21 results found
Karmpadakis I, Swan C, Christou M, 2019, Laboratory investigation of crest height statistics in intermediate water depths, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 475, ISSN: 1364-5021
This paper concerns the statistical distribution of the crest heights associated with surface waves in intermediate water depths. The results of a new laboratory study are presented in which data generated in different experimental facilities are used to establish departures from commonly applied statistical distributions. Specifically, the effects of varying sea-state steepness, effective water depth and directional spread are investigated. Following an extensive validation of the experimental data, including direct comparisons to available field data, it is shown that the nonlinear amplification of crest heights above second-order theory observed in steep deep water sea states is equally appropriate to intermediate water depths. These nonlinear amplifications increase with the sea-state steepness and reduce with the directional spread. While the latter effect is undoubtedly important, the present data confirm that significant amplifications above second order (5–10%) are observed for realistic directional spreads. This is consistent with available field data. With further increases in the sea-state steepness, the dissipative effects of wave breaking act to reduce these nonlinear amplifications. While the competing mechanisms of nonlinear amplification and wave breaking are relevant to a full range of water depths, the relative importance of wave breaking increases as the effective water depth reduces.
Jaouen F, Waals O, de Jong M, et al., Methodology for the design of LNG terminals in a nearshore environment, 35th Conference of Ocean, Offshore and Arctic Engineering
Makri I, Rose S, Christou M, et al., Examining field measurements of deep-water crest statistics, Conference of Ocean, Offshore and Arctic Engineering
Wu Y, Randell D, Christou M, et al., 2016, On the distribution of wave height in shallow water, Coastal Engineering, Vol: 111, Pages: 39-49, ISSN: 1872-7379
The statistical distribution of the height of sea waves in deep water has been modelled using the Rayleigh (Longuet-Higgins, 1952) and Weibull distributions (Forristall, 1978). Depth-induced wave breaking leading to restriction on the ratio of wave height to water depth requires new parameterisations of these or other distributional forms for shallow water. Glukhovskiy (1966) proposed a Weibull parameterisation accommodating depth-limited breaking, modified by van Vledder (1991). Battjes and Groenendijk (2000) suggested a two-part Weibull–Weibull distribution. Here we propose a two-part Weibull-generalised Pareto model for wave height in shallow water, parameterised empirically in terms of sea state parameters (significant wave height, HS, local wave-number, kL, and water depth, d), using data from both laboratory and field measurements from 4 offshore locations. We are particularly concerned that the model can be applied usefully in a straightforward manner; given three pre-specified universal parameters, the model further requires values for sea state significant wave height and wave number, and water depth so that it can be applied. The model has continuous probability density, smooth cumulative distribution function, incorporates the Miche upper limit for wave heights (Miche, 1944) and adopts HS as the transition wave height from Weibull body to generalised Pareto tail forms. Accordingly, the model is effectively a new form for the breaking wave height distribution. The estimated model provides good predictive performance on laboratory and field data.
Christou M, Ewans K, 2014, Field Measurements of Rogue Water Waves, JOURNAL OF PHYSICAL OCEANOGRAPHY, Vol: 44, Pages: 2317-2335, ISSN: 0022-3670
Gibson R, Christou M, Feld G, 2014, The statistics of wave height and crest elevation during the December 2012 storm in the North Sea, OCEAN DYNAMICS, Vol: 64, Pages: 1305-1317, ISSN: 1616-7341
Spinneken J, Christou M, Swan C, 2014, Force-controlled absorption in a fully-nonlinear numerical wave tank, Journal of Computational Physics, Vol: 272, Pages: 127-148, ISSN: 0021-9991
An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank.In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain.The paper presents an extensive numerical validation which demonstrates the success of the method for a wide range of wave conditions including regular, focused and random waves. The numerical investigation also highlights some of the limitations of the method, particularly in simultaneously generating and absorbing large amplitude or highly-nonlinear waves. The findings of the present numerical study are directly applicable to related fields where optimum absorption is sought; these include physical wavemaking, wave power absorption and a wide range of numerical wave tank schemes.
Gibson R, Christou M, Feld G, 2013, EXAMINING FIELD MEASUREMENTS DURING THE DECEMBER 2012 STORM IN THE NORTH SEA, PROCEEDINGS OF THE 13TH INTERNATIONAL WORKSHOP ON WAVE HINDCASTING & FORECASTING & 4TH COASTAL HAZARDS SYMPOSIUM, Banff, Canada
Maris J, Christou M, Huijsmans R, 2012, Investigating the Use of the Hilbert-Huang Transform for the Analysis of Freak Waves, PROCEEDINGS OF THE 31ST CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
Christou M, Ewans K, 2011, Examining a comprehensive dataset with thousands of freak wave events. Part 1 - Description of the data and the quality control procedure, PROCEEDINGS OF THE 30TH CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
Christou M, Ewans K, 2011, Examining a comprehensive dataset with thousands of freak wave events. Part 2 - Analysis and findings, PROCEEDINGS OF THE 30TH CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
Christou M, Rijnsdorp DP, Ewans K, 2011, Analysis of shallow water wave measurements recorded at the Field Research Facility, PROCEEDINGS OF THE 12TH INTERNATIONAL WORKSHOP ON WAVE HINDCASTING & FORECASTING & 3RD COASTAL HAZARDS SYMPOSIUM
Buchner B, Forristall G, Ewans K, et al., 2011, New insights in extreme crest height distributions - A summary of the CresT JIP, PROCEEDINGS OF THE 30TH CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
Christou M, Ewans K, Clauss GF, et al., 2010, The spatial evolution of the spectral characteristics of the Draupner new year wave, 29TH CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
Christou M, 2009, Fully Nonlinear Computations of Waves and Wave-structure Interaction
Christou M, Hague CH, Swan C, 2009, The reflection of nonlinear irregular surface water waves, ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS, Vol: 33, Pages: 644-653, ISSN: 0955-7997
Christou M, Tromans P, Vanderschuren L, et al., 2009, Second-order crest statistics of realistic seas states, PROCEEDINGS OF THE 11TH INTERNATIONAL WORKSHOP ON WAVE HINDCASTING & FORECASTING & 2ND COASTAL HAZARDS SYMPOSIUM
Christou M, Swan C, Gudmestad OT, 2008, The interaction of surface water waves with submerged breakwaters, Coastal Engineering, Vol: 55, Pages: 945-958, ISSN: 0378-3839
Christou M, Swan C, Gudmestad OT, et al., 2008, The interaction of nonlinear waves with the submerged caissons of a gravity-based structure, PROCEEDINGS OF THE 27TH CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
Christou M, Ewans K, Buchner B, et al., 2008, Spectral characteristics of an extreme wave measured in a laboratory basin, PROCEEDINGS OF THE 3RD CONFERENCE ON ROGUE WAVES
Christou M, SWAN C, GUDMESTAD OT, 2007, The description of breaking waves and theunderlying water particle kinematics, PROCEEDINGS OF THE 26TH CONFERENCE OF OFFSHORE MECHANICS & ARCTIC ENGINEERING
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