Quasi-three-dimensional modeling of rip current systems

[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.