Numerical Analysis of the Flow Field in a Sloshing Tank with a Horizontal Perforated Plate

Liquid sloshing is a type of free surface flow inside a partially filled water tank.Sloshing exerts a significant effect on the safety of liquid transport systems;in particular,it may cause large hydrodynamic loads when the frequency of the tank motion is close to the natural frequency of the tank.Perforated plates have recently been used to suppress the violent movement of liquids in a sloshing tank at resonant conditions.In this study,a numerical model based on OpenF OAM(Open Source Field Operation and Manipulation),an open source computed fluid dynamic code,is used to investigate resonant sloshing in a swaying tank with a submerged horizontal perforated plate.The numerical results of the free surface elevations are first verified using experimental data,and then the flow characteristics around the perforated plate and the fluid velocity distribution in the entire tank are examined using numerical examples.The results clearly show differences in sloshing motions under first-order and third-order resonant frequencies.This study provides a better understanding of the energy dissipation mechanism of a horizontal perforated plate in a swaying tank.

Flow Field Analysis of Submerged Horizontal Plate Type Breakwater

Submerged horizontal plate can be considered as a new concept breakwater. In order to reveal the wave elimination mechanism of this type breakwater, boundary element method is utilized to investigate the velocity field around plate carefully. The flow field analysis shows that the interaction between incident wave and reverse flow caused by submerged plate will lead to the formation of wave elimination area around both sides of the plate. The velocity magnitude of flow field has been reduced and this is the main reason of wave elimination.

Magnetohydrodynamic flow over a moving plate in a parallel stream with an induced magnetic field

一粘滞在在有一个经常的磁场的一条平行溪流的一个动人的扁平的盘子上的电子上进行的液体的边界层流动在边界层平行外面适用于板被调查。部分微分方程的 goveming 系统用类似转变被转变到平常的微分方程。类似方程然后用作为 Keller 盒子方法知道的一个有限差别的计划数字地被解决。皮肤磨擦系数，速度侧面，和导致的磁场侧面的数字结果为动人的参数，磁性的参数，和相互的磁性的 Prandtl 数字的一些价值被获得。当板和液体搬到相反的方向直到动人的参数的批评的值时，结果显示双解决方案存在，其值取决于磁性的参数的值。

Anti-flooding of polymer electrolyte membrane fuel cell with in-plate adverse-flow flow-field

The stoichiometric ratios and related regimes, which can promote anti-flooding of polymer electrolyte membrane fuel cell (PEMFC) with in-plate adverse-flow flow-field (IPAF), were investigated. Two flow combinations, which are the simple and complex adverse-flow between plates (ABP) that can be realized by IPAF, were employed. Constant stoichiometric ratios examination indicates that the complex ABP could improve anti-flooding of PEMFC better in the medium (greater than 200 mA/cm2 and less than 1 000 mA/cm2 ) and high (greater than 1 000 mA/cm2 ) current densities than the simple ABP. More stoichiometric ratios were introduced to find the cathode critical stoichiometry. Under the condition of cathode critical stoichiometry, the maximal local relative humidity of both electrodes of complex ABP is equal to 100% and below while the anti-flooding of the cathode of simple ABP is not satisfactory in the medium and high current densities. Further study shows that the mechanism of fuel cell, which is the interdependence between the electrodes effect, can make significant contribution to anti-flooding.

Flow Field and Thermal Analysis of the Divertor Target Plate for HL-2A Tokamak

In the initial phase of the physics experiment, the double-null divertor plates used consist of graphite armor tiles, Mo-alloy intermediate layers and Cu-alloy coolant tubes. In the later operating phase, tungsten will be used as armor tiles. A multi-physical field numerical analysis method is used in this paper. Its analysis model reflects more realistically the real divertor structure than other models. Two-dimensional （2D） and three-dimensional （3D） fluid flow field, temperature distribution and thermal stress analyses of the divertor plates are carried out by the ANSYS code. During the physics experimental phase with a heat flux of 1 MW/m2, a coolant velocity of 5.48 m/s, and a thermal stress of 750 kg/cm2, the graphite armor tiles successfully meet the requirements of temperature, thermal stress and sputtering erosion. The tungsten armor will be considered as a second candidate. The result of simulation can be used for upgrading the design parameters of the HL-2A poloidal divertor.

