Wave flume

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

The large scale dolos flume study

Abstract: In 1993, the U.S. Army Corps of Engineers, Waterways Experiment Station, Coastal Engineer Research Center conducted the Large Scale Dolos Flume Study (LSDFS) in order to investigate the structural response of concrete armor units. The study was primarily carried out in the large wave flume at the O.H. Hinsdale Wave Research Laboratory, Oregon State University. Over 300 model dolos units with a mass of 26 kg and a waist ratio of 0.32 were used. The units were cast from concrete. The instrumented dolosse were fitted with surfacemounted strain gages then subjected to a wide range of wave loading conditions. This strain gaging and the state-of-the-art data acquisition system increased the signal-to-noise ratio so that accurate measurements of static, quasi-static, wave-induced hydrodynamic, and unit-to-unit impact loading could be recorded. The LSDFS included a standard calibration series, static ramp tests, dry-land impact tests, and regular and irregular wave flume tests. Hydrodynamic instrumentation in the flume tests consisted of a very dense array of wave gages, current meters, runup-rundown gages, pore pressure transducers, hydrophones, digital video, and still photography in the nearshore zone. This paper presents previously unpublished details of the LSDFS specifically pertaining to instrumentation, calibration, dry-land impact tests, and some preliminary results of impact response captured in the flume tests.

Implementation of boundary conditions for locked waves

Abstract: This report refers to the work done at the Fluid Mechanics Section within the framework of the Netherlands Centre for Coastal Research (NCK). As shown by Reniers et al. (2000) there are strong indications that wave-group related phenomena are important in the development of rip channels. It is to be expected that edge waves caused by wave-group induced long waves can be of significant influence on the development of the bathymetry and shoreline. In the development of research models for morphodynamic evolution in the coastal zone the first step is an accurate description of the flow field. In this project use is made of the Delft3D-flow solver to model waves at the scale of wave groups in the coastal zone. The Delft3D model was originally developed to model tide induced flow in sea, coast and estuaries. In this project we use the version of the model which uses the depth averaged flow option. For the boundary conditions used in a model intended for time scales corresponding with tidal flow the demands are not very high. The waves modelled by such models are extremely long and the phase changes along the open boundaries of the model very small. The Delft3D program therefore had a simplified version of the Riemann boundary conditions, effectively using the assumption that outgoing waves at the boundary were travelling perpendicularly to the boundary. On a time and space scale of wave groups this assumption proves to be insufficient as shown in Petit et. al. (2000). A program not equipped with boundary conditions that allow both locked and free waves to enter the domain and free waves to leave the domain without significant (non-physical) reflections, cannot be used for modeling long waves in the coastal zone accurately. It was shown that the Riemann boundary conditions developed by Van Dongeren and Svendsen (1997) could very well offer a solution to this problem. Tests with a simplified model t.hen showed that. these boundary condit.ions indeed performed very well. In the simplified test model use was made of prescribed wave forces. These were not related to numerically determined carrier wave densities. In the Delft3D adaptions, t.he wave forces are determined as minus the divergence of t.he radiation-stress tensor. This involves numerical differentiation of (multiples of) the carrier-wave energy. One of the problems encountered in making the Delft3D program suit.able for the simulation of short wave induced flow proved the determination of the wave forces near weakly reflective boundaries. This report describes a number of one-dimensional test cases used to locate the problems of the numerical approach. For one problem, regarding the numerical determination of the wave forces near the boundary, a solution was found by using extrapolation and by using a different discretization for the transport of wave energy near the boundary.

Wave dynamics at coastal structures: development of a numerical model for free surface flow

Abstract: The development of third generation wave models is needed for a detailed study of wave dynamics and impact at coastal structures. This would require the modelling of wave flows with high distortion of the free surface at confined boundaries. In our opinion, the Volume of fluid method, which uses concepts of local advection of fluid in free surface flow modelling, is the prime candidate for simulating realistic flows at sea defences and walls. In this paper, the numerical techniques for the simulation of waves with highly distorted water/air interfaces at a slope, using the volume of fluid method, are considered.

Numerical model of cnoidal wave flume

Abstract: The volume of fluid (VOF) method is used to set up a wave flume with an absorbing wave maker of cnoidal waves. Based on the transfer function between wave surface and paddle velocity obtained by the shallow water wave theory, the velocity boundary condition of an absorbing wave maker is introduced to absorb reflected waves that reach the numerical wave maker. For H/d ranging from 0.1 to 0.59 and T g/d from 7.9 to 18.3, the parametric studies have been carried out and compared with experiments.

Swash zone sediment transport

Abstract: The coastal area is a busy area, many people live in these areas or use the coastal area for recreational purposes. The beach profile in the coastal area is continuously changing under the changing field conditions. These changes are induced by the changing sediment transports in the sea under changing field conditions. Several models have been developed to simulate and predict these changes in sediment transport and their related profile changes. However, these models fail in a region close to the shoreline, since the parameterized wave models (like Battjes Janssen, 1978) fail in this region. In this thesis a model has been developed to compute the sediment transport rates up to zero meter water depth. This Inner Surf Zone (ISZ) sediment transport model is based on the ISZ model of Aarninkhof, 2000, which models the wave height decay and the associated flow field up to zero meter water depth. The ISZ sediment transport model uses the energy approach of Bailard (1963;1966) for the sediment transport computations. According to Bailard the sediment transport is related to the work done by the fluid, the dissipated energy. The sediment transport is divided in two layers in the ISZ sediment transport model, an upper and a lower layer. In the lower layer suspended and bed load sediment transport is taken into account. In the upper layer only suspended sediment transport is computed, based on the shear stresses near the bottom. The sediment concentrations in the upper layer are assumed to decrease, when the water depth increases, resulting in a decreasing sediment transport in the upper layer. Implementation of this assumption by an empirical formula into the model works encouraging well. The model is calibrated against the tests of Koomans in the Scheldt flume (2000). The model is valid for spilling breaking and the computation area is determined by the non-linearity parameter of the waves. The non-linearity parameter depends on the wave period and so does the range of the model. Different field conditions have been investigated in this thesis. Changing transport rates for varying beach slope and sediment composition can be modelled encouragingly well by the developed ISZ sediment transport model. The ISZ sediment transport model requires adjustment when field conditions like wave height and wave period change, since the friction factor and the sediment concentrations change under changing field conditions. Based on the described changes in sediment transport in literature, under these changing field conditions, a recommendation is made how to adjust the model parameters. The friction and the bed/suspended load efficiency factors are used to represent the described changes in sediment transport under these changing field conditions.