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1.
Estimation of loads derived from shipping water events in naval and offshore structures is of importance to improve their structural design or to predict changes in their dynamics. For the case of vertical loads on deck of a fixed structure, it is possible to estimate analytically their evolution in time by considering the distribution of shipping water elevations. However, the classical approach to estimate this distribution (i.e., dam-break method) tends to overestimate the amount of water on deck and does not follow the generated decay trends observed experimentally. In the present work, the time evolution of the vertical loads due to shipping water events was studied analytically and experimentally. The validation of the use of a convolution model to estimate the time evolution of vertical loads is presented, aiming to improve the results obtained with classical approaches. A systematic experimental study has been conducted using the wet dam-break method to generate isolated shipping water events, measuring the slow-varying vertical loads on a rectangular fixed structure. A force balance and a high-speed camera have been used at the same sampling rate to monitor the vertical loads and the shipping water evolution on the deck. Results demonstrated that the use of the convolution model improved the representation of the time series of loads compared with the traditional dam-break approach. With this new method, it was possible to capture the peaks and the decay tendencies observed in the experimental data in an approximated way. 相似文献
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The objective of this study is to simulate three-dimensional behavior of shipping water and to predict the impact pressure on the deck using a particle method. An experiment carried out in a two-dimensional wave tank with a fixed deck model was numerically analyzed in three dimensions. The fluid motion, the surface elevation, and the impact pressure on the deck were compared between the experiment and the calculation and good agreement was obtained. 相似文献
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Marmara Sea (MS) lies in the strategic crossroad, accommodating one of the busiest shipping routes in the world. In general, there is a two-layer current system in the MS and Turkish Straits system; the brackish waters originating in the Black Sea (BS) (18 PSU) moving southward to the Aegean Sea (AS), and a lower layer return flow of saltier Aegean waters (38.5 PSU) back to the BS. This variability poses a challenging task within the modeling perspective. In this research, 3D hydrodynamic modeling of MS is performed in order to investigate the spatial and temporal behavior of elevations between years 2000 and 2015. During the calibration process, the grid configuration, time step, and model coefficients (Manning bed roughness coefficient, a wind drag coefficient and horizontal viscosity are coefficients) are adjusted until the computed solution produced the best match to the observed data such as water surface elevations, velocities, and net discharges. To this end, a series of simulations are made. As a result, the observed and the predicted water surface elevations follow each other very closely. The developed model could accurately estimate the net discharge as well. In order to understand the behavior of MS, elevation pattern is calculated and depicted both on annual and seasonal scales. It is demonstrated that the influence of seasonally varying strong fresh water river discharges of Danube in BS have strong influence on the water mass characteristics of the MS. 相似文献
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A combined wind and wave energy converter concept, named STC concept was proposed. Model tests were performed in terms of operational and survival modes. Water entry and exit phenomena as well as green water on deck were observed during the survivability model tests. In this paper, a nonlinear numerical model based on a blended station-keeping potential-flow solver with a local impact solution for bottom slamming events and an approximated model for the water shipped on the deck is proposed to simulate these nonlinear phenomena. Physical investigation of the water entry and exit process was firstly carried out and uncertainty analysis of the model test results were performed. Numerical comparisons between the nonlinear solver and model test results are then performed in terms of mean, wave frequency and double wave frequency motion response components. The slamming and green water involved in the water entry process are specially investigated, in terms of the physical evolution and the effects on the dynamic motion responses. The validation work on the occurrence of slamming and water on deck as well as the slamming pressure are performed. 相似文献
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A sea water intake well of size 20 m diameter and 15.5 m height in a water depth of 9.8 m is proposed north of the Visakhapatnam Port for a project to extract magnesia from sea water. A 1:25 scale model of the intake well was tested in the wave basin of the Ocean Engineering Centre, Indian Institute of Technology, Madras to measure the wave forces and moments on the intake well and the variation of water levels inside and outside the well. Accordingly, an intake well model of 0.8 m diameter and 0.62 m height was fabricated and fixed over a false bottom in a wave basin. The well model was subjected to the action of both regular waves for two test conditions, intake well inlet closed during installation and intake well inlet open. The experimental results on wave forces and moments were compared with the results of the Linear Diffraction Theory. The water level inside the well was measured to determine the submergence of suction pipes of pumps and location of the inlet opening of the intake well. The wave crest elevation in front of the well was also measured in order to fix the deck level of the well so as to avoid water overspill onto the deck. The salient results of the present study are presented and discussed in this paper. 相似文献
