Wave flume

About: Wave flume is a research topic. Over the lifetime, 1627 publications have been published within this topic receiving 23335 citations.

New Wave Parameter for Coastal Structure Design

Abstract: A new parameter representing the maximum depth-integrated wave momentum flux occurring in a wave is proposed for characterizing wave processes at coastal structures. This parameter I s physically relevant descriptor of wave forcing; and having units of force, it is useful for developing meaningful physical formulations between the waves and the process occurring at the structure. This paper overviews the development of the wave momentum flux parameter, and it presents an empirical formula was estimating the parameter for nonlinear steady waves of permanent form. New formulas for irregular wave rump on plane, impermeable slopes are given in terms of wave momentum flux parameter as an example application.

Sediment transport and beach morphodynamics induced by long waves

Abstract: New laboratory data are presented on the influence of long waves on sediment transport in the surf zone. Due to the very significant difficulties in isolating the morphodynamic processes induced by long waves in field conditions, the laboratory study was designed practically to measure the net sediment transport rates, and gradients in sediment transport, arising from the interaction between long waves and short waves in the surf zone. The bathymetric evolution of model sand beaches, with dB50B = 0.2 mm, was observed under monochromatic short waves, long-wave short-wave combinations (free long waves), and bichromatic wave groups (forced long waves). The beach profile change and net cross-shore transport rates, Q(x), were extracted and compared for conditions with and without long waves. The experiments include a range of wave conditions, e.g. high-energy, moderate-energy, low-energy waves, and the beaches evolve to form accretionary, erosive, and intermediate beach states. Hydrodynamic measurements were made to identify the influence of long waves on short waves and to determine the correlation between surf zone bars and standing long waves. A shallow water wave model was modified for this application to surf zone morphodynamics and compared to both hydrodynamics and measured sediment transport. This data clearly demonstrate that free large-amplitude long waves influence surf zone morphodynamics not only under accretive conditions, by promoting onshore sediment transport, but also under erosive conditions, by decreasing offshore transport. For the dominant berm-bar feature, the strong surf beat induces offshore transport in the inner surf zone and onshore transport around the outer surf zone and throughout the shoaling zone. In contrast, forced (bound) long waves and wave groups correlated with bichromatic short wave groups play a pronounced role under erosive conditions, increasing offshore sediment transport across the whole beach profile. For accretionary conditions, only a very narrowbanded wave group promotes onshore sediment transport across the whole beach profile, while broader banded wave groups again promote offshore transport. The modified numerical model of Li et al. (2002) provides good predictions of the standing long wave pattern for the long-wave short-wave combinations, but generally poor agreement for the bichromatic wave groups. Similarly, this model performs poorly in terms of predicting the net sediment transport for all waves, even after optimising the sediment transport coefficients. This is because the model cannot predict the correct hydrodynamics around the breakpoint position and does not correctly represent net sediment transport mechanics. Overall, the model does not correctly predict the trends in beach profile evolution induced by the long waves and wave groups. Further, there is little evidence that the long wave nodal structure plays a dominant role. The influence of the free long waves and wave groups is consistent with the concept of the Gourlay parameter, H/wBsBT, as a dominant parameter controlling net erosion or accretion. Free long waves tend to reduce H/wBsBT, promoting accretion, while wave groups tend to increase H/wBsBT, promoting erosion.

A vorticity-based model for gas transfer under breaking waves : Special topic on : Ocean-atmosphere interactions

Abstract: This paper presents a new renewal model for gas transfer under the influence of breaking waves. It is proposed that the renewal rate is proportional to the vorticity of the waves at the water surface. Constants were evaluated from experimental data obtained in a wave flume at the Laboratory of Harbour Works Athens. Experiments on oxygenation due to breaking waves on a uniformly sloping beach and on a rubble mound breakwater of the S-type were performed. The water was chemically deoxygenated and dissolved oxygen (D.O.) concentration was followed over time in characteristic locations. Experimental data showed that the transfer velocity increased with increasing wave height for waves of the same frequency. Experiments with waves of the same wave height but increasing wave frequency showed also an increase in transfer velocity. The one-dimensional transport equation was used for the determination of the transfer coefficients. Preliminary analysis of the data indicated that the transfer coefficients varied almost linearly with the vertical wave velocity at the water surface. A rather good linear correlation was obtained for the breaking wave data, with a much higher slope as compared to the case of non-breaking waves. Further, an additional positive influence of the wave steepness on the dimensionless transfer coefficient was shown. However, in both of these correlations there was a distinct difference between sets with different wave frequencies. For the vorticity-based model presented in the paper no such difference appears between different sets of data. Two equations, with high correlation coefficients, are obtained, one for the breaking waves on the sloping beach and one for the breaking waves on the breakwater. The breakwater data give lower transfer velocities as compared to the sloping beach data for the same wave characteristics.

Calculation Method of Wave Forces on Large Round-Ended Caisson Foundation

Abstract: This paper presents an analytical formula for estimating the longitudinal wave forces on a large roundended caisson foundation. The establishment of the formula is based on the superposition of the theoretical formula of wave forces on a large circular cylinder and the empirical formula of wave forces on a large rectangular cylinder. With the formula transformed into an inertial force form, a specific inertia coefficient with an exact expression is extracted from the formula. The numerical calculations of the wave forces on round-ended cylinders are carried out by the boundary-element method. The undetermined coefficients in the expression of the inertial coefficient are determined by the numerical results. It is obvious that the numerical values can be well expressed by the computation values from the established formula. By a model experiment carried out in laboratory wave flume, the correctness of the analytical formula is further verified by the measured wave forces on a test model of a round-ended bridge caisson foundation. The comparison shows that the experimental forces can be approximately estimated by this simple calculation method.