深圳大运会主体育场罩棚风压分布的数值模拟

为了求得体育场罩棚的风载体型系数,基于Reynolds时均N-S方程和RSM模型对深圳大运动会主体育场罩棚风压分布特性进行了数值模拟.采用有限体积法对控制微分方程进行离散,并采用SIMPLE压力校正算法来实现非线性方程的迭代求解.将数值计算结果与风洞试验结果进行了对比,两者吻合较好,在此基础上,分析了风向角和风攻角对风压分布的影响,探讨了罩棚周围流场的绕流特性,并根据罩棚的结构形式及风压分布特点,给出了最不利风向下罩棚表面的区域平均风压系数以及罩棚设计风荷载的计算方法.结果表明:风向角对风荷载的影响较大,不同风向角下,来流的分离和漩涡脱落作用均有较大的不同.风攻角对罩棚表面风压分布的影响不大,对罩棚局部峰值的影响在15%以内,整体影响在5%以内.     

超声波钢包精炼冷态模拟

以某钢厂180t钢包为原型,进行超声波改善钢包熔池搅拌效果的冷态模拟实验。通过记录pH计示数变化研究底吹气体搅拌均混时间及超声波搅拌均混时间。实验结果表明,在底吹空气水模实验中,当吹气位置在距离中心为0．33R,流量为0．1m3／h时,底吹气体搅拌所需的均混时间最短为50s;超声波水模实验中,当波源伸入钢包的中心液面下25cm处,输出功率1．8kw,均混时间最短为35s;在超声波和底吹气体联合实验中。当吹气位置在距离中心为0．33R,流量为0．1m^3／h,波源伸入钢包的中心液面下25cm处,输出功率1．8kw时,均混时间最短为48s;可以看出超声波可明显缩短钢包均混时间,改善钢包精炼动力学条件。     

模糊控制在光电稳定平台跟踪控制中的应用

对光电稳定平台中的跟踪环控制系统提出了一种基于遗传算法的模糊控制策略,简要介绍了模糊变量的选择、模糊机的建立以及最优比例调节因子的获取方法,最后通过仿真验证了该方法的有效性。     

全固态激光器中泵浦速率分布的数值模拟

以LD端面泵浦的固体激光器为例,讨论了泵浦光源在激光晶体中的分布模型,计算了泵浦速率分布函数的归一化,并对分布函数进行了数值模拟。     

高压输电线路不平衡度影响因素分析

不平衡度是电能质量的重要指标之一.对高压输电线路不平衡度的影响因素,如线路长度、电压等级、杆塔因素、线路导线分裂数、避雷线,以及系统相角等进行了研究,利用ATP和MATLAB工具进行了仿真和计算,提出了一些减少不平衡度的方法.     

管板和传热管胀接应力应变的数值模拟及分析

蒸汽发生器是核电厂一回路与二回路的枢纽,传热管和管板的连接处为事故多发区,而机械加工过程残留的应力是引起裂纹的主要原因.应用有限元软件对某型蒸汽发生器中的传热管和管板的胀接过程进行瞬态模拟,得到不同胀接压力下的管板和传热管的残余应力和残余应变值,为传热管和管板最佳胀接参数的确定以及工作过程中应力腐蚀的预防提供理论依据.研究结果标明,管板孔表面的残余径向应力和残余径向应变值都是随胀接压力的增加而增加,且沿着轴向的变化规律相似.     

U型埋管换热器及其周围土壤非稳态传热的数值分析

针对地源热泵U型换热器埋管、周围回填材料及土壤传热过程,建立了将U型管壁的边界换热取为第三类对流换热条件的二维非稳态传热模型,并对其温度分布进行了数值模拟分析．分析结果表明：U型埋管换热器管壁内对流换热热阻和管壁导热热阻对U型埋管换热器及其周围土壤非稳态传热过程的影响较小,但相互热干扰造成进、出水管壁自身各角度的温度存在明显差异．各处土壤温度达到准稳定阶段所需要的时间随其与U型埋管的距离增加而增加．     

New explicit algebraic stress and flux model for active scalar and simulation of shear stratified cylinder wake flow

On the numerical simulation of active scalar, a new explicit algebraic expression on active scalar flux was derived based on Wikstr?m, Wallin and Johansson model (a ^WWJ model). Reynolds stress algebraic expressions were added by a term to account for the buoyancy effect. The new explicit Reynolds stress and active scalar flux model was then established. Governing equations of this model were solved by finite volume method with unstructured grids. The thermal shear stratified cylinder wake flow was computed by this new model. The computational results are in good agreement with laboratorial measurements. This work is the development on modeling of explicit algebraic Reynolds stress and scalar flux, and is also a further modification of the a ^WWJ model for complex situations such as a shear stratified flow. Supported by the National Nature Science Foundation of China (Grant Nos. 50679019, 50009001), the National Basic Research Program of China (“973” Project) (Grant No. 2008CB418202), the Project of “Six Talent Peak” of Jiangsu Province (08-C), Social Technology Development Foundation of Jiangsu Province (Grant No. BS2006095) and the “908” Special Foundation of Jiangsu Province (Grant No. JS-908-02-06)     

Mold deformation in soft UV-nanoimprint lithography

UV-nanoimprint lithography (UV-NIL) using a soft mold is a promising technique with low cost and high throughput for producing the submicron scale large-area patterns. However, the deformations of the soft mold during imprinting process which can cause serious consequences have to be understood for the practical application of the process. This paper investigated the deformation of the soft mold by theoretical analyses, numerical simulations, and experimental studies. We simulated the mold deformation using a simplified model and finite element method. The simulation and the related experimental results agree well with each other. Through the investigation, the mechanism and affected factors of the mold deformation are revealed, and some useful conclusions have been achieved. These results will be valuable in optimizing the imprinting process conditions and mold design for improving the quality of transferred patterns.     

基于哈密顿系统原理的PMSM自适应阻尼注入控制

基于能量成形和端口受控哈密顿（PCH）系统原理,针对永磁同步电机（PMSM）参数不确定性所引起的转速误差,利用自适应阻尼注入控制方法,设计了负载转矩恒定已知和未知情况下的控制器。采用最大转矩/电流（MTPA）控制原理确定系统期望平衡点,并分析其稳定性。仿真结果表明,将自适应阻尼注入控制方法应用到PMSM的PCH控制中,对参数不确定性所引起的转速误差具有很好的抑制作用,从而使系统具有较好的转速跟踪性能。