SHG-Ⅱ-Z型脱硫除尘设备内三维两相流场的数值模拟

采用RNG k-ε湍流模型,应用Fluent软件对SHG—Ⅱ—Z型脱硫除尘装置内三维两相流场进行了数值模拟,给出了压力、速度、湍流动能、湍流强度等参数的分布,并对固体颗粒的运动轨迹进行了计算。结果显示烟气在塔内旋转上升及壁面水膜有利于提高除尘效率,从人口底部进人设备的颗粒越容易被分离。计算结果对设备现场运行工艺参数优化及脱硫除尘塔的设计有一定的指导意义。     

多管束管柱式气液旋流分离器的数值仿真

研究一种多管束管柱式气液旋流分离器的设计,并对性能进行研究.根据流体力学方法,采用雷诺应力输运模型(RSM)和大涡仿真相结合的方式进行数值仿真,得到不同进口速度工况下分离效率的变化情况和湍流流动情况.结果显示:流体总流量一定时,分离效率与各个管进口的流量分配有关,处理量与竖直管的数目有关.分离效率在仿真中给定的速度工况条件下可调范围在44.93％-87.12％,证明三根管气液旋流分离器的处理能力是一根管的3倍,大大增强了分离效率.     

新型导流式旋流分离器的数学模型及仿真

新型导流式固-液旋流分离器在实际操作中存在参数无法确定的问题,设备经常跑粗.为了实际操作参数提供理论依据,并建立数学模型,运用流体力学公式结合T.D哈帝冈柱形旋流器模型建立了新型导流式固-液旋流分离器的数学模型.通过仿真,得出了旋流分离器的分流比、流量-密度-压强和分割尺寸-速度-压强等三维关系图.结果表明,实际工况中旋流分离器的分流达到近似固定值,分割尺寸范围广,适合在多种不同水域下工作.当旋流器的进料口速度在5m/s左右时,压强、离散相密度和流量呈局部线性关系且流场稳定.     

新型气液旋流分离器的模拟研究

为了分离气液喷射反应器的产物,开发了一种新型气液旋流分离器。分别采用Muschelknautz模型、改进的Muschelknautz模型和计算流体力学(CFD)离散相模型对新型气液旋流分离器进行了模拟计算,对新型气液旋流分离器的压力场、分离效率、液滴运行轨迹进行了考察。结果表明:相对于传统Muschelknautz模型,改进的Muschelknautz模型与CFD的模拟结果更为接近,能更加准确地对旋流分离器的分离性能和压降进行预测:在设计条件下,液滴直径越小,颗粒在旋流分离器中的运动轨迹就越紊乱,>3μm的液滴颗粒的分离效率超过80%:颗粒的入口位置会影响颗粒的运动轨迹。     

双层桨搅拌浸出槽固液两相流场的数值仿真

在石煤提钒搅拌浸出槽的研究中,针对双层桨搅拌浸出槽固液悬浮特性以及混合浸出效果进行了研究.由于实验成本大、操作困难,提出了数值仿真的方法.运用计算流体力学(CFD)软件FLUENT对石煤提钒搅拌浸出槽进行流场仿真,用GAMBIT建立流场实体模型,采用k-ε湍流模型以及多重参考系法(MRF)处理搅拌桨区.探讨了双层桨同向旋转和双层桨异向旋转两种情况下的搅拌效果,结果表明在相同的情况下,双层桨异向旋转时湍动能分布更为合理,并且能够缓解底部沉积,搅拌混合效果更好.仿真结果对于研究搅拌反应容器内部流场规律,进而对搅拌反应容器的结构优化和浸出率的提高具有一定参考价值.     

压气机三维流场数值仿真及湍流模型研究

本文利用商用CFD软件对压气机转子通流部分建立了一个三维的数值模拟计算平台.对NASA Rotor 37跨音速压气机转子全工况特性进行了计算,与NASA Rotor37的实验结果对比表明,本文的网格生成技术和数值模拟方法都是比较成功的,满足一定的数值求解精度,具有工程技术应用价值.在湍流模型方面引入Baldwin-Lonax(B-L)湍流模型和Spalart-All-maras(S-A)湍流模型,并对模拟结果进行了分析对比研究.对跨音速压气机转子内流场的数值模拟结果表明:S-A湍流模型对跨音速压气机转子的模拟能力优于B-L湍流模型.     

