A New Method for Modeling Bottom Shear Stress under Irregular Waves

Taufiqur Rachman, Suntoyo Suntoyo

Abstract


The bottom shear stress estimation is the most important step to device an input to all the practical sediment transport models. In this paper, the modeling of bottom shear stress in a rough turbulent bottom boundary layer under irregular waves of experimental result is examined by a new calculation method of bottom shear stress based on incorporating velocity and acceleration terms simultaneously. A new acceleration coefficient is proposed to formulate the bottom shear stress under irregular waves. The new formula is further examined with a basic harmonic wave cycle modified with the phase difference and square of the instantaneous friction velocity incorporating the acceleration effect as proposed by the previous researchers. The new method gave the smallest the RMSE value indicating that the new method has the best agreement with the bottom shear stress of experimental results. Therefore, it can effectively be utilized in a beach evolution model by combining it with the irregular wave transformation model.

Keywords


bottom shear stress; irregular wave; and turbulent bottom boundary layer

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References


T.W. Hsu, and S.H. Ou, “Wave boundary layers in rough turbulent flow”, Ocean Engineering, Elsevier, Vol. 24, No. 1, pp. 25-43, 1997.

J. Fredsøe, R. Deigaard, “Mechanics of coastal sediment transport”, New York: World Scientific, 1992, pp. 369.

P. Nielsen, “Coastal bottom boundary layers and sediment transport”, Singapore: World Scientific, 1992, pp. 324.

G. Simarro, A. Orfila, A. Galan and G.A. Zarruk, “Bottom friction effects on linear wave propagation”, Wave Motion, Vol. 46, pp. 489-497, 2009.

R.L. Soulsby, L. Hamm, G. Klopmann, D. Myrhaug, R.R. Simons and G.P .Thomas, “Wave-current interaction within and outside the bottom boundary layer”, Coastal Engineering, Vol. 21, pp. 41–69, 1993.

Y. Zhao and K. Anastasiou, “Bottom friction effects in the combined flow field of random waves and current”, Coastal Engineering, Vol. 19, pp. 223–243, 1993.

D. Myrhaug, “Bottom friction beneath random waves”, Coastal Eng. Vol. 24, pp. 259–273, 1995.

D. Myrhaug, O.H. Slaattelid, and K.F. Lambrakos, “Seabed shear stresses under random waves: predictions vs. estimates from field measurements”, Ocean Engineering, Vol. 25, No. 10, pp. 907–916,

L.E. Holmedal, D. Myrhaug and H. Rue, “Seabed shear stresses under irregular waves plus current from Monte Carlo simulations of parameterized models”, Coastal Engineering, Vol. 39, pp. 123–147, 2000.

L.E. Holmedal, D. Myrhaug and H. Rue, The sea bed boundary layer under random waves plus current”, Continental Shelf Research, Vol. 23, pp. 717–750, 2003.

M.A. Samad and H. Tanaka, “Estimating instantaneous turbulent bottom shear stress under irregular wave”, Journal of Hydroscience and Hydraulic Engineering”, Vol. 17, No. 2, pp. 107-126, 1999.

H. Tanaka and M.A. Samad, “Prediction of instantaneous bottom shear stress for turbulent plane bed condition under irregular wave”, Journal of Hydraulic Research, Vol. 44, No. 1, pp. 94-106, 2006.

H. Tanaka, T. Suzuki, Suntoyo and H. Yamaji, “Time-variation of bottom shear stress under irregular waves over rough bed”, Journal of Hydroscience and Hydraulic Engineering, Vol. 25, No. 2, pp. 217-225, 2002.

G. Huo, Y. Wang, B. Yin and Z. You, “The study of the bed shear stress on the irregular waves”, presented at 17th 2007 International Offshore and Polar Engineering Conference (ISOPE 2007), Code 70675, 1- 6 July 2007, Lisbon, 2007.

T.J. Hsu and D.M .Hanes, “Effects of wave shape on sheet flow sediment transport”, Journal of Geophysical Research, Vol. 109, C05025, 2004.

Suntoyo, H. Tanaka and A. Sana, “Characteristics of turbulent boundary layers over a rough bed under saw-tooth waves and its application to sediment transport”, Coastal Engineering, Vol. 55, No. 12, pp. 1102-1112, 2008.

Suntoyo and H. Tanaka, “Effect of bed roughness on turbulent boundary layer and net sediment transport under asymmetric waves”, Coastal Engineering, Vol. 56, No. 9, pp. 960-969, 2009.

F.R. Menter, “Two-equation eddy-viscosity turbulence models for engineering applications”, AIAA Journal, Vol. 32, No. 8, pp. 1598-1605, 1994.

J.F.A. Sleath, “Turbulent oscillatory flow over rough beds”, Journal of Fluid Mechanics, Vol. 182, pp. 369-409, 1987.

P. Justesen, “Turbulent wave boundary layer”, Series Paper No. 43, ISVA, Technical University of Denmark, 1998.

P. Nielsen, “Coastal and estuarine processes”, Advanced Series on Ocean Engineering, Singapore: Word Scientific Pub., Vol. 29, pp. 343, 2009.

P. Nielsen, “Shear stress and sediment transport calculations for swash zone modeling”, Coastal Engineering, Vol. 45, pp. 53–60, 2002.




DOI: http://dx.doi.org/10.12962/j20882033.v22i2.60

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