三维物理-热工耦合过程的网格优化

在反应堆物理-热工耦合过程中,网格划分尺度会影响计算精度和计算时间。利用蒙特卡罗程序和FLUENT程序,对压水堆单棒模型进行不同尺度的网格划分,评估网格划分尺度对耦合结果的影响,得到单个网格中密度差值、温度差值对有效增殖因子和功率分布引入的误差。研究表明当燃料温度差值小于50 K,慢化剂密度差值3 kg/m3时,有效增殖因子相对误差小于10-4,功率相对误差小于1%。使用该规律,对典型的压水堆单棒模型和33通道模型进行网格划分并进行耦合计算。结果表明,单棒模型网格总数减少至1/100,计算时间减少至1/4,33通道模型网格总数减少至1/50,计算时间减少至1/10,但其结果仍然精确有效。     

基于JMCT和FLUENT的物理-热工耦合计算

基于蒙特卡罗程序JMCT2.2和商用CFD程序FLUENT,通过C++语言,采用外耦合的方式开发了一套耦合接口程序。利用JMCT网格和FLUENT计算域之间一一映射的方式完成物理模型和CFD模型之间的网格匹配,实现了物理模型的简单划分和CFD模型网格的精细划分。利用该耦合程序计算了压水堆单根燃料棒模型和3×3带水洞的燃料子组件模型,并与MCNP与FLUENT耦合计算结果进行对比。计算结果表明,使用本文的方法,耦合JMCT程序与FLUENT程序能够用于物理-热工耦合计算并准确提供其反馈参数。     

Backscattering from small-scale breaking wave turbulence structure generated by FLUENT

A breaking wave can exert a great influence on the electromagnetic（EM） scattering result from sea surfaces. In this paper, the process of small-scale wave breaking is simulated by the commercial computational fluid dynamics（CFD）software FLUENT, and the backscattering radar cross section（RCS） of the turbulence structure after breaking is calculated with the method of moments. The scattering results can reflect the turbulent intensities of the wave profiles and can indicate high polarization ratios at moderate incident angles, which should be attributed to the incoherent backscatter from surface disturbance of turbulence structure. Compared with the wave profile before breaking, the turbulence structure has no obvious geometrical characteristic of a plunging breaker, and no sea spikes are present at large incident angles either.In summary, the study of EM scattering from turbulence structure can provide a basis to explain the anomalies of EM scattering from sea surfaces and help us understand the scattering mechanism about the breaking wave more completely.     

脉冲电流作用下TIG电弧的数值分析

建立了脉冲电流下自由燃烧的TIG电弧的二维轴对称数学模型,利用FLUENT软件,通过选择合适的边界条件和强烈耦合控制方程组对脉冲TIG电弧进行了数值模拟,得到了在焊接电流周期性变化下电弧形态、电弧温度场、电弧轴线方向上的温度和速度及焊接工件表面电弧压力的变化情况;针对电弧压力,得到了不同峰值电流、占空比、脉冲频率作用下的分布情况,并分析了它们在脉冲电流作用下的周期性变化规律.分析结果表明:当脉冲电流发生突变时,它们的变化滞后于脉冲电流的变化,且从基值电流向峰值电流变化时的响应速度更快,并最终达到一个相对稳 关键词： 脉冲TIG焊 电弧 数值模拟 FLUENT     

基于FLUENT/MATLAB联合优化的移动终端功耗预算分配方法

移动终端的功耗预算分配是其热设计的重要环节,而传统方法却面临着效率低下和效果不佳等一系列问题.为此,本文提出FLUENT/MATLAB联合优化方法以实现功耗的高效分配.其中,FLUENT提供精确的功耗-温度热模型,MATLAB提供可靠的优化算法函数库,并通过WinSock网络编程技术实现FLUENT和MATLAB间的数...     

Numerical simulation of heat transfer enhancement for natural convection in a cubical enclosure filled with Al2O3/water and Ag/water nanofluids

In the present study, the natural convective heat transfer in a cube filled with Al₂O₃/H₂O and Ag/H₂O nanofluids is investigated numerically. Commercial CFD code FLUENT has been used to simulate water-based nanofluid considering it as a single-phase fluid. The influence of different parameters, such as the Rayleigh number and the nanoparticle volume fraction, is studied. The velocity vectors and the isotherm profiles are plotted. The variation of the Average Nusselt number at the hot wall and the variation of y-component of velocity are presented and discussed. The numerical results show a decrease in the heat transfer with the increase in the particle volume fraction and the same trend in the increase of the Nusselt number with the Rayleigh number.     

Effect of an axial magnetic field on a DC argon arc

In this paper a commercial CFD （computational fluid dynamics） code FLUENT has been used and modified for the axisymmetric swirl and time-dependent simulation of an atmospheric pressure argon arc in an external axial magnetic field （AMF）. The computational domain includes the arc itself and the anodic region. Numerical results demonstrate that the AMF substantially increases the tangential component of the plasma velocity. The resulting centrifugal force for the plasma rotation impels it to travel to the arc mantel and as a result, a low-pressure region appears at the arc core. With the AMF, the arc presents a hollow bell shape and correspondingly, the maximal values of the temperature, pressure and current density on the anode surface are departing from the arc centreline.     

WP6涡轮部件设计状态及实验状态的数值模拟

本文对WP6涡轮部件按照折合转速及膨胀比相等的准则设计了两套实验方案,并对设计状态及设计的两套实验方案进行了S2正问题计算和S1流面计算。计算表明,所没计的实验方案与设计状态马赫数相似,达到了实验设计的目的。为校验所用S2正问题计算和S1流面计算程序,对设计状态进行了S2正问题计算、S1流面计算及FLUENT计算,总参数如流量、效率等吻合较好,叶表马赫数分布趋势也很相似。     

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自然界中鱼类尾鳍形状各种各样,但前体大部分都是扁平的椭圆形状. 该文研究了不同形状 的前体对尾鳍推进的影响. 尾鳍统一采用月牙形状; 前体采用了两种模型： A-鱼类扁平椭圆形状和B-潜艇水滴回转体形状. 通过以Strouhal数为控制参数的FLUENT数 值模拟,发现前体形状对于尾鳍的静止状态和运动状态有不同的作用,采用模型A的前体形 状更有利于长时间巡游,故鱼类采用模型A这种前体形状是自然界优胜劣汰的进化必然选择.