IMPROVEMENT OF BOTTOM BOUNDARY LAYERS MODELING UNDER INTERACTIONS OF WAVE AND WAVE-INDUCED CURRENT

Jinhai Zheng, Chi Zhang, Yigang Wang, Zeki Demirbilek

Abstract


The bottom boundary layer characteristics beneath waves transforming on a natural beach are specifically affected both by wave and wave-induced current. This study presents an improved approach for coastal bottom boundary layers modeling under interactions of wave and wave-induced current. The improvement is achieved by formulating the mean horizontal pressure gradient term in the boundary layer equation with wave parameters and mean water level. This formulation represents the balance between the wave excess momentum flux gradient and the hydrostatic pressure gradient in a spatially transforming wave field, accounting for the effect of the wave-induced cross-shore current. Model is validated with experimental data for normally incident shoaling wave over a sloping bed. Calculated results agree well with data for instantaneous velocity profiles, wave oscillating amplitudes and mean velocity profiles. In particular, model reasonably reproduces the observed local onshore mean flow near the bottom beneath shoaling wave. It is revealed that the proposed formulation of the mean horizontal pressure gradient plays an important role in bottom boundary layer modeling under wave transforming over an variable near-shore bathymetry, and that the present model can be conveniently and reliably coupled with a sediment transport model to study coastal processes in engineering applications.

Keywords


wave boundary layer; wave-induce current; wave-current interactions; numerical model

References


Bakker, W.T., and T. Van Doorn. 1978. Near-bottom velocities in waves with a current, Proceedings of 16 th International Conference on Coastal Engineering, ASCE, 1394-1413.

Davies, A.G., R.L. Soulsby, and H.L. King. 1988. A numerical model of the combined wave and current bottom boundary layer, Journal of Geophysical Research, 93, 491-508. http://dx.doi.org/10.1029/JC093iC01p00491

Fredsøe, J., and R. Deigaard. 1992. Mechanics of coastal sediment transport, World Scientific, Singapore.

Grant, W.D., and O.S. Madsen. 1979. Combined wave and current interaction with a rough bottom, Journal of Geophysical Research, 84, 1797-1808. http://dx.doi.org/10.1029/JC084iC04p01797

Guizien, K., M. Dohmen-Janssen, and G. Vittori. 2003. 1DV bottom boundary layer modeling under combined wave and current: Tubulent separation and phase lag effects, Journal of Geophysical Research, 108, 3000-3016. http://dx.doi.org/10.1029/2001JC001292

Henderson, S.M., J.S. Allen, and P.A. Newberger. 2004. Nearshore sandbar migration predicted by an eddy-diffusive boundary layer model, Journal of Geophysical Research, 109, doi: 1. 1029/2003JC002137.

Holmedal, L.E., D. Myrhaug, and K.J. Eidsvik. 2004. Sediment suspension under sheet flow conditions beneath random waves plus current, Continental Shelf Research, 24, 2065-2091. http://dx.doi.org/10.1016/j.csr.2004.06.021

Kemp, P.H., and R.R. Simons. 1982. The interaction of waves and a turbulent current: waves propagating with the current, Journal of Fluid Mechanics, 116, 227-250. http://dx.doi.org/10.1017/S0022112082000445

Lin, C., and H.H. Hwung. 2002. Observation and measurement of the bottom boundary layer flow in the prebreaking zone of shoaling waves, Ocean Engineering, 29, 1479-1502. http://dx.doi.org/10.1016/S0029-8018(01)00094-4

Malarkey, J., and A.G. Davies. 1998. Modeling wave-current interactions in rough turbulent bottom boundary layers, Ocean Engineering, 25, 119-141. http://dx.doi.org/10.1016/S0029-8018(96)00062-5

Reniers, A.J.H.M., E.B. Thomton, T.P. Stanton, and J.A. Roelvink. 2004. Vertical flow structure during Sandy Duck: observations and modeling, Coastal Engineering, 51, 237-260. http://dx.doi.org/10.1016/j.coastaleng.2004.02.001

Sana, A., A.R. Ghumman, and H. Tanaka. 2007. Modification of the damping function in the k-ε model to analyze oscillatory boundary layers, Ocean Engineering, 34, 320-326. http://dx.doi.org/10.1016/j.oceaneng.2005.11.018

Shi, J.Z., and Y. Wang. 2008. The vertical structure of combined wave-current flow, Ocean Engineering, 35, 174-181. http://dx.doi.org/10.1016/j.oceaneng.2007.07.003

Stive, M.J.F., and H.J. De Vriend. 1994. Shear stresses and mean flow in shoaling and breaking waves, Proceedings of 24 th International Conference on Coastal Engineering, ASCE, 594-608.

Svendsen, I.A. 1984. Mass flux and undertow in a surf zone, Coastal Engineering, 8, 345-365. http://dx.doi.org/10.1016/0378-3839(84)90030-9

You, Z.J. 1994. A simple model for current velocity profiles in combined wave-current flows, Coastal Engineering, 23, 289-304. http://dx.doi.org/10.1016/0378-3839(94)90007-8

Zheng, J.H. 2007. Depth-dependent expression of obliquely incident wave induced radiation stress, Progress in Natural Science, 17, 1067-1073.

Zheng, J.H., H. Mase, Z. Demirbilek, and L. Lin. 2008. Implementation and evaluation of alternative wave breaking formulas in a coastal spectral wave model, Ocean Engineering, 35, 1090-1101. http://dx.doi.org/10.1016/j.oceaneng.2008.05.001

Zheng, J.H., and Y. Tang. 2009. Numerical simulation of spatial lag between wave breaking point and location of maximum wave-induced current, China Ocean Engineering, 23, 59-71.


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