Large-wave simulation of three-dimensional, cross-shore and oblique, spilling breaking on constant slope beach

2011 ◽  
Vol 58 (8) ◽  
pp. 790-801 ◽  
Author(s):  
Aggelos S. Dimakopoulos ◽  
Athanassios A. Dimas
Keyword(s):  
Three Dimensional ◽  
Large Wave ◽  
Wave Simulation ◽  
Slope Beach ◽  
Constant Slope

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.

Numerical Simulation of Oblique Wave Breaking and Wave-Induced Currents in the Surf Zone

2014 ◽  
Author(s):  
Gerasimos A. Kolokythas ◽  
Athanassios A. Dimas
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Surf Zone ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Maximum Magnitude ◽  
Longshore Current ◽  
Large Wave ◽  
Constant Slope

In the present study, the three-dimensional, incompressible, turbulent, free-surface flow, developing by the propagation and breaking of nonlinear gravity waves over a constant-slope beach, is numerically simulated. The main objective is to investigate the flow structure in the surf zone as a result of the interaction between the longshore and the undertow current, induced by spilling wave breaking, oblique to the shoreline. The simulations are performed employing the so-called large-wave simulation (LWS) method coupled with a numerical solver for the Navier-Stokes equations. According to the employed LWS methodology, large velocity and free-surface scales are fully resolved, while the effect of subgrid scales is modeled by eddy-viscosity stresses, similar to large-eddy simulation (LES) methodology. In order to validate our model, the case of incoming Stokes waves with wavelength to inflow depth ratio λ/dI ≈ 6.6 and wave steepness H/λ ≈ 0.025, propagating normal to the shore over a bed of constant slope 1/35, is investigated. Our results are compared to published experimental measurements, and it is found that the LWS model predicts adequately the wave breaking parameters — breaking height and depth — and the distribution of the undertow current in the surf zone. Two cases of oblique breaking waves, with inflow angles φI = 20° and 30°, and all other parameters identical to that of the validation case, are considered. The gradual breaking of the refracted waves is captured, as well as the three-dimensional structure of the flow in the surf zone. LWS-predicted profiles of the undertow and the longshore current at several positions in the surf zone, are presented. It is indicated that the undertow prevails in the outer surf zone, while the longshore current becomes stronger in the inner surf zone and reaches its maximum magnitude close to the shore.

Large-Wave Simulation of Spilling Breakers Over Constant-Slope Bed

2008 ◽  
Author(s):  
Aggelos S. Dimakopoulos ◽  
Athanassios A. Dimas
Keyword(s):  
Free Surface ◽  
Euler Equations ◽  
Surf Zone ◽  
Surface Elevation ◽  
Scale Model ◽  
Free Surface Elevation ◽  
Large Wave ◽  
Wave Simulation ◽  
Subgrid Scales ◽  
Constant Slope

A subgrid scale model is presented for the large-wave simulation (LWS) of spilling breaking waves over bottom of arbitrary shape and finite depth. According to LWS formulation, large velocity and free-surface scales are fully resolved, while subgrid scales are accounted for by an eddy viscosity model, similar to large-eddy simulation (LES). The LWS-based model is applied on the two-dimensional wave propagation over a constant-slope bed. Fluid motion is described by the Euler equations for inviscid but rotational flow, subject to the fully non-linear free-surface boundary conditions. The application of LWS is facilitated by a boundary-fitted transformation, which introduces free-surface elevation terms in the Euler equations and simplifies the numerical implementation. Subgrid velocity scales are modeled similarly to LES, while the effect of free-surface subgrid scales are modeled by wave SGS stresses model. The resulting equations are solved numerically by a two-stage fractional time-step scheme, while an absorption zone is placed in the outflow region to minimize reflection by the outgoing waves. The simulation is carried out for the propagation and breaking of waves over a flat bed with constant slope 1/35 and results are compared to available experimental data. The numerical predictions for the breaking height, the breaking depth and the free-surface elevation dissipation in the surf zone agree very well with the corresponding measurements. The model predicts the vorticity generation in the breaking face of the wave and the appearance of the undertow current in the surf zone. The predicted shear of the undertow current is higher than the measured one.

