Comparisons between sediment transport models and observations made in wave and current flows above plane beds

As a part of the MAST2 G8-M Coastal Morphodynamics project, the predictions of four sediment transport models have been compared with detailed laboratory data sets obtained in the bottom boundary layer beneath regular waves, asymmetrical waves, and regular waves superimposed co-linearly on a current. Each data set was obtained in plane bed, sheet flow, conditions and each of the four untuned numerical models has provided a one-dimensional vertical (1DV), time-varying, representation of the various experimental situations. Comparisons have been made between the model predictions and measurements of both time-dependent sediment concentration, and also wave-averaged horizontal velocity and concentration. For the asymmetrical waves and for the combined wave-current flows, comparisons have been made with vertical profiles of the cycle-averaged sediment flux, and also with the vertically-integrated net sediment transport rate. Each of the turbulence diffusion models gives an accurate estimate of the net transport rate (invariably well within a factor of 2 of the measured value). In contrast, none of the models provides a good detailed description of the time-dependent suspended sediment concentration, due mainly to the inability of conventional turbulence diffusion schemes to represent the entrainment of sediment into suspension by convective events at flow reversal. However, in the cases considered here, this has not seriously affected the model predictions of the net sediment flux, due to the dominance of the near-bed transport. The comparisons in this paper are aimed not only at testing the predictive capability of existing sediment transport modelling schemes, but also at highlighting some of their deficiencies

Fricción y tensión tangencial por fondo con ola y corriente

[ES] Se calcula la tensión tangencial debido a ola y corriente mediante un modelo numérico con cierre turbulento K-L, donde K es la energía cinética turbulenta y L es la escala longitudinal de turbulencia. Se obtiene el coeficiente de fricción parametrizado para el caso de flujo turbulento rugoso, siguiendo a Soulsby et al. (1994) y se amplía al caso de flujo turbulento liso. La comparación de estos resultados con otros existentes en la literatura, especialmente los proporcionados por Tanaka y Thu (1994) muestra un buen ajuste.Se propone una nueva parametrización de la serie temporal de la tensión tangencial que incluye el coeficiente de fricción local obteniéndose mejores resultados que aplicando la parametrización propuesta por Soulsby et al. (1994).Este trabajo se ha llevado a cabo en el ámbito del Proyecto “Modelación de Régimen Turbulento en Zonas Costeras-Aplicaciones a la Dinámica de Sedimentos y Dispersión de Contaminantes”, financiado por la Fundação para a Ciencia e a Tecnología (FCT), bajo el contrato de investigación PBIC/C/MAR/2247/95. Asimismo, se reconoce la contribución de los projectos “SEDMOC-Modelación del Transporte de Sedimentos en Entornos Marinos Costeros” y “Parametrización del Coeficiente de Fricción en Régimen Variable: Aplicaciones al Golpe de Ariete y Transporte de Sedimentos”, financiados por la UE con el contrato nº MAS3-CT97-0115 y por la FCT con el contrato nº PRAXIS//3.1/CEG/2503/95, respectivamente.Antunes Do Carmo, JS.; Temperville, A.; Seabra Santos, F. (2003). Fricción y tensión tangencial por fondo con ola y corriente. Ingeniería del agua. 10(2):177-188. https://doi.org/10.4995/ia.2003.2583OJS177188102Antunes do Carmo J.S., F.J. Seabra-Santos and E. Barthlemy, 1993. Surface waves propagation in shallow-water: a finite element model. Int. J. Num. Meth. in Fluids, Vol. 16, No. 6, 447-459.Arnskov M.M, J. Fredsøe and B.M. Sumer, 1993. Bedshear stress measurements over a smooth bed in three-dimensional wave-current motion. Coastal Engineering, 20,277-316.Fredsøe J., 1984. Turbulent boundary layer in wave-current-motion. J. Hydraul. Eng., 110 (8), 1103-1120.Huynh Thanh S., 1990. Modélisation de la couche limite turbulente oscillatoire générée par l'interaction houle courant en zone côtière. Thèse à l'Institut National Polytechnique de Grenoble.Huynh Thanh S. and A. Temperville, 1991. A numerical model of the rough turbulent boundary layer in combined wave and current interaction. In: R.L. Soulsby and R. Betess (Editors), Sand Transport in Rivers, Estuaries and the Sea. Balkema, Rotterdam, pp. 93-100.Jensen B.L., B.M. Sumer and J. Fredsøe, 1989. Turbulent oscillatory boundary layers at high Reynolds numbers. Journal of Fluid Mechanics, 206, 265-297.Jonsson I.G., 1966.Wave boundary layers and friction factors. Proc. 10th Int. Conf. Coastal Eng., Tokyo, 127-148.Jonsson I.G. and N.A. Carlsen, 1976. Experimental and theoretical investigations in an oscillaory turbulent boundary layer. Journal of Hydraulics Research, 14(1), 45-60.Kamphuis J.W., 1975. Friction factor under oscillatory waves. J. Waterw. Port Coastal Ocean Eng., 101 (WW2), 135-144.Ockendenand M.C., R.L.Soulsby, 1994. Sediment transport by currents plus irregular waves. Report SR 376, HR Wallingfort, HR Wallingfort Ltd. Howbery Park, Wallingfort, Oxfordshire, OX10 8BA, UK.Sleath J.F.A., 1987. Turbulent oscillatory flow over rough beds. Journal of Fluid Mechanics, 182, 369-409.Sleath J.F.A., 1991. Velocities and shear stresses in wavecurrent flows. Journal of Geophysical Research, Vol. 96, No. C8, 15, 237-15, 244.Soulsbyand R.L., M.C.Ockenden, 1994. Sediment transport by currents plus irregular waves. Report SR 237, HR Wallingfort.Soulsby R.L., L. Hamm, G. Klopman, D. Myrhaug,Simons R.R and G.P. Thomas, 1994. Wave-current interaction within and outside the bottom boundary layer. Coastal Eng., 21, 41-69.Sumer B.M., B.L. Jensen and L. Fredsøe, 1987. Turbulence in oscillatory boundary layers. In Advances in Turbulence. Springer, Heidelberg, 556-567.Swart D.H., 1974. Offshore sediment transport and equilibrium beach profiles. Delft Hydraulics Lab., Publ. 131.Tanaka H. and N. Shuto, 1981. Friction coefficient for a wave-current coexistent system. Coastal Eng. Japan, 24, 105-128.Tanaka H. and N. Shuto, 1984. Friction laws and flow regimes underwave and current motion. Journal of Hydraulic Research, 22(4), 245-261.Tanaka H. and A. Thu, 1994. Full-range equation of friction coefficient and phase difference in a wave-current boundary layer. Coastal Eng., 22, 237-254.Tran Thu T. and A. Temperville, 1994. Numerical model of sediment transport in thewave-current interaction. Proc. of the Advanced Seminar on Modelling of Coastal and Estuarine Processes. Coimbra, Portugal, 271-282.Tran Thu T., 1995. Modélisation numérique de l'interaction houle-courant-sédiment. Thèse à l'Université Joseph Fourier-Grenoble I

