多因素耦合影响亚音速喷口强化气体流场分布研究

为了研究多因素耦合条件下亚音速喷口内气体流场分布演变的作用机制与影响规律,基于标准k-ε湍流模型,对压力-流速-收缩比耦合条件下的亚音速喷口构造均匀气体流场进行了数值模拟,通过定义top-hat流场分布关键参数的方式,定量评估压力-流速-收缩比对强化后流场分布的耦合影响.结果表明:多因素耦合条件下,亚音速喷口通过影响压...     

烟草专用标准恒流孔的研究

为了更好地测量卷烟吸阻和滤棒压降,基于计算流体动力学的角度对烟草专用恒流孔进行了研究,采用有限体积法和Realizable k-ε的湍流模型进行三维数值仿真,能够模拟烟草专用恒流孔的内部流动情况,并进行了理论、数值仿真和实验研究。实验数据和在浙江中烟标准化实验室测得的标准恒流孔入口端的体积流量的实验数据对比,综合分析后发现标准恒流孔能在其前端保持恒定的体积流量。     

管道空腔流动被动控制方法的实验研究

采用高频响粒子图像测速技术,对长深比为5的管道空腔流场进行实验研究。同时在空腔前缘安置三种不同形状和具有相同扰动速度（34 m/s）的扰流体（圆柱形、锯齿形和矩形）对空腔流动进行被动控制。实验结果表明,圆柱扰流体能够增大剪切层厚度,并且可减小剪切层速度脉动和涡量值。矩形和锯齿形扰流体明显地将剪切层向主流区抬起,导致剪切层与空腔后缘未发生正面碰撞。     

水平细通道内CO_2流动沸腾换热流态特性实验研究

本文对水平细通道内CO_2流动沸腾换热过程中流态及其转变特性进行理论分析和可视化实验研究。根据可视化实验结果,更新了CO_2在低蒸发温度下的理论流动状态预测模型。实验工况为:热流密度(7. 5～30 k W/m2)、质量流率(50～600kg/(m2·s))、饱和温度(-40～0℃)、干度(0～1)、内径(1. 5 mm)。理论分析表明:质量流率对换热过程中经历的流态形式有决定性作用,热流密度对环状流-干涸区域、干涸区域-雾状流边界转变曲线影响较大,饱和温度对流态转变具有重要影响。可视化研究表明:基于理论流态图对于CO_2在细通道内流动沸腾换热的流态能够较好的预测,也能反映不同工况下流态的变化趋势,但理论流态图对干涸区域和雾状流区域预测偏差较大;在实验数据的基础上,增加了液气黏度比的无量纲因子,并提出一种新的临界热流密度预测模型。在考虑质量流率和热流密度影响的情况下,根据更新后临界热流密度预测模型和实验数据,引入沸腾数Bo对理论流态图中环状流-干涸区域、干涸区域-雾状流及间歇流/弹状流-环状流边界转变曲线进行了更新,可视化研究获得的流态数据中89. 4%符合更新后的CO_2理论流态预测模型。     

RH真空精炼吹氩参数对循环流动影响的数值分析

为研究RH真空脱气过程中的流动行为,建立了描述气泡驱动下的RH循环气-液两相流动的数学模型.基于欧拉-欧拉两流体模型,利用计算流体力学(CFD)商业软件FLUENT6.0,对不同充气量条件下的循环流量进行了预测.计算结果与实验数据的比较表明两者具有较好的一致性.应用该模型对充气压强与循环流量、充气量与上升管内气相及液相速度分布关系进行了数值模拟,用以理解其中的流动规律,为工程技术改进提供参考.     

基于矩形流道流场分析及气动实验的轴流风机结构参数优化设计

本文通过提取导流罩的轴向长度及叶顶间隙两个设计参数,构建了矩形流道内轴流风机的流场结构及仿真模型,进行了数值模拟和实验分析。结合仿真模型分析了矩形风道下轴流风机内部和出口流场特性的变化规律,构建了风机设计参数与气动性能之间的映射关系模型。通过风机气动性能实验可得:风机出口静压、体积流量和效率与间隙因子成反比,而与长度因子成正比,对比模拟值和实验值验证了模型的正确性。基于量化映射关系模型得到风机设计参数间隙因子和长度因子的最优值分别为0.8%和12.5%,为风机设计和冰箱风道优化提供量化参考。     

CFD Simulation of the Flow Field Inside Screw Powder Feeder

A screw powder feeder is an important device for industrial applications.There are many parameters which affect the performance of the screw powder feeder,such as the shapes of the helical screw impeller,the number of screw pitches,etc.This paper presents an analysis of a gas-solid two-phase through screw powder feeder by using a commercial Computational Fluid Dynamics(CFD) code,Fluent.The κ-ε model is used to simulate gas flow.Particle trajectory is obtained by the use of a discrete phase model.The results show the effects of gas velocity and particle size on the transportation performance.     

