LOCAL CONCENTRATION OF SLOWLY VARYING WAVE AND CURRENT FIELDS AROUND THE ABRUPTLY CHANGING BOTTOM SLOPES ALONG THE SHORE

Yoshimitsu Tajima, Shinji Sato

Abstract


This study aims to investigate physical mechanisms of locally concentrated nearshore hydrodynamic forces under interactive fields of waves and currents on abruptly changing coastal bathymetry. Laboratory experiments were first performed to represent such phenomena and a newly developed monitoring system based on image processing techniques successfully captured the local concentrations of wave fields as quantitative high-resolution data sets. Numerical experiments were then performed to investigate the physical mechanisms of the observed features. It was found that, among the other various possible factors, slowly varying wave-induced nearshore currents have one of the most significant impacts on local concentrations of waves around the abruptly changing bathymetry.

Keywords


wave-current interaction; wave breaking; wave envelope; nearshore current; long wave

References


Janssen, T.T., J.A. Battjes, and A.R. van Dongeren. 2003. Long waves induced by short-wave groups over a sloping bottom, J. Geophy. Res. 108, C8, 3252, doi:10.1029/2002JC001515. http://dx.doi.org/10.1029/2002JC001515

Larson, M. and N.C. Kraus. 1991. Numerical model of longshore current for bar and trough beaches, J. Waterway, Port, Coast. and Ocea. Eng., vol.117, No.4, 326-347. http://dx.doi.org/10.1061/(ASCE)0733-950X(1991)117:4(326)

List, J.H. 1992. Wave groupiness variation in the nearshore, Coast. Eng., vol.15, 475-496. http://dx.doi.org/10.1016/0378-3839(91)90024-B

Longuet-Higgins, M.S. and R.W. Stewart. 1962. Radiation stress and mass transport in gravity waves, with application to "surf beat," J. of Fluid Mechanics, vol.13, 481-504. http://dx.doi.org/10.1017/S0022112062000877

Madsen, O. S. 1994. Spectral wave-current bottom boundary layer flows, Proc. 24th Int. Conf. on Coast. Eng., 384-398.

Ohnaka, S., A. Watanabe and M. Isobe. 1989. Numerical computation of wave field by the unsteady mild slope equation extended to wave-current coexisting field, Proc. of Coast. Eng., JSCE, 91-95 (in Japanese).

Seki, K., and Y. Mizuguchi. 2008. Shoaling of long period waves induced by grouping short-waves on sloping bottom. J. of the Japan Society of Civil Engineers B, JSCE, vol.64, 62-70 (in Japanese).

Tajima, Y., H. Liu and S. Sato:Dynamic changes of waves and currents over the collapsing sandbar of the Tenryu river mouth observed during Typhoon T0704, Proc. Coastal Dynamics 2009, CDROM published by World Scientific.

Tajima, Y., S. Sato, T. Shimozono and M. Isobe. 2007. Characteristics and modeling of wave-induced current around submerged detached breakwaters, Proc. Int. Conf. on Coastal Structures, 725-736.

Tajima, Y. and S. Sato. 2009. Numerical investigations of locally concentrated damages on Seisho coast sue to typhoon T0709, Proc. of 5th Int. Conf. on Asian and Pacific Coasts.


Full Text: PDF

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