Part A Applied Science and Manufacturing ◽

10.1016/j.compositesa.2017.03.016 ◽

2017 ◽

Vol 98 ◽

pp. 136-146 ◽

Cited By ~ 4

Author(s):

Yuta Kumagai ◽

Sota Onodera ◽

Yoshiko Nagumo ◽

Tomonaga Okabe ◽

Kenichi Yoshioka

Keyword(s):

Free Surface ◽

Multiscale Modeling ◽

Crack Formation ◽

Surface Effect

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Numerical investigations of the free surface effect in three-dimensional polycrystalline aggregates

Computational Materials Science ◽

10.1016/j.commatsci.2012.11.052 ◽

2013 ◽

Vol 70 ◽

pp. 150-162 ◽

Cited By ~ 29

Author(s):

Yoann Guilhem ◽

Stéphanie Basseville ◽

François Curtit ◽

Jean-Michel Stéphan ◽

Georges Cailletaud

Keyword(s):

Free Surface ◽

Surface Effect ◽

Three Dimensional ◽

Numerical Investigations ◽

Polycrystalline Aggregates

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HARBOR AGITATION DUE TO OFFSHORE SHIP WAVES USING SWASH: A CASE STUDY OF KUMKAPI YACHT PARK, ISTANBUL

Coastal Engineering Proceedings ◽

10.9753/icce.v36.currents.12 ◽

2018 ◽

pp. 12

Author(s):

CÃ¼neyt Baykal ◽

GÃ¼lizar Ã–zyurt TarakcÄ±oÄŸlu ◽

Emrecan IÅŸÄ±k

Keyword(s):

Numerical Modeling ◽

Free Surface ◽

Numerical Model ◽

Coastal Waters ◽

Rotational Flow ◽

Ship Waves ◽

Safety Requirements ◽

Flow And Transport ◽

Bosphorus Strait

This study presents the results of a numerical modeling study on the harbor agitation in case of offshore ship waves using SWASH (acronym for Simulating WAves till SHore), a numerical model developed for the simulating unsteady, non-hydrostatic, free-surface, rotational flow and transport phenomena in coastal waters as driven by waves, tides, buoyancy and wind forces (Zijlema et al. 2011). The study area is the Kumkapi Yacht Park, at the Marmara coast of Istanbul, 2.5 km west of the southern entrance of Bosphorus strait. The yacht park is currently used as a fishery harbor, which is severely affected by the ship waves of ferries and sea buses passing nearby almost parallel to the main breakwater of the harbor (aligned from west to east). The park is planned to berth a total of 140 yachts varying from 5 m to 40 m in length (Figure 1). For this purpose, the present harbor layout together with several alternative plans have been studied numerically to investigate agitation due to ship waves of ferries and sea buses considering the design safety requirements of ASCE (2012) for the safe mooring and berthing of yachts.

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