工业油水分离器湍流两相流场的数值模拟

本文应用双流体模型及ｋ－ε－ｋｐ两相湍流模型，研究了水力旋流器内油水两相湍流流场。建立了适用于旋流分离器中两种液体混合物的有旋湍流流动的ｋ－ε－ｋｐ模型。并针对影响旋流器分离效率的不同影响因素，进行了变更入口流动参数及分离器几何参数的数值实验，为工业用油水旋流分离器的优化设计提供了一个有效的数值模拟工具。     

带入口旋流器的文丘利油燃烧器出口热态流场的数值模拟

针对带入口旋流器的新型文丘利油燃烧器出口流动燃烧的特点，建立了相应的数学物理模型和数值算法。在数值模拟一、二次风道内部流动及出口等温流场的基础上，对新型油燃烧器出口的热态流场进行了数值模拟，并与未装设入口旋流器的文丘利油燃烧器出口冷热态模拟结果进行了对比分析。模拟结果为该型油燃烧器的进一步改进设计、运行及布置提供了重要依据。图9表1参10     

低排放塔式同轴分级旋流配比对燃烧流场的影响

以天然气-低排放塔式同轴分级燃烧室为研究对象，采用Realizablek-ε湍流模型和FGM燃烧模型研究了旋流器旋流数对热态流场的影响．结果表明：随着二级旋流数增加，中心级和一级流量增加，二级流量减少，燃料掺混均匀性提高，均匀指数最大提高0.061；压力损失小幅增加，而CO排放显著减少，燃烧效率提高且超过99%；模拟的各工况温度分布均匀，均形成稳定的回流区，燃烧稳定；对16种不同的旋流器方案进行筛选，选出0.7/0.8旋流器方案为最佳方案．     

水平管降膜蒸发器中不同形式的布液器对内部流场流动影响的数值模拟

应用Fluent两相流VOF模型,数值模拟水平管降膜蒸发器内部流场流动的过程。提出3种不同结构的布液器,分别对蒸发器内部流动特性进行了比较分析,得到气液两相图、速度云图、XY图等。模拟结果表明:中间开孔布液器使两部分蒸发管阵产生的蒸汽通过中间蒸汽排气口疏导出去,换热面大,使液体分配较均匀,更为合理,有利于蒸发器内部整体流场的优化设计。研究结果可为降膜蒸发器的优化设计提供理论依据。     

固相浓度对水-煤管道输送的影响研究

数值模拟了管道输送水-煤两相流动的流场,结果发现液固两相流中确实存在壁面滑移层,且滑移情况随固相浓度含量变化而变化。在煤粒径为1 mm的情况下,管内存在煤粒子向管道中心聚集的正滑移现象,这将有利于固相输送中能耗的降低,但固相浓度含量越高,粒子的这种聚集现象越不明显,而且单位管长的压降随输送煤浓度的增加而增大。     

竖缝式鱼道水力特性三维数值模拟

以斯洛文尼亚布兰卡水电站竖缝式鱼道为例,分别用大涡模拟(LES)和RNGκ-ε紊流模型计算鱼道三维流场,并利用实测数据对两种模型的数值计算结果进行验证,进而对比分析了不同时刻典型截面的流场结构。结果表明,两种计算模型均可满足鱼道工程设计的基本要求,较RNGκ-ε紊流模型仅能提供时均水流特性,大涡模拟有力补充了鱼道内瞬态涡结构细节,可为进一步明确鱼道内水流的瞬态特性与鱼类上溯行为的内在关联提供有效的分析工具。     

带入口旋流器的文丘利调风器的内外部等温流场的数值模拟

针对带入口旋流器的新型文丘利调风器流场的数值模拟，提出了一种分析模型和处理方法。通过模拟结果与试验数据的对比分析，表明本文作者建立的模型及处理方法是成功的，据此进一步对某船用锅炉带入口旋流器的新型文丘利调风器的内外部等温流场进行了预测分析。     

双径向反向旋流器燃烧室冷态流场数值研究

文章采用数值模拟的方法对一种新设计的双径向旋流器燃烧室的冷态流场进行了研究,并对旋流器的重要设计参数进行了计算和验证.研究表明:双径向反向旋流器能在燃烧区形成有效的回流区,同时反向旋转加强了燃料空气混合,有利于污染控制.从旋流数来看,燃烧区旋流数均大于0.6,旋流强度足以形成有效的回流区用于稳燃.最后文章研究了此结构下两级旋流器的流量系数并与初始设计用值进行了比较.     

