Shallow water SPH for flooding with dynamic particle coalescing and splitting     

《Advances in water resources》2013

In this paper an adaptive algorithm for Smoothed Particle Hydrodynamics (SPH) for the Shallow Water Equations (SWEs) is presented. The area of a particle is inversely proportional to depth giving poor resolution in small depths without particle refinement. This is a particular limitation for flooding problems of interest here. Higher resolution is created by splitting the particles, while particle coalescing (or merging) improves efficiency by reducing the number of the particles when acceptable. The new particle coalescing procedure merges two particles together if their area becomes less than a predefined threshold value. Both particle splitting and coalescing procedures conserve mass and momentum and the smoothing length of new particles is calculated by minimizing the density error of the SPH summation. The new dynamic particle refinement procedure is assessed by testing the numerical scheme against analytical, experimental and benchmark test cases. The analytical cases show that with particle splitting and coalescing typical convergence rates remain faster than linear. For the practical test case, in comparison to using particle splitting alone, the particle coalescing procedure leads to a significant reduction of computational time, by a factor of 15. This makes the computational time of the same order as mesh-based methods with the advantage of not having to specify a mesh over a flood domain of unknown extent a priori.  相似文献   

A numerical system to study the transport properties in the Ria de Aveiro lagoon     

Jo?o Miguel?DiasEmail author  José Fortes?Lopes  Ivan?Dekeyser 《Ocean Dynamics》2003,53(3):220-231

This work presents results from numerical modelling studies on the hydrodynamics and sediments and passive particles transport properties in Ria de Aveiro, a shallow lagoon located on the Portuguese Northwest Atlantic coast. The hydrodynamic of the lagoon was systematically studied, from both the Eulerian and Lagragian point of view, in order to understand the overall circulation in the lagoon, characterize the dynamics of its different channels and assess the transport of suspended cohesive sediments.Responsible Editor: Hans Burchard  相似文献   

Modelling transport dynamics of contaminated sediments in the headwater of a hydropower plant at the Upper Rhine River     

George Jacoub  Bernhard Westrich 《洁净——土壤、空气、水》2006,34(3):279-286

Sediments are an essential habitat compartment in rivers, which is a subject to dynamic transport processes. In many rivers, the fine deposited sediments are contaminated with heavy metals and organic compounds. Contaminated deposits are considered as potential hot spots because of the risk of the mobilization under erosive hydraulic conditions. Numerical models for particulate contaminant transport are then necessary and can be applied to estimate and predict the potential impact of mobilized contaminants as an important contribution to sediment management. This paper focuses on the quantification of the amount of contaminated sediments resuspended during the extreme flood event in 1999 and the prediction of deposition one year after the flood event. To assess such erosive flood event, a 2D numerical transport model was developed to analyse the dynamics of erosion and sedimentation processes in the headwater of a cross dam at the Upper Rhine River. The dam consists of a weir, a hydropower plant, and a navigation lock. As the weir is operating only for flood management, a huge amount of sediment highly contaminated with the hexachlorobenzene (HCB) was deposited in the weir zone. Therefore, numerical simulations were performed to determine the spatial and temporal distribution of deposited contaminated sediments as depending on the river discharge and its distribution to the hydraulic structures. The numerical investigation presented here is taken as a retrospective analysis of the contaminated sediment dynamics in the headwater to improve future sediment management.  相似文献   

Instability of isothermal stellar wind bowshocks     

John M. Blondin  Joel F. Koerwer 《New Astronomy》1998,3(8):1431-582

We present hydrodynamical simulations illustrating the instability of stellar wind bowshocks in the limit of an isothermal equation of state. In this limit, the bowshock is characterized by a thin dense shell bounded on both sides by shocks. In a time-averaged sense the shape of this bowshock shell roughly matches the steady state solution of Wilkin (1996)[ApJ, 459, L31], although the apex of the bowshock can deviate in or out by a factor of two or more. The shape of the bowshock is distorted by large amplitude kinks with a characteristic wavelength of order the standoff distance from the star. The instability is driven by a strong shear flow within the shock-bounded shell, suggesting an origin related to the nonlinear thin-shell instability. This instability occurs when both the forward bowshock and the reverse wind shock are effectively isothermal and the star is moving through the interstellar medium with a Mach number greater than a few. This work therefore suggests that ragged, clumpy bowshocks should be expected to surround stars with a slow, dense wind (which leads to rapid cooling behind the reverse wind shock), whose velocity with respect to the surrounding interstellar medium is of order 60 km s⁻¹ (leading both to rapid cooling behind the forward bowshock and sufficiently high Mach numbers to drive the instability).  相似文献   

The abnormal pressure regime of the Pennsylvanian No. 8 coalbed methane reservoir in Liulin–Wupu District, Eastern Ordos Basin, China     

Xianbo Su  Liping Zhang  Ruilin Zhang 《International Journal of Coal Geology》2003,53(4):227-239

