粗格栅间的设计与运行控制

从构筑物设计,工艺设计及主要设备三方面详细介绍了粗格栅间的设计,具体阐述了粗格栅间的运行,结合阳泉市污水处理厂的运行情况总结了粗格栅间在运行控制和设计方面应注意的问题,从而保证污水处理厂运行的可靠性。     

Development of adaptive coarse grid generation methods for fast fluid dynamics in simulating indoor airflow

The control of indoor air quality and thermal comfort requires faster-than-real-time simulations of air distribution. One approach to achieve such simulations is to use coarse grid. This study developed two adaptive coarse grid generation methods by analysing the grid-related truncation errors in the solution of the Navier–Stokes equations by fast fluid dynamics (FFD). Method 1 generates a grid that is coarser than that for a grid-independent solution but can still provide accurate FFD predictions. Method 2 generates a very coarse grid that provides acceptable FFD predictions. This study assessed the performance of the developed methods by using them to simulate three typical indoor airflows. The assessment showed that the coarse grid generated by Method 1 accelerated the FFD simulation by at least two to five times, with similar computational accuracy. The coarse grid generated by Method 2 provided faster-than-real-time FFD simulations for the cases tested in this study.     

室内不同通风方式下生物颗粒的分布比较

针对当前严重急性呼吸综合症 (SARS :severeacuterespiratorysyndrome)肆虐这一情况 ,以性质和SARS病毒颗粒性质类似的颗粒为对象 ,采用数值方法对置换通风、混合通风以及自然风形成的穿堂风房间 ,在相同的送风量和同样的颗粒产生源情况下的颗粒分布进行了模拟和比较。为了进一步比较颗粒产生源位置的影响 ,对穿堂风情况计算了两种颗粒源位置的颗粒浓度分布。结果表明通风形式对室内生物颗粒的分布有着重要影响 ,对于文中列举的算例 ,穿堂风形式下的室内生物颗粒浓度最低 ,防御生物污染的能力最好。     

Feasibility of utilizing numerical viscosity from coarse grid CFD for fast turbulence modeling of indoor environments

Computational fluid dynamics (CFD) is a useful tool in building indoor environment study. However, the notorious computational effort of CFD is a significant drawback that restricts its applications in many areas and stages. Factors such as grid resolution and turbulence modeling are the main reasons that lead to large computing cost of this method. This study investigates the feasibility of utilizing inherent numerical viscosity induced by coarse CFD grid, coupled with simplest turbulence model, to greatly reduce the computational cost while maintaining reasonable modeling accuracy of CFD. Numerical viscosity introduced from space discretization in a carefully specified coarse grid resolution may have similar magnitude as turbulence viscosity for typical indoor airflows. This presents potentials of substituting sophisticated turbulence models with inherent numerical viscosity models from coarse grid CFD that are often used in fast CFD analysis. Case studies were conducted to validate the analytical findings, by comparing the coarse grid CFD predictions with the grid-independent CFD solutions as well as experimental data obtained from literature. The study shows that a uniform coarse grid can be applied, along with a constant turbulence viscosity model, to reasonably predict general airflow patterns in typical indoor environments. Although such predictions may not be as precise as fine-grid CFDs with well validated complex turbulence models, the accuracy is acceptable for indoor environment study, especially at an early stage of a project. The computing speed is about 100 times faster than a fine-grid CFD, which makes it possible to simulate a complicated 3-dimensional building in real-time (or near real-time) with personal computer.     

弹性曲弯空间网壳结构的找形与承载设计

弹性曲弯网壳结构不同于常规形式的空间网壳结构,具有特殊的建造方式.本文对这种特殊空间网壳结构的找形分析和承载设计过程进行了研究,对其设计中的材料选择条件、建造过程中的顶升找形特征以及承载计算中的杆件曲弯影响进行了深入的分析探讨.     

Comparison of different optimum criteria for sensor placement in lattice towers

Placing sensors at appropriate locations is an important task in the dynamic assessment of the mechanical systems, and its role is central in structural health monitoring. All sensors have to be placed on the structure so that all sought system features be obtained from the experimental tests. Sensor network design is rather diffused in laboratory applications, but there are scarce investigations on real civil structures, and they are not so well documented. In order to give a contribution in this framework, the present paper deals with the optimal sensor placement problem in lattice towers. With reference to six of the most diffused existing optimum criteria and according to mechanical and energetic formulations, several sensor network configurations are calculated for two broadcasting antennas, adopted as benchmark cases of studies. The final topological configurations of the networks are compared, and the most relevant differences are discussed. Moreover, the information content behaviour is computed to investigate the connection between sensor network topology and its ability to withstand the presence of undesired signals (e.g., noise) during the measurements. The results illustrated here may be useful for sensor network design for this special class of structures. Copyright © 2010 John Wiley & Sons, Ltd.     