Interaction houle-courant-sédiment

Nous présentons la modélisation du transport en suspension de sédiment non-cohésif sous l'action d'un écoulement du type houle plus courant à l'aide d'un modèle numérique 1 DV de fermeture K-L. On ne traitera dans ce chapitre que le cas d'un fond plat, rugueux et on s'intéresse seulement à la partie sédimentaire du modèle : Le choix de la concentration de référence au fond, l'influence de l'amortissement de la turbulence sur la distribution de la concentration, la variation temporelle de la concentration, le débit solide. Les comparaisons intensives avec les expériences montrent les limites de ce type de modèle ainsi que leurs applications possibles dans le génie côtier.Tran Thu T., Temperville A. Interaction houle-courant-sédiment. In: L'eau, l'homme et la nature. 24èmes journées de l'hydraulique. Congrès de la Société Hydrotechnique de France. Paris, 18-19-20 septembre 1996. 1996

Analytical approximate wave form for asymmetric waves

A simple analytical formulation that reproduces a skewed, nonlinear near-bed wave orbital velocity is presented. It contains four free parameters, where two are solely related to the velocity and acceleration skewnesses. The equation is compared with other models and is validated against field and laboratory experiments. The results reveal that it can simulate a wide range of nonlinear wave shapes, reproducing satisfactorily the measured nonlinear wave particle velocity. Also, the new expression overcomes some limitations of the other models. The new formulation is therefore capable of being used in many engineering applications that require the use of representative wave forms.publishe