垂直式MOCVD反应器中热泳力对浓度分布的影响分析

从分子动力学理论出发,推导出垂直式MOCVD反应器中热泳力和热泳速度与温度、温度梯度、压强、粒子直径的关系式,以及热泳速度与扩散速度、动量速度平衡时的关系式.在典型的生长条件下,计算得到在温度T=605K时,热泳速度与扩散速度、动量速度动量平衡,TMGa浓度达到最大.然后在不考虑化学反应和考虑化学反应两种情况下,针对垂直式MOCVD反应器内的热泳力对粒子浓度分布和沉积的影响进行数值模拟,模拟给出反应粒子在反应器不同进口温度、衬底温度时的温度分布、浓度分布和反应速率.并与文献中的实验值进行对比,模拟结果与实验值有很好的吻合.     

温压炸药坑道内爆炸冲击波的数值模拟研究

基于二次反应理论,采用AUTODYN程序对温压炸药(RDX/AP/AL/粘合剂=20/43/25/12,质量比)坑道内爆炸冲击波进行了数值模拟研究。将温压炸药与传统炸药TNT的计算结果进行了比较,结果表明:①在爆炸近区,温压炸药比TNT的爆炸冲击波超压峰值低。但在爆炸远区,温压炸药的爆炸冲击波超压峰值则逐渐超过了TNT,最高达到了TNT的1.48倍;温压炸药爆炸冲击波的冲量峰值始终高于TNT,约为TNT的1.33～1.43倍。②最小二乘拟合得到了温压炸药坑道内爆炸冲击波超压峰值随距离衰减的计算公式,具有一定参考价值。     

对流弥散方程的时间依赖反应系数反演及应用

探讨了一维对流弥散方程的时间依赖反应系数函数的反演问题及其在一个土柱渗流试验中的应用.借助一个积分恒等式,讨论了正问题单调解的存在条件及反问题的数据相容性.进一步考虑一个扰动土柱试验模型模拟问题,应用一种最佳摄动量正则化算法,对反应系数函数进行了数值反演模拟,并应用于实际试验数据的反分析,反演重建结果不仅与相容性分析一致,而且与实际观测数据基本吻合.     

Ⅰ型拉伸试样金属注射成形多相流动的三维数值模拟

将粉末注射成形充模过程视为粘结剂、粉末和空气的三相流动过程，基于多相流理论给出金属注射成形的多相流动控制方程。根据金属注射成形的工艺特点确定多相流动控制方程的初边界条件，用多相流数值分析软件CFX对Ⅰ型拉伸试样的铁粉注射成形充模流动过程实现了三维数值模拟，分析了模腔中不同位置处粘结剂一粉末流动的速度曲线。数值模拟结果表明在Ⅰ型拉伸试样金属注射成形充模流动过程中发生过两相分离的现象，数值模拟的瞬态信息可用于金属注射成形产品缺陷的分析与控制。     

仿长耳鸮翼型的参数化研究

以长耳鸮翼型为仿生原型,采用逆向工程方法提取鸮翼翼型下表面特征点并利用B样条曲线进行拟合建立鸮翼仿生重构模型。通过数值求解耦合Langtry-Menter SST模型的雷诺时均Navier-Stokes方程,研究了仿生翼型的前缘弧线曲率、前缘厚度、前端倾角、翼型中部下表面曲率以及尾部厚度等参数对翼型升阻比的影响,获得了一种能有效抑制大攻角下流动分离发生的仿生翼型。正交试验结果表明:翼型前缘厚度对仿生翼型的升阻比影响最大,随着翼型前缘厚度的减少,翼型升阻比增加;翼型下表面中部曲率和翼型尾部厚度均存在最优值使仿生翼型升阻比最大。     

室温磁制冷主动式磁蓄冷器数值模拟

提出了一个研究工作参数、设计参数对主动式磁蓄冷器(AMR)制冷性能影响的数值模型。三个主要参数包括:质量流量m、频率f、蓄冷器孔隙率ε,被用来表征AMR的制冷能力。数值模拟的结果表明:对一个AMR而言,存在一个最佳孔隙率;在某一确定孔隙率条件下,AMR存在最佳换热流体质量流量和最佳工作频率;与高频相比,AMR在较低频率下有更好的制冷性能,一味提高频率并不一定能提高AMR的制冷量。模拟结果对磁制冷样机的设计、工作参数的选择有很大的指导意义。     

Numerical simulation of trajectory and deformation of bubble in tip vortex

According to the behaviors of a bubble in the ship wake flow,the numerical simulation is divided into two stages,quasi-spherical motion and non-spherical motion,based on whether the bubble is captured by the vortex or not.The one-way coupled particle tracking method(PTM) and the boundary element method(BEM) are adopted to simulate these two stages,respectively.Meanwhile,the initial condition of the second stage is taken as the output of the first one,and the entire simulation is connected and completed.Based on the numerical results and the published experimental data,the cavitation inception is studied,and the wake bubble is tracked.Besides,the split of the bubble captured by the vortex and the following sub-bubbles are simulated,including motion,deformation,and collapse.The results provide some insights into the control on wake bubbles and optimization of the wake flow.     

粘弹性方程全离散化有限体积元格式及数值模拟

 本文利用有限体积元方法研究二维粘弹性方程, 给出一种时间二阶精度的全离散化有限体积元格式, 并给出这种全离散化有限体积元解的误差估计, 最后用数值例子验证数值结果与理论结果是相吻合的. 通过与有限元方法和有限差分方法相比较, 进一步说明了全离散化有限体积元格式是求解二维粘弹性方程数值解的最有效方法之一.     

High frequency forcing on nonlinear systems

High-frequency signals are pervasive in many science and engineering fields.In this work,the effect of high-frequency driving on general nonlinear systems is investigated,and an effective equation for slow motion is derived by extending the inertial approximation for the direct separation of fast and slow motions.Based on this theory,a high-frequency force can induce various phase transitions of a system by changing its amplitude and frequency.Numerical simulations on several nonlinear oscillator systems show a very good agreement with the theoretic results.These findings may shed light on our understanding of the dynamics of nonlinear systems subject to a periodic force.     

A planar chiral nanostructure with asymmetric transmission of linearly polarized wave and huge optical activity in near-infrared band

Just like an electronic diode that allows the electrical current to flow in one direction only, a kind of chiral metamaterial structure with a similar functionality for the electromagnetic wave is proposed. The designed nanostructure that consists of twisted metallic split-ring resonators on both sides of a dielectric substrate achieves asymmetric transmission for a forward and backward propagating linearly polarized wave by numerical simulation in near-infrared band. Difference in transmission efficiency of the optimized structure between the same polarized waves incident from opposite directions can reach a maximum at the communication wavelength （1.55 μm）. Moreover, the simulation results of this structure also exhibit strong optical activity and circular dichroism.