Study on Hydrodynamic Coefficients of Double Submerged Inclined Plates

Added mass and damping coefficients are very important in hydrodynamic analysis of naval structures. In this paper,a double submerged inclined plates with ‘/\’ configuration is firstly considered. By use of the boundary element method(BEM) based on Green function with the wave term, the radiation problem of this special type structure is investigated. The added mass and damping coefficients due to different plate lengths and inclined angles are obtained. The results show that: the added mass and damping coefficients for sway are the largest. Heave is the most sensitive mode to inclined angles. The wave frequencies of the maximal added mass and damping coefficients for sway and roll are the same.

Numerical Solution of MHD Convection and Mass Transfer Flow of Viscous Incompressible Fluid about an Inclined Plate with Hall Current and Constant Heat Flux

The present numerically study investigates the influence of the Hall current and constant heat flux on the Magneto hydrodynamic (MHD) natural convection boundary layer viscous incompressible fluid flow in the manifestation of transverse magnetic field near an inclined vertical permeable flat plate. It is assumed that the induced magnetic field is negligible compared with the imposed magnetic field. The governing boundary layer equations have been transferred into non-similar model by implementing similarity approaches. The physical dimensionless parameter has been set up into the model as Prandtl number, Eckert number, Magnetic parameter, Schmidt number, local Grashof number and local modified Grashof number. The numerical method of Nactsheim-Swigert shooting iteration technique together with Runge-Kutta six order iteration scheme has been used to solve the system of governing non-similar equations. The physical effects of the various parameters on dimensionless primary velocity profile, secondary velocity profile, and temperature and concentration profile are discussed graphically. Moreover, the local skin friction coefficient, the local Nusselt number and Sherwood number are shown in tabular form for various values of the parameters.

Chemical Reaction and Thermal Diffusion Effects on Mass Transfer Flow through an Inclined Plate

A numerical investigation of boundary layer mass transfer flow through an inclined plate with the effect of chemical reaction and thermal diffusion is presented in this study. The governing partial differential equations (PDE) are transformed to a system of dimensionless non-similar coupled PDEs. The transformed, non-similar conservations equations (momentum balance equation, energy balance equation and concentration balance equation) are then solved using a numerical approach known as explicit finite difference method (EFDM). Basically EFDM introduced for the unsteadiness in the momentum, temperature, and concentration fluid fields is based on the time dependent fluid velocity, temperature and concentration of the boundary surface. During the course of discussion, it is found that the various parameters related to the problem influence the calculated resultant expressions. The computed numerical solution results for the velocity, temperature, and concentration distribution with the effect of various important dimensionless parameters (Grashof number, Modified Grashof number, Prandtl number, Schmidt number, Soret number, Dufour number, chemical reaction parameter and inclination parameter) entering into the problems are critically analyzed and discussed graphically. It can be seen that two physical phenomena chemical reaction and thermal diffusion can greatly effect on the boundary layer fluid flows through an inclined plate.

Fluid flow characteristics of single inclined circular jet impingement for ultra-fast cooling

The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technology.The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters,and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction,and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s.However,the fluid flow velocity is relatively smaller near the stagnation point,and increases gradually along the radius outwards,then declines.There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°,jet diameter is 5 mm,jet length is 8 mm and jet height is 50 mm.

Numerical Modelling of Non-similar Mixed Convection Heat and Species Transfer along an Inclined Solar Energy Collector Surface with Cross Diffusion Effects

