蒸发条件下冬小麦田土壤水热耦合运移模拟

综合考虑了根区土壤水分动态、根系吸水、蒸发蒸腾、地表能量分配和土壤中温度分布5个子系统,建立了冬小麦蒸发条件下土壤水热耦合运移模拟模型,经实测资料检验其精度较高.该模型可用于田间水分动态、根系吸水、蒸发蒸腾、地表能量分配和土壤中温度分布的模拟或预测.     

蒸发条件下冬小麦田土壤水热耦合运移模拟

综合考虑了根区土壤水分动态、根系吸水、蒸发蒸腾、地表能量分配和土壤中温度分布5个子系统，建立了冬小麦蒸发条件下土壤水热耦合运移模拟模型，经实测资料检验其精度较高。该模型可用于田间水分动态、根系吸水、蒸发蒸腾、地表能量分配和土壤中温度分布的模拟或预测。     

用边界元法研究冻土的温度分布状况

冻土,即具有负温和含冰的土体岩石.本文主要以数值方法数值模拟研究二维水热耦合问题,从宏观尺度上研究冻土在外界温度一定时,系统本身的温度分布状况.     

用于田间作物-水分关系研究的ThuSPAC模型

:田间作物水分关系是土壤植物大气连续体(Soil Plant Atmosphere Continuum,简称SPAC)理论的重要研究内容.本研究介绍的ThuSPAC(Tsinghua University SPAC)模型,包含土壤水热运移(Soil)模型、冠层(Canopy)模型、土壤-植物-大气连续体(SPAC)模型、冬小麦生长模拟(Wheat)模型、冬小麦生长与SPAC水热运移耦合的WheatSPAC模型5个独立的模型.利用ThuSPAC模型,可以根据土壤条件、冬小麦品种参数、气象条件及灌溉条件等,动态模拟土壤、冠层中水分温度的分布规律、冬小麦生长过程及最终产量.模型的开发语言为Visual Basic,界面友好,在相关领域的研究中具有广泛的应用前景.     

基于FINE/Turbo的高压涡轮叶片流热耦合分析

为验证FINE/Turbo软件对高压涡轮流热耦合求解问题的准确性,将Mark Ⅱ型燃气涡轮叶片作为分析对象,选用不同的湍流模型和转捩模型进行数值模拟,得到叶片表面压力分布,B2B面的压力、温度、马赫数和湍流动能分布,叶片内部温度分布以及叶片表面传热系数分布,并与试验数据进行比较.结果表明:对于流热耦合问题,FINE/T...     

汽轮机转子碰摩热弯曲动力特性研究

本文简化了汽轮机转子模型,并根据转子碰摩理论建立了一种简单的求解碰摩截面热分布的计算模型,使得碰摩截面热分布的计算大大简化.依据转子动力学理论推导了本模型的运动方程,并作无量纲化以便于MATLAB数值求解收敛,最终建立了转子系统由摩擦引起的弹性热弯曲——碰摩耦合故障动力模型.利用四阶Runge-Kutta方法求解微分方程组得到了在不平衡力、碰摩力和碰摩热弯矩耦合作用下转子系统的响应,并对低于、接近和高于临界转速下碰摩热弯曲转子的动力学特性进行了数值仿真研究,包括时域、频谱、轴心轨迹以及碰摩力的变化.结果表明,转子在低于和接近临界转速运行发生碰摩,转子的振动由平稳状态逐渐发散,而在高于临界转速发生碰摩时转子的振动会逐渐减小.     

用边界粒子法求解柯西反问题的数值计算软件包

为推动无网格方法在反问题中的应用及相关计算软件的发展,介绍基于MATLAB开发的用边界粒子法(Boundary Particle Method,BPM)数值模拟柯西反问题的计算软件包;描述数值算法的理论基础,并结合标准算例介绍软件包的基本功能和使用方法.该软件包可求解含不同形式源项(多项式函数、三角函数、指数函数及其耦合函数等)的椭圆型偏微分方程,并且可用于处理任意几何区域问题.本软件包具有简单易用的图形用户界面,在数值模拟柯西反问题时仅需边界测量数据,且效率高、精度高.     

基于多源极轨气象卫星热红外数据的近地表气温反演研究

以上海作为研究区,采用多源极轨气象卫星热红外波段数据,在进行数据预处理的基础上选择264个时相,与52个气象站点的同步气温数据进行耦合,建立了分季度、分时段的两种气温遥感反演模型.结果表明,基于多源遥感数据的大量样本可用于建立稳定的气温反演模型,而且通过实测的单个站点数据进行模型修正能够提高气温水平分布的反演精度.     

