Unsteady mixed convective heat transfer of two immiscible fluids confined between long vertical wavy wall and parallel flat wall

The combined effects of thermal and mass convection of viscous incom- pressible and immiscible fluids through a vertical wavy wall and a smooth flat wall are analyzed. The dimensionless governing equations are perturbed into a mean part （the zeroth-order） and a perturbed part （the first-order）. The first-order quantities are ob- tained by the perturbation series expansion for short wavelength, in which the terms of the exponential order arise. The analytical expressions for the zeroth-order, the first-order, and the total solutions are obtained. The numerical computations are presented graph- ically to show the salient features of the fluid flow and the heat transfer characteristics. Separate solutions are matched at the interface by using suitable matching conditions. The shear stress and the Nusselt number are also analyzed for variations of the governing parameters. It is observed that the Grashof number, the viscosity ratio, the width ratio, and the conductivity ratio promote the velocity parallel to the flow direction. A reversal effect is observed for the velocity perpendicular to the flow direction.

Fluid Flow and Mixed Heat Transfer in a Horizontal Channel with an Open Cavity and Wavy Wall

Heat exchangers are utilized extensively in different industries and technologies.Consequently,optimizing heat exchangers has been a major concern among researchers.Although various studies have been conducted to improve the heat transfer rate,the use of a wavy wall in the presence of different types of heat transfer mechanisms has not been investigated.This study thus investigates the mixed heat transmission behavior of fluid in a horizontal channel with a cavity and a hot,wavy wall.The fluid flow in the channel is considered laminar,and the governing equations including continuity,momentum,and energy are all solved numerically.The numerical solution is stabilized by using a first-order multi-dimensional characteristic-based scheme in combination with a fifth-order Runge-Kutta method.The flow and heat transfer effects of varying Richardson numbers,Reynolds numbers,wave amplitude,wavelength,channel height,and cavity width are examined.The results indicate that the mean Nusselt number increases with an increase in Reynolds number,wave amplitude,and cavity width,while it decreases with an increase in Richardson number,wavelength,and channel height.The minimum Nusselt number is calculated to be 0.7,whereas the maximum Nusselt number is 27.09.The Nusselt number has only increased by 40%in the higher depths of the cavity,despite the Richardson number being 10,000 times larger.But this figure increases to 130%at lower depths.The mean Nusselt number is thus significantly influenced by channel height and cavity width.The influence of wave amplitude on the mean Nusselt number is twice that of wavelength.

The Continuum Analytical Method of Steel Frame- Reinforced Concrete Shear Wall Mixed Structure

The inter-story drift stiffness considered the semirigidity of beam and column joints connection, and P-Delta second order effect of steel frame parts in the mixed structure is presented in the paper. After considering on the influence of semirigidity between steel beams and steel columns, second order effect of beam-column members for steel frame and structural second order effect, the traditional continuum analytial method used in RC shear-frames wall structure is developed to steel frames-reinforced concrete shear wall mixed structure subject to horizontal load in this paper. A continuum approach, which is suitable for analyzing steel frames-reinforced concrete shear wall mixed structure subject to horizontal load, is presented. The method is relatively simple and more practical. It will be referred to structural design for steel frames-reinforced concrete shear wall mixed structure.

Soil-cement mixture properties and design considerations for reinforced excavation

soil-cement is a mixture produced by grouting or mixing cement with soils. This paper reviews and discusses the general classifications of grouting techniques and the suitability of their applications.The mechanical properties of soil-cement mixture and the influence of sodium silicate added are discussed. Design considerations for deep soil mixed wall(DSMW) for excavation support and vault arch for tunnelling stabilisation are presented. Parameters for the numerical analysis of soil-cement mixture are evaluated and recommended.

NUMERICAL CALCULATION OF THREE-STREAM MIXING FLOW WITH WALL COOLING

The flow and the temperature in the threestream mixing flow of the lobed nozzle mixer-ejector with double-wall diffuser are numerically investigated. The domain of computation is divided into sub-domalns according to the shapes of the double-plate and lobed nozzle. The three-dimensional body-fitted coordinated grids are generated respectively in these sub-domains by solving Lapalace's equations. Grids are dense on the boundaries and orthogonal at the lobe. The grids of all sub-domains compose the whole grid of the domain. In order to avoid the divergence of the computation as the serious non-orthogonality of the grid from the lobe, the co-located grid, SIMPLEC and Chen-Kim modified k-εturbulence model are applied. The great viscosity, the linear and simultaneous cooperation under-relaxation factors are used to solve the coupling of the fluid and solid. Results show that the air is ejected into the double wall section to form the cooling flow. The wall temperature of the double-wall diffuser is lower than that of the single-wall diffuser. The average wall temperature goes down as the diffuser angle increases at the range of 0～5°,otherwise, the result at the range of 5～10°is opposite.

