Numerical Simulations of Ship Bow and Shoulder Wave Breaking in Different Advancing Speeds

2018 ◽  
Author(s):  
Zhen Ren ◽  
Jianhua Wang ◽  
Decheng Wan
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Wave Breaking ◽  
Wave Pattern ◽  
Breaking Wave ◽  
Wake Field ◽  
Bow Wave ◽  
Calm Water ◽  
Wave Phenomena ◽  
Good Agreement

The KCS model is employed for the numerical simulations to investigate the wave breaking phenomena of the bow and shoulder wave. RANS approach coupled with high resolution VOF technique is used to resolve the free surface. In order to study the speed effects on the phenomena of ship wave breaking, four different speeds, i.e. Fr = 0.26, 0.30, 0.32, 0.35, are investigated in calm water. Predicted resistance and wave patterns under Fr = 0.26 are validated with the available experiment data, and good agreement is achieved. For the Fr = 0.26 case, the wave pattern is steady, and the alternate variation of vorticity appear near the free surface is associated with the wake field. The breaking wave phenomena can be observed when the Froude number is over 0.32 and the Fr = 0.35 case shows most violent breaking bow wave. For the Fr = 0.35 case, the process of overturning and breaking of bow wave is observed clearly, and at the tail of bow wave, some breaking features of free surface are also captured. The reconnection of the initial plunger with the free surface results in a pair of counter-rotating vortex that is responsible for the second plunger and scar.

Study of a Container Ship with Breaking Waves at High Froude Number Using URANS and DDES Methods

2019 ◽  
Author(s):  
Jianhua Wang ◽  
Zhen Ren ◽  
Decheng Wan
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
High Speed ◽  
Hydrodynamic Performance ◽  
Small Scale ◽  
Breaking Wave ◽  
Container Ship ◽  
Ship Model ◽  
Bow Waves ◽  
Bow Wave

The KRISO container ship model is used for numerical simulations to investigate hydrodynamic performance under high speeds. Unsteady Reynolds-Averaged Navier-Stokes (URANS) and delayed detached eddy simulation (DDES) approaches are used to resolve the flow field around the ship model. High-resolution Volume of Fluid (VOF) technique in OpenFOAM is used to capture the free surface. The present work focuses on the wave-breaking phenomena of high-speed ships. To study the speed effects on the phenomenon of ship bow wave breaking, three different speeds, i.e., Fn = .26, .35, and .40, are investigated for a fixed ship model in calm water. Predicted resistance and wave patterns under Fn = .26 are validated with available experimental data, and a good agreement is achieved. The breaking wave phenomena can be observed from both URANS and DDES results for Froude numbers greater than .35. And the Fn = .40 case shows more violent breaking bow waves. The process of overturning and breaking of bow wave is more complex in the DDES results, and some small-scale free surface features are also captured. The predicted bow wave is compared with the experiment conducted at the China Ship Scientific Research Center. It shows that the DDES results are more accurate. Wave profiles and vorticity field at several cross sections are presented to illustrate the relationship between bow waves and vortices. It is found that the free surface vorticity dissipates quickly in the URANS simulation, which leads to the difference compared with the DDES results.

scholarly journals Study on bow wave breaking around ultra large block coefficient ship

2013 ◽  
Vol 10 (2) ◽  
pp. 69-80 ◽  
Author(s):  
Md Ashim Ali ◽  
Kazuo Suzuki ◽  
Sou Miyauchi
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Research Work ◽  
Maritime Transportation ◽  
Large Block ◽  
Surface Integral ◽  
Bow Wave ◽  
Surface Disturbance ◽  
The Relationship ◽  
Disturbance Function