管道内冰浆流动压降特性模拟和实验研究

本文采用以颗粒相动力学为基础的Euler-Euler模型,利用FLUENT研究冰浆在水平直管、90°弯管和T型管中的流动压降特性(计算过程不考虑相变)。模拟结果显示,在管道入口处压降较明显,90°弯管拐弯后内侧压力小于外侧,T型管在分流直角拐角处出现压力最高点和最低点。冰浆流动实验发现,冰浆单位压降随流速和含冰率的增加而增大,且3种管型中直管压降最小,T型管压降最大。对比实验与模拟结果,单位压降随流速的变化趋势一致,且误差在20%以内,但在大流速时,模拟值大于实验值。     

从导弹战斗部用钛合金的研究看材料的开发

从高速冲击动力学的角度出发，分析了影响导弹战斗部同目标撞击时的因素，讨论了层状结构的钛合金用作高速半穿甲战斗部的可能性，进而表述了服役效能在材料开发中的核心地位。     

高速列车外部流场和车内噪声模拟计算

研究表明,高速列车气流噪声主要取决于车身表面脉动压力,所以研究列车车身表面脉动压力对进一步研究和控制高速列车气流噪声具有重要的意义。采用有限元法对高速列车外流场进行数值模拟,计算结果反映高速列车外流场特性。在此基础上,进一步对高速列车表面脉动压力进行数值模拟计算,并通过声固耦合的方法得到车内某点的声压级,得到一些有意义的结论。     

喷射成形工艺中限制型喷嘴雾化气流场的数值模拟

利用CFD技术对在粉末冶金和喷射成形工艺中广泛使用的限制型雾化喷嘴的气体流场进行了计算。结果表明在限制型喷嘴中气流的会聚角度对金属液导流管前端的压力场和气体流场有很大的影响。平行气流可以在负压的作用下会聚到轴线上。随会聚角度增加,导液管前端的压力提高,金属导液管前端的压力场由负压向正压转变,气流沿导液管轴线方向速度的最大值也随会聚角的增加而增大,气流在会聚点处的动能也随之增加。限制型喷嘴的气体流场还受到金属导液管位置的影响,随导液管的伸出可以促进负压区的形成,提高抽吸力,保证金属液的顺利流出。     

Modeling Performance of a Tangential Flow Cyclone: Effects of Secondary Outlet Geometry and Boundary Conditions

Numerical calculation of the performance of cyclones for gas-particle separation is becoming a popular tool for cyclone analysis and design. A traditionally accepted way to treat these problems is by solving the flow field and particle transport equations in the spatial domain (C1) limited by the inlet and overflow outlet cross-sections, where the flow is usually assumed fully developed, and the dust outlet cross-section. Formulation of the boundary conditions for the flow and particles’ transport at the dust outlet cross-section remains an open question. We address this problem numerically by comparing results of calculations performed by the above traditional approach, i.e., treating the problem in configuration C1, as well as in extended domains, namely those including a dust collecting bin (configuration C2) and a downcomer tubular outlet (configuration C3). Two boundary conditions at the downflow outlet were checked for each configuration, namely, a blocked outlet (zero velocity) and an open outlet (zero gas flow rate). Toward this goal, an efficient computational fluid dynamic (CFD) model of turbulent flow based on the Reynolds Stress turbulent closure scheme was developed, validated, and used to calculate velocity field and the pressure drop as well as particle cut size and separation efficiency in several Stairmand-type tangential flow cyclones. The results were tested and corroborated against the experimental data reported in the literature, including careful measurements performed by Gottschalk and Bohnet (1995 Gottschalk , O. , and M. Bohnet . 1995 . Two stage circuit for the separation of fine particles. PARTEC 95, Europ. Symposium on Separation of Particles from Gases, Nurnberg, March.  [Google Scholar], 1998 Gottschalk , O. , and M. Bohnet . 1998 . Calculation of grade efficiency and pressure drop of aerocyclones with suction of partial gas stream. PARTEC 98, European Symposium Separation of Particles from Gases, Nurnberg, March.  [Google Scholar]) for a 225 mm tangential flow cyclone, with downflow outlet connected to a tubular extension.

Particle separation in the traditional C1 cyclone configuration was shown to be most sensitive with respect to the choice of the boundary conditions at the downflow outlet, whereas with the dust outlet connected to a bin (C3 configuration) this condition has a much weaker effect on the fractional efficiency. Solutions for the C1 and C2 configurations, both combined with the blocked downflow outlet boundary condition yielded the cyclone's pressure drop in agreement with the Gottschalk and Bohnet's data. However, C2 configuration which contained a downcomer tubular extension was found preferable for correlating the measured fractional efficiency.     

箱梁断面静风力系数的CFD数值模拟

用计算流体力学(CFD)方法模拟了桥梁跨中断面周围的风场特征,不仅能得到流场的压力、速度和涡旋的分布,还提取了箱梁断面的三分力系数。分别采用不同密度网格划分对主梁断面进行数值模拟,并将数值模拟结果与风洞试验值进行比较,选取最合理的网格划分方法。然后,对某一大跨度桥梁跨中断面的箱梁模拟了从-5°至+5°共11个整数度风攻角工况的三分力系数。并将数值模拟结果与风洞试验进行了对比,给出了不同攻角下的压强和速度分布,验证了采用CFD技术模拟桥梁三分力系数方法的可行性与可靠性。     

Steady Fault Characteristic Analysis of a Missile Power System Based on a Differential Evolution Algorithm

The differential evolution (DE) algorithm is applied to solving the models‘ equations of a whole missile power system, and the steady fault characteristics of the whole system are analyzed. The DE algorithm is robust, requires few control variables, is easy to use and lends itself very well to parallel computation. Calculation results indicate that the DE algorithm simulates faults of a missile power system very well.     