An analysis is performed to study thermo-diffusion and diffusion-thermo effects on mixed convection heat and mass transfer boundary layer flow along an inclined (solar collector) plate. The resulting governing equations are transformed and then solved numerically using the local nonsimilarity method and Runge-Kutta shooting quadrature. A parametric study illustrating the influence of thermal buoyancy parameter (&#950), Prandtl number (Pr), Schmidt number (Sc), Soret number (Sr), Dufour number (Du) and concentration-to- thermal-buoyancy ratio parameter, N, on the fluid velocity, temperature and concentration profiles as well as on local skin-friction, Nusselt and Sherwood numbers is conducted. For positive inclination angle of the plate (&#947 = 70 degrees), flow velocity (f') is strongly increased i.e. accelerated, with thermal buoyancy force parameter (&#950), in particular closer to the plate surface;further into the boundary layer, &#950 has a much reduced effect. Conversely temperature (&#952) and concentration (&#968) is decreased with increasing thermal buoyancy parameter, &#950. For negative plate inclination, the flow is accelerated whereas for positive inclination it is decelerated i.e. velocity is reduced. Conversely with negative plate inclination both the temperature and concentration in the boundary layer is reduced with the opposite apparent for positive inclination. Increasing Prandtl number strongly reduces temperature in the regime whereas an increase in Schmidt number boosts temperatures with temperature overshoots near the plate surface for Sc = 3 and 5 (i.e. for Sc > 1). Concentration is reduced continuously throughout the boundary layer, however, with increasing Schmidt number. A positive increase in concentration-to-thermal-buoyancy ratio parameter, N, significantly accelerates the flow in the domain, whereas negative N causes a deceleration. A velocity overshoot is also identified for N = 20, at intermediate distance from the plate surface. Negative N (thermal and concentration buoyancy forces oppose each other) induces a slight increase in both fluid temperature and concentration, with the reverse observed for positive N (thermal and concentration buoyancy forces assisting each other). Increasing Dufour number respectively causes a rise in temperature and a decrease in concentration, whereas an increase in Soret number cools the fluid i.e. reduces temperature and enhances concentration values. In the absence of Soret and Dufour effects, positive N causes a monotonic increase in local Nusselt number, NuxRex-1/2 with &#950 Cos &#947, for N = -1 the local Nusselt number remains constant for all values of parameter, &#950 Cos &#947. Local Sherwood number, ShxRex-1/2 is boosted considerably with higher Schmidt numbers and also with positive N values. The computations in the absence of Soret and Dufour effects correlate accurately with the earlier study by Chen et al. (1980).

Thermal criticality for a reactive gravity driven thin film flow of a third-grade fluid with adiabatic free surface down an inclined plane

This study is devoted to the investigation of thermal criticality for a reactive gravity driven thin film flow of a third-grade fluid with adiabatic free surface down an inclined isothermal plane. It is assumed that the reaction is exothermic under Arrhenius kinetics, neglecting the consumption of the material. The governing non-linear equations for conservation of momentum and energy are obtained and solved by using a new computational approach based on a special type of Hermite-Padé approximation technique implemented in MAPLE. This semi-numerical scheme offers some advantages over solutions obtained with traditional methods such as finite differences, spectral method, and shooting method. It reveals the analytical structure of the solution function. Important properties of overall flow structure including velocity field, temperature field, thermal criticality, and bifurcations are discussed.

Influence of melt pouring temperature and plate inclination on solidification and microstructure of A356 aluminum alloy produced using oblique plate

The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by counter flowing water. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed/fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. Melt pouring temperature provides required condition of solidification whereas plate inclination enables necessary shear for producing semisolid slurry of desired quality. Slurry obtained was solidified in metal mould to produce semisolid-cast billets of desired microstructure. Furthermore, semisolid-cast billets were heat treated to improve surface quality. Microstructures of both semisolid-cast and heat-treated billets were analyzed. Effects of melt pouring temperature and plate inclination on solidification and microstructure of billets produced using oblique plate were described. The investigations involved four different melt pouring temperatures (620, 625, 630 and 635 °C) associated with four different plate inclinations (30°, 45°, 60° and 75°). Melt pouring temperature of 625 °C with plate inclination of 60° shows fine and globular microstructures and it is the optimum.

软岩地基中新型倒肋式风机基础力学性能有限元分析

目的 提出一种新型倒肋式风机基础,解决软岩地基中采用梁板式风机基础带来的挖方量大、模板支设繁琐、施工成本高、周期长等问题。方法 以2.5 MW风机为例,采用ABAQUS有限元分析软件,建立相同尺寸的倒肋式与梁板式风机基础模型,对比两种基础在极端工况下的倾斜率、水平位移、破坏特征等,并结合挖方量、模板工程量对两者的经济性进行分析。结果 倒肋式基础的水平位移为0.444 mm、倾斜率为0.012 1%,均满足规范要求;倒肋式基础的肋梁受力特征与悬臂梁相似,在基底反力作用下肋梁与墩台连接处承受的剪力及弯矩较大,容易开裂破坏,可通过增加肋梁截面高度改善;倒肋式基础相较于梁板式基础土方挖量可节省54%、模板工程量可节省48%。结论 倒肋式基础充分发挥出了倒置肋梁与软岩地基之间齿槽嵌固的优势,相较于梁板式基础不仅具有更优的抗滑移稳定性和受力性能,而且减少了挖方和模板工程量,经济效益显著。

汽车激光雷达盖板的双色注塑模具设计

根据某车型激光雷达盖板的双色结构及形状,采用动模型芯旋转式结构的模具方案,设计了一套一出二的热流道双色注塑模具。利用Moldflow软件进行了双色成型分析,双色注塑第一次注射成型透明的PMMA材料的产品,第二次注射成型黑色ASA材料的产品。为实现该双色产品的结构成型,在定模处设计了2组不同结构的型腔,在动模处设计了2组左右对称的型芯,并且,在型芯侧设计了双斜导柱抽芯机构,冷却系统设计为“直通式+隔水片”的随形循环水路;顶出系统设计为2组独立的液压油缸,在产品顶出取件中,第一次注射成型的PMMA产品不顶出,第二次注射成型的ASA材料的产品采用“直顶+斜顶”的组合机构将双色产品推出,最终通过机械手完成产品的取件。实践生产证明了该双色模具结构合理、运行稳定、成型的双色塑件表面无缺陷。

