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针对气液两相非等温渗流模型高度非线性的特点,发展了适宜的数值离散方法。根据相态转换准则和控制方程的性质,采用最低饱和度法简化算法。空间离散方面,使用有限体积法;时间离散方面,设计了一套包含合理求解顺序的Picard迭代法,解决了方程组强耦合的问题。利用上述数值方法对高温高压气体的迁移行为进行数值模拟,证明了气体在低含水率介质和等效孔隙度的干燥介质内的运动基本一致,并分析了空腔内的气液相态转变过程。在此基础上,研究了多孔介质孔隙度和渗透率对气体压强演化和示踪气体迁移的影响。研究表明,孔隙度越小(相同渗透率)、渗透率越高(相同孔隙度),示踪气体的迁移距离越远,并给出了估算不同孔隙度和渗透率下迁移距离的半经验公式。 相似文献
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针对气液两相非等温渗流模型高度非线性的特点,发展了适宜的数值离散方法。根据相态转换准则和控制方程的性质,采用最低饱和度法简化算法。空间离散方面,使用有限体积法;时间离散方面,设计了一套包含合理求解顺序的Picard迭代法,解决了方程组强耦合的问题。利用上述数值方法对高温高压气体的迁移行为进行数值模拟,证明了气体在低含水率介质和等效孔隙度的干燥介质内的运动基本一致,并分析了空腔内的气液相态转变过程。在此基础上,研究了多孔介质孔隙度和渗透率对气体压强演化和示踪气体迁移的影响。研究表明,孔隙度越小(相同渗透率)、渗透率越高(相同孔隙度),示踪气体的迁移距离越远,并给出了估算不同孔隙度和渗透率下迁移距离的半经验公式。 相似文献
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储罐会因腐蚀或人为误操作等原因引发泄漏,造成泄漏气体扩散或气云爆炸事故。为了揭示此种事故的发展过程及影响规律,应用计算流体力学软件FLACS,研究了泄漏和环境风两个主要影响因素对乙烯气体扩散及爆炸的影响。结果表明:气云扩散距离和体积随泄漏速率增加而增大;当泄漏速率低于6 kg/s时,不同泄漏方向上的气云扩散距离及体积相近;当泄漏速率高于6 kg/s时,气体泄漏扩散和气云形成过程因受到障碍物影响,随阻塞率增大,气云扩散距离减小,气云体积增加。当泄漏方向垂直于储罐组中轴线,泄漏速率为18 kg/s时,气云扩散距离最大为81.5 m;当泄漏方向平行于储罐组中轴线,泄漏速率为24 kg/s时,气云体积最大达到9 604 m3。爆炸波的冲击压力随泄漏速率升高而升高;环境风会加快可燃气体稀释,有效降低气云爆炸发生的概率,降低爆炸强度,达到爆炸压力峰值的时间更早,可使高温在更短的时间内下降。泄漏速率为24 kg/s时,与泄漏储罐紧邻的储罐表面上被冲击到的爆炸超压仅为6.88 kPa,但温度高达2 384 K,因此,为避免事故发生时的二次灾害,救援中对储罐组的冷却降温尤为重要。 相似文献
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为探究含油轴承基体渗流及压力扩散对接触面间油膜润滑性能的影响,建立双级孔含油轴承系统的渗流润滑模型,研究轴承摩擦面上油膜分布规律与双级孔隙中压力扩散行为,分析摩擦副倾角与轴承表层渗透率变化对油膜润滑性能的影响.结果表明,流体动压力产生于摩擦界面的收敛区,并逐渐由摩擦界面向轴承基体扩散,在油压扩散过程中流体压力的作用面积增大,压力数值降低.油膜的润滑性能随倾角增大或表层渗透率减小而得到改善,相比单层含油轴承,具有致密表层的双级孔含油轴承具有较好的润滑性能.不同表层渗透率下,倾角对油膜摩擦系数的影响差异显著:在本文中计算参数下,当表层渗透率小于7×10-15 m2时,油膜的摩擦系数随倾角增大而减小;当表层渗透率高于7×10-15 m2时,油膜的摩擦系数随倾角增大而增大.倾角和表层渗透率影响含油轴承基体中的油液渗流和压力扩散行为,最终使油膜的润滑性能发生改变.研究工作为明晰含油轴承润滑机理提供一定理论依据. 相似文献
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近年来氢的使用范围逐渐发展到各个领域, 含氢多元混合物气体在工业生产及生活燃料中被普遍使用. 为了保障含氢气体在生产、运输、使用等各个环节的安全性, 构建了开放空间混合气体爆炸测试实验系统, 研究了H2/CH4/空气混合气体爆炸压力及火焰传播特性, 给出了不同氢摩尔分数(100%, 75%, 66.67%, 50%, 33.33%)、混合气体当量比(0.8, 1.0, 1.1, 1.2, 1.4)、可燃云团尺寸(1 m3, 4 m3, 8 m3)及障碍物约束等因素对混合气体爆炸压力及火焰的影响规律. 基于经典TNT当量法, 建立了考虑混合气体组分比及可燃云团尺寸的最大爆炸超压预测模型, 修正了爆炸火焰传播半径理论模型. 结合高精度数值模拟技术揭示了加气站内建筑结构对混合气体爆炸的影响. 研究表明, 氢气的加入能够明显增强气体爆炸强度, 最大爆炸超压、火焰传播速度均随氢摩尔分数的增加而增大, 随当量比的增大先增大后减小, 当量比为1.1~1.2时最大; 通过对大尺度混合气体爆炸数值仿真与分析发现, 加气站内不同建构筑物条件下爆炸火焰传播距离、传播速度、最大爆炸超压等关键参数明显不同, 顶部和背部同时约束时, 爆炸伤害范围及事故后果最严重, 因此在划定加气站安全距离时, 应充分考虑不同建筑结构的影响. 相似文献
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低温可导致人员冻伤及物品脆裂,气体爆炸传播规律是爆炸演化过程和事故分析的基础。采用数值模拟方法,研究液化天然气大面积泄漏汽化过程、甲烷与空气混合过程及爆炸传播过程。结果表明:随着扩散距离的增大,低温区域的温度谷值升高,且升高趋势变缓;在距泄漏源中心110 m范围内,温度低于273 K;随着风速的增加,温度谷值呈线性下降;随着泄漏时间的延长,温度谷值降低,且下降趋势变缓;随着距泄漏中心距离的增加,爆炸后超压峰值先升高后降低;在距泄漏源中心200 m范围内,爆炸产生的高温会对人员造成伤害。 相似文献
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考虑颗粒间碰撞的气固两相流拉格朗日模拟 总被引:3,自引:3,他引:0
在均匀,稳定的各向同性气固两相紊流场颗粒弥散的拉格朗日模拟计算方法基础上,进一步考虑了流场中颗粒之间的碰撞对于模拟计算结果的影响。与Lavieville用大涡模拟所做的计算结果进行了对比,以对本方法进行验证,并考察了颗粒间的碰撞分别对流体相和颗粒相的影响。 相似文献
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以全隐式气藏数值模拟的核心——线性方程组的解法为突破口 ,研究了裂缝性边水气藏全隐式数值模拟方法 ,并研制了模拟软件。对双重介质全隐式模型形成的线性代数方程组采用块系数强隐式预处理正交极小化算法 ,与其它算法相比 ,显示出其快速、稳定的优越性。研制的模拟软件经过理论气藏及川东新市气藏实例计算 ,表明解法的优越性及软件的有效性 ,应用此算法及软件可对同类气藏进行多方位的系统研究 ,指导气藏科研及生产。 相似文献