Horizontal gas mixing in rectangular fluidized bed:A novel method for gas dispersion coefficients in various conditions and distributor designs

In a rectangular fluidized bed combustor, the tracer gas is injected continuously into the bed from a point source at the center of the distributor plate. In this study, a general governing equation is formulated for tracer gas dispersion in the bed. An analytical solution is derived to estimate the dispersion coefficients, Dxand Dy, in a horizontal plane. The concentration profiles at different sampling heights with various gas velocities are plotted.Subsequently, to estimate the dispersion coefficients, surface fitting of the obtained analytical solution to the experimental data is performed. The dispersion coefficients obtained from this model are compared with those of a conventional model. Additionally, the effect of walls, bed height and gas injection rate on the dispersion coefficients in a horizontal plane is investigated, and the effect of distributor design on the dispersion coefficients in a horizontal plane is investigated with different tracer positions. It is found that Dxand Dyare nearly equivalent at a lower tracer gas ratio of the injected gas to the total gas flow rate. It is also demonstrated that the effect of bed height on Dxis minor. This model is also able to estimate the dispersion coefficients in the case of a multihorizontal nozzle distributor.

EXPONENTIAL CONVERGENCE FOR NONLINEAR SPDES WITH DOUBLE REFLECTING WALLS

The present article is devoted to nonlinear stochastic partial differential equations with double reflecting walls driven by possibly degenerate,multiplicative noise.We prove that the corresponding Markov semigroup possesses an exponentially attracting invariant measure through asymptotic coupling,in which Foias-Prodi estimation and the truncation technique are crucial for the realization of the Girsanov transform.

Cyclic testing of moment-shear force interaction in reinforced concrete shear wall substructures

Previous quasi-static cyclic tests of shear walls,which routinely used an incremental lateral displacement test protocol with a constant axial load,failed to reflect the character of moment-shear force interaction of prototype buildings.To study the effect of the moment-shear force interaction on the seismic performance of shear walls,three identical 2-story shear wall specimens with different loading patterns were constructed at 1/2 scale,to represent the lower portion of an 11-story high-rise building,and were tested under reversed cyclic loads.The axial force,shear force and bending moment were simultaneously applied to simulate the effects of gravity loads and earthquake excitations on the prototype.The axial force and bending moment delivered from the upper structure were applied to the top of the specimens by two vertical actuators,and the shear force was applied to the specimens by two horizontal actuators.A mixed force-displacement control test program was adopted to ensure that the bending moment and the lateral shear were increased proportionally.The experimental results show that the moment-shear force interaction had a significant effect on the failure pattern,hysteretic characteristics,ductility and energy dissipation of the specimens.It is recommended that moment-shear force interaction should be considered in the loading condition of RC shear wall substructures cyclic tests.

渠式切割水泥土连续墙的应用和发展

作为超深、等厚、连续、可靠的截水挡土帷幕,渠式切割水泥土连续墙在国内有广泛应用。本文概括了渠式切割水泥土连续墙在国内的引进、应用和发展历程。结合对国内200多个既有应用案例的统计分析,研究了渠式切割水泥土连续墙的施工设备保有情况、成墙深度范围、常用墙体厚度和主要应用场景;罗列了渠式切割水泥土连续墙在复杂地层施工的辅助措施以及典型案例;指出了渠式切割水泥土连续墙在敏感环境微扰动施工的控制要点;介绍了渠式切割预制装配式混凝土连续墙的设计要求和用途,尤其是内插预制板材的截面设计和制造工艺;最后用工程实例表明渠式切割预制装配式混凝土连续墙同时继承了渠式切割微扰动和地下连续墙支护刚度好的特点,无论是切割成墙期间还是土方开挖期间,施工对周边环境的影响都较小。

烷烃类混合碳五馏分分离工艺模拟与优化

利用隔壁精馏塔替代混合碳五馏分原有分离流程中的脱丁烷塔和碳五预分离塔,通过Aspen Plus V12软件对混合碳五馏分的提纯流程进行稳态模拟,在此基础上运用灵敏度分析工具,对隔壁精馏塔的操作参数进行优化。结果表明:采用隔壁精馏塔替代脱丁烷塔和碳五预分离塔,最佳原料进料位置为第11块塔板、最佳质量回流比为5、最佳侧线采出位置为第7块塔板、最佳侧线采出量为500 kg h,气相回流位置为第37块塔板,液相回流位置为第12块塔板;在相同进料条件和相同碳五馏分纯度的前提下,与采用常规精馏工艺相比,采用隔壁塔精馏工艺时冷却能耗降低17.04%,加热能耗降低16.69%。