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We present results from a series of piezometers installed in the foreshore flat and mangrove environments of the Gillman Marshes, South Australia in an interdisciplinary study of the propagation of the ocean tide into the coastal aquifers. A unique feature of the analysis is that all water level records were harmonically analysed so that the behaviour of the four major tidal constituents could be independently examined. The main findings were that: (1) the decay of the groundwater tide in the coastal aquifers was greater than that predicted by the Ferris solution. A theoretical model has been developed and applied to the study site. The model suggests that this behaviour is due to the occurrence of a time delay in the Darcian response in the shelly and muddy sand substrate; (2) when the tide is incident over a gently sloping bank, the time delay in response gives rise to a spiked signal in which high water is confined to a small fraction of the tidal cycle; and (3) at the coastal interface tidal propagation across a sloping bank causes a rise in the water table relative to mean sea level which is proportional to the variance of tidal elevation and inversely proportional to the decay constant of the groundwater tide. The model developed in this study is also applicable to other coastal groundwater systems with tidal influence. 相似文献
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《Ocean Engineering》1999,26(4):363-380
A sea water intake well of size 20 m diameter and 15.5 m height in a water depth of 9.8 m is proposed north of the Visakhapatnam Port for a project to extract magnesia from sea water. A 1:25 scale model of the intake well was tested in the wave basin of the Ocean Engineering Centre, Indian Institute of Technology, Madras to measure the wave forces and moments on the intake well and the variation of water levels inside and outside the well. Accordingly, an intake well model of 0.8 m diameter and 0.62 m height was fabricated and fixed over a false bottom in a wave basin. The well model was subjected to the action of both regular waves for two test conditions, intake well inlet closed during installation and intake well inlet open. The experimental results on wave forces and moments were compared with the results of the Linear Diffraction Theory. The water level inside the well was measured to determine the submergence of suction pipes of pumps and location of the inlet opening of the intake well. The wave crest elevation in front of the well was also measured in order to fix the deck level of the well so as to avoid water overspill onto the deck. The salient results of the present study are presented and discussed in this paper. 相似文献
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Experiments carried out with models of floating production, storage and offloading platforms (FPSOs) showed that the flow of water over the deck edge, onto the deck resembled a suddenly released wall of water rather than a breaking wave. Therefore green water flow onto the deck was simulated using dam breaking theory, but the theory’s shallow-water assumptions may be limiting. In this paper a non-linear dam breaking problem is formulated. Equations of motion in the Lagrangian form are used and the solution is sought as an infinite series in time. Comparisons with the shallow water approximation are carried out. 相似文献
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In this paper the probability of green water occurrence is investigated by taking into account the threshold of the vertical relative motion exceeding the freeboard. The number of wetting of the unit/vessel is predicted using probabilistic method. This paper compares the significant load, due to shipping of green water with the works of other researchers, and the loads are found to be close with the results presented in this paper. There is no direct relation between the velocities in the waves and the water velocity over the deck. The water velocities around the bow are heavily distributed by the presence of the bow. This scenario makes the flow very complex for schematic modelling. 相似文献
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A statistical model is developed to predict wave overtopping volume and rate of extreme waves on a fixed deck. The probability density function for the volume and rate of overtopping water are formulated based on the truncated Weibull distribution with the assumption of local sinusoidal profile for small amplitude waves. Sensitivity to the wave nonlinearity parameter and deck clearance is discussed. The statistical model is compared to laboratory data of the instantaneous free surface elevation measured in front of a fixed deck, and overtopping volume and overtopping rate measured at the leading edge of the deck. The statistical theory compared well with the measured exceedance probability seaward of the deck. The model prediction of the exceedance probability of deck overtopping gave qualitatively good agreement for large overtopping values. 相似文献
