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详细介绍了当前国外在离子推力器放电室理论分析模型和数值计算模型方面的研究进展。并就每种模型的特点、应用范围、前景及所采用的模拟方法进行了叙述。 相似文献
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岩爆的力学模型及物理数值模拟述评 总被引:3,自引:0,他引:3
结合现有的岩爆研究情况,对岩爆发生机制的力学模型以及在室内实验和数值模拟方面所做的工作进行总结,介绍可资岩爆借鉴的研究领域,提出岩爆的研究方向。 相似文献
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基于甲烷-空气火焰法合成纳米颗粒的实验,建立了二维轴对称湍流火焰模型,在标准壁面函数和非平衡壁面函数的近壁面处理条件下采用RSM、Standard k-ε和RNG k-ε湍流模型对实验中的火焰进行数值模拟,给出了火焰温度场和火焰长度的数值计算结果。通过与实验结果对比,确定了用非平衡壁面函数下的RNG k-ε湍流模型进行火焰数值计算的合理性。用此模型对不同甲烷、空气流速下的火焰进行模拟,分析了影响温度场分布的主要因素,并与实验结果进行比较,两者相符,从而证明了该模型的有效性。 相似文献
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脉动热管(PHP/OHP)是一种新型的高效传热元件,在航天领域、电子器件冷却以及节能技术方面极具应用潜力。这里首先介绍了脉动热管的特点和工作原理,然后分别从实验研究、理论研究和实际应用等方面介绍了目前该领域的研究现状。实验研究方面着重介绍了流动可视化应用以及纳米流体和功能流体通过强化换热提高脉动热管性能等相关研究热点。同时指出,目前脉动热管的理论分析受限于两相流理论的发展,主要研究重点在于非线性分析;数值模拟方面,特别是同纳米流体以及功能流体应用相结合将会成为下一个研究热点。 相似文献
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《低温学》2016
This paper presents a numerical model of a system-level test bed—the multipurpose hydrogen test bed (MHTB) using the Generalized Fluid System Simulation Program (GFSSP). MHTB is representative in size and shape of a space transportation vehicle liquid hydrogen propellant tank, and ground-based testing was performed at NASA Marshall Space Flight Center (MSFC) to generate data for cryogenic storage. GFSSP is a finite volume-based network flow analysis software developed at MSFC and used for thermofluid analysis of propulsion systems. GFSSP has been used to model the self-pressurization and ullage pressure control by the Thermodynamic Vent System (TVS). A TVS typically includes a Joule–Thompson (J–T) expansion device, a two-phase heat exchanger (HEX), and a mixing pump and liquid injector to extract thermal energy from the tank without significant loss of liquid propellant. For the MHTB tank, the HEX and liquid injector are combined into a vertical spray bar assembly. Two GFSSP models (Self-Pressurization and TVS) were separately developed and tested and then integrated to simulate the entire system. The Self-Pressurization model consists of multiple ullage nodes, a propellant node, and solid nodes; it computes the heat transfer through multilayer insulation blankets and calculates heat and mass transfer between the ullage and liquid propellant and the ullage and tank wall. A TVS model calculates the flow through a J–T valve, HEX, and spray and vent systems. Two models are integrated by exchanging data through User Subroutines of both models. Results of the integrated models have been compared with MHTB test data at a 50% fill level. Satisfactory comparison was observed between tests and numerical predictions. 相似文献
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排队网络可以用来模拟诸如通信网络这样的复杂系统。对排队网络的研究中的一个主要议题是建立其在某些特殊的规则下稳定的充要条件。本文的研究对象是一类具有两类顾客输入的Kelly-型排队网络。利用流体模型以及Lyapunov函数等工具,建立了该排队网络在所有非闲置的规则下稳定的充分条件。最后,对条件的充分性作了说明。 相似文献
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研究了磁流体的阻尼力特性,提出了基于粘性阻尼和回滞阻尼组成的迟滞阻尼力模型,进行了磁流变阻尼器阻尼力的响应谱分析,并用Newmark数值积分方法分析了带有磁流变流体阻尼器梁结构的多自由度振动系统在不同磁场强度和激励频率作用下的位移响应.结果表明:迟滞阻尼力模型能够很好地描述磁流体阻尼器的力学性能,而且形式简单,概念明确,适合实际应用. 相似文献
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Analysis of self-pressurization phenomenon of cryogenic fluid storage tank with thermal diffusion model 总被引:1,自引:0,他引:1