饱和地基中劲芯水泥土墙隔振的二维BEM-FEM耦合分析

振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基中劲芯水泥土墙的隔振问题,饱和地基采用饱和土半解析边界元法(boundary element method,BEM)建模,劲芯水泥土墙采用有限元法(finite element method,FEM)建模,根据饱和地基-水泥土墙交界面的平衡和连续性条件,分别建立了劲芯水泥土墙对入射Rayleigh波(瑞利波)的远场被动隔振和对动力机器基础振动近场主动隔振的半解析BEM-FEM耦合分析方法,并对劲芯水泥土墙的隔振效果进行了计算分析。研究结果表明:饱和地基中设置劲芯水泥土墙能够起到较好的隔振作用,其隔振效果与混凝土墙基本相当且远优于纯水泥土墙;预制芯墙在劲芯水泥土墙隔振系统中起关键作用,为避免弹性波从芯墙底绕射而降低隔振效果,预制芯墙深度应与水泥土墙深度保持一致;增大芯墙厚度对隔振效果提升不大。在等深芯墙条件下,增大墙深能显著提高远场隔振效果,但对近场隔振效果提升较小;增大墙厚也可提高隔振效果,但提高幅度不大。实际工程中,建议结合工程造价和施工工艺,选择合适的水泥土墙和预制芯墙墙厚。此外,屏障距振源距离对主动隔振效果影响较小,建议根据被保护建筑与振源之间的实际情况,选择合适位置构建隔振屏障。

地下障碍物众多的软土地区“两墙合一”施工技术

鉴于地下连续墙良好的围护性能与结构性能,“两墙合一”施工技术能最大限度地利用地下空间,因此被越来越广泛地应用于城市中心工程。沿海城市地质情况普遍较复杂,多为软弱土层,对地下连续墙成槽护壁质量要求高,通常采用TRD水泥土搅拌墙或三轴水泥搅拌桩两种工艺作为连续墙护壁兼外围护止水帷幕。通过结合工程实际对地下连续墙及其两侧护壁、内衬墙施工质量控制等关键技术进行研究分析,为类似复杂环境条件下的“两墙合一”施工提供参考。

一种融合KPCA、FastICA及SVD的腹壁源胎儿心电 信号提取算法研究

目的:为实现从母体腹壁混合信号中提取高信噪比和波形清晰的胎儿心电信号,提出一种融合核主成分分析(kernel principal component analysis,KPCA)、快速独立成分分析(fast independent component analysis,FastICA)及奇异值分解(singular value decomposition,SVD)的胎儿心电信号提取算法。方法:首先,采用KPCA对母体心电信号进行降维,再利用改进的基于负熵的FastICA处理降维后的数据,得到独立成分。随后,引入样本熵进行信号通道选择,挑选出包含最多母体信息的信号通道。在选中的母体通道上进行SVD,得到母体心电信号的近似估计,再用腹壁源信号减去该信号得到胎儿心电的初步估计。最后,采用改进的基于负熵的FastICA成功分离出纯净的胎儿心电信号。在腹部和直接胎儿心电图数据库(Abdominal and Direct Fetal Electrocardiogram Database,ADFECGDB)和PhysioNet 2013挑战赛数据库中对提出的算法进行验证。结果:提出的算法在主观视觉效果和客观评价指标上都表现出优越的性能。在ADFECGDB数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.74%、98.85%和99.30%;在PhysioNet 2013挑战赛数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.10%、97.87%和98.48%。结论:融合KPCA、FastICA及SVD的胎儿心电信号提取算法在提取胎儿心电信号的同时有效处理了附加噪声,为胎儿疾病的早期诊断提供了有力支持。

Velocity transformation for compressible wall-bounded turbulence——An approach through the mixing length hypothesis

In an endeavor to establish a connection between the mean velocity profile in compressible wall-bounded turbulence and its incompressible analogue,a refined version of the Trettel and Larsson's(TL)transformation is systematically derived and rigorously assessed across diverse flow scenarios.Incorporating the recently proposed intrinsic compressibility effects and modeling the multi-layer structure of mixing lengths,the proposed transformation demonstrates exceptional performance in collapsing 57canonical flow cases,including cooled channel and pipe flows,channel flows with pseudo heat sources,as well as adiabatic and diabatic boundary layer flows.Furthermore,the transformation seamlessly extends to low Reynolds number cooled channel and pipe flows,achieving a level of accuracy unparalleled by other transformations in the current state-of-the-art.

