Author(s): Choonghun Shin; Junwoo Choi; Jaeseok Bae; Sungbum Yoon
Linked Author(s):
Keywords: Rip current; Haeundae beach; Numerical simulation; COULWAVE
Abstract: In this study CCTV image analyses and numerical simulation were conducted for the investigation of the rip current occurring at Haeundae Beach of Busan, Korea. Analyses of CCTV images showed that the rip current occur when the waves of honeycomb pattern incident and break on the beach. The honeycomb pattern of waves can be generated by the two wave trains propagating with slightly different directions. The crest lines make hexagons with a shorter axis in the direction of wave propagation, and the nodal lines exist between the crest lines. Along the nodal lines the wave height becomes zero, and the radiation stresses are much weaker. Thus, the excess mass of water carried by the incident breaking waves is piled up on the beach and is concentrated at the nodal point. The excess water mass returns to the offshore along the nodal line in the form of a strong jet called rip current. This mechanism of rip current generation is different from the research results conducted earlier for the Haeundae Beach. To demonstrate the generation mechanism newly found based on the CCTV image analyses, numerical simulation are also performed using COULWAVE, a fully nonlinear Boussinesq equation model with moving boundary capability. The numerical simulation confirms that rip currents are generated on a straight beach as well as a pocket beach. The findings in this study can be useful to forecast the occurrence of rip currents in the summer season at the Haeundae beach where dangerous rip currents occurs frequently every year.
Year: 2012