scholarly journals THREE DIMENSIONAL FLOW PROFILES ON LITTORAL BEACHES

1988 ◽  
Vol 1 (21) ◽  
pp. 52 ◽  
Author(s):  
Ib A. Svendsen ◽  
Rene S. Lorenz
Keyword(s):  
Perturbation Method ◽  
Poisson Equation ◽  
Surf Zone ◽  
Three Dimensional ◽  
Longshore Current ◽  
Current Profile ◽  
Three Dimensional Flow ◽  
Flow Profiles ◽  
Current Variation ◽  
Averaged Models

The problem of combined cross-shore and longshore currents generated by waves in and around a surf zone is considered in its full three-dimensional formulation. The equations for the two current components are decoupled and it is found that for a cylindrical coast with no longshore variations the longshore current variation with depth and distance from the shoreline satisfies a Poisson equation. This equation is solved by a perturbation method and it is shown that the longshore velocities are always larger than the velocities found by classical theory. In the simple uncoupled case, the full 3-D current profile is constructed by combining the results with cross - shore velocities determined in previous publications. Also, the total velocities are larger than velocities found from simple depth averaged models.

scholarly journals AN HEURISTIC MODEL OF WAVE HEIGHT DISTRIBUTION IN SURF ZONE

1980 ◽  
Vol 1 (17) ◽  
pp. 15 ◽  
Author(s):  
Masaru Mizuguchi
Keyword(s):  
Surf Zone ◽  
Experimental Result ◽  
Height Distribution ◽  
Heuristic Model ◽  
Longshore Current ◽  
Current Profile ◽  
Beach Profile ◽  
Wave Height Distribution ◽  
Constant Slope ◽  
Step Type

Until now, almost every study on coastal processes has considered the basic type of two-dimensional beach profile as being of constant slope. However, as our knowledge on this problem advances, we realize the importance of the influences of the bottom configuration on the hydrodynamic phenomena in a given area. Figure 1 shows a recent experimental result on the longshore current profile on a step type beach. ( Here the step type beaches are defined as those which have a step in the bottom profile, whether the beaches are of accretion type or not.)

Nearshore mixing and dispersion

1994 ◽  
Vol 445 (1925) ◽  
pp. 561-576 ◽  
Keyword(s):  
Surf Zone ◽  
Three Dimensional ◽  
Dispersion Effect ◽  
Longshore Current ◽  
Turbulent Length Scale ◽  
Interaction Terms ◽  
Longshore Currents ◽  
Order Of Magnitude ◽  
Lateral Mixing ◽  
The One

Longshore currents have in the past been analysed assuming that the lateral mixing could be attributed to turbulent processes. It is found, however, that the mixing that can be justified by assuming an eddy viscosity v t = l√k where l is the turbulent length scale, k the turbulent kinetic energy, combined with reasonable estimates for l and k is at least an order of magnitude smaller than required to explain the measured cross-shore variations of longshore currents. In this paper, it is shown that the nonlinear interaction terms between cross-and longshore currents represent a dispersive mechanism that has an effect similar to the required mixing. The mechanism is a generalization of the one-dimensional dispersion effect in a pipe discovered by Taylor (1954) and the three-dimensional dispersion in ocean currents on the continental shelf found by Fischer (1978). Numerical results are given for the dispersion effect, for the ensuing cross-shore variation of the longshore current and for the vertical profiles of the longshore currents inside as well as outside the surf zone. It is found that the dispersion effect is at least an order of magnitude larger than the turbulent mixing and that the characteristics of the results are in agreement with the sparse experimental data material available.

scholarly journals Series Solution for Steady Three-Dimensional Flow due to Spraying on Inclined Spinning Disk by Homotopy Perturbation Method

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Saeed Dinarvand
Keyword(s):  
Perturbation Method ◽  
Series Solution ◽  
Homotopy Perturbation Method ◽  
Three Dimensional ◽  
Free Surface Flows ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Homotopy Perturbation ◽  
Spinning Disk ◽  
Through Flow

The steady three-dimensional flow of condensation or spraying on inclined spinning disk is studied analytically. The governing nonlinear equations and their associated boundary conditions are transformed into the system of nonlinear ordinary differential equations. The series solution of the problem is obtained by utilizing the homotopy perturbation method (HPM). The velocity and temperature profiles are shown and the influence of Prandtl number on the heat transfer and Nusselt number is discussed in detail. The validity of our solutions is verified by the numerical results. Unlike free surface flows on an incline, this through flow is highly affected by the spray rate and the rotation of the disk.

scholarly journals A NUMERICAL INVESTIGATION OF THE LONGSHORE CURRENT PROFILE FOR MULTIPLE BAR/TROUGH BEACHES

1986 ◽  
Vol 1 (20) ◽  
pp. 73 ◽  
Author(s):  
Steven K. Baum ◽  
David R. Basco
Keyword(s):  
Numerical Model ◽  
Wave Height ◽  
Water Depth ◽  
Balance Equation ◽  
Surf Zone ◽  
Momentum Balance ◽  
Longshore Current ◽  
Current Profile ◽  
Momentum Balance Equation ◽  
Wave Decay

A numerical model is developed which calculates the longshore current profile for an arbitrary bottom profile. The basis of the model is the use of radiation stress theory in a longshore momentum balance equation which includes a driving stress, a bottom stress, and a lateral mixing stress. Each of the stresses is derived from previously developed formulations, rederiving them to take into account separate cross shore variations in the wave height and the water depth, as well as the wave approach angle. This is done to dispense with the constant wave breaking index assumption used to model wave decay in the surf zone, which is rejected as unrealistic for natural beaches. A numerical model is used to calculate distributions of the wave height and water depth across the surf zone for arbitrary, yet realistic, bottom profiles. A numerical model of the theoretically derived longshore momentum balance equation is developed and solved using the distributions obtained from the wave decay model. The profiles calculated are compared to previous theoretical models and to laboratory and field measurements.

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.

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