SWASH: An operational public domain code for simulating wave fields and rapidly varied flows in coastal waters

Recent advances on the numerical modelling of turbulent flows

A theoretical model is developed for wave heights and set-up in a surf zone. In the time averaged equations of energy and momentum the energy flux, radiation stress and energy dissipation are determined by simple approximations which include the surface roller in the breaker. Comparison with measurements shows good agreement. Also the transitions immediately after breaking are analysed and shown to be in accordance with the above mentioned ideas and results.

/pdf/wave-heights-and-set-up-in-a-surf-zone-39q6lqmhg5.pdf

Wave Heights and Set-up in a Surf Zone

http://www.hunter.cuny.edu/catalyst/catalyst-seminar-documents/spring-2012-documents/macmahanripreview06.pdf

Rip current review

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

[1] The focus of the paper is the analysis of the flow in rip current systems generated by channels in longshore bars on a beach. The horizontal variations of rip current systems are described through the use of the quasi-three-dimensional nearshore circulation model SHORECIRC. Model predictions are compared to laboratory measurements of waves and current velocities throughout the entire rip current system and show reasonable agreement. The rips in the two channels are found to behave differently because of the depth variation across the basin. It is found that higher bottom stress leads to more stable flow where the rip current meanders less and fewer eddies are generated. The wave current interaction creates forcing which reduces the distance rip currents flow offshore and can lead to a slow pulsation of the rip current. This pulsation is in addition to the instabilities of a jet which can also be present in rip currents. The three dimensionality of the rip current system is found to have a significant effect on the overall circulation patterns. INDEX TERMS: 4255 Oceanography: General: Numerical modeling; 4512 Oceanography: Physical: Currents; 4546 Oceanography: Physical: Nearshore processes; KEYWORDS: rip currents, nearshore circulation, numerical modeling, waves

/pdf/quasi-three-dimensional-modeling-of-rip-current-systems-1gni3nq4v4.pdf

Quasi-three-dimensional modeling of rip current systems

Numerical simulation of breaking waves by a multi-scale turbulence model

In this paper, the VOF method for free surface flow is applied to simulate breaking waves incident on a submerged reef. An efficient numerical wave channel with two absorbing boundaries is developed. Corresponding boundary conditions are prescribed. Smagorinsky's sub-grid scale model is incorporated to account for the sub-grid scale turbulence. Numerical results are compared with laboratory measurements.

https://icce-ojs-tamu.tdl.org/icce/index.php/icce/article/download/5656/5326

Numerical simulation of breaking waves by large eddy simulation and vof method

[1] Most studies on shear waves to date have assumed the flow is depth uniform (two dimensional). In the present study, we utilize the quasi-three-dimensional (quasi-3D) nearshore circulation model SHORECIRC to study shear waves. Our results show that shear wave flow is more organized in the quasi-3D simulation than in the 2D simulation. In the 2D simulation, the vortices are moving farther offshore of the bar, while in the quasi-3D simulation, they are more confined to the shoreward side of the bar. Moreover, the shear waves in the quasi-3D simulation are much less energetic than in the 2D simulation, though the total momentum mixing for the two cases is not significantly different. To understand which mechanisms cause the differences in the 2D and the quasi-3D simulation, the momentum, kinetic energy, and enstrophy equations for the mean flow and the shear waves are derived. The momentum, energy, and enstrophy balances are discussed using the numerical results from the idealized SUPERDUCK topography and the wave conditions on October 16, 1986. The effects of the quasi-3D dispersion due to the depth varying currents on shear waves are illustrated. Analysis of the mean momentum balance shows that both the shear waves and the quasi-3D current pattern contribute to the momentum transfer, and the momentum transfer provided by the shear waves is sometimes larger than that by the quasi-3D dispersive terms. The kinetic energy balance of the shear waves shows that the quasi-3D dispersive terms will extract kinetic energy from the depth-averaged shear waves. Furthermore, the enstrophy equation demonstrates that the quasi-3D dispersion terms provide vortex tilting, which allows three-dimensional vortex interactions.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2002JC001306

Qun Zhao

Papers

Quasi-three-dimensional modeling of rip current systems

Numerical simulation of breaking waves by a multi-scale turbulence model

Numerical simulation of breaking waves by large eddy simulation and vof method

Three-dimensional effects in shear waves

Analysis of Rip Current Systems