倾角对平板型LHP 运行性能的影响

通过改变内部毛细芯结构达到改善环路热管性能、减小环路热管体积的目的,取消储液腔,将传统的长矩形蒸汽槽道更改为特斯拉阀形状,并且将蒸发器进出口设置在蒸发器两侧。研究该热管在不同倾角下的启动性能、运行特性。结果显示:相对于0°倾角运行,倾角的存在能够减少环路热管的启动时间,降低蒸发器温度,存在倾角的条件下启动特性差别不大。随着功率的增加,不同倾角的环路热管热阻减小,仅在倾角(10°以下)较低时有较大的热阻。随着倾角的增加,环路热管热阻随功率的变化无较大改变。

基于CFD的斜板沉淀池沉淀特性分析

采用欧拉-拉格朗日方法研究了普通斜板沉淀池内水流的流态,利用单向耦合的离散项模型(DPM),计算了普通斜板沉淀池在不同工况条件下颗粒沉积特性及池内流动特性。针对普通斜板沉淀池沉淀效果差,颗粒容易再次上浮,设计了一种改良V型斜板沉淀池,并且结合标准k-ε模型,利用PISO算法,通过北京云超算中心计算了不同颗粒粒径下改良V型斜板沉淀池内颗粒运动的轨迹。结果表明:使用改良V型斜板后,颗粒物的沉降性路径减小,但是涡流强度增加,此时能量耗散更快,有利于固液分离;粒径大的颗粒也更容易沉淀。

Experimental and numerical investigations on acoustic damping of monoclinic crystalline wideband sound absorbing structures

In order to overcome the limitations of traditional microperforated plate with narrow sound absorption bandwidth and a single structure,two multi-cavity composite sound-absorbing materials were designed based on the shape of monoclinic crystals:uniaxial oblique structure(UOS)and biaxial oblique structure(BOS).Through finite element simulation and experimental research,the theoretical models of UOS and BOS were verified,and their sound absorption mechanisms were revealed.At the same time,the influence of multi-cavity composites on sound absorption performance was analyzed based on the theoretical model,and the influence of structural parameters on sound absorption performance was discussed.The research results show that,in the range of 100-2000 Hz,UOS has three sound absorption peaks and BOS has five sound absorption peaks.The frequency range of the half-absorption bandwidth(α>0.5)of UOS and BOS increases by 242% and 229%,respectively.Compared with traditional microperforated sound-absorbing structures,the series and parallel hybrid methods significantly increase the sound-absorbing bandwidth of the sound-absorbing structure.This research has guiding significance for noise control and has broad application prospects in the fields of transportation,construction,and mechanical design.

水平冻结中导向板钻具组合造斜能力的影响因素研究

目前水平冻结孔定向钻进中,导向板钻具组合的使用存在造斜理论不明的问题。基于材料力学理论,以钻头转角形变量为造斜评价指标,结合冻结法特点建立钻具造斜力学模型,并讨论参数的影响,同时结合实测数据验证该模型的可行性。结果表明:(1)导向板钻具组合钻头转角与岩土层物理力学参数、钻具抗弯刚度、导向板钻头的结构参数(如导向角,钻具长度,导向板斜面面积)、钻具面向角相关;(2)全角变化率在钻具面向角接近0°时最小,接近䥺SymbolqB@180°时最大,其余钻头转角变化均在此范围内,并随着导向角的增大而增大;(3)随着岩土层强度提高,相同导向角对应的全角变化率更大,导向板钻具组合的造斜能力更强。

改良斜管沉砂和旋流除砂在汉江中下游原水预处理中的应用

汉江承担着重要的水资源供应任务,其下游含有较多粒径在200μm以下的微细砂,给水厂处理系统带来了一系列问题。以汉江中下游原水迁改工程为例,介绍了“改良斜管沉砂+旋流除砂”工艺在工程中的应用情况,并通过旋流除砂工艺对废水进行除砂回用,形成了一套较好的微细砂沉降去除及废水回收利用工艺,既满足了标准要求,又实现每天节约水量约1.7‰,为含微细砂预处理设计提供经验。

