Hydraulic modelling of fish habitat in urban rivers during high flows

In urban rivers, flow regime and channel morphology are the drivers of physical habitat quality for aquatic species. Peak discharges are increased at high flows as a result of impermeable catchments and channel engineering for flood protection schemes. Hazardous conditions and flashy hydrographs mean that measurement of velocities at high flows is a difficult task. This research uses a three‐dimensional computational fluid dynamics (3D‐CFD) model to simulate hydraulic patterns in two urban river channels. A 3D‐CFD code, called SSIIM, was used to simulate hydraulic conditions in two engineered river reaches of the River Tame, Birmingham, UK. These two sites represent channels with different levels of engineering. Models were calibrated and tested using field measurements. Results show that modelled water surface levels and velocity profiles are well simulated. Calibrated roughness heights are compared with those derived from field measurement of sediment size. Numerical experiments are used to assess the relationship between grid resolution in the vertical dimension and the form of the modelled velocity profiles. Biologists have used laboratory experiments to determine maximum sustainable swimming speeds (MSSS) of fish, often in order to assess what level of a particular pollutant may be tolerable. In this work, simulations of high‐flow hydraulic patterns are used to compare velocity patterns with fish MSSS. Results show that when the water levels rise to fill the first channel of the two‐stage channels at the sites, which occurred 16 times in 2000, MSSS are surpassed in the majority of available habitat, suggesting that excessive velocities at high flows are one factor that limits fish habitat. A comparison between the two reaches shows that there is less available habitat in the more modified reach. Conclusions suggest that an approach that integrates water quality issues and physical channel characteristics must be taken in river rehabilitation schemes, as improvements to water quality alone may not be sufficient to improve habitat quality to the desired level. Copyright © 2002 John Wiley & Sons, Ltd.     

Multiphase model for inclusion‐reinforced geostructures: Application to rock‐bolted tunnels and piled raft foundations

A multiphase model is proposed to describe the mechanical behaviour of geomaterials reinforced by linear inclusions. This macroscopic approach considers the reinforced soil or rock mass as the superposition of continuous media. Equations of motion and constitutive laws of the model are first derived. Its implementation in a finite element computer code is then detailed. A modified implicit algorithm for elastoplastic problems is proposed. The model and its implementation are fully validated for rock‐bolted tunnels (comparison with scale model experiments) and piled raft foundations (comparison with the classical ‘hybrid method’). The Messeturm case history is finally presented to assess the handiness of the approach for real structures. Copyright © 2001 John Wiley & Sons, Ltd.     

中国开放政策对区域发展的作用

在对中国对外开放政策作用进行了定性分析的基础上 ,利用计量经济模型方法 ,就近 2 0年来中国对外开放政策对中国东部沿海地区的经济发展作用效果进行了计算模拟分析。首次 ,从数量上 ,探讨了中国对外开放政策对区域经济发展的作用效果。 ( 1 )在对外开放中 ,通过提供各种优惠政策 ,吸引来了大量的建设资金 ,缓解了区域经济发展中资金不足的问题 ;( 2 )对外开放政策的实施加快了区域经济增长速度 ,促进了区域经济发展 ;( 3)对外开放政策促进了区域外向型经济的发展 ,使中国经济的外向度得到了很大提高 ,在较短的时间内成为世界贸易大国 ;( 4 )对外开放政策 ,改变了中国经济发展布局 ,加快了基础产业发展 ,较好地解决了以往长期制约国民经济发展的能源、原材料等基础工业发展滞后问题。通过模型计算 ,在对外开放的 2 0年中 ,中国东部沿海地区的 GDP增长总额为 9670 .42× 1 0 8元 ,其中对外开放政策的贡献作用达 2 0 68.0 7× 1 0 8元 ,即 2 0世纪 80年代初开始的对外开放政策对东部沿海地区 GDP的作用效果达 2 0 68.0 7× 1 0 8元 ,平均作用效率达 2 1 .39%。     

武山铜矿西风井机房基础发生裂缝和沉降的机制分析

对武山铜矿西风井机房基础发生裂缝和沉降的原因从几何、地质、力学等方面进行分析研究，指出该裂缝和沉降是由于采空区引起的地应力释放、岩层的急倾性、软弱夹层的韵律性分布、构造裂隙的发育与密集、风机运转产生的循环载荷、暴雨期间渍水的灌入与下渗等多种因素综合作用的结果。本文还为采空区的下盘稳定性分析提出了一个简单方便的计算模型。     