Self-pressurization phenomenon is one of the most important problems in the storage of cryogenic liquid. Until now, it has been difficult to predict exact pressurization process due to its complex non-equilibrium thermal behavior. This paper analyzes the self-pressurization with the trend of pressurization curves from experiment using liquid nitrogen with various heat leaks and liquid fractions. The trend of pressurization curves are classified on the basis of shape of pressurization curve. The qualitative relation between transient period, heat leak and liquid fractions is suggested. Thermal diffusion model (TDM) considering thermal stratification and thermal equilibrium model (TEM) can properly predict the respective pressurization curves with suitable condition for each model. 相似文献
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基于双粘本构模型的汽车磁流变液减振器阻尼特性分析 总被引:2,自引:0,他引:2
将磁流变液在环形阻尼通道的流动简化为无限宽平板间的准稳态流动,建立了磁流变液平板准静态流动方程,利用磁流变液的双粘本构模型、边界条件和相容条件,得出了磁流变液速度分布,并分析了不同粘度比对磁流变液的流动速度分布的影响,在给定活塞速度和环形通道的几何尺寸条件下,对汽车磁流变减振器的阻尼特性进行理论预测,并研究了磁流变液减振器的双粘阻尼特性.按照长安之星微型汽车前悬架的技术要求,设计和制作了微型汽车磁流变减振器,在山川减振器公司对此进行了台架试验研究,试验结果表明应用所提出的理论分析模型和设计原理是可行的. 相似文献
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从物理机理出发,用双线性滞后模型描述了隔振器中密封件与活塞缸壁之间的干摩擦作用,利用谐波平衡法对系统频域特性进行了分析,解释了实验中隔振性能受激励幅值影响的现象。同时还对影响隔振平台性能的参数进行了分析,为流体作动器隔振平台设计和使用提供参考依据。 相似文献
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一种新的汽车液力减振器阻力特性模拟模型 总被引:2,自引:0,他引:2
减振器是汽车悬架系统最为关键的零部件之一。用计算机精确地模拟减振器的阻力持性不仅可有效地预测汽车行使平顺性和操作稳定性,同时可大大缩短汽车设计调试周期与费用。本文利用粘性流体力学知识对汽车双简液力减振器内部流体特性进行离散分析和数值计算,并揉合润滑理论的粘—压—温特性概念,建立了一种全新的汽车双简液力减振器阻力特性计算模型,全面考虑了减振器各种参数对减振器阻力特性的影响,为实现汽车悬架系统的主动控制及开发新品种减振器提供理论依据。 相似文献
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《低温学》2018
Thermodynamic effects on cryogenic cavitating flow is important to the accuracy of numerical simulations mainly because cryogenic fluids are thermo-sensitive, and the vapour saturation pressure is strongly dependent on the local temperature. The present study analyses the thermal cavitating flows in liquid nitrogen around a 2D hydrofoil. Thermal effects were considered using the RNG k-ε turbulence model with a modified turbulent eddy viscosity and the mass transfer homogenous cavitation model coupled with energy equation. In the cavitation model process, the saturated vapour pressure is modified based on the Clausius-Clapron equation. The convection heat transfer approach is also considered to extend the Zwart-Gerber-Belamri model. The predicted pressure and temperature inside the cavity under cryogenic conditions show that the modified Zwart-Gerber-Belamri model is in agreement with the experimental data of Hord et al. in NASA, especially in the thermal field. The thermal effect significantly affects the cavitation dynamics during phase-change process, which could delay or suppress the occurrence and development of cavitation behaviour. Based on the modified Zwart-Gerber-Belamri model proposed in this paper, better prediction of the cryogenic cavitation is attainable. 相似文献
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磁场作用下磁流变液剪切性能的实验分析 总被引:1,自引:0,他引:1
本文研究了磁流变液的力学性能,制备了羰基铁粉体积分数为20%的硅油基磁流变液,观察了磁流变液在磁场作用下的微观变化,测试了磁流变液的剪切性能。实验表明,无磁场作用下,磁流变液为牛顿流体;在磁场作用下,随着剪切速率的增加,剪切应力趋于稳定,表观粘度呈现指数式下降,磁流变液具有剪切稀化效应,符合广义Bingham模型。磁流变液剪切应力和外加电流的依赖关系为:在电流较小时,剪切应力表现为指数增长,指数值约为1.5;随着外加电流的增大,剪切应力表现为线性增长,最终达到稳定值。 相似文献