基于Ordered-RAMP模型的热固耦合结构多材料拓扑优化方法

针对传统单材料热固耦合拓扑优化设计难以实现结构材料与性能综合最优的问题,提出一种基于变密度理论有序材料属性有理近似模型的多材料拓扑优化方法.该方法通过搭建比例系数与平移系数,将多种材料属性采用[0,1]连续分布的单设计变量进行描述,并研究和比较与有序固体各向同行惩罚微结构模型的优缺点;其次借助归一化加权方法定义以结构柔度最小化和散热弱度最小化为目标函数的数学模型.结合设计变量敏度分析,详细推导多材料、多目标条件下热固耦合结构拓扑优化的迭代公式.通过数值算例分析对比了不同权系数以及不同材料属性组合对优化结果的影响;结果表明,所提出的优化方法在热固耦合结构多材料多目标拓扑优化设计中具有可行性和有效性.     

用边界元法研究冻土的温度分布状况

冻土,即具有负温和含冰的土体岩石。本文主要以数值方法数值模拟研究二维水热耦合问题,从宏观尺度上研究冻土在外界温度一定时,系统本身的温度分布状况。     

A parameterized model of heat storage by lake sediments

A model of seasonal heat storage by lake sediments is proposed oriented at applications in climate modeling and at lake parameterization in numerical weather prediction. The computational efficiency is achieved by reformulating of the heat transfer problem as a set of ordinary differential equations for evolution of the temperature wave inside the upper sediment layer. Arising temperature and depth scales completely replace the conductivity of the sediment in the heat transfer equation and can be easily achieved from the lake water temperature observations without any data on the sediment thermal properties. The method is proposed for the scales estimation from the inverse solution of the model equations in special case of the constant water-sediment heat flux in ice-covered lakes. The method is tested on data from sediments of Lake Krasnoye, North-Western Russia. The long-term (1961–2002) modeling of temperature in German lakes Müggelsee and Heiligensee with a coupled one-dimensional model of lake water column and sediments has demonstrated an appreciable effect of the sediment heat storage on near-bottom temperatures in both lakes. Thus, incorporation of the sediment layer into lake temperature models can essentially improve, at low computational costs, the model performance, especially for shallow lakes. In addition, a better forecast of near-bottom temperature evolution on climatic scales can provide a better understanding of the response of lake benthic communities to global warming.     

Electroheating modeling in metal processing: a review

The current development of electroheating modeling and its application to metal industry are reviewed in this paper. Particular attention is given to formulating the coupled electromagnetic and induced heat transfer and fluid flow problems that arise in the metal industry. Following a brief introduction of the nature of electroheat problems, the formulation of electromagnetic, heat transfer, and fluid dynamic phenomena is presented. The numerical methods used for electromagnetic modeling including the finite element, and finite difference are then examined. Several commercially available software packages for electromagnetic modeling are also briefly assessed. Finally, the applications of these modeling efforts to the induction heating or melting problems are discussed.     

An integrated crop and hydrologic modeling system to estimate hydrologic impacts of crop irrigation demands

The present paper discusses a coupled gridded crop modeling and hydrologic modeling system that can examine the benefits of irrigation and costs of irrigation and the coincident impact of the irrigation water withdrawals on surface water hydrology. The system is applied to the Southeastern U.S. The system tools to be discussed include a gridded version (GriDSSAT) of the crop modeling system DSSAT. The irrigation demand from GriDSSAT is coupled to a regional hydrologic model (WaSSI). GriDSSAT and WaSSI are coupled through the USDA NASS CropScape data to provide crop acreages in each watershed. The crop model provides the dynamic irrigation demand which is a function of the weather. The hydrologic model responds to the weather and includes all other anthropogenic competing uses of water. Examples of the system include an analysis of the hydrologic impact of future expansion of irrigation and the real-time impact of short-term drought.     

基于水膜耦合导波传感器的复合材料检测研究

复合材料因其具有各种优异性能而被广泛应用于航空航天领域,同时对其检测方法也提出了更高的要求。提出了基于水膜耦合导波传感器检测方法,通过理论计算与时频分析确定了水膜耦合导波传感器耦合材料、角度和频率的选择;采用SolidWorks三维建模软件完成了水膜耦合导波传感器的结构设计并加工成型;最后搭建了检测实验平台,在复合材料板上完成了水膜耦合导波传感器的测试。该方法可以有效解决检测的耦合剂使用问题,为自动化检测提供了技术支持。     

Simulation of magmatic and metamorphic fluid production coupled with deformation,fluid flow and heat transport

A methodology for simulating magmatic and metamorphic fluid production coupled with mechanical deformation, fluid flow and heat transport is presented. The methodology is implemented in FLAC3D, a lagrangian finite difference code designed for simulation of coupled deformation, fluid flow and heat transport in porous media. The rate of metamorphic fluid production is governed by the rate of temperature change and an approximation of the variation in bound water content of appropriate lithologies with temperature. Magmatic fluid production is governed by the rate of cooling and the variation in free water content of a mafic granitic magma with temperature. Changes in porosity and fluid pressure due to fluid production, deformation, and thermal expansion are taken into account. Dilation associated with thermal expansion and fluid production leads to rotation of the principal stresses around fluid source regions. Fluid properties are calculated using an equation of state for pure water. The methodology has been applied to examples representing aspects of Archaean gold mineralisation in Western Australia, providing insight into the role of magmatic and metamorphic fluids in mineralisation, and effects arising from interactions between deformation, heat transport and fluid production.     

