Wave flume

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

Loading and Dynamic Response of Jacket Structures to Breaking and Non-breaking Waves

Abstract: Among different types of loads on jacket structures, wave loads, especially breaking wave loads, are the most likely to threat the stability of the structure; therefore, the correct estimation of the wave loading of an offshore jacket structure is crucial for the design of these structures. Despite the importance of the correct estimation of breaking wave induced forces on jacket structures, so far, no slamming formulae to predict these forces are available in the design standards and guidelines or in other publications. Moreover, the implications of such extreme wave load events and the associated uncertainties for the dynamic response of the entire jacket structure, including the response of the foundation piles, are still not fully clarified. This PhD study attempts to improve the understanding of processes associated with the interaction of waves and jacket structures and to develop reliable wave slamming formulae for the prediction of breaking wave-induced loads on jacket structures. First, the present knowledge is analysed to identify the processes involved in the interaction as well as the related knowledge gaps. Second, the data available from previous tests performed on a truss structure under breaking and non-breaking waves in the Large Wave Flume (GWK tests) in Hannover are analysed to identify the most relevant influencing parameters and to provide reliable slamming formulae for breaking waves on legs and braces of jacket structures. Third, using a CFD model set-up for the waves generated in the large wave flume GWK and a CSD model for the truss structure tested in GWK, the laboratory tests are reproduced and a methodology is proposed to predict total forces induced by near-breaking and breaking waves on jacket structures. Finally, the proposed methodological approach including the slamming force formulae developed in this study is implemented to calculate total forces by breaking waves on a full-scale jacket structure (OC4 jacket). The Finite Element FE model of the OC4 jacket is extended by pile foundation model and the structural performance of the entire structure was examined by comparing the results by those of the numerical models developed for the same jacket structure. Finally, the dynamic response of the jacket structure with pile foundation to breaking waves is systematically analysed to achieve a substantially improved understanding of the processes involved in the wave-jacket-pile foundation interaction.

Sediment dynamic processes in the vicinity of offshore breakwaters

Abstract: A composite approach is used to study hydrodynamic and sediment dynamic processes, in the vicinity of offshore breakwaters situated in a macro-tidal environment; this combines field measurements, numerical modelling and grain size trend analysis. Field measurements were undertaken at an offshore breakwater scheme (Elmer, West Sussex), in order to investigate the key processes in the vicinity of the breakwaters. The investigation into the hydrodynamics included measurements offshore and inshore of the breakwaters, under various wave and tidal conditions. The dependence of sediment transport on wave asymmetries and water depth, especially during higher energy conditions, was identified. Numerical modelling was utilised for simulating the tidal and wave processes, at different stages of the tidal cycle. The interaction of the tidal currents with the structures, over the entire area of the scheme, was studied for a spring-neap tidal cycle. Significant alterations of the tidal currents in the landward area of the breakwater were observed; these included flow channelisation between the structures and the coastline, together with flow acceleration over the salients. The design characteristics of the scheme, (i.e. gap width, offshore distance, relative angle in respect to the tidal currents) are found to influence the magnitude of the acceleration. The accelerated currents increase the sediment transport locally over the top of the salients, regulating their growth. Wave energy immediately to seaward of the structures was regulated by the tidal elevation. However, in the shadow areas of the structure and over the salients wave height and associated sediment transport were controlled, by the water level (i.e. tidal stage) and the period of the incoming wave. The identification of the sediment transport pathways in the vicinity of the offshore islands was undertaken using the ‘Gao and Collins Method’; this is based upon correlating spatial resolution of sediment parameters. A sensitivity analysis of the transport pathways, under different sampling strategies (regular vs. irregular grids and variable grid spacing) and the analytical techniques (settling velocity vs. sieving), was undertaken. The importance of settling velocity in determining the statistical parameters of the grain-size distribution was identified, especially for the coarser-grained sediments (fine-medium sand). The combination of the results obtained using the different methodologies verify the processes controlling sediment dynamics in the vicinity of the structures; these are applicable to schemes located in similar environments.

Seabed scour beneath an unburied pipeline under regular waves

Abstract: The scouring of seabed beneath an unburied pipeline under regular waves was investigated in a large wave flume. Sands and silts were employed for the contrast experiment and the results obt...

Wave attenuation due to ice cover: an experimental model in a wave-ice flume

Abstract: Waves penetrate deep into the ice covered seas, inducing breakup of the ice cover. Concomitantly, the ice cover attenuates the wave energy over distance, so that wave impacts die out eventually. Observations of wave attenuation and concurrent wave-induced breakup in the literature are serendipitous due to difficulties in making measurements in ice covered seas. Hence understanding of wave-ice interactions remain uncertain. Here we present measurements of wave propagation through ice covered waters in the new experimental wave-ice facility at the University of Melbourne. The facility comprises of a 14m long and 0.76m wide flume in a refrigerated chamber, where temperatures can be lowered down to-12 degrees Celsius to generate a continuous ice cover on the water surface. A wave maker, installed at one end, is used to generate regular waves, ranging from gently-sloping to storm-like conditions. Wave attenuation rates are determined from video-camera images of the displacements of markers embedded in the ice cover. The experiments investigated wave propagation through the continuous ice cover, breakup, and propagation through the broken ice cover. Spatial evolution of the breakup and geometrical properties of floes are monitored and correlated with incident wave properties. Wave attenuation over broken ice is investigated and compared against the continuous ice case.