计算流体力学技术及常用软件简介

计算流体力学技术,近年来在我国得到广泛的应用,本文介绍了计算流体力学技术的基本原理、计算过程以及目前常用的一些CFD软件的特点和应用领域.     

快速式燃气热水器燃烧系统模拟

模拟了一种常规快速式燃气热水器的燃烧系统,研究了不同压力状况下的燃烧工况.得到的数值模拟结果与实验获得的数据吻合得较好,证明了所用物理模型和数学模型的合理性.结果显示,火焰高度和过剩空气系数依赖于系统出口和入口的静压差,而与燃烧室内的绝对压力无关.该静压差和系统中用于燃烧的空气量显著影响CO的生成,与CO的生成量呈反比关系,并同时影响燃烧区域内的温度场和速度场.为降低CO排放水平,必须增加进入燃烧系统的空气量,因此需要增加风机输出功率以提供足够的空气压头.该研究为设计快速式燃气热水器提供了一种行之有效的方法.     

室内^222Rn/^220Rn浓度分布的CFD模拟

室内^222 Rn/^220 Rn危害的评估与防护中,^222 Rn/^220 Rn浓度水平与空间分布的准确计算是一个关键问题。通过对室内^222 Rn/^220 Rn水平影响因素的分析,建立较真实的物理模型,运用CFD技术研究固定外界^222 Rn/^220 Rn浓度与壁面析出率时,不同通风状况下室内^222 Rn/^220 Rn浓度的平均值与三维分布情况。     

Daily natural heat convection in a historical hall

The use of numerical simulation methods for the Cultural Heritage is of increasing importance for the analysis, conservation, restoration and appreciation of works of art. This is particularly important when their preservation and planned maintenance is the primary aim. Today museums, and particularly historical buildings converted to museums, should be considered as places where precious artefacts should have first-rate protection and conservation. It is a question of solving the compromise between protection, conservation and comfort for works of art and/or visitors, with the consequence that preservation and planned maintenance criteria must prevail over use requirements. Refurbishment and conservation of a building, and requirements for visitor presence and works of art need different thermo-physical indoor parameter values. The present paper concerns the thermal and air velocity analysis of the Salone dei Duecento (the Hall of the Two Hundred of the Palazzo Vecchio (Old Palace)) in Florence. In this paper an appropriate transient 3D model by Computational Fluid Dynamics (CFD) software based on the finite element method (FEM) was used. Variations and interaction between indoor and outdoor microclimatic conditions, and thermo-physical behaviour of the building connected to lighting, visitor presence and cooling–heating fan coils system were considered. The 3D modelling method provided by the present paper can be applied to several situations where there is interaction between outdoor and indoor climate variations and the building structure. It can be very useful for defining measures to preserve tapestries, understanding deterioration processes, and developing new conservation techniques and strategies for care and exhibition.     

高超声速复杂流动中湍流模式的研究

研究了标准k ε模式 ,双尺度湍流模式 ,并对其在壁面附近作出长度尺度修正 在此基础上 ,选择了几个基准流动 :二维可压缩拐角、锥柱裙组合体绕流和斜激波 /平板湍流边界层干扰 ,进行数值计算 .通过数值计算和实验结果的比较 ,发现修正湍流模式对流动分离、摩阻和热流的计算具有更好的效果 .     

CFD Analysis of Gas Distributor in Packed Column--Prediction of Gas Flow and Effect of Tower Internals Geometry Structure

Computational fluid dynamics (CFD) simulations were carried out on the gas flow patterns of twin-tangential annular deflector gas distributor in the absence of liquid flow in a packed column (6.4 m in diameter), and the gas flow field in the column was presented close to reality on the whole. Furthermore, after ame-lioration of this gas distributor frame, turbulence energy and turbulence energy dissipation rate were both decreased greatly.Simulation results showed that the flow pattern and the distribution of gas flow were strongly affected by the column bottom frame; the proper column bottom frame could decrease the flow pressure drop greatly. Multifold factors, such as the column bottom geometry structure and distributor structure which affects the distribution capacity, must be considered.     

Computational fluid dynamic simulation of an inter-phasing pulse tube cooler

An inter-phasing pulse tube cooler （IPPTC） consists of two pulse tube units, which are connected to each other at hot ends of the pulse tubes through a needle valve. This paper presents the computational fluid dynamic （CFD） results of an IPPTC using a 2D axis-symmetrical model. General results such as the phase difference between pressure and velocity at cold end and hot end, the temperature profiles along the wall, the available lowest temperature as well as its oscillations and the coefficient of performance （COP） for IPPTC are presented. The formation of DC flow and its effects on the performance of the cooler are investigated and analyzed in detail. Turbulence, which is partially responsible for the poor overall performance of a single orifice pulse tube cooler （OPTC）, is found to be much reduced in IPPTC and its performance is improved significantly compared with the single OPTC.     

Numerical simulation of a direct internal reforming solid oxide fuel cell using computational fluid dynamics method

A detailed mathematical model of a direct internal reforming solid oxide fuel cell （DIR-SOFC） incorporating with simulation of chemical and physical processes in the fuel cell is presented. The model is developed based on the reforming and electrochemical reaction mechanisms, mass and energy conservation, and heat transfer. A computational fluid dynamics （CFD） method is used for solving the complicated multiple partial differential equations （PDEs） to obtain the numerical approximations. The resulting distributions of chemical species concentrations, temperature and current density in a cross-flow DIR-SOFC are given and analyzed in detail. Further, the influence between distributions of chemical species concentrations, temperature and current density during the simulation is illustrated and discussed. The heat and mass transfer, and the kinetics of reforming and electrochemical reactions have significant effects on the parameter distributions within the cell. The results show the particular characteristics of the DIR-SOFC among fuel cells, and can aid in stack design and control.     

车用三元催化转化器流场的数值模拟与结构优化设计

分析了催化转化器内部流场及其结构影响因素,建立了催化转化器内部流场数学模型,应用CFD软件对催化转化器内部流场进行了数值模拟,得到不同结构参数下载体前端面速度和压力分布规律,从而得出比较理想的改进方案。