Control of rainfall-runoff particulate matter （PM） and PM-bound chemical loads is challenging; in part due to the wide gradation of PM complex geometries of many unit operations and variable flow rates. Such challen...Control of rainfall-runoff particulate matter （PM） and PM-bound chemical loads is challenging; in part due to the wide gradation of PM complex geometries of many unit operations and variable flow rates. Such challenges and the expense associated with resolving such challenges have led to the relatively common examination of a spectrum of unit operations and processes. This study applies the principles of computa- tional fluid dynamics （CFD） to predict the particle and pollutant clarification behavior of these systems subject to dilute multiphase flows, typical of rainfall-runoff, within computationally reasonable limits, to a scientifically acceptable degree of accuracy. The Navier-Stokes （NS） system of nonlinear partial differential equations for multi- phase hydrodynamics and separation of entrained particles are solved numerically over the unit operation control volume with the boundary and initial conditions defined and then solved numerically until the desired convergence criteria are met. Flow rates examined are scaled based on sizing of common unit operations such as hydrodynamic separators （HS）, wet basins, or filters, and are examined from 1 to 100 percent of the system maximum hydraulic operating flow rate. A standard turbulence model is used to resolve flow, and a discrete phase model （DPM） is utilized to examine the particle clarification response. CFD results closely follow physical model results across the entire range of flow rates. Post-processing the CFD predictions provides an in-depth insight into the mechanistic behavior of unit operations by means of three dimensional （3-D） hydraulic profiles and particle trajectories. Results demon- strate the role of scour in the rapid degradation of unit operations that are not maintained. Comparisons are provided between measured and CFD modeled results and a mass balance error is identified. CFD is arguably the most powerful tool available for our profession since continuous simulation modeling.展开更多
【目的】研究曝气池中气泡浮力羽流的动力特性,为提高深层曝气方式的污水处理效率提供依据。【方法】分别采用欧拉双流体模型和混合模型结合标准κ-ε紊流模型,对气泡浮力羽流进行数值模拟,讨论了这2种模型计算流场的精确性和边界条件...【目的】研究曝气池中气泡浮力羽流的动力特性,为提高深层曝气方式的污水处理效率提供依据。【方法】分别采用欧拉双流体模型和混合模型结合标准κ-ε紊流模型,对气泡浮力羽流进行数值模拟,讨论了这2种模型计算流场的精确性和边界条件的适应性,并使用压力隐式算子分裂PISO(Pressure-Implicit with splitting of operators)算法进行了速度与压力耦合求解。【结果】通过模拟得到了气泡羽流的瞬时性及其尾部的摆动规律等流动特性,模拟的速度矢量沿水深方向呈增加趋势,但表现并不稳定,在上部区域气泡羽流出现了摆动,而在下部区域气泡羽流的摆动不明显,但这一部分的速度相对较大。【结论】欧拉双流体模型结合标准κ-ε紊流模型模拟气泡浮力羽流动力特性优于混合模型。展开更多
防火间距是石油化工企业平面设计中的一个重要参数，开放环境下的火灾热辐射受大气稳定程度的影响。本文从计算流体力学角度出发，应用CFD（Computational Fluid Dynamics）软件Fluent，基于SCI爆炸火灾工程试验“Pool Fire A”的大气...防火间距是石油化工企业平面设计中的一个重要参数，开放环境下的火灾热辐射受大气稳定程度的影响。本文从计算流体力学角度出发，应用CFD（Computational Fluid Dynamics）软件Fluent，基于SCI爆炸火灾工程试验“Pool Fire A”的大气条件，对“有风情况下，直径为10m的苯液池火灾”进行数值模拟，得出非绝热条件下．苯燃烧的峰温以及产物组分、池火灾对周围环境热辐射的空间分布。温度最高点在对称面y=0上，最高温度为1478K、火焰倾斜角度为32。（与竖直方向的夹角）、火焰高10．2m。对于锰钢材料、内径为10m苯储罐，2～3级风力情况下，相邻两储罐间最小安全距离在上风向为20m，下风向为27m。最后对模拟结果进行了分析。展开更多
文摘Control of rainfall-runoff particulate matter （PM） and PM-bound chemical loads is challenging; in part due to the wide gradation of PM complex geometries of many unit operations and variable flow rates. Such challenges and the expense associated with resolving such challenges have led to the relatively common examination of a spectrum of unit operations and processes. This study applies the principles of computa- tional fluid dynamics （CFD） to predict the particle and pollutant clarification behavior of these systems subject to dilute multiphase flows, typical of rainfall-runoff, within computationally reasonable limits, to a scientifically acceptable degree of accuracy. The Navier-Stokes （NS） system of nonlinear partial differential equations for multi- phase hydrodynamics and separation of entrained particles are solved numerically over the unit operation control volume with the boundary and initial conditions defined and then solved numerically until the desired convergence criteria are met. Flow rates examined are scaled based on sizing of common unit operations such as hydrodynamic separators （HS）, wet basins, or filters, and are examined from 1 to 100 percent of the system maximum hydraulic operating flow rate. A standard turbulence model is used to resolve flow, and a discrete phase model （DPM） is utilized to examine the particle clarification response. CFD results closely follow physical model results across the entire range of flow rates. Post-processing the CFD predictions provides an in-depth insight into the mechanistic behavior of unit operations by means of three dimensional （3-D） hydraulic profiles and particle trajectories. Results demon- strate the role of scour in the rapid degradation of unit operations that are not maintained. Comparisons are provided between measured and CFD modeled results and a mass balance error is identified. CFD is arguably the most powerful tool available for our profession since continuous simulation modeling.
文摘【目的】研究曝气池中气泡浮力羽流的动力特性,为提高深层曝气方式的污水处理效率提供依据。【方法】分别采用欧拉双流体模型和混合模型结合标准κ-ε紊流模型,对气泡浮力羽流进行数值模拟,讨论了这2种模型计算流场的精确性和边界条件的适应性,并使用压力隐式算子分裂PISO(Pressure-Implicit with splitting of operators)算法进行了速度与压力耦合求解。【结果】通过模拟得到了气泡羽流的瞬时性及其尾部的摆动规律等流动特性,模拟的速度矢量沿水深方向呈增加趋势,但表现并不稳定,在上部区域气泡羽流出现了摆动,而在下部区域气泡羽流的摆动不明显,但这一部分的速度相对较大。【结论】欧拉双流体模型结合标准κ-ε紊流模型模拟气泡浮力羽流动力特性优于混合模型。
文摘防火间距是石油化工企业平面设计中的一个重要参数，开放环境下的火灾热辐射受大气稳定程度的影响。本文从计算流体力学角度出发，应用CFD（Computational Fluid Dynamics）软件Fluent，基于SCI爆炸火灾工程试验“Pool Fire A”的大气条件，对“有风情况下，直径为10m的苯液池火灾”进行数值模拟，得出非绝热条件下．苯燃烧的峰温以及产物组分、池火灾对周围环境热辐射的空间分布。温度最高点在对称面y=0上，最高温度为1478K、火焰倾斜角度为32。（与竖直方向的夹角）、火焰高10．2m。对于锰钢材料、内径为10m苯储罐，2～3级风力情况下，相邻两储罐间最小安全距离在上风向为20m，下风向为27m。最后对模拟结果进行了分析。