The effect of side walls on particles mixing in rotating drums

In this paper, we study the effects of the presence and shape of side walls and of the overall length of rotating cylindrical drums on the mixing of particles with differing sizes by application of the discrete element method (DEM). By varying the semi-axis of the spheroidally shaped side walls and the length of the overall drum, we observe the formation of circulation patterns near the side walls. Although there is a vast amount of literature studying mixing regimes in rotating drums, little is known about the effect of the side walls of the drum on particle mixing. The results of our study demonstrate that introducing curved side walls induces a strong circulation pattern near these side walls, but has, paradoxically, a negative impact on mixing and actually promotes segregation. The cause for this segregation is the difference in velocity of differently sized particles near the curved side walls. Large particles accumulate at the curved side walls, whereas small particles move away from the curved side walls. When the length of the drum is increased, the overall effect of the side walls is decreased, although it does remain observable, even in very large drums.

高土石坝心墙砾石土料掺配施工技术

高砾石土心墙土石坝防渗体砾石土料的质量对坝体结构稳定和长期安全运行至关重要,通过对不同土料掺配施工技术研究,制定出精确掺配的相关施工工艺参数,解决了常规施工存在的诸多问题,提高了高土石坝砾石土料掺拌和填筑施工质量,节约了工程施工成本,确保了坝体结构稳定和运行安全,为工程正常有序施工及完建创造了良好的条件。

弹性建筑涂料不合格配方的新特点研究

论文分析了弹性建筑涂料的标准、性能影响因素和拉伸性能的分布规律;提出了按照新标准仍有3种不合格配方的分类;给出了每种分类的样品的拉伸曲线特点和动态热机械分布规律。论文加深了对弹性建筑涂料混拼类产品的理解,提出的分析测试方法能够指导混拼类产品的配方研发。

预制H型混凝土板桩在软土地区深大基坑中的应用

以上海天安豪园二期C区项目为例,将五轴搅拌桩内插预制H型混凝土板桩应用到上海软土地区地下2层基坑中。详细介绍了H型板桩的设计方法、施工要点,采用规范算法预测基坑开挖期间围护结构变形,并与现场实测数据进行对比分析,结果表明,支护结构及周边环境均处于安全稳定状态,从而验证H型板桩围护的有效性。

复合黏土心墙材料在土石坝中的应用分析

本文结合东阿水库大坝,对具有垂直心墙和两种不同材料纯黏土和混合黏土的土坝进行了一系列数值分析,并结合大坝施工期间心墙内的固结条件完全不排水和部分排水条件两种类型进行了分析。分析结果表明:对于完全不排水,当岩芯由纯黏土组成时,施工期间岩芯内产生的超孔隙水压力相对较高。对于部分排水,两种类型岩心中的超孔隙水压力值取决于施工和固结速率,如果岩芯排水受阻,则由纯黏土组成的岩芯中的沉降相对较高。当允许固结岩芯时,由纯黏土和混合黏土组成的岩芯沉降差异不大。由纯黏土材料组成的岩心的水平位移值高于由混合黏土组成的岩心的相应值,应进行进一步推广及应用。

不同搅拌方式下多壁碳纳米管对UHPC力学性能的影响研究

研究双卧轴搅拌和振动搅拌2种搅拌方式对掺入多壁碳纳米管(MWCNTs)的超高性能混凝土(UHPC)拌合物性能和力学性能的影响,结果表明,掺入MWCNTs后,UHPC的拌合物性能在双卧轴搅拌时明显降低,在振动搅拌时变化不大;采用双卧轴搅拌和振动搅拌,掺入MWCNTs均能一定程度提高UHPC的轴心抗压、弹性极限轴心抗拉及抗弯性能,且振动搅拌的效果更优;采用振动搅拌,MWCNTs掺量为0.05%时,与空白组相比,UHPC的轴心抗压、轴心抗拉及抗弯强度分别提高了3.0%、30.0%、38.0%,弯曲韧性指数I_(5)、I10、I_(20)分别增大了50.8%、71.6%、85.6%,弯曲韧性比提高了63.7%,MWCNTs具有很好的增强增韧效果。