An algorithm for calculating convection coefficients for internal building surfaces for the case of mixed flow in rooms

The treatment of convective heat transfer at internal building surfaces has a significant impact on the simulation of heat and air flow. Accurate approaches for the range of flow regimes experienced within buildings (buoyant flow adjacent to walls, buoyant plumes rising from radiators, fan-driven flows, etc.) are required, as is the ability to select an appropriate method for the case at hand and to adapt modelling to changes in the flow.A new approach — drawing upon previously published methods — has been developed for modelling mixed convection within mechanically ventilated rooms. It is applicable for rooms ventilated with ceiling mounted diffusers and is appropriate for both heating and cooling. ESP-r simulations performed with the mixed flow model indicate that the prediction of heating and cooling loads is highly sensitive to the treatment of surface convection and that significant errors can result if an inappropriate model is employed. The results also reveal that the choice of convection algorithm can influence design decisions drawn from a simulation-based analysis.     

流量阶跃变化时供暖房间内温度场的数值模拟

两位通断式调节是一种计量供热系统控制模式,与欧洲供热系统控制模式不同的是,其温控阀只有启、闭两种状态.用数值模拟方法研究了该调控模式对室内热环境的影响规律.     

A lattice Boltzmann exploration of two-phase displacement in 2D porous media under various pressure boundary conditions

While experimental designs developed in recent decades have contributed to research on dynamic nonequilibrium effects in transient two-phase flow in porous media, this problem has been seldom investigated using direct numerical simulation (DNS). Only a few studies have sought to numerically solve Navier–Stokes equations with level-set (LS) or volume-of-fluid (VoF) methods, each of which has constraints in terms of meniscus dynamics for various flow velocities in the control volume (CV) domain. The Shan–Chen multiphase multicomponent lattice Boltzmann method (SC-LBM) has a fundamental mechanism to separate immiscible fluid phases in the density domain without these limitations. Therefore, this study applied it to explore two-phase displacement in a single representative elementary volume (REV) of two-dimensional (2D) porous media. As a continuation of a previous investigation into one-step inflow/outflow in 2D porous media, this work seeks to identify dynamic nonequilibrium effects on capillary pressure–saturation relationship (P_c–S) for quasi-steady-state flow and multistep inflow/outflow under various pressure boundary conditions. The simulation outcomes show that P_c, S and specific interfacial area (a_nw) had multistep-wise dynamic effects corresponding to the multistep-wise pressure boundary conditions. With finer adjustments to the increase in pressure over more steps, dynamic nonequilibrium effects were significantly alleviated and even finally disappeared to achieve quasi-steady-state inflow/outflow conditions. Furthermore, triangular wave-formed pressure boundary conditions were applied in different periods to investigate dynamic nonequilibrium effects for hysteretical P_c–S. The results showed overshoot and undershoot of P_c to S in loops of the nonequilibrium hysteresis. In addition, the flow regimes of multistep-wise dynamic effects were analyzed in terms of Reynolds and capillary numbers (Re and Ca). The analysis of REV-scale flow regimes showed higher Re (1 < Re < 10) for more significant dynamic nonequilibrium effects. This indicates that inertia is critical for transient two-phase flow in porous media under dynamic nonequilibrium conditions.     

我国房地产策划与建筑策划的比较

运用对比方法,将我国房地产策划与建筑策划从其基本概念、主要目标、研究对象、服务对象、人员构成、工作程序以及实际应用等方面进行了比较,认识到了两者在实际运用中存在的不足,从而提出了在房地产策划中引入建筑策划的观念,即提出房地产的项目建筑策划概念。     

Optimisation of structured grid spacing parameters for separated flow simulation using mathematical optimisation

This paper describes the use of computational fluid dynamics (CFD) and mathematical optimisation techniques to minimise the error in predicting the recirculation zone for a separated flow topology. Grid spacing parameters are varied in the optimisation process. The accuracy of separated flow solutions is known to be dependent on the grid resolution and clustering. Although general guidelines have been developed for grid generation of separated flow topologies, the flow solutions using the resulting grids often under-predict features like recirculation zones. This study addresses this aspect by providing an automatic tool for optimising the grid for solution accuracy. This approach has until recently been too expensive, but is becoming more viable with ever-increasing computer power. A two-dimensional sinusoidal hill is used as an example of a separated flow topology. The CFD simulation employs the commercial CFD solver STAR-CD to solve the Reynolds-Averaged Navier–Stokes equations with the RNG k– turbulence model. CFD solution time is drastically reduced by making use of initial field restarts. The optimisation is carried out by means of Snyman's DYNAMIC-Q method, which is specifically designed to handle constrained problems where the objective or constraint functions are expensive to evaluate. Six design variables (grid spacing parameters) are considered in this study. The results indicate that the re-attachment point of the recirculation zone is predicted to within 1% of the specified experimental value in four optimisation iterations and therefore represents a cost-effective way to determine grids based on solution accuracy.     