Mathematical Analysis of Unsteady MHD Blood Flow through Parallel Plate Channel with Heat Source

In the present study, a mathematical model of unsteady blood flow through parallel plate channel under the action of an applied constant transverse magnetic field is proposed. The model is subjected to heat source. Analytical expressions are obtained by choosing the axial velocity;temperature distribution and the normal velocity of the blood depend on y and t only to convert the system of partial differential equations into system of ordinary differential equations under the conditions defined in our model. The model has been analyzed to find the effects of various parameters such as, Hartmann number, heat source parameter and Prandtl number on the axial velocity, temperature distribution and the normal velocity. The numerical solutions of axial velocity, temperature distributions and normal velocity are shown graphically for better understanding of the problem. Hence, the present mathematical model gives a simple form of axial velocity, temperature distribution and normal velocity of the blood flow so that it will help not only people working in the field of Physiological fluid dynamics but also to the medical practitioners.

燃料电池极板过渡区结构的优化设计

为解决质子交换膜燃料电池(proton exchange membrane fuel cells,PEMFC)反应区流道燃料分配不均匀性,采用计算流体力学方法对流道燃料流动进行仿真,采用变异系数对不同方案进行评价,研究过渡区中圆柱体积占比、圆柱排列方式、圆柱到流道距离、过渡区圆柱开孔率对燃料分配均匀性的影响。结果表明:采用圆柱导流的燃料分配均匀性优于导流道导流;过渡区圆柱采用正方形排列时燃料分配均匀性最佳;增加圆柱到流道的距离,各流道燃料分配均匀性呈现先升高后下降的趋势,距离为3 mm时均匀性较好;过渡区开孔率约为11.4%时燃料分配均匀性较好,过大过小都会造成分配均匀性恶化。

立式余热锅炉底部护板布置方式对流场影响的对比分析

为优化立式余热锅炉烟气流场,基于ANSYS软件,采用标准κ-ε双方程湍流模型对烟气流场进行数值模拟,研究进口烟道底部护板布置方式对流场的影响,得到不同底部护板布置方式下进口烟道出口端面的速度分布,并且利用速度均匀性指数对模拟结果进行定量分析。结果表明:底部护板采用45°倾角布置方式时的流场均匀性优于0°倾角和23°倾角。模拟结果可为立式余热锅炉进口烟道底部护板的布置提供参考。

Local Contribution Method for Efficiency of Large Plates

From the measurement of liquid flow field on a large plate by a hot-film anemometer, three different regions on the large plate were presented, including a liquid circulation area near the inlet down-comer, a region with very slow moving or stagnant liquid on the side of the tray and an active Row region at the center of the plate. According to the contribution of the three regions, the tray efficiency for large plates was proposed. The prediction plate efficiency by the present model are compared with the experimental data in the literature and those calculated by other models. It is shown that the present model is more accurate for prediction of efficiency of large plates, and the calculation is simpler.

基于CFD的滑靴副多场耦合特性研究

滑靴副作为斜盘式轴向柱塞泵的主要摩擦副之一,长期工作于高速、高压、高温等一些复杂极端环境中.本文建立了滑靴副中流场的基本控制方程,构建了滑靴副多物理场耦合的有限元模型,通过CFD技术对滑靴副流场进行模拟分析,并在此基础上对滑靴副流-固-热多物理场耦合进行仿真,得到不同工况下油液的压力场和速度场的变化规律以及流体的压力和温度对滑靴副的总变形量、应力的影响.结果表明,随着工作压力增大,油液在阻尼管路中压力损失增加,油腔内涡旋个数及尺寸增大.除此之外还发现滑靴副变形量和最大应力对油液温度较为敏感.本文工作为滑靴副的结构设计提供了一定的技术支持,并且对于提高滑靴副的整体性能有着重要的意义.

