WAVE FLUME-BASED EVALUATION OF SUSPENDED SAND TRANSPORT IN BREAKING WAVES

Junichi Otsuka, Yasunori Watanabe

Abstract


In this study, suspended sediment concentration and velocity in surf zones was measured in a small-scale wave flume with three breaker types (plunging, spilling and intermediate) using an optical concentration sensor and an ultrasonic velocity profiler (UVP). The sediment pickup rate was also calculated from the depth-averaged concentration and the wave energy flux dissipation rate. In plunging breakers, relatively large amounts of sediment are suspended in the transition region due to strong three-dimensional turbulent flows generated by large-scale vortices. In spilling breakers, sediment concentration is lower than that seen in plunging breakers because smaller- scale vortices typically develop below the water surface in the transition region. Concentrations in both breaker types remain at lower levels in bore regions because the vortices fully develop into weak turbulent bores. Comparison in the same range of wave energy flux dissipation rates showed that the sediment pickup rates in these small-scale experiments were approximately 103 times greater than those calculated by Goda (2010) using various data compiled from large-scale experiments and field observations.

Keywords


breaking wave; sediment transport; ultrasonic velocity profiler

References


Goda, Y., 2010, Quantitative assessment of sediment pickup rate within surf zone based on large-scale data, Proceedings of Coastal Engineering, JSCE, 66, 421-425 (in Japanese).

Nadaoka, K., Hino, M. and Koyano, Y., 1989, Structure of the turbulent flow field under breaking waves in the surf zone, Journal of Fluid Mechanics, 204, 359-387.http://dx.doi.org/10.1017/S0022112089001783

O'Donoghue, T. and Wright, S., 2004, Flow tunnel measurements of velocities and sand flux in oscillatory sheet flow for well-sorted and graded sands, Coastal Engineering, 51, 1163-1184.http://dx.doi.org/10.1016/j.coastaleng.2004.08.001

Takeda, Y., 1995, Instantaneous velocity profile measurement by ultrasonic Doppler method, JSME Int. J., 8-16.

Watanabe, Y., H. Saeki and R. J. Hosking, 2005, Three-dimensional vortex structures under breaking waves, Journal of Fluid Mechanics, 545, 291-328.http://dx.doi.org/10.1017/S0022112005006774


Full Text: PDF

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.