Air–water two-phase flow modeling of turbulent surf and swash zone wave motions

Abstract

Wave breaking and wave runup/rundown have a major influence on nearshore hydrodynamics, morphodynamics and beach evolution. In the case of wave breaking, there is significant mixing of air and water at the wave crest, along with relatively high kinetic energy, so prediction of the free surface is complicated. Most hydrodynamic studies of surf and swash zone are derived from single-phase flow, in which the role of air is ignored. Two-phase flow modeling, consisting of both phases of water and air, may be a good alternative numerical modeling approach for simulating nearshore hydrodynamics and, consequently, sediment transport. A two-phase flow tool can compute more realistically the shape of the free surface, while the effects of air are accounted for. This paper used models based on two-dimensional, two-phase Reynolds-Averaged NavierStokes equations, the Volume-Of-Fluid surface capturing technique and different turbulence closure models, i.e., k-ε, k-ω and Re-Normalized Group (RNG). Our numerical results were compared with the available experimental data. Comparison of the employed method with a model not utilizing a two-phase flow modeling demonstrates that including the air phase leads to improvement in simulation of wave characteristics, especially in the vicinity of the breaking point.The numerical results revealed that the RNG turbulence model yielded better predictions of nearshore zone hydrodynamics, although the k-ε model also gave satisfactory predictions. The model provides new insights for the wave, turbulence and means flow structure in the surf and swash zones.

Assessing the Hydro-Morphodynamic Response of a Beach Protected by Detached, Impermeable, Submerged Breakwaters: A Numerical Approach

“…They also demonstrated that changes in the wave characteristics mainly influence the distribution of turbulent kinetic energy, and consequently sediment transport, in the inner surf zone rather than in the swash zone (see also Bakhtyar et al, 2010). As a partial support, the numerical tests in this study highlight that larger periods provide larger sand erosion/deposition in the surf zone, especially in the gap between the breakwaters.…”

Numerical experiments on interactions between wave motion and variable-density coastal aquifers

“…similarity parameter values are ζ = 0.45 < 0.5 and ζ = 0.91 > 0.5, respectively, which represent, respectively, (i) a spilling breaker and (ii) a plunging breaker. As the influence of swash-swash interactions becomes proportionally larger for shorter period waves and the turbulence and wave energy under the plunging breaker are much higher than for a spilling breaker (Bakhtyar et al, 2010b), sediment transport and beach profile variations are more important in a plunging breaker.…”

Characteristics of Wave Breaking and Blocking by Spatially Varying Opposing Currents

“…The Reynolds-Averaged Navier-Stokes (RANS) solver along with a Volume of Fluid (VOF) free surface capturing scheme and a turbulence closure model has become popular in studying breaking waves in the surf zone (Bakhtyar et al, 2010;Chella et al, 2016;Jacobsen et al, 2012Jacobsen et al, , 2014Lin & Liu, 1998a, 1998bMayer & Madsen, 2000;Pedrozo-Acuña et al, 2010;Wang et al, 2009b;Xie, 2013). Brown et al (2016) evaluated the performance of five turbulence models in OpenFOAM for simulating the surf zone breakers and found that all five models reasonably predict, some even overpredict, the maximum wave height at the breaking onset.…”