Due to the increase of maritime transportation volume day by day it is necessary to design a ship hull having large carrying capacity with low resistance. In case of slow moving ships, usually wave breaking occurs in front of bow. A considerable portion of resistance occurs due to the energy dissipation of such wave breaking in case of Ultra Large Block coefficient Ship (ULBS) suggested by the authors. The key objective of this research work is to investigate the relationship between bow wave breaking and free surface disturbance function that may be used as a parameter for numerical prediction of bow wave breaking. In this regard, the experiments and numerical calculations have been carried out for six models of ULBS. From the results, it can be concluded that the wave breaking area in front of bow increases with the increase of surface integral of the square of free surface disturbance function, Froude number and block coefficient.DOI: http://dx.doi.org/10.3329/jname.v10i2.16104 

Evolution of a quasi-steady breaking wave

1995 ◽  
Vol 302 ◽  
pp. 29-44 ◽  
Author(s):  
J. C. Lin ◽  
D. Rockwell
Keyword(s):  
Free Surface ◽  
Froude Number ◽  
Large Scale ◽  
Mixing Layer ◽  
Stationary Wave ◽  
Wave Pattern ◽  
Small Scale ◽  
Radius Of Curvature ◽  
Breaking Wave ◽  
Large Radius

The stages of evolution of a quast-steady breaker from the onest of a capillary pattern to a fully evolved breaking wave are cgaracterized using high-image-density particle image velocimetry, which provides instrantaneous representations of the free surface and the patterns of vorticity beneath it. The initial stage, which sets in at a low value of Froude number, involves a capillary pattern along each trough-crest surface of a quasi-stationary wave. The successive crests of the capillary pattern exhihit increasing scale and culminate in a single largest-scale crest of the free surface. Immediately upstream of the large-scale crest, the capillary pattern shows counterclockwise concentrations of vorticity at its troughs and regions of clockwise vorticity beneath its crests. The onset of the final, largest-scale crest exhihits two forms: one involving no flow sparation; and the other exhibiting a small-scale separaed mixing layer. At an intermediate value of Froude number, a breaker occurs and the acpillary pattern is replaced by large-scale distortions of the free surface. The onset of separation, which involves flow deceleration along a region of the free surface having a large radius of curvature, leads to formation of a long mixing layeer, which has substantial levels of vorticity. Downstream of this breaker, the long-wavelength wave pattern is suppressed. At the largest value of Froude number, the onset of flow sparation rapidly occurs in conjunction with an abrupt change in slope of the surface, giving rise to vorticity concentrationa in the mixing layer.

Higher Order Boundary Element Method Applied to the Hydrofoil Beneath the Free Surface

2009 ◽  
Author(s):  
Hassan Ghassemi ◽  
Ahmad Reza Kohansal ◽  
Abdollah Ardeshir
Keyword(s):  
Free Surface ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Three Dimensional ◽  
Wave Pattern ◽  
Higher Order ◽  
The Body ◽  
Hydrodynamic Characteristics ◽  
Good Agreement ◽  
Element Method

In this paper a three-dimensional numerical model using the higher order boundary element method (HOBEM) is developed to analyze hydrodynamic characteristics of hydrofoils beneath the free surface. The method uses combinations of the source and doublet by linear disctribution on each element of the body and free surface. The geometry of the element is represented by quadratic bilinear elements. The method is applied to three-dimensional hydrofoils of the symmetric Joukowski and NACA4412 profiles moving beneath the free surface in constant speed. Some results (pressure distribution, lift, wave-making drag and wave elevation and wave pattern) are presented. It is shown that this approach is accurate, efficient and the results are in good agreement with the experimental measurements and other calculated results.

scholarly journals Channelized free-surface flow of cohesionless granular avalanches in a chute with shallow lateral curvature

1999 ◽  
Vol 392 ◽  
pp. 73-100 ◽  
Author(s):  
M. WIELAND ◽  
J. M. N. T. GRAY ◽  
K. HUTTER
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Smooth Transition ◽  
Lateral Confinement ◽  
Lateral Curvature ◽  
Granular Deposit ◽  
Good Agreement