Coalbed methane reservoir pressure is an important parameter used to assess the producibility of coalbed methane wells. Practices indicate that high production of coalbed methane well is partly related closely to abnormally high pressure. Permo-Carboniferous coalbed methane resources are very abundant in the Liulin–Wupu District, Eastern Ordos Basin, which has been the highlight of coalbed methane exploration in China in recent years. In this district, the abnormally high pressure is present locally in the Pennsylvanian No. 8 coalbed methane reservoir (the Taiyuan Formation). Based on the distribution of the abnormally high pressure, burial history, hydrocarbon generation, hydrodynamics, and sealing regimes, the authors suggest that the abnormal coalbed methane reservoir pressure is related closely to local hydrodynamic trapping. The gas generated during the qualification is preserved, owing to the confinement of lower permeable roof and floor rock layers, and water trapping in the updip direction (like the “fairway” in San Juan Basin). As a result of pressure reconstruction event, the abnormally high pressure is formed during the uplifting stage. The current coalbed methane wells with high production are always located in abnormally high pressure areas. Therefore, the areas with abnormally high pressure in Liulin–Wupu District can be the preferred areas for commercial coalbed methane development.  相似文献   

Probabilistic modeling of ship powering performance using full-scale operational data     

《Applied Ocean Research》2019

The energy efficiency of ocean-going vessels can be increased through various operational considerations, such as improved cargo arrangements and weather routing. The first step toward the goal of maximizing the energy efficiency is to analyze how the ship's powering performance changes under different operational settings and weather conditions. However, existing analytical models and empirical methods have limitations in reliably estimating the powering performance of full-scale ships in real operating conditions. In this study, machine learning techniques are employed to estimate the powering performance of a full-scale ship by constructing regression models using the ship's operational data. In order to minimize the risk of overfitting in the regression process, domain knowledge based on physical principles is combined into the regression models. Also, the uncertainty of the estimated performance is evaluated with consideration of the environmental uncertainties. The obtained regression models can be used to predict the ship speed and engine power under different operational settings and weather conditions.  相似文献   

我国依港管船机制探究     

朱晖  张新聪 《海洋开发与管理》2019,36(7):12-19

"依港管船"制度的提出是我国对渔船管理模式的探索和创新,也是贯彻落实党的十九大精神,推进海洋生态文明的重要举措。文章通过对"依港管船"制度内涵与外延的阐述,从"依港管船"制度的法理基础与现实需求角度入手,研究其合理性与必要性。并且对国外港口建设与船舶管理制度进行分析,总结出目前日本、美国、韩国、德国等国家实施"依港管船"制度的相似性及主要差异,为我国"依港管船"制度的完善与实施提供了参照。并给出了完善"依港管船"以及"渔港生态"立法;明晰渔港产权制度;强化渔船管理制度建设;建立主管部门驻港管理机制;实行部门执法联动等对策建议。  相似文献   

全球邮轮船型参数发展趋势研究          下载免费PDF全文

朱园园  程爵浩 《海洋开发与管理》2021,38(7):37-42

近年来,随着世界邮轮旅游发展的强劲势头及亚太新兴市场的崛起,中国邮轮旅游市场也在蓬勃发展。通过对全球知名邮轮官网与Berlitz中收录的2019年全球在营293艘邮轮关键参数进行统计,对邮轮船型进行参数拟合研究,得到全球邮轮船型发展的特点与趋势。结合2019年在华市场运营邮轮与我国邮轮港口接待条件分析,发现目前中国中高端邮轮市场有待填补,“小而精”邮轮或将成为一个重要方向,成为潜在有利市场。  相似文献   

Minimal Time Ship Routing Using IRS-P4 (MSMR) Analyzed Wind Fields     

J. K. Panigrahi  P. A. Umesh 《Marine Geodesy》2008,31(1):39-48

Minimal time ship routing is studied between Mumbai port (India) to Mombasa port (Kenya) using model hindcast wave climate over the Arabian Sea. With the launch of IRS-P4 (OCEANSAT-I), it became possible now to carry out routine wave hindcasting over the Indian Ocean. The MSMR channel of the satellite gives scalar wind, which is analyzed at NCMRWF, India, for converting to vector winds. The same is used as input to third-generation spectral wave model WAM for regional grid system for simulating the rough weather period of July 2000. This simulated wave climate formed the basis for computing effective ship velocity in the irregular seaway. This study gives a quantitative estimation of change in ship velocity in the open Indian Ocean for a bulk carrier. The minimal time path is charted using Dijkstra's algorithm for optimum route voyage. The optimum track information has broad scope for obtaining a safer route, least time route by avoiding delay in schedule with minimum fuel consumption.  相似文献   

Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters     

Roland A. Smith  James Lazarus  Matthias Hohenberger  Alastair S. Moore  Joseph S. Robinson  Edward T. Gumbrell  Mike Dunne 《Astrophysics and Space Science》2007,307(1-3):131-137

Collisions between shocks are commonly found in many astrophysical objects, however robust numerical models or laboratory analogues of these complex systems remain challenging to implement. We report on the development of scaled laboratory experiments which employ new techniques for launching and diagnosing colliding shocks and high Mach number blast waves, scalable to a limited subset of astrophysically-relevant regimes. Use of an extended medium of atomic clusters enables efficient (>80%) coupling of 700 fs, 1 J, 1054 nm laser pulses to a “cluster” gas with an average density of ≈10¹⁹ particles cm⁻³, producing an initial energy density >10⁵ J cm⁻³, equivalent to ≈5×10⁹ J/g. Multiple laser foci are used to tailor the spatial profile of energy deposition, or to launch pairs of counter-propagating cylindrical shocks which then collide. By probing the collision interferometrically at multiple view angles in 5^{^} increments and applying an inverse Radon transform to the resulting phase projections we have been able to tomographicall reconstruct the full three-dimensional, time-framed electron density profile of the system.  相似文献