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1 IntroductionThe shallow water equations (SWE) are frequent-ly used as a mathematical model for water flows incoastal areas, lakes, estuaries, etc. Thus, they are animportant tool to simulate a variety of problems relat-ed to coastal engineering, environment, ecology, etc.(Bermúdez et al., 1998). On the basis of solving theone-dimensional (1D) SWE, Hu et al. (2000) have de-veloped a model capable of simulating storm wavespropagating in the coastal surf zone and overtopping asea wall. Ano… 相似文献
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The design of deep water offshore platforms requires the analysis of wave-structure interaction phenomena which have not been as critical for shallower water platform designs. In the case of tension leg platforms (TLPs) interaction phenomena such as wave run-up on the vertical legs and the amplification of the waves beneath the deck are major design considerations. The research investigation reported here focuses on a series of small scale wave tank tests on four column TLP models examining these phenomena. The role of vertical leg spacing and comparative tests of the TLP models with and without pontoons was investigated. As the vertical legs were moved closer an increase in wave run-up and a shifting of the incident wave period corresponding to the maximum wave upwelling were noted. Comparisons with wave measurements for single cylinders from previous experimental studies and the TLP configurations used in this study are presented. A design formula for estimating wave run-up on TLPs is suggested based upon these experiments. The wave run-up on a leg directly in the wake of another leg is presented. A comparison of the wave upwelling measurements with previously published numerical results are discussed. A wave uplift force model which allows for the inclusion of the experimentally obtained wave upwelling measurements is presented and discussed with regard to the design specification of platform deck elevation. 相似文献
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多向不规则波浪的确定性模拟 总被引：1，自引：0，他引：1
波浪波动时间过程及波列的模拟，对于开展实际波浪对于工程建筑物的作用具有重要的意义。本文采用线性叠加的单叠加模型，建立了多向不规则波浪的确定性模拟方法。基于理论模拟的规则波、单向不规则波和多向不规则波，验证了波浪确定性模拟方法的有效性。定性地对比分析了模拟波列和已知波列的一致性；定量地研究了模拟波浪在空间范围rr/Ls的误差分布情况(rr表示指定位置与给定位置的空间距离，Ls为有效波长)。并且建议，采用本文方法进行波浪确定性模拟时，最佳的浪高仪间距应小于0.12Ls。 相似文献
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提出了一种用于对不连续压力采样序列的傅立叶分析方法.此方法将周期函数展开成傅立叶级数,但在数值积分时取函数周期内有采样值的区间作为积分域,然后求解线性方程组得到傅立叶级数的系数值.为了检验本方法的有效性,利用此方法对解析函数进行了拟合,当一个周期内的取样时间大于1/2周期时,利用此方法能够得到满意的结果.利用实验方法研究了波浪作用下截断圆柱表面的压力分布.在波浪作用下静水面附近的测点在露出水面时没有压力值.利用所提出的傅立叶分析方法对略低于静水面位置的实测压力进行了分析,拟合结果与实测结果吻合很好,说明此方法在处理物理模型实验中间断采样得到的数据是有效的.利用数值方法对波浪压力进行了计算,并将一阶和二阶波压力的数值结果与实测值进行了比较. 相似文献
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This paper studies the moonpool resonance of two heaving rectangular bodies in a two-layer fluid. A mathematical model is proposed based on an eigenfunction matching approach. The motion of the two-dimensional bodies is assumed to be vertical and harmonic. Heave added mass and damping coefficients are computed to examine the hydrodynamic behavior of the twin bodies. The free surface and internal wave elevations are obtained near the resonant frequencies. The presented results and analyses reveal that there exist both Helmholtz and higher-order resonances in the two-layer fluid system, which is similar to the single-layer fluid case. It is also found that the resonances are closely associated with the free surface elevation inside moonpool gap, not the wave elevation at the interfacial surface. In addition, parametric studies have been performed to identify the dependencies of hydrodynamic behavior on geometry and density stratification. 相似文献
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The purpose of this study is to investigate the phenomenon of free surface flow impacting on elastic structures, which is a research topic of great interest in ship and ocean engineering. A series of quasi two-dimensional experiments on dam-break with an elastic plate are conducted. The main features of free surface flow impacting on elastic structures including large impacting force, structural vibration, violent free surface flow, are investigated. The coupled FDM–FEM method developed by the authors is applied for numerical simulation of such dam-break problem. Extensive analysis and discussion based on the comparisons between experimental data and numerical results are made and presented in this paper. 相似文献
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SERR-1D is a 4th-order finite volume 1D Boussinesq model including wave breaking energy dissipation through extra diffusive-like terms. This model has been primarily conceived to compute wave propagation in coastal areas and has been validated for breaking and non-breaking waves propagating over uneven bathymetries (Cienfuegos et al., 2005, 2006a, b, 2007). The present paper aims at investigating the ability of SERR-1D to simulate challenging fluvial hydraulic applications such as sudden gate operation in open channels generating short waves, dam-break flows and a steady hydraulic jump over a bump. The performance of the absorbing-generating boundary condition implemented in SERR-1D is first analysed in the context of fluvial applications where relatively short waves must be evacuated from the computational domain without producing spurious reflection. Next, by comparing numerical results to analytical and experimental dam-break test cases we show that the model is able to reproduce the overall features of these flows, but that additional care should be paid to the representation of energy dissipation and front speed in order to accurately represent bore dynamics. 相似文献