Estimating soil thermal properties from sequences of land surface temperature using hybrid Genetic Algorithm–Finite Difference method

Most models used in land surface hydrology, vadose zone hydrology, and hydro-climatology require an accurate representation of soil thermal properties (soil thermal conductivity and volumetric heat capacity). Various empirical relations have been suggested to estimate soil thermal properties. However, they require many input parameters such as soil texture, mineralogical composition, porosity and water content, which are not always available from laboratory experiments and field measurements. In this paper, to overcome the above challenge, a hybrid numerical method, Genetic Algorithm–Finite Difference (GA–FD), is proposed to estimate soil thermal properties using land surface temperature (LST) as the only input. The genetic algorithm (GA) optimization method coupled with the finite difference (FD) modeling technique is a viable hybrid approach for estimating soil thermal properties. The finite difference method is employed to solve the heat diffusion equation and simulate LST, while a robust optimization technique (GA) is used to retrieve soil thermal properties by minimizing the difference between observed and simulated LST. Furthermore, a generalization of the hybrid model is developed for inhomogeneous soil, in which soil thermal properties are not constant throughout the soil slab. The proposed model is applied to the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE). The results show that the proposed hybrid numerical method is able to estimate soil thermal properties accurately, and therefore effectively eliminate the need for the unavailable soil parameters which are required by empirical methods for determining the soil thermal conductivity and volumetric heat capacity. Remarkably, the temporal variation of the retrieved soil thermal conductivity is consistent with the volumetric water content, even though no water content information is used in the model.     

基于偏最小二乘回归和SVM的水质预测

针对传统水质预测方法中水质因子的多重相关性造成预测精度低的问题,提出了一种将偏最小二乘法和支持向量机相耦合的水质预测方法。利用偏最小二乘法提取对水质因子影响强的成分,从而克服了信息冗余问题,并降低了支持向量的维数。利用支持向量机建模可以较好地解决高维非线性小样本问题。同时利用改进的PSO算法优化SVM参数,减小参数搜索的盲目性。研究结果表明,本耦合模型的预测精度和运行效率明显优于常用的BP人工神经网络和传统的支持向量机,可以更好地应用于水质预测。     

Examination of thermo-physical and material property interactions in cereal foams by means of Boltzmann modeling techniques

Cereal foam is a high complex material undergoing several temperature-dependent processes under thermal treatment, such as phase transitions, biochemical reactions and structural changes. Simultaneous heat and mass transfer plays an important role to investigate optimization studies in cereal-based foams. In porous media such as cereal foams, thermal conduction is of minor impact on the overall heat transfer, since the major part of heat is transferred through the gas phase filled with water vapor. This becomes evident comparing the thermal diffusivities of solid and gaseous components of the foam, where the difference is in the order of five magnitudes. The objective of this study is to model the coupled heat and mass diffusion processes in cereal-based foam under thermal treatment by means of Lattice Boltzmann methods. The proposed model is then used to perform parameter variation studies, showing the impact of material property changes offering the possibility on optimizing heat transfer through the foam.     

Polymeric Thermal Microactuator With Embedded Silicon Skeleton: Part I—Design and Analysis

This paper presents the modeling of a new design of a polymeric thermal microactuator with an embedded meander-shaped silicon skeleton. The design has a skeleton embedded in a polymer block. The embedded skeleton improves heat transfer to the polymer and reinforces it. In addition, the skeleton laterally constrains the polymer to direct the volumetric thermal expansion of the polymer in the actuation direction. The complex geometry and multiple-material composition of the actuator make its modeling very involved. In this paper, the main focus is on the development of approximate electrothermal and thermoelastic models to capture the essence of the actuator behavior. The approximate models are validated with a fully coupled multiphysics finite element model and with experimental testing. The approximate models can be useful as an inexpensive tool for subsequent design optimization. Evaluation, using the analytical and numerical models, shows that the polymer actuator with the embedded skeleton outperforms its counterpart without a skeleton, which is in terms of heat transfer and, thus, response time, actuation stress, and planarity.$hfill$ [2007-0193]      

Manipulation of numerical coastal flow and water quality models

Nowadays, numerical flow and water quality models are widely applied to solve coastal engineering problems. The outcomes of the algorithmic execution often deviate from those anticipated, particularly when the model is set up initially. This necessitates the modeler to perform the manipulation procedure, which comprises feed back and modification. As such, it is desirable that expert system technology be integrated into the modeling system to furnish assistance for the novice user who lacks the requisite knowledge to establish the model and assess the results. In this paper, a prototype expert system on manipulation of numerical coastal flow and water quality models is developed and implemented by employing an expert system shell, Visual Rule Studio, as an Active Designer under Microsoft Visual Basic environment. Through the successful development of this prototype system, it is shown that the expert system technology can be coupled into numerical modeling for mimicking the manipulation process. It assists the user to formulate a suitable strategy for striking a balance between accuracy and effectiveness and to tune the model to accomplish satisfactory modeling of real phenomena. It is able to bridge the existing gap between numerical modelers and practitioners in this field.