水—汽浸没凝结射流两相流动的数值研究

本文对水－汽浸没凝结射流两相流动采用单流体模型及ｋ－ε湍流模型进行了数值研究，得到了速度，温度，密度和气相体积分数等物理量的分布以及穿透区（含气区）的形状，穿透区的长度与相关的由实验得到的经验公式符合得很好，计算结果表明水的汽－液浸没凝结射流经历了气相流动，气液两相流动和液相流动等不同流动型态的变化，具有复杂的流场结构。     

气液搅拌流场中不同通气结构的CFD模拟

使用数值模拟的方法研究了气液两相在同一种搅拌反应器、4种不同氧化喷枪结构的流场特点.采用Euler-Euler双流体模型,用RNG k-∈两方程湍流模型分析流场、多重参考系法处理搅拌桨区域,获得了不同氧化喷枪结构的流场气含率.结果表明:90°弯管带翼结构可以达到更好的搅拌效果,速度场更合理,气泡轨迹更理想,并且在典型平面上的气含率更高.     

SIMULATION OF SWIRLING TURBULENT FLOWS OF COAXIAL JETS IN A COMBUSTOR

A numerical simulation of swirling turbulent flows of coaxial jets in a combustor is presented in this paper. The new algebraic Reynolds stress model (ASM) is employed for the closure of the time-averaged governing equations for swirling turbulent flows. Two cases of the swirling flow, i.e., a coswirl jet flow and a counterswirl jet flow, are simulated. The calculated results of the axial and tangential velocities, static pressure, and turbulent fluctuating velocity are compared with the measured data for both cases. The results illustrate that the predictions by the new ASM are closer to the measurements than those obtained by the k-epsilon model.     

Numerical study of stratified oil-water two-phase turbulent flow in a horizontal tube

Stratified oil-water two-phase turbulent flow in a horizontal tube is numerically simulated using a volume of fluid model. A single momentum equation is solved throughout the domain. The RNG k-ε model combined with a near-wall low-Re turbulence model is applied to each phase, and a continuum surface force approximation is adopted for the calculation of surface tension. The simulation is performed in a time-dependent way and the final solution which corresponds to steady-state flow is analyzed. Results of pressure loss, slip ratio, local phase fraction profile and the axial velocity profile are verified by experimental data in literature. Based on the numerical results of extensive calculations, the flow field characteristics are explored and correlations for pressure loss and hold-up are presented.     

旋风筒内强旋湍流流动的实验研究

本文采用能同时测定流场方法和速度的旋转式一孔探针，对不同结构的旋风筒内强度旋湍流流动进行了实验研究，给出了不同的入口位置和出口结构对流场中轴向切向速度分布和回流位置等特性的影响规律，研究结果对旋风炉及旋风除尘器的设计有着重要的参考价值。     

进口结构对方形旋风分离器性能影响的数值研究

利用CFD模拟研究了一种具有双矩形进口的方形截面的旋风分离器内部的流动特点,其中气相模型采用了雷诺应力湍流模型（Reynolds stress model,RSM）,颗粒相采用随机轨道模型。计算结果与文献实验数据的对比表明模型具有可靠性。模拟结果表明：在分离器内部的排气管和分离器壁面间的区域为强旋湍流区,靠近分离器壁面和排气管壁面的区域旋流强度较弱;排气管下的分离器内出现了回流;进口结构影响分离器内的旋流分布特点和回流开始位置及湍动能的分布,从而影响了分离效率和阻力,其中倾斜双进口的方形分离器内旋转向下的气流运动区域更大,回流开始位置更低,因此其分离效果更好;进口结构影响分离器内局部湍动能的分布特点和大小,从而决定了分离器的阻力大小;倾斜双进口的方形分离器内的局部湍动能小于对应的垂直单、双进口分离器,因此其阻力系数最小。     

NUMERICAL INVESTIGATION OF AN INTERNAL LAYER IN TURBULENT FLOW OVER A CURVED HILL

The development of an internal layer in a turbulent boundary layer flow over a curved hill is investigated numerically. The turbulent flow equations are solved by a control volume based, finite-difference method. The turbulence is described by a multiple-time-scale turbulence model. Computational results show that the internal layer is a strong turbulence field that develops beneath the external boundary layer and is located very close to the wall. The turbulence field of the boundary layer flow over the curved kill is compared with that of a turbulent flow over a symmetric airfoil (which has the same geometry as the curved hill except that the leading and trailing edge plates were removed) to study the influence of a strongly curved surface on the turbulence field. The turbulence structure in the near-wall region of the curved hill is almost the same as that of the airfoil in most of the curved region even though the approaching external flows are quite different. Results show that the development of the wall shearing stress and separation of the boundary layer at the rear of the curved hill depend mostly on the streamline curvature and are only slightly influenced by the external boundary layer flow.     