基于FLUENT的气液分离器内流场仿真研究

基于计算流体动力学(CFD)方法,应用流体仿真软件FLUENT对两种气液分离装置内部流场进行仿真研究,得到分离器内部流场速度分布规律和相分布规律,发现合理改变排气通道的直径,可以提高分离效率。同时分析比较了流场模拟结果,发现排气通道直径改变处存在涡流。     

二相湍流爆轰流场的数值仿真

研究脉冲轰发动机效率优化设计问题,由于湍流对两相爆轰流场有较大影响,要求明确两相爆轰流场的特点.为了进一步明确上述问题,提出建立轴对称两相爆轰低雷诺数湍流模型,应用求解元与守恒元方法(简称CE/SE方法)进行数值仿真.仿真结果表明,湍动能随着爆轰波的传播而前进,且湍动能值在管子的中心部位较大.明确气相轴向速度在爆轰波阵面上比径向速度大的特点.仿真也为爆轰湍流流场效能的认识和提高脉冲发动机效能的设计提供了理论指导.     

小型轴流压气机清洗两相流场的数值模拟

针对某小型航空发动机单级轴流压气机的清洗需求,以数值模拟结合实验的方法对压气机清洗流场的各种参数进行了分析研究.在初步确定清洗方案的基础上,建立了基于S-A湍流模型的离散相数值模拟理论模型,以经验公式估算喷嘴形成的初始液滴分布,并对喷嘴的实验参数进行了校准,最后以CFD软件进行了流场的数值模拟,计算结果表明：清洗液滴不会对压气机的流场产生明显影响,平面扇形喷嘴在该小型压气机上能获得较好的清洗效果.     

烧结烟气氨法脱硫塔气液两相流数值模拟

为研究脱硫塔内的气液分布情况对脱硫效率的影响,选用FLUENT作为计算工具,以烧结烟气氨法脱硫塔作为研究对象,对塔内气相湍流采用Euler方法描述,对喷淋液滴采用Lagrange颗粒轨道模型描述,研究烟气入口倾角和入口距离浆液池液面高度对脱硫塔内气液两相流场分布的影响,并对脱硫塔的关键参数取值给出建议.     

Numerical simulation of three-dimensional flow past bluff bodies

An improved understanding of the aerodynamics of bluff bodies, such as buildings and road vehicles, can lead to significant reductions in wind damage and gasoline consumption and to the increased safety and comfort of human occupants. To achieve this goal, improved theoretical and experimental techniques are urgently needed. This paper explores in a general way the potential of using numerical simulation methods for predicting and interpreting aerodynamic phenomena affecting bluff bodies. As a basis for discussion a prototype finite difference method is described and illustrated with sample calculations of air flow about simple bluff bodies. The limitations of this scheme are then discussed in detail, together with some suggestions for extensions that could be realized in the immediate future. The paper concludes with speculations on what could be achieved in the next five to ten years to produce a generally useful research tool for bluff body aerodynamics.     

液-液旋流器内近壁湍流处理方法及数值模拟

无论k-ε模型及其修正模型,还是广泛应用于水力旋流器数值模拟的雷诺应力模型(RSM),都只是针对湍流核心区,对近壁区无效,如何确定液.液水力旋流器湍流场模拟的近壁处理方法亟待深入研究.在介绍湍流近壁区流动特点和处理方法的基础上,引入了2种湍流近肇处理函数--标准的和非平衡的壁面函数,在相同的网格系统和计算条件下计算了双锥双柱型水力旋流器内湍流场,结果与激光多普勒测速仪(LDV)测试结果基本吻合,但采用非平衡的壁面函数预报结果更为可信,为进一步精确研究旋流器内的流动过程打下良好的基础.     

Numerical modeling of two-phase transonic flow

Our work is aimed at the development of numerical method for the modeling of transonic flow of wet steam including condensation/evaporation phase change. We solve a system of PDE’s consisting of Euler or Navier-Stokes equations for the mixture of vapor and liquid droplets and transport equations for the integral parameters describing the droplet size spectra. Numerical method is based on a fractional step technique due to the stiff character of source terms, i.e. we solve separately the set of homogenous PDE’s by the finite volume method and the remaining set of ODE’s either by explicit Runge-Kutta or implicit Euler method. The finite volume method is based on the Lax-Wendroff scheme with conservative artificial dissipation terms for structured grid. We also note result achieved by recently developed finite volume method with VFFC scheme. We discuss numerical results of steady and unsteady two-phase transonic flow in 2D nozzle, 2D and 3D turbine cascade and 2D turbine stage with moving rotor cascade.     

Numerical simulation of two-phase free surface flows

Free surface flows are of most interest in many engineering or mathematical problems and many methods have been developed for their numerical resolution in various fields of the physics or the engineering. In this work, the volume-of-fluid method is used for the numerical simulation of two-phase free surface flows involving an incompressible liquid and a compressible gas and taking into account the surface tension effects. The incompressible Navier-Stokes equations are assumed to hold in the liquid domain, while the dynamical effects in the ideal gas are disregarded. A time splitting scheme is used together with a two-grids method for the space discretization. An original algorithm is introduced to track the bubbles of gas trapped in the liquid. Numerical results are presented in the frame of mold filling and bubbles and droplets flows. Some theoretical results concerning free boundary problems are also summarized.     

