Wave flume

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

Current Effects on Nonlinear Wave-Body Interactions by a 2D Fully Nonlinear Numerical Wave Tank

Abstract: Nonlinear wave-current interactions with fixed or freely floating bodies are investigated by a two-dimensional (2D) fully-nonlinear numerical wave tank (NWT). The NWT is developed based on the potential theory and boundary element method (BEM) with constant panels. Mixed Eulerian-Lagrangian (MEL) time marching scheme (material-node approach) is used with fourth-order Runge-Kutta fully updated time integration, regriding, and smoothing techniques, and acceleration-potential formulation and direct mode-decomposition method. Specially devised ϕn −η type artificial damping zones (i.e., numerical beach) are implemented to prevent wave reflection from the end wall and wave maker. Using the developed NWT, nonlinear wave-current interactions (1) without bodies; (2) with a stationary body; and (3) with a floating body for various wave and current conditions have been investigated and some of the NWT simulations are compared with the results of Boussinesq’s equation and perturbation theory. It is seen that the NWT ...

Wave groups and sediment resuspension processes over evolving sandy bedforms

Abstract: High resolution measurements of the water velocity, bedforms and suspended sediment concentration were made using an Acoustic Doppler Velocimeter, acoustic bedform scanners and an Acoustic Backscatter System, under irregular free-surface waves. The waves were generated in a large scale flume facility above a number of bedform types. These data were analysed in (i) the frequency domain in order to examine the frequency at which sediment suspensions occurred in the oscillatory bottom boundary layer and the free stream; and (ii) the time domain in order to examine the instantaneous entrainment and vertical transport of sediment at intra-wave, wave average and wave group time scales. During the course of the experiments the significant wave height was systematically incremented enabling the character of sediment suspensions to be studied under a number of flow and bedform regimes. Wave groups were identified as an important control over sediment suspensions in both the wave boundary layer and free stream, with fluctuations in the suspended sediment concentration occurring at low, wave group, frequencies. However, the initial entrainment process, within the wave boundary layer, occurred at intra-wave frequencies. In contrast, in the free stream, sediment suspensions were dominated by the vertical transport of sediment at wave group time scales. During wave groups the sediment suspension field was characterised by the upward transport of sediment due to the continual injection of turbulence under a series of waves which generated a wave pumping effect. The character of a wave group is considered to be an important control over sediment suspensions in the free stream. Four distinct types of wave group were identified and the instantaneous sediment suspension field below each type examined. Such comparisons were possible using the high resolution Acoustic Backscatter System which enabled both intra-wave and wave group processes to be resolved up to 0.8 m above the bed.

Application of a sediment transport model

Abstract: A mathematical model for sediment transport under waves has been developed from concepts that have been used successfully for unidirectional flow. This model has been combined interactively with numerical models of wave refraction, wave diffraction, longshore currents and circulation currents in order to predict local topographical changes in the vicinity of a cooling water intake basin for a nuclear power station. The sediment model is calibrated using field data of sediment concentration profiles. Verification and adjustments may be made by analysing deep water wave statistics corresponding to periodic beach and hydrographic surveys. The model can be used to investigate the effects of any wave climate and consequently different layouts of coastal structures can be examined very rapidly. For the particular problem considered it was necessary to optimise the configuration of the breakwaters forming a cooling water intake basin in order to minimise the sediment concentration at the intake, estimate maintenance dredging quantities and investigate extreme events.

Sediment transport concentrations and sediment transport in case of irregular non-breaking waves with a current

Abstract: In many coastal, engineering problems the sediment transport plays a part. A transport gradient causes accretion or erosion. Various models, such as that of Bijker, Engelund and Hansen (van de Graaff and van Overeem, 1979) and Nielsen (1985) are available to estimate the sediment transport rate if the hydraulic and environmental conditions (wave height, current velocity and direction, sediment size) are known. Since reliable data under field conditions are extremely scarce, the reliability of these models is not known, while also no understanding of the basic relations between the sediment transport, current velocity and wave height can be obtained. To extend the knowledge of the basic phenomena, a laboratory study was carried out. Fluid velocities and sediment concentrations have been measured in case of irregular non-breaking waves alone, and in combination with following or opposing currents.

Sand transport under full-scale progressive surface waves

Abstract: The morphology of coastal areas is constantly changing under the influence of sediments being transported to, from and along the coast. Under storm conditions with high waves and flow velocities, bed forms are being washed out and large quantities of sand are transported in a thin, mm to cm thick layer close to the bed called the sheet-flow layer. Since sand transport under storm conditions is primarily controlled by small scale near-bed processes, development of well-founded methods for predicting near-bed sand transport are critical for estimating sand budget in coastal areas. Various transport models have been developed to predict both the quantities and directions of sediment transport under storm conditions. The majority of the existing models are based on data obtained from oscillatory flow tunnel experiments. Even though oscillatory flow tunnels provide a good approximation of the flow experienced at the sea bed, theory and former experiments indicate that flow differences between full scale progressive surface waves and oscillatory flow tunnels may have a substantial effect on the net sand transport. The research presented in this thesis focuses on the influence of surface wave effects on sand transport under sheet-flow conditions. For the first time, detailed measurements of wave boundary layer flow and sheet-flow layer transport processes under full scale surface waves are presented and analysed. These results give new insights and provide quantitative data of wave boundary flow, sheet-flow layer concentrations, sediment fluxes and net transport rates under velocity skewed surface waves for different wave conditions and types of sediment.