A series of laboratory experiments and numerical simulations have been performed to investigate the rapid fluid-like flow of a finite mass of granular material down a chute with partial lateral confinement. The chute consists of a section inclined at 40° to the horizontal, which is connected to a plane run-out zone by a smooth transition. The flow is confined on the inclined section by a shallow parabolic cross-slope profile. Photogrammetric techniques have been used to determine the position of the evolving boundary during the flow, and the free-surface height of the stationary granular deposit in the run-out zone. The results of three experiments with different granular materials are presented and shown to be in very good agreement with numerical simulations based on the Savage–Hutter theory for granular avalanches. The basal topography over which the avalanche flows has a strong channelizing effect on the inclined section of the chute. As the avalanche reaches the run-out zone, where the lateral confinement ceases, the head spreads out to give the avalanche a characteristic ‘tadpole’ shape. Sharp gradients in the avalanche thickness and velocity began to develop at the interface between the nose and tail of the avalanche as it came to rest, indicating that a shock wave develops close to the end of the experiments.

Numerical simulations of stratified inviscid flow over a smooth obstacle

1994 ◽  
Vol 260 ◽  
pp. 1-22 ◽  
Author(s):  
Kevin G. Lamb
Keyword(s):  
Numerical Simulations ◽  
Wave Breaking ◽  
Finite Depth ◽  
Inviscid Flow ◽  
Wave Drag ◽  
Experimental Results ◽  
Buoyancy Frequency ◽  
Lee Waves ◽  
Boussinesq Fluid ◽  
Good Agreement

Results of numerical simulations of the flow of a non-rotating, inviscid, Boussinesq fluid over smooth two-dimensional obstacles are described. The fluid has finite depth and a rigid lid. Far upstream of the obstacle the horizontal velocity and buoyancy frequency are uniform. Comparisons with linear theory for small-amplitude obstacles are made and the long-time behaviour is compared with steady-state Long's model solutions. Comparisons with the time-dependent results of Baines (1979) are done. For Froude numbers between ½ and 1 the obstacle amplitude is varied in order to determine the amplitudes needed to initiate wave breaking. These results are compared with the predictions of Long's model and with the experimental results of Baines (1977) showing good agreement with the latter. It is found that wave breaking occurs for amplitudes significantly lower than Long's model predicts for a large range of Froude numbers. This is shown to be the result of the generation of large-amplitude lee waves with wavelengths longer than that of stationary lee waves, but not long enough to propagate upstream. The behaviour of these waves is coupled to the generation of both longer mode-one waves which do propagate upstream from the obstacle and to mode-two waves which propagate against the flow as they are advected downstream. It is also coupled to oscillations in the wave drag. The periods of the wave drag oscillations are compared to experimental results showing good agreement with cases for which oscillations have been observed. The behaviour of these large transient lee waves is compared with the theoretical results contained in Grimshaw & Yi (1991), showing some similarities. As the Froude number approaches 0.5 the breaking behaviour is no longer due to these large waves, with the result that wave breaking occurs much later.

scholarly journals LARGE-WAVE SIMULATION OF TURBULENT FLOW INDUCED BY WAVE PROPAGATION AND BREAKING OVER CONSTANT SLOPE BED

2012 ◽  
Vol 1 (33) ◽  
pp. 65
Author(s):  
Gerasimos Kolokythas ◽  
Aggelos Dimakopoulos ◽  
Athanassios Dimas
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Wave Breaking ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Surface Boundary ◽  
Large Wave ◽  
Wave Simulation ◽  
Constant Slope ◽  
Good Agreement