Numerical Simulation of Nonlinear Wave Propagation and Breaking Over Constant-Slope Bottom

2006 ◽  
Author(s):  
Aggelos S. Dimakopoulos ◽  
Athanassios A. Dimas
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Surface Boundary ◽  
Nonlinear Wave Propagation ◽  
Large Wave ◽  
Slope Bottom ◽  
Wave Heights ◽  
Constant Slope

The numerical simulation of the two-dimensional free-surface flow resulting from the propagation of nonlinear gravity waves over constant-slope bottom is presented. The simulation is based on the numerical solution of the Euler equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow conditions using a hybrid finite-differences and spectral-method scheme. Wave breaking is accounted for by a surface roller model. The formulation includes a boundary-fitted transformation and is suitable for future extension to incorporate large-eddy and large-wave simulation terms. Results are presented for the simulation of the free-surface flow over two different bottom topographies, with constant slope values of 1:10 and 1:50, and three different inflow wave heights. Over the bottom slope, waves of small wave heights are modified according to linear theory. For nonlinear waves, wavelengths are becoming shorter, the free surface elevation deviates from its initial sinusoidal shape and wave heights increase with decreasing depth. Breaking is observed for the cases with the larger initial wave height and the smaller outflow depth.

Global Laser Rangefinder Profilometry: Initial Test and Uncertainty Analysis

2006 ◽  
Author(s):  
Jason B. Carneal ◽  
Paisan Atsavapranee
Keyword(s):  
Three Dimensional ◽  
Laser Rangefinder ◽  
Large Wave ◽  
Wave Measurements ◽  
Surface Ship ◽  
Measuring Surface ◽  
Calm Water ◽  
Wave Heights ◽  
Surface Profiles ◽  
Probe Measurements

Global Laser Rangefinder Profilometry (GLRP) is a novel optical technique for instantaneous measurement of complex three-dimensional surfaces. A functional GLRP system has been constructed in the Maneuvering and Seakeeping Basin (MASK) at the Naval Surface Warfare Center, Carderock Division (NSWCCD). The system is capable of measuring surface height displacements over 800 measurement points at 30 Hz. The MASK GLRP system was used to measure the surface profiles of large waves produced by wave-makers in the MASK and bow waves generated by a surface ship remote-controlled model (RCM). Several large wave measurements were performed at various wave heights and compared to sonic probe measurements. The large wave measurements were found to be consistent with sonic probe measurements to within 5%. The results from the large wave measurements and RCM model bow wave measurements are presented and discussed. Data was collected in calm water to quantify sources of error, including optical jitter. The random error of the GLRP system is estimated at approximately 1.6 mm. The purpose of this work was to test the ability of the GLRP system for use in tests commonly performed at NSWCCD.

Hydroelastic Analysis of a Hybrid-Type VLFS in Water of Variable Depth

2008 ◽  
Author(s):  
Tomoaki Utsunomiya ◽  
Eiichi Watanabe ◽  
Takatoshi Noguchi ◽  
Syuji Yamamoto ◽  
Tadasu Kusaka ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Plate Model ◽  
Flat Bottom ◽  
Hybrid Type ◽  
Quadrilateral Plate ◽  
Dimensional Finite Element ◽  
Hydroelastic Analysis ◽  
Three Dimensional Finite Element ◽  
Constant Slope

This paper presents a hydroelastic analysis of a hybrid-type VLFS in variable sea depth. The VLFS model is the prototype of a floating runway with dimension 3120m in length, 524m in width, 1.5m in draft for pontoon part and 11.5m in draft for semisubmersible part. A three dimensional Finite Element model using beams and quadrilateral plate elements are used in the hydroelastic analysis in order to obtain an accurate approximation. An equivalent plate model having the same eigenfrequencies and eigenmodes in air is also used in the analysis. The results using the 3D model and the plate model have been compared and their agreement is satisfying. In order to examine the variable sea depth at the expected site, the hydroelastic analysis is carried out for a flat bottom, a constant slope, and a variable sea depth case. The effect of variable sea depth is found to be significant.

Exact solutions of a three-dimensional nonlinear Schrödinger equation applied to gravity waves

1979 ◽  
Vol 93 (1) ◽  
pp. 117-133 ◽  
Author(s):  
W. H. Hui ◽  
J. Hamilton
Keyword(s):  
Schrödinger Equation ◽  
Nonlinear Schrödinger Equation ◽  
Gravity Waves ◽  
Schrodinger Equation ◽  
Three Dimensional ◽  
Nonlinear Schrodinger Equation ◽  
Wave Groups ◽  
Large Wave ◽  
Nonlinear Schrödinger ◽  
Permanent Wave

The three-dimensional evolution of packets of gravity waves is studied using a nonlinear Schrödinger equation (the Davey–Stewartson equation). It is shown that permanent wave groups of the elliptic en and dn functions and their common limiting solitary sech forms exist and propagate along directions making an angle less than ψc= tan−1(1/√2) = 35° with the underlying wave field, whilst, along directions making an angle greater than ψc, there exist permanent wave groups of elliptic sn and negative solitary tanh form. Furthermore, exact general solutions are given showing wave groups travelling along the two characteristic directions at ψcor − ψc. These latter solutions tend to form regions of large wave slope and are used to discuss the waves produced by a ship, in particular the nonlinear evolution of the leading edge of the pattern.

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