大热流背景下蜂窝板结构参数的多目标优化

为研究大热流背景下不同结构参数对蜂窝板传热和阻力性能的综合影响,基于ANSYS Workbench平台的目标驱动优化系统,对蜂窝板进行数值建模,并采用中心组合设计优化算法对其进行场态分析和多目标优化。结果表明:流体在蜂窝板内的流动传热呈周期性变化,流经焊点时受到强烈扰动并生成射流与小旋涡,能有效强化传热;鼓胀高度H对传热和阻力性能的影响最大,焊点直径D次之,焊点间距L的影响最小。通过优化计算最终得到了3组较优的结构参数搭配,可为蜂窝板的优化设计提供参考。

阴极疏水微槽流场板对DMFC的性能影响研究

设计并制作了一种具有疏水性的亚毫米级线性单向微槽结构的直接甲醇燃料电池(DMFC)阴极流场板,测试了该微槽结构的疏水性,并研究了微槽结构对电池性能的影响。实验测试结果表明:在甲醇浓度为8 mol/L的条件下,电池的极限电流密度值和极限功率密度值分别提高了6.894%和14.747%。通过对比实验得到了微槽结构的最佳结构参数,当微槽结构的切槽宽度为400μm,切槽深度为600μm时,电池性能最佳。

下游调压阀喘振对上游孔板流量计的影响

在实际生产中,压缩机喘振及下游用户节点用气不均匀等原因易引起调压阀频繁启动,从而产生周期性的压力、流量瞬变,而周期性脉动流会使孔板流量计出现计量偏差。为解决此问题,以站间长输管道为研究对象,研究其中压力及流量波动向上游传播的规律。首先,以下游站场站内调压阀喘振为管道出口边界,采用高精度TVD算法模拟调压阀喘振引起的压力及流量波动反向传播;同时,以压力及流量波动规律为孔板内流场边界条件,建立孔板内流场瞬变流动模型。

内置均流板箱式热处理炉流场与温度场仿真优化

针对实际应用过程中箱式结构热处理炉普遍存在靠炉门处低温气流不均匀引起温度过低的问题,提出了一种内置均流板的炉门气流流场优化与温度场优化方案。采用数值模拟方法研究了不同结构均流板方案对炉内气流流场分布及温度分布的影响,并将其应用于箱式热处理炉进行试验验证。结果表明:与优化前相比,优化后炉门气流流入炉膛内部的流场均匀性得到显著提升,设置的均流板因射流间相互干扰导致流入的速度降低,减弱靠炉门端气流与工件间的对流传热,同时工件在均流板的阻挡作用下辐射散热减少,从而提升工件靠炉门端的温度,栅板的提升效果大于孔板,模拟结果与实际相符,炉膛温度均匀性可提升37.95%。

耙腔流场分析与结构优化

针对耙吸挖泥船的耙头在挖掘黏土时,其内部流场情况不明晰的问题,本文对耙腔内部流场进行了仿真计算、分析及优化。采用计算流体动力学(CFD)值模拟计算技术,分析新老耙头的总压差、静压差及截面流速的变化情况。得出设置反弧形导流板后,腔体内部漩涡区域减少,能量损失降低,清水流动性能提高。结果表明:新耙头内部设置流线型腔体,可使流动平顺,输送阻力降低,截面流速趋于合理。其各项性能均优于老耙头。

整流支板和火焰稳定器的一体化设计及性能分析

一体化加力燃烧室设计是将涡轮后框架整流支板、火焰稳定器以及燃油喷射装置进行集成设计,是未来加力燃烧室研究探索的主要方向之一。目前,国内外对于整流支板稳定器形状的研究较少,特别是在带偏转角的低压涡轮来流气体下会造成较大的流动损失。根据主燃烧室涡轮后缘角的气流来流角度设计支板前缘角,根据来流速度设计支板后缘角,是一种新型的一体化加力燃烧室整流支板的设计方案。模拟计算结果显示:(1)所有计算模型的冷态总压恢复系数均在97.6%以上,且新型整流支板与传统对称型整流支板相比具有更低的流动损失,最大相差1.21%;(2)随着入口气流速度的增大,为得到较高总压恢复系数,新型整流支板模型后缘角的设计值也应随之增大;(3)在加力状态下,新型整流支板模型装配的一体化加力燃烧室燃烧效率约为85.6%。