LONG VALID TIME ENERGY PERFECT CONSERVATIVE FIDELITY SPECTRAL SCHEMES OF BAROTROPIC PRIMITIVE EQUATIONS*

In accordance with a new compensation principle of discrete computations,the traditional meteorological global (pseudo-) spectral schemes of barotropic primitive equation (s) are transformed into perfect energy conservative fidelity schemes,thus resolving the problems of both nonlinear computational instability and incomplete energy conservation,and raising the computational efficiency of the traditional schemes.As the numerical tests of the new schemes demonstrate,in solving the problem of energy conservation in operational computations,the new schemes can eliminate the (nonlinear) computational instability and,to some extent even the (nonlinear) computational diverging as found in the traditional schemes,Further contrasts between new and traditional schemes also indicate that,in discrete operational computations,the new scheme in the case of nondivergence is capable of prolonging the valid in-tegral time of the corresponding traditional scheme,and eliminating certain kind of systematical computational "climate drift",meanwhile increasing its computational accuracy and reducing its amount of computation.The working principle of this paper is also applicable to the problem concerning baroclinic primitive equations.     

Numerical Study on Plume Interaction Above An Alternating Diffuser in Stagnant Water

1.IntroductionOcean outfall diffusers are used in most sewage disposal schemes to discharge the wastewater asmultiple buoyant jets which can be rapidly mixed with and diluted by the ambient current.Diffuserstake ona varietyof forms,rangingfromone withjets…     

Numerical Simulation of Biological Impact Caused by Direct Injection of Carbon Dioxide in the Ocean

The direct injection of CO₂ in the deep ocean is a promising way to mitigate global warming. One of the uncertainties in this method, however, is its impact on marine organisms in the near field before CO₂ is diluted widely in the ocean. Since field experiments cost enormously, computational simulations are expected to show detailed information on the dilution process near injection points and its impact on marine organisms. In general, the LC50 concept is widely applied for testing the acute impact of a toxic agent on organisms. As a biological impact model we therefore consider mortality, which reflects recent laboratory experiments on zooplankton at various concentrations of CO₂. Here we regard the sigmoid-transformed mortality as a linear function of time in the logarithmic scale, and not just of the concentration of CO₂ in the logarithmic scale. This model was installed in a computational simulation code for the reconstruction of small-scale ocean turbulence. The results suggest that the biological effect is not significant when the ship speed is 4 knots and CO₂ is injected at 0.1 ton/sec in the form of a spray through 100 nozzles provided vertically on a pipe at 10 m intervals. It is therefore considered that the moving-ship method is effective for direct CO₂ injection. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Local Tsunami Alert System [``SLAT']: A Computational Tool for the Integral Management of a Tsunami Emergency

During a tsunami emergency numerous local authorities responsible for the security oflocal persons and businesses which function in the coastal zone are required to makecritical decisions within a very short time frame. It is known that the consequencesof the situation will depend on the quality and quantity of decisions which they makeor allow to occur at the critical time. Based on this concept, the Local System of Tsunami Alert (SLAT; Spanish) was developed. This is a computational tool designed for the automatic implementation of integral management for an emergency of this type.The System is able to immediately evaluate possible risks and determine thetype of alert represented (Red, Yellow, Green, Blue, and Celeste) if relevantdata such as coordinates of the epicenter, magnitude, date, and origin of theearthquake (>6.5° on the Richter scale) threatening the Pacific areknown. Other relevant data include location of the coastal or marine epicentreand the superficial hypocenter. The relevant data may now be obtained fromthe internet from international seismological services, and fed into the programto give the most probable time for arrival of the first wave train at a given pointof interest, whether this be a port, bathing area, generating plant, or coastal city.The program also gives the time required for the first wave train to arrive at agiven coast, and displays a menu of previously planned actions to be taken accordingto the type of alert. It also permits dissemination of a bulletin with critical data and action plans by fax or e-mail to scattered users as well as for storage on the computer disc. The system is designed in a way that the user always confirms with authorities that anevent has in fact been generated. On a local scale, the user is required to prepare an operative emergency plan of action to be followed by his company, community, or municipality, to be followed for each type of alert.The System permits carrying out test exercises with the users, as well as simulationof past events. Knowledge concerning past events permits understanding correctdesign of emergency action plans for mitigation of potential present and future events.This software is specifically designed for the Pacific Coast of South America, and isprepared in Spanish, with the intention of improving responses of inhabitants of coastalareas to the potential threat from tsunamis.