计算流体动力学在液体火箭发动机中的应用

对计算流体动力学（ＣＦＤ）在液体火箭发动机中的应用情况进行了全面的回顾与分析,提出了今后的发展趋势与方向。     

非均一系动态过滤问题电路模拟解

本文根据从管道流体系统中导出的电路模拟元件,分析了层流状态下过滤单元的造型,指出了动态固、液分离的可行性,给出了网络模型,讨论了有关设计中的问题。     

滑移边界条件的收敛性分析及应用

用速度滑移与温度跳跃边界条件代替通常假定的无滑移边界条件,可有效地提高计算流体力学模型对高空滑移流区域流动的预测精度。应用Maxwell滑移边界条件时,通过直接计算速度梯度及温度梯度而得到速度滑移和温度跳跃量的处理方法在网格较密的时候会出现迭代计算发散的问题。理论分析表明,直接计算梯度的方法使边界条件的时间推进过程等价于雅克比迭代过程,因此必须满足相应的收敛性条件。为了消除收敛性条件的限制,给出了一种在任意网格密度下均收敛的边界条件处理方法并通过数值算例验证了该方法的正确性。针对高空高超声速流动,以空天飞机为例,对比了滑移/无滑移边界条件所得结果的差异,分析了滑移效应对飞行器气动特性及热环境的影响。     

无限质量降落伞充气动力学数值模拟

为分析降落伞火星再入环境下的超声速开伞性能,基于任意欧拉-拉格朗日罚函数法和多介质任意拉格朗日欧拉算法,求解可压缩流场与降落伞结构的耦合动力学模型。数值模拟盘缝带伞超声速开伞过程外形变化,预测气动力作用下的伞衣织物三维结构动力学行为。结合风洞试验数据,对比分析降落伞开伞性能和前置体对伞衣充气外形的影响。最终给出超声速伞周围非稳态流场的尾流和激波分布。仿真结果表明:盘缝带伞在超声速开伞过程中被完全充满且充气效果良好,未出现塌陷情况;随着来流马赫数的增加,降落伞阻力系数逐渐减小,充气时间缩短。仿真结果与试验结果保持一致,验证了所提方法的有效性。     

平流层飞艇强迫对流特性数值仿真分析

强迫对流换热特性对平流层飞艇热状态有重要影响。以平流层飞艇流线型封闭囊体为研究对象,基于囊体内部纯导热传热的假设,采用计算流体力学方法建立平流层飞艇外部流场三维数值模型,对飞艇外部强迫对流换热特性进行仿真分析,得到了不同太阳照射角度、风速和攻角条件下的飞艇表面温度分布和内部平均温度变化规律,为平流层飞艇热状态预测和热控设计提供参考依据。     

An approximate dynamic programing approach to the development of heuristics for the scheduling of impatient jobs in a clearing system

A single server is faced with a collection of jobs of varying duration and urgency. Each job has a random lifetime during which it is available for nonpreemptive service. Should a job's lifetime expire before its service begins then it is lost from the system unserved. The goal is to schedule the jobs for service to maximize the expected number served to completion. Two heuristics have been proposed in the literature. One (labeled π^S) operates a static priority among the job classes and works well in a “no premature job loss” limit, whereas the second (π^M) is a myopic heuristic which works well when lifetimes are short. Both can exhibit poor performance for problems at some distance from the regimes for which they were designed. We develop a robustly good heuristic by an approximative approach to the application of a policy improvement step to the asymptotically optimal heuristic π^S, in which we use a fluid model to obtain an approximation for the value function of π^S. The performance of the proposed heuristic is investigated in an extensive numerical study. © 2010 Wiley Periodicals, Inc. Naval Research Logistics 2010     

Design and analysis of a scheme for the naval gun test shell entering the bore

The test shell without projectile belt is widely used in the teaching, inspection and maintenance of modern automatic naval guns. In order to ensure the normal work of each mechanism, it is very important to design the buffer and limit of the test shell during the process of entering the bore. Taking a certain type of medium caliber naval gun as the research object, the design of colloidal fluid damper and cartridge lock was proposed to ensure the reliability of entering the bore and closing the breechblock. By combining the simulation methods of computational fluid dynamics (CFD) and multibody system dy-namic (MBD), it was analyzed whether the structural design can meet the engineering requirements. The research results show that the colloidal fluid damper can dissipate a large amount of kinetic energy of the shell, and the cartridge lock can limit the rebound movement. The combination of the two ensures the smooth process of closing the breechblock. The research provides a design method for the process of the test shell entering the bore, and provides theoretical support for the feasibility of the method.     

平板翼流体动力边界积分多重网格计算

讨论了平板翼流体动力边界积分法多重网格计算模型,给出了残差计算格式和函数修正值计算公式,推导出与步长无关的环量多重网格计算公式.计算结果表明,利用多重网格方法加快了收敛速度,其数值计算的流体动力与试验值吻合.     

电流变液的光学特性及其应用研究

电流变液是一种极具发展前景的新型智能材料．文中介绍了目前国内外电流变液的光学特性研究动态,分析了其机理,并展望了应用前景．力求能准确反映电流变液光学特性研究的发展现状,旨在促进电流变液在光学领域的研究．