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根据有效应力原理,建立瓦斯压力和煤体变形之间的耦合关系. 在地应力和瓦斯压力的共同作用下,煤体发生弹脆性破坏,之后发展为层裂-粉化破坏,据此判断发生煤与瓦斯突出的危险性. 根据一维煤激波管瓦斯突出实验,结合一维混相流动模型,进行了数值验证,证实了模型的可靠性. 相似文献
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The present paper investigates the impact of the velocity and density ratio on the turbulent mixing process in gas turbine
blade film cooling. A cooling fluid is injected from an inclined pipe at α=30° into a turbulent boundary layer profile at a freestream Reynolds number of Re ∞ = 400,000. This jet-in-a-crossflow (JICF) problem is investigated using large-eddy simulations (LES). The governing equations
comprise the Navier–Stokes equations plus additional transport equations for several species to simulate a non-reacting gas
mixture. A variation of the density ratio is simulated by the heat-mass transfer analogy, i.e., gases of different density
are effused into an air crossflow at a constant temperature. An efficient large-eddy simulation method for low subsonic flows
based on an implicit dual time-stepping scheme combined with low Mach number preconditioning is applied. The numerical results
and experimental velocity data measured using two-component particle-image velocimetry (PIV) are in excellent agreement. The
results show the dynamics of the flow field in the vicinity of the jet hole, i.e., the recirculation region and the inclination
of the shear layers, to be mainly determined by the velocity ratio. However, evaluating the cooling efficiency downstream
of the jet hole the mass flux ratio proves to be the dominant similarity parameter, i.e., the density ratio between the fluids
and the velocity ratio have to be considered. 相似文献
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A new method is proposed to produce gas from oceanic gas hydrate reservoir by combining the ocean surface warm water flooding with depressurization which can efficiently utilize the synthetic effects of thermal, salt and depressurization on gas hydrate dissociation. The method has the advantage of high efficiency, low cost and enhanced safety. Based on the proposed conceptual method, the physical and mathematical models are established, in which the effects of the flow of multiphase fluid, the kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, salt inhibition, dispersion, convection and conduction on the hydrate dissociation and gas and water production are considered. The gas and water rates, formation pressure for the combination method are compared with that of the single depressurization, which is referred to the method in which only depressurization is used. The results show that the combination method can remedy the deficiency of individual producing methods. It has the advantage of longer stable period of high gas rate than the single depressurization. It can also reduce the geologic hazard caused by the formation deformation due to the maintaining of the formation pressure by injected ocean warm water. 相似文献