侧出湿式静电除尘器流场优化研究

针对湿式静电除尘器在实际工程中存在内部烟气偏流的问题,利用Ansys fluent软件对某电厂300 MW机组侧出湿式静电除尘器(以下简称除尘器)内部流场分布特性进行模拟,对导致烟气偏流的关键因素进行预测,以入口烟气分布均匀性和维持系统压损为优化标准,对除尘器入口导流装置进行结构调整,并通过工程案例进行可行性验证。结果表明,在常规圆环形均流板上方铺设板条进行封堵,能够有效改善烟气偏流现象,提高烟气分布均匀性,阳极管束区域速度分布偏差系数CV由0.31降低至0.18,整体除尘效率由86.2%提高至92.4%。

基于风洞模拟的不同出风口高度导风板的聚风效应

[目的]揭示不同出风口高度导风板下的风速流场特征及规律,阐明其聚风效能,进而为导风板配置模式提供理论支撑。[方法]应用风洞模拟手段,测定不同风向夹角(β=90°,β=60°,β=45°和β=30°)条件下,不同出风口高度(h=3 cm,h=5 cm,h=7 cm,h=9 cm)导风板的流场特征,分析1/2出风口高度处的相对风速。从而选取风向夹角(β)、出风口高度(h)、来流风速(V 0)以及距离导风板的水平距离(x)等对导风板1/2出风口高度处各点位风速〔V(x)〕进行多元回归建模。[结果](1)各风向夹角条件下,不同出风口高度导风板均形成一定范围的强风区和增速区,但不同出风口高度及风向夹角下其流场特征存在差异。β=90°时,h=3 cm和h=5 cm导风板的增速区和强风区影响范围分别为最大;β=60°时,h=9 cm导风板形成的增速区和强风区影响范围均最大;β=45°和β=30°时,h=9 cm导风板增速区和集流加速区影响范围均最大。(2)β=90°和β=60°时,各导风板1/2出风口高度处相对风速随水平距离的变化近似呈“N”形。由于狭管效应,在0.5 H(H为模型高度)处达到相对风速峰值,而后气流发生扩散,到2 H处降至最低值。随迎风夹角减小,导风板垂直风向投影面积急剧减小,过境气流在板后汇集,此时对水平测点1 H后气流有较强加速效果。(3)1/2出风口高度处导风板风速预测模型为V(x)=-0.144+0.145 h+(-0.022)β+0.808 V_(0)+0.092 x(R^(2)=0.758)。[结论]风向夹角β=60°时,h=9 cm导风板聚风效果最优;构建的预测模型参数选用较为合理,模型拟合程度较高,可为导风板干扰下1/2出风口高度处各点位风速预测提供理论支撑。

汽车底盘流场分析及优化

某车型在苛刻工况下(满载、高环境温度、高速),手动变速箱的机油温度达到150℃,而根据该产品属性签发要求,机油的正常工作温度应控制在130℃以下。本文应用计算流体力学(CFD)工具来模拟计算该车型底盘流场分布情况,分析油温过高的原因、找到问题的解决方案。底盘流场分析结果:由于发动机油底壳的遮挡,导致其后方的变速箱周围风速很小,造成壳体外表面与空气进行强制对流热交换不充分。为优化变速箱壳体尤其是油底壳附近区域流场,在横梁下方增加了一块引流式导流板,它能把横梁之下区域的高速气流引向变速箱油底壳周围。后经实车路试验证,该优化方案可以满足油温签发要求。

陶瓷膜过滤器管束末端板开孔数量对流场影响的数值模拟

使用Fluent软件,模拟陶瓷膜管管束末端板上是否开孔以及开孔数量对膜过滤器内流场的影响。结果表明:膜管管束末端板上开孔可以增加流体流动空间,使末端板上、下表面处的流动死区减小,流体流速更加均匀;随着开孔数量的增加,流体位于末端板周围的最大流动速度得到有效降低,膜过滤器进、出口压降降低,膜过滤器内部流场的流动阻力减小,当开孔数量为12个时,膜过滤器内的流动效果最佳。