倾斜式钢箱拱结构分析与设计

钢箱拱应用广泛,以往的研究主要针对竖直的拱或水平的曲梁,对于倾斜钢箱拱研究较少。该文采用板单元对倾斜钢箱拱进行数值模拟,在考虑几何非线性和材料非线性的情况下模拟失稳的全过程,并对内力变化和极限稳定状态下的变形、应力分布进行分析。分析表明,倾斜钢箱拱从局部屈曲到整体失稳发展很快,工程中应注意稳定承载力的安全储备;倾斜钢箱拱的第二体系影响很大,钢箱拱的构造直接影响局部变形和第二体系应力,工程中应注意合理布置。

悬挑式下挂箱形结构施工技术总结及概述

针对具有岭南特色的“歇山顶”建筑风格而采用的悬挑式下挂箱形结构传统施工工艺遇到的材料浪费严重、质量差、工效低、成本高等问题,广东仲元中学第二校区工程项目技术团队通过分析该项目下挂式箱形结构的特点,通过将传统现浇结构优化为预制斜挂板单元式构件与现浇楼板支模体系相结合的施工技术,实现了悬挑式下挂箱形结构装配化、标准化、快速施工、绿色环保和降本增效等多个目标。

固定矫治器结合斜面导板联合矫治安氏Ⅱ类1分类错[牙合]的疗效

目的分析固定矫治器与斜面导板联合矫治安氏Ⅱ类1分类错[牙合]的疗效。方法选取2020年10月—2023年10月新沂市人民医院口腔科收治的99例安氏Ⅱ类1分类错[牙合]患者作为研究对象,根据不同矫治方法分为两组,对照组(n=45,固定矫治器)、观察组(n=54,固定矫治器结合斜面导板)。比较两组患者矫治情况(牙齿排列、后牙边缘嵴高度、牙根远近中倾斜度)、模型测量值(覆合、覆盖)、临床疗效。结果治疗前,两组矫治情况各项评分、模型测量值对比,差异无统计学意义(P均>0.05)。治疗后,两组牙齿排列、后牙边缘嵴高度、牙根远近中倾斜度评分及覆合、覆盖值均低于治疗前,且观察组牙齿排列、后牙边缘嵴高度及牙根远近中倾斜度评分均低于对照组,差异有统计学意义(P均<0.05)。治疗后,组间模型测量对比,观察组覆盖值低于对照组,差异有统计学意义(P<0.05)。观察组治疗有效率(98.15%)(53/54)高于对照组(86.67%)(39/45),差异有统计学意义(χ^(2)=4.924,P<0.05)。结论安氏Ⅱ类1分类错[牙合]患者矫治中选择固定矫治器联合斜面导板,矫治效果更佳,覆盖关系有所改善的同时,临床疗效更加显著。

付村选煤厂粗煤泥回收系统技术改造实践

为解决付村选煤厂在粗煤泥回收工艺系统中存在的问题,通过采取对倾斜板沉淀器系统升级、使用ZKJ系列叠层筛替代原分级旋流器+高频筛工艺系统、优化筛下水管理等措施完成了粗煤泥回收系统改造。改造结果表明:解决了倾斜板沉淀器错配物较多,分级效果差,高频筛筛下水跑粗、筛上物灰分高的问题;保证了选煤厂粗煤泥环节高效稳定运行,提高了粗精煤回收率,减轻了浮选系统负荷,避免了重介精煤“背灰”问题。

钢箱梁与倾斜钢墩连接节点受力性能分析

文章以某人行景观天桥为工程背景,通过有限元分析,获得了钢箱梁与倾斜钢墩连接节点的应力分布状态。研究结果表明,对于倾斜钢墩与钢箱梁的连接,锐角侧应力集中现象明显强于钝角侧,实际工程中应注意锐角侧受力情况。在应力集中部位,墩梁连接点处先进入塑性,同时von Mises应力值随加载历程呈现出先直线上升,后趋于平缓的上升趋势;在连接节点处,钢墩的加劲肋端部会出现应力集中现象,若在该部位对应的钢箱梁底板处设置加劲肋或补强钢板,可大幅减小应力值。因此,在钢结构桥梁的设计中,应在钢墩与钢箱梁底板连接处设置加劲肋,以提高桥梁的稳定性。

大万山隧道通风斜井中隔墙优化设计方案研究

大万山隧道设有两道通风斜井,长度共计3155m。原设计斜井中隔墙采用钢筋混凝土结构。鉴于钢筋混凝土中隔墙施工进度较慢,延缓整体工期,故文章提出将中隔墙优化为波纹钢板中隔墙的设计方案。该优化方案契合国家推广使用钢结构的理念,可降低施工难度,加快施工进度。经过结构受力验算,采用波纹钢板中隔墙满足受力要求,该方案具有可行性。