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Lee, J.L. Lee, J.Y. and Kim, I.H., 2011. A mathematical approach of low-frequency rip current oscillation. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 557 - 560. Szczecin, Poland, ISSN 0749-0208
In the present study, a simple undulated rip current model is presented. Field measurements of nearshore currents facing large waves often indicate that seaward currents can exhibit unsteady oscillations. This unexpected unsteadiness often initiates dangerous fatal accidents. However, a mechanism for unsteady rip currents has not yet been clearly addressed. It has been believed that these oscillations might be generally attributed to long period modulations in incoming waves or to the presence of low-frequency wave motions. Recently, it has also been suggested that these oscillations might arise from the instability of longshore currents. However, even in the presence of steady wave forcing, such low-frequency rip currents are often obtained in a laboratory experiment which generates rip currents or considers wave deformation due to inlet flow. The present mathematical model for the wave-averaged rip current is governed by two governing equations in order to produce the rip current oscillations. The two equations are composed of a wave action equation and an alternative form of wave energy equation. The wave action equation has been derived by Lee (1993) from the free surface boundary condition, thus it differs from the typical wave action equation which is another form of wave energy equation. The validation of the proposed wave action equation was already established by Lee (1993) through the comparison with surf zone height and surface current variations. The model shows that rip currents can be highly unstable with increasing beach slope when facing the opposing waves.
- 出版日期2011