顶部开窗对空气源冷热水机组外部流场影响的数值模拟分析

应用FLUENT软件对某空气源冷热水机组外部流场进行了模拟与分析,模拟针对四种情况进行,得到了不同条件下该机组外部气流的温度场和速度场。研究发现,对于摆放位置受限的风冷热泵冷热水机组而言,周围的建筑遮挡对机组外部流场影响甚大。采取上开窗的形式可以有效改善机组周围流场,避免上述问题,对提高机组性能存在潜在好处。     

用于湿度独立控制的送风气流组织研究

利用计算流体力学（CFD）对5种不同的气流组织形式进行模拟分析，对每种气流组织下形成的空气含湿量分布进行研究。指出个性化送风和地板送风方式对于去除室内余湿较为有效，有可能作为适于湿度独立控制的送风气流组织形式。     

Computational Fluid Dynamics Study of Flow and Aerosol Concentration Patterns in a Ribbed Smoked Sheet Rubber Factory

A computational fluid dynamics (CFD) method was used to investigate velocity, temperature, particles trajectories, and aerosol concentration in a natural ribbed smoked sheet rubber factory. A model to improve the smoke aerosol particle ventilation was proposed. The simulation was performed using turbulent free convection flows where the Rayleigh number was between 5.3838 × 10¹⁰ and 33.2003 × 10¹⁰. A total of 2,159,347 mesh volumes were applied to the entire ribbed smoked sheet rubber cooperative. Results from the CFD simulation and experiment showed positive results. The air containing smoke particles moved naturally from ventilating lids of the smoke room to the roof. The smoke particles followed the airflow fields at the junction of the roof and traveled to workplace areas. Results show that the thick cloud of smoke particles remained in the workplace after traveling for more than 200 m. Particle concentration was high in the area above the ceiling and lower along the elevation in a downward direction. This is potentially harmful to the employees who work in the factory for long periods of time. Modification of the roof to include a ridge vent showed considerable improvement in ventilation, which largely decreased the aerosol particle concentration inside the factory.     

Chemically Amplified Multiplex Detection of SARS-CoV-2 and Influenza A and B Viruses via Paint-Programmed Lateral Flow Assays

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) continues to threaten lives by evolving into new variants with greater transmissibility. Although lateral flow assays (LFAs) are widely used to self-test for coronavirus disease 2019 (COVID-19), these tests suffer from low sensitivity leading to a high rate of false negative results. In this work, a multiplexed lateral flow assay is reported for the detection of SARS-CoV-2 and influenza A and B viruses in human saliva with a built-in chemical amplification of the colorimetric signal for enhanced sensitivity. To automate the amplification process, the paper-based device is integrated with an imprinted flow controller, which coordinates the routing of different reagents and ensures their sequential and timely delivery to run an optimal amplification reaction. Using the assay, SARS-CoV-2 and influenza A and B viruses can be detected with ≈25x higher sensitivity than commercial LFAs, and the device can detect SARS-CoV-2-positive patient saliva samples missed by commercial LFAs. The technology provides an effective and practical solution to enhance the performance of conventional LFAs and will enable sensitive self-testing to prevent virus transmission and future outbreaks of new variants.     

Characteristics of a typical lifting symmetric supercritical airfoil

The theoretical aerodynamic characteristics of a typical lifting symmetric supercritical airfoil demonstrating its superiority over thenaca 0012 airfoil from which it was derived are presented in this paper. Further, limited experimental results confirming the theoretical inference are also presented. Invited Lecture given at the 3rd Asian Congress on Fluid Mechanics, held in Tokyo during 1–5 September, 1986     

烟支吸附装置流场分析与优化设计

目的 针对烟支传递与包装平稳性差的缺点,采用计算流体动力学（CFD）方法对烟支吸附通道内部流场进行三维数值分析。方法 研究关键部位流动特性,分析流速、压力分布及湍流耗散,提出结构改进方案。结果 流场压力和流速在烟支吸附口与风机连接位置分布不合理,拐角处湍流动能高,烟支吸附口至风机位置压力损失为5 268 Pa。风机管道存在逆压梯度,产生气流漩涡,压力损失值为14 000 Pa,高于工业需求。优化模型中,风机管道包含2个拐角时,压力损失降低了7 000 Pa,烟支吸附效果提升了350%。风机管道包含一个拐角时,压力损失降低了6 200 Pa,烟支吸附效果提升了390%,通道流场分布合理性得到改善。结论 基于仿真结果,优化风机与出风口管道连接方式,通过流场分析可为烟支吸附装置的优化设计提供一定技术支持。