圆筒形地下立体停车库火灾火源位置与火势蔓延规律研究

选取一个典型的圆筒形地下立体停车库作为研究对象,运用star-ccm+软件,采用数值模拟的方法对车库内自然通风条件下的火灾场景进行模拟计算。分别选择负一层、负六层以及负十层作为起火点,计算得出:火源位置越深入地下,着火车位顶棚中心温度越高,最高可达942℃,与起火点同层的车位顶棚中心温度均高于200℃。当某车辆发生火灾后,其相邻车辆、上方车辆、相对车辆将分别在起火后的240、312、322 s左右被引燃;火源位置越往下,引燃附近车辆的时间越短。同时,通过计算值与理论值的对比,讨论了计算火源附近车辆被引燃时间理论公式的适用性。     

火灾烟气扩散数值模拟与控制研究

描述了高层建筑火灾危险性的特点和现实情况,分别介绍了目前国内外在建筑火灾烟气扩散领域的研究和成果,指出了需进一步改进的问题,并提出了采用分区模拟的手段来实现高层建筑火灾烟气扩散的计算机模拟。     

基于格子Boltzmann方法的地下矿巷道系统突水与蔓延数字模拟

采用格子Boltzmann方法建立了巷道突水蔓延二维仿真模型.将物理巷道划分为网格模型,确定每个网格节点的基本物理量,对水粒子在网格模型内碰撞和迁移过程做了定义,巷道边界使用修正反弹格式,针对复杂巷道,使用分块耦合算法,将巷道分块处理,各块只在边界处进行数据交换,实现了不同块之间流场的耦合,简化计算,提高了程序效率.仿...     

Dispersion and slip effects in hydraulic hoisting of solids

Concentration changes which occur in cyclical hydraulic hoisting operations can be modelled with a form of the convection-diffusion equation. In order to solve this equation it is necessary to specify the axial dispersion coefficient and the effective slip of the particles relative to the mean velocity. The effective slip depends upon drag and particle migration effects. Experimental observations of these concentration changes are interpreted with numerical solutions of the appropriate equation. Fine particles develop a near-Gaussian concentration distribution while coarse particles produce a saw-tooth pulse. Axial dispersion coefficients are similar to those observed with solutes in turbulent slurry flows and slip velocities are shown to be concentration dependent.     

在役涡轮搅拌桨混合过程流热耦合有限元分析

化工搅拌装置内的流体流动伴随着显著的传热过程,由于搅拌流动的复杂性以及温度的分布难以测量,采用试验法具有一定的局限性。利用计算流体力学(CFD)软件,采用标准k-ξ紊流模型,分析了非稳态非等温情况下,涡轮搅拌桨混合过程中搅拌槽中流体的三维紊流流场和温度场的分布。结果表明,大型搅拌反应装置采用搅拌桨通蒸汽加热方式,能够使搅拌槽温度分布更加均匀,热量扩散更加迅速。     

轴流桨搅拌槽三维流场数值模拟

利用k -ε湍流模型预测了搅拌槽在不同操作条件下宏观速度场 ,模型成功预测了搅拌槽内速度分布 ,计算结果与实验结果吻合较好 .模型预测结果表明 ,搅拌槽内宏观流动场受搅拌桨槽径比影响较大 .对单层搅拌桨 -槽体系 ,挡板前后宏观流动场差别很大 ,在挡板以前区域 ,轴向流动较强 ,在整个r -z断面上形成一个整体循环 ;而在挡板后面区域 ,流体在桨叶安装位置高度附近转向轴心流动 ,槽体上半部区域形成二次循环区域 ,且二次循环区域内流体以向下流动为主 .     

气固多相双通道同轴射流湍流场的数值模拟(1)

以气体湍流运动方程组、ｋε双方程湍流模型及颗粒群运动的轨道模型为基础,气体湍流场的计算采用ＳＩＭＰＬＥ数值计算方法,颗粒群的运动方程采用ＲｕｎｇｅＫｕｔａ方法求解,开发研制出相应的通用计算软件,可以理论模拟预测工程气固流动中的气体湍流场的速度分布、颗粒运动速度场及颗粒的空间运动轨迹等。     

气固多相双通道同轴射流湍流场的数值模拟(2)

运用气固多相流数值模拟软件对双通道同轴气固射流湍流场进行了数值模拟研究,预测结果与ＬＤＶ激光测速仪测得的固体颗粒速度分布值进行了比较,结果表明,吻合较好,该软件为气固多相流工程设备的快速、经济的开发研究提供了相应的辅助工具,同时,也是理论研究气固多相化学反应流的基础。     

射流泵湍流场的数值模拟与实验研究

采用k-ε湍流模型和非等间距加密网格,对射流泵流场进行了数值模拟和分析,并对相应的流场进行了实验研究.结果表明,流场轴向速度剖面在扩散管段具有较好的自相似性,而在喉管段则不然;这种速度剖面变化的转折点与喉管的长度有关;流场的湍动能分别在喷嘴出口与扩散管入口处产生峰值,并且前者远大于后者,可见射流泵流场中,湍流主要发生在喉管入口处,湍动能的不平衡将导致额外的能量损失.本研究结果对工程应用有指导意义.     

Turbulent Diffusion Combustion under Conditions of Limited Ventilation: Flame Projection Through an Opening

Development of turbulent diffuse flame in a compartment with a vertical opening is studied experimentally and numerically. Flame projection through the opening observed under conditions of limited naturalconvective ventilation is considered. The measurements are performed in a laboratory box designed for compartmentfire simulation. The critical (minimum) flow rate of the fuel sufficient for flame projection is determined, as well as the delay between fuel ignition and flame projection with subsequent establishment of external combustion. Dimensionless variables for processing experimental data are proposed. A generic empirical dependence of the dimensionless time of flame projection on the dimensionless flow rate of the fuel is obtained for various opening sizes, burner positions, and box sizes. The dimensionless critical flow rate of the fuel obtained is in agreement with the previously published measurements performed for gaseous and condensed fuels. Unsteady stages of flame evolution before the projection and scenarios of flame projection through the opening are identified and analyzed. A threedimensional numerical model is developed for calculating turbulent diffusion combustion in a compartment with an opening. The model takes into account the conjugate radiativeconvective heat transfer on solid surfaces and the thermal conductivity of the wall and floor materials. The experimentally observed stages of flame development, flame projection through the opening, and stabilization of external combustion are reproduced in numerical calculations. The numerical values of flameprojection time are in good agreement with the measurement results and proposed empirical relation.     

用扩散流动模型分析悬浮床内的气固两相向上流动

A mathematical model of two-dimensional turbulent gas-particle two-phase flow based on the modified diffusion flux model (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux model, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by κ-ε-κp two-fluid model, which shows a reasonable agreement. It is confirmed that the modified diffusion flux model is suitable for simulating the multi-dimensional gas-particle two-phase flow.     

A Numerical Sirnulation of Gas-Particle Two-Phase Flow in a Suspension Bed Using DifFusion Flux Model

A mathematical modei of two-dimensional turbulent gas-particle twophase flow based on the modified diffusion flux modei (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux modei, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by k-ε-kp two-fluid modei, which shows a reasonable agreement. It is confirmed that the modified diffusion flux modei is suitable for simulating the multi-dimensional gas-particle two-phase flow.