大颗粒流化床内气固两相流稳定性试验研究

以自身开发的大颗粒流化床冷态试验模型为研究对象,分析了粒径在4.0～8.0 mm范围内的大颗粒物料发生稳定流态化所需工艺参数的取值范围、各参数间的相互关系;分析了大颗粒流化床容易出现的空床、棚料等异常现象时工艺参数突变特征,提出了确保流化床稳定运行的三项可行措施.对进一步开展热态模型研究有借鉴作用.     

远程公网电话报警信息的实时处理技术

本文探讨了远程公网报警信息的获取路径及显示平台的构筑方式 ,提出了大幅图的设计方法及片图地名信息的压缩处理方法 ,并对显示方式作了深入的探讨     

视频火焰实时监测系统的研究与实现

对国内外在基于图像处理的火灾探测系统方面的相关研究进行归纳和总结,并据此设计了视频火焰监测系统,同时提出了可区分大空间(隧道、仓库、博物馆等建筑物)中闪烁车灯和真实火焰的算法.介绍了此系统的硬件模块组成及算法实现流程,并实验验证了此算法的有效性.实验结果表明,此算法可以有效地区分闪烁车灯与真实火焰,降低了误报率.并且具有多路监测的实时性.     

Truncated vortex generators for part-depth wind-tunnel simulations of the atmospheric boundary layer flow

A modified design of the ‘Counihan’ vortex generator was proposed for purposes of part-depth atmospheric boundary layer (ABL) wind-tunnel simulations. Three redesigned vortex generators were manufactured and their applicability was tested in a boundary layer wind tunnel together with a castellated barrier wall and a fetch of roughness elements. Using this hardware, neutrally stratified ABL developing above rural, suburban and urban terrains was successfully reproduced. A hot-wire anemometry system was applied for measurements of mean velocity and velocity fluctuations. Comparisons of wind-tunnel results with full-scale data and/or with theoretical models are presented, including mean velocity, turbulence intensity, integral length scale of turbulence and power spectral density of velocity fluctuations. The analysis of obtained results indicates the adequacy of redesigned ‘Counihan’ vortex generators for part-depth ABL wind-tunnel simulations, as the obtained wind-tunnel results compare well with the full-scale rural, suburban and urban ABL.     

基于AHP法的房地产项目投资方案的比较选择

指出房地产投资不但有其内在的规律,在对投资进行分析时还需特定的理论与方法,在认真总结国内现有理论与方法的基础上,对房地产项目经济评价进行研究,并把房地产项目多方案评价作为重点进行分析。     

Coupled simulations for naturally ventilated rooms between building simulation (BS) and computational fluid dynamics (CFD) for better prediction of indoor thermal environment

The coupling strategies for natural ventilation between building simulation (BS) and computational fluid dynamics (CFD) are discussed and coupling methodology for natural ventilation is highlighted. Two single-zone cases have been used to validate coupled simulations with full CFD simulations. The main discrepancy factors have also been analyzed. The comparison results suggest that for coupled simulations taking pressure from BS as inlet boundary conditions can provide more accurate results for indoor CFD simulation than taking velocity from BS as boundary conditions. The validation results indicate that coupled simulations can improve indoor thermal environment prediction for natural ventilation taking wind as the major force. With the aids of developed coupling program, coupled simulations between BS and CFD can effectively improve the speed and accuracy in predicting indoor thermal environment for natural ventilation studies.     

Mathematical modeling of sewers under surcharge for real time control of combined sewer overflows

The efficiency of real time control (RTC) to decrease storm overflows from combined sewers to receiving waters was demonstrated in several case studies. Global predictive control (GPC), an effective strategy to perform real time management of sewers, requires simulation models to anticipate the future state of the system (flow rates and water levels). To compute these predictions, a hydraulic model using an implicit discretization scheme to solve simplified continuity and momentum equations was developed. The performance of the model is evaluated by comparison with the USEPA EXTRAN model results. This comparison shows that the model gives results similar to those of the EXTRAN model, with the advantage of producing faster and more stable results regardless of space and time steps used. Additional validation with the SUPERLINK model is also presented.     

西安房地产发展与其他同等城市的比较分析

通过对西安与全国其他同等城市的横向对比,借以明确西安房地产市场的总体发展水平,了解制约西安市房地产发展的宏观约束条件,并找出西安房地产发展的潜力与不足,以便于为未来西安房地产业的健康有序发展,为政府有关部门制定政策提供决策依据。