MULTIGRID ACCELERATION OF COMPUTATIONS OF TURBULENT PARTICLE-LADEN FLOWS

A computational procedure is presented with a multigrid-acceleration scheme for an efficient modeling of turbulent recirculating and highly curved two-phase flows in general coordinates. The two-phase flows consist of a fluid phase governed by Eulerian equations and a particle phase governed by Lagrangian equations. The fluid turbulence-induced particle dispersion is simulated with an eddy-interaction model. Numerical results are presented and compared with available experimental measurements for a particle-laden liquid flow in a sudden-expansion pipe and a particle-laden gaseous flow in a 90° bend. The multigrid computational efficiency is assessed against the conventional single-grid iteration. Results show that the multigrid method substantially enhances the computational efficiency on the fine grids as compared to the single-grid method. In addition, numerical predictions agree favorably with experimental measurements.     

基于大涡模拟的发动机缸内湍流流动及拟序结构

应用大涡模拟方法对发动机缸内湍流流场进行了三维瞬态数值分析.主要从湍流脉动、湍动能和缸内拟序结构演变等方面考察了发动机缸内流场特性.计算结果表明:相比雷诺平均模型,大涡模拟方法可以更真实地反映发动机循环过程中缸内气体流动的细节和规律.利用大涡模拟结合Q准则判别法可以较好地识别缸内大尺度湍流拟序结构;拟序结构对于缸内大尺度动能的产生及湍流的维持具有关键的作用.RANS类模型则不具备充分捕获大尺度拟序结构的能力.湍流脉动与活塞平均运行速度接近于成正比.     

Large eddy simulation of heat and mass transport in turbulent flows. Part 1: Velocity field

Localized residual or subgrid-scale (SGS) models are presented for use in large eddy simulation of heat and mass transport in turbulent flows. In part (1) (this paper), we discuss the SGS stress models for the velocity field. The models for the scalar field are presented in part (2). The new SGS stress closures are compared with the dynamic-Smagorinsky model (DSM) and the dynamic two-parameter mixed model (DTMM). All models are applied “locally” and their performances are assessed via both a priori and a posteriori analyses with detailed comparisons against data obtained from direct numerical simulation of homogeneous isotropic, homogeneous shear and temporal mixing layer flows. The results of a priori assessments indicate that the new closures predict the SGS stresses better than both DSM and DTMM in all simulated flows. The results of a posteriori assessments also show that the SGS stresses and the statistics of the filtered velocity are more accurately predicted with the new models.     

Simulation of shape dynamics of a long flexible fiber in a turbulent flow in the hydroentanglement process

This paper presents the numerical investigation of dynamics of the shape of a long flexible fiber subjected to a turbulent flow field caused by impinging jets in the hydroentanglement process. The shape change of a long flexible fiber is simulated utilizing the rod–chain model following the method developed in Wang et al. [G. Wang, W. Yu, C. Zhou, Optimization of the rod chain model to simulate the motion of a long flexible fiber in simple shear flows, European Journal of Mechanics B/Fluids 25 (2006) 337–347.]. The method is extended to simulate the fiber movement in a turbulent flow field; two-dimensional simulations are performed. The shape of the fiber is determined by forces and torques exerted on it by the surrounding fluid as well as by the neighboring fibers. Numerical results are obtained for two model representations of the same fiber which differ by the number of rods used to represent the fiber.     

Numerical Investigation of Thermo Fluid Mechanics of Differentially Heated Rotating Tubes

Three-dimensional simulation of incompressible flow in rotating tubes for both laminar and turbulent flows has been performed using a finite-volume method for elliptic flows. The influence of Reynolds number on the velocity field and the effects of temperature gradient on temperature profiles have been presented by numerical simulations. Also the effects of velocity field, flow regime, and temperature distribution along the tube have been studied from different points of view. The results have been calculated for rotational Reynolds numbers ranging from 1000 to 320,000. The comparisons between numerically calculated velocity field and the Nusselt number have shown satisfactory agreement with the experimental data.