Numerical simulation of the unsteady three-dimensional flow in confined domains crossed by moving bodies

A numerical method devoted to the prediction of unsteady flows in complex domains with moving boundaries is presented. Based on the unsteady Euler equations with source terms to take diffusive effects into account as well as additional mass, momentum or enthalpy sources, it has been specially developed to model the thermal and dynamic behavior of the ambient air inside underground stations in the presence of moving trains. The numerical solution method is a unstructured finite-volume cell-centered scheme using the SIMPLE algorithm coupled with a second-order intermediate time stepping scheme. The spatial discretization is realized with an automatic Cartesian grid generator, complemented by a technique of sliding grids to handle straight moving bodies inside the domain.     

Numerical simulation of two-phase flow in deformable porous media: Application to carbon dioxide storage in the subsurface

In this paper, conceptual modeling as well as numerical simulation of two-phase flow in deep, deformable geological formations induced by CO₂ injection are presented. The conceptual approach is based on balance equations for mass, momentum and energy completed by appropriate constitutive relations for the fluid phases as well as the solid matrix. Within the context of the primary effects under consideration, the fluid motion will be expressed by the extended Darcy's law for two phase flow. Additionally, constraint conditions for the partial saturations and the pressure fractions of carbon dioxide and brine are defined. To characterize the stress state in the solid matrix, the effective stress principle is applied. Furthermore, the interaction of fluid and solid phases is illustrated by constitutive models for capillary pressure, porosity and permeability as functions of saturation. Based on this conceptual model, a coupled system of nonlinear differential equations for two-phase flow in a deformable porous matrix (H²M model) is formulated. As the displacement vector acts as primary variable for the solid matrix, multiphase flow is simulated using both pressure/pressure or pressure/saturation formulations. An object-oriented finite element method is used to solve the multi-field problem numerically. The capabilities of the model and the numerical tools to treat complex processes during CO₂ sequestration are demonstrated on three benchmark examples: (1) a 1-D case to investigate the influence of variable fluid properties, (2) 2-D vertical axi-symmetric cross-section to study the interaction between hydraulic and deformation processes, and (3) 3-D to test the stability and computational costs of the H²M model for real applications.     

Multi-level adaptive simulation of transient two-phase flow in heterogeneous porous media

An implicit pressure and explicit saturation (IMPES) finite element method (FEM) incorporating a multi-level shock-type adaptive refinement technique is presented and applied to investigate transient two-phase flow in porous media. Local adaptive mesh refinement is implemented seamlessly with state-of-the-art artificial diffusion stabilization allowing simulations that achieve both high resolution and high accuracy. Two benchmark problems, modelling a single crack and a random porous medium, are used to demonstrate the robustness of the method and illustrate the capabilities of the adaptive refinement technique in resolving the saturation field and the complex interaction (transport phenomena) between two fluids in heterogeneous media.     

Numerical simulation of separating boundary-layer flow

A two-dimensional boundary-layer flow over a bump has been studied computationally by solving the incompressible Navier–Stokes equations. The numerical solution procedure uses a mapping transforming the physical coordinate system into a Cartesian one. The resulting system is solved using a mixed finite differences––Chebyshev collocation discretization. We compare the influence matrix technique with a fractional time-step procedure used to enforce the divergence-free condition. Numerical experiments are performed for bumps with different aspect ratios. The separation structure is investigated for increasing Reynolds number and self-induced vortex shedding is reproduced numerically.     

Numerical study on two-phase flow through fractured porous media

Based on the flux equivalent principle of a single fracture,the discrete fracture concept was developed,in which the macroscopic fractures are explicitly described as(n-1)dimensional geometry element.On the fundamental of this simplification,the discrete-fractured model was developed which is suitable for all types of fractured porous media.The principle of discrete-fractured model was introduced in detail,and the general mathematical model was expressed subsequently.The fully coupling discrete-fractured ma...     

Numerical simulation of two-phase flows in the presence of a magnetic field

A set of non-dimensional model equations, which can simulate incompressible, immiscible two-phase flows in the presence of a magnetic field, has been derived and solved numerically with a finite difference method using the HSMAC algorithm. In this study, dynamics of a falling droplet of liquid metal into a horizontal liquid metal layer and of a rising air bubble in water subject to a magnetic field are presented as examples. The numerical results reveal that the Lorentz force acts to dampen the motion of electric conducting fluid as the Hartmann number increases. On the other hand, even for ordinary non-conducting fluids such as water and air, a substantial body force due to magnetization influences the air bubble behaviour in water under a gradient magnetic field.