In the present study, the three-dimensional, incompressible, turbulent, free-surface flow, developing by the propagation of nonlinear breaking waves over a rigid bed of constant slope, is numerically simulated. The main objective is to investigate the process of spilling wave breaking and the characteristics of the developing undertow current employing the large-wave simulation (LWS) method. According to LWS methodology, large velocity and free-surface scales are fully resolved, and subgrid scales are treated by an eddy viscosity model, similar to large-eddy simulation (LES) methodology. The simulations are based on the numerical solution of the unsteady, three-dimensional, Navier-Stokes equations subject to the fully-nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow boundary conditions. The case of incoming second-order Stokes waves, normal to the shore, with wavelength to inflow depth ratio λ/dΙ = 6.6, wave steepness H/λ = 0.025, bed slope tanβ = 1/35 and Reynolds number (based on inflow water depth) Red = 250,000 is investigated. The predictions of the LWS model for the incipient wave breaking parameters - breaking depth and height - are in very good agreement with published experimental measurements. Profiles of the time-averaged horizontal velocity in the surf zone are also in good agreement with the corresponding measured ones, verifying the ability of the model to capture adequately the undertow current.

scholarly journals FULL PARTICLE PIC MODELLING OF THE SURF AND SWASH ZONES

2012 ◽  
Vol 1 (33) ◽  
pp. 30 ◽  
Author(s):  
David Matthew Kelly
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Free Surface Flows ◽  
Test Cases ◽  
Coastal Structures ◽  
Wetting And Drying ◽  
Surface Flows ◽  
Particle In Cell ◽  
Pic Method ◽  
Good Agreement

In this paper a hybrid Eulerian Lagrangian solver based on the full–particle Particle–In–Cell (PIC) method is outlined. The solver is capable of simulating incompressible free–surface flows in domains with arbitrary, free–slip, solid boundaries. The flexibility of the approach allows for simulation of wetting and drying and pooling as well as wave breaking, splash–up over complex obstacles and the overtopping of coastal structures. The method has been validated for a wide variety of test cases and results are in good agreement with the numerical and experimental results of other researchers.

Study of Planing Hydrodynamics Using Strips of Transversely Variable Pressure

1994 ◽  
Vol 38 (01) ◽  
pp. 30-41
Author(s):  
Xiaoming Cheng ◽  
J. F. Wellicome
Keyword(s):  
Free Surface ◽  
Pressure Distribution ◽  
Numerical Solutions ◽  
Variable Pressure ◽  
Large Aspect Ratio ◽  
Free Surface Elevation ◽  
Sine Series ◽  
Calm Water ◽  
The Mean ◽  
Good Agreement

A pressure strip method is developed for the prediction of hydrodynamic forces acting on planing hulls moving on the surface of calm water. Within the frame of linearized potential flow theory, the presence of a planing surface is represented by an assemblage of strips of transversely variable pressure placed on the mean free surface. The unknown pressure distribution on each strip is represented by a sine series with unknown coefficients which are determined by solving an integral equation relating the pressure distribution to the free-surface elevation underneath the planing hull. Numerical solutions are obtained for the planing of 3-D flat plate and three basic profiles of 2-D planing surfaces, which are taken as the extreme cases of large-aspect-ratio 3-D planing surfaces. The results are compared with experimental data and good agreement is achieved.

The laminar free surface boundary layer of a solitary wave

2012 ◽  
Vol 696 ◽  
pp. 423-433 ◽  
Author(s):  
Christian A. Klettner ◽  
Ian Eames
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Solitary Wave ◽  
Numerical Simulations ◽  
Numerical Results ◽  
Analytical Models ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Good Agreement

AbstractThe laminar free surface boundary layer beneath a solitary wave is investigated using numerical simulations. Across the boundary layer $\partial {u}_{s} / \partial {x}_{n} $ and $\partial {u}_{n} / \partial {x}_{s} $ are comparable in magnitude, where $u$ is the velocity, $x$ position and subscripts $s$ and $n$ refer to components tangential and normal to the free surface. In this region $\partial {u}_{n} / \partial {x}_{s} $ is approximately constant across the boundary layer while $\partial {u}_{s} / \partial {x}_{n} $ varies with ${x}_{n} $ and outside the boundary layer tends to ${\ensuremath{-} } \mathop{ (\partial {u}_{s} / \partial {x}_{n} )} \nolimits _{n= 0} $. The numerical results are compared to analytical models and good agreement is found.

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