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A parallel DSMC method based on a cell‐based data structure is developed for the efficient simulation of rarefied gas flows on PC‐clusters. Parallel computation is made by decomposing the computational domain into several subdomains. Dynamic load balancing between processors is achieved based on the number of simulation particles and the number of cells allocated in each subdomain. Adjustment of cell size is also made through mesh adaptation for the improvement of solution accuracy and the efficient usage of meshes. Applications were made for a two‐dimensional supersonic leading‐edge flow, the axi‐symmetric Rothe's nozzle, and the open hollow cylinder flare flow for validation. It was found that the present method is an efficient tool for the simulation of rarefied gas flows on PC‐based parallel machines. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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A theoretical analysis has been developed to predict the critical height of the onset of gas entrainment (OGE) during dual and triple discharge from a stratified two-phase region. The two and three discharge branches are mounted on a circular wall, resembling a circular reservoir of a CANDU header–feeder configuration. A point sink model has been developed to predict the critical height and to map the velocities and acceleration flow fields during OGE. The model was verified by comparing the theoretically predicted critical height with the available experimental results. The theoretically predicted critical height is found to be a function of the branch Froude number, the location of the secondary branch with respect to the primary branch, and the angle between the branches. The effect of these variables on the predicted OGE height was investigated and is presented in this paper. Predictions of the critical height were shown to be within 25% of experimental values in both dual and triple discharge. 相似文献
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Fluid Dynamics - A theoretical analysis of laminar-turbulent transition in supersonic gas flow is performed basing on the results of direct numerical simulation of flow around a flat plate within... 相似文献
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A numerical strategy, based on an adaptive finite element method, is proposed for the direct two‐dimensional simulation of the expansion of small clusters of gas bubbles within a Newtonian liquid matrix. The velocity and pressure fields in the liquid are first defined through the Stokes equations and are subsequently extended to the gas bubbles. The liquid–gas coupling is imposed through the stress exerted on the liquid by gas pressure (ruled by an ideal gas law) and by surface tension. A level set method, combined with a mesh adaptation technique, is used to track liquid–gas interfaces. Many numerical simulations are presented. The single bubble case allows to compare the simulations to an analytical model. Simulations of the expansion of small clusters are then presented showing the interaction and evolution of the gas bubbles to an equilibrium state, involving topological rearrangements induced by Plateau's rule. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献