冷却水工程中湍浮力射流的三维数值模拟

本文作者针对冷却水工程的实际问题，应用浮力修正的ｋ－ε双方程湍流模型及控制容积法，对有横向来流条件下的表面湍浮力射流进行了三维的数值模拟，成功地预测了由温度引起的分流现象，拓宽了湍流模型在该领域的应用。     

同流中不同流速比对多孔热浮射流的影响

利用雷诺应力模型对同向流动环境中3孔热水浮射流进行数值模拟,得出了不同流速比下的速度场,温度场,并对结果进行了对比分析。探讨了不同流速比时各股射流之间的相互影响,最后得出3种流速比下的射流轨迹线。     

湍浮力射流形成区内特性的预报

应用作者所提出的数学模型和计算方法,对浮力射流形成区内的特性进行了预报。得出了形成区内中线流速、温度和湍动能的沿程变化,以及射流核的长度和掺入速度。也得出了流速、温度和湍动能在断面上的分布。并分析和讨论了出口条件及环境分层对这些特性的影响。     

湍浮力射流形成后区特性的预报

应用作者所提出的数学模型和计算方法,对浮力射流形成后区的特性进行了预报。得出中性浮力点以前的形成后区,可分为非浮力区、过渡区和卷流区。得到了非浮力区和卷流区的时均流速、时均温差、雷诺切应力、湍动能及其耗散率的分布和湍动能的平衡。这些预报结果与试验资料基本吻合。     

矩形槽中矩形边墩周围流速分布试验研究

利用声学多普勒流速仪,对矩形断面明渠中矩形边墩周围三维流速进行测量,并对时均流速3个方向分量进行了研究.通过对边墩周围不同垂直及水平面流速的分析表明:受柱体的影响,柱体上游行进水流与壁面产生分离,并有涡旋产生;柱体下游纵向水流逆向运动,产生回流,横向流速和垂向流速非常小,可以忽略不计.     

非静态环境中负浮力射流模拟研究

以计算流体学软件Fluent为基础,通过求解基于雷诺数平均法(RANS)的标准紊流模型对非静态环境中第一种形式的负浮力射流进行了模拟和研究,并用Tecplot处理了Fluent计算求得的曲线,由此得出了该种形式的负浮力射流从开始到结束过程中不同时刻的水流流态图以及整个流动过程的流线分布图。将模拟结果与理论计算结果进行对比、分析,表明该模拟结果与理论计算结果和实际情况吻合,说明该模型和方法能够计算此类负浮力射流。     

脉冲式浮射流水力特性的实验研究

目前污水的海洋排放方式可大致分为 2种 :恒定或准恒定流量排放 ;脉冲式的非恒定排放。对工程中更为常见的脉冲式排放在环境受纳水体中的浮射流运动特性 ,动量尺度、底边界对浮射流的影响进行实验研究 ,此项研究方法及初步成果为河底射流冲淤排沙研究工作奠定了基础。     

大底坡复合圆弧曲线急流弯道水力特性试验研究

西安市黑河引水一期工程－石砭峪水库泄洪洞弯段布置为大底坡急流弯道，为调整其体形和水流流态，进行了水工模型。根据隧洞已开挖成洞的现状，又要较好地控制道段水流态的要求，试验中道对不同弯道体形进行了多次比较和修改，其中复合圆弧曲线弯道体形较好地控制了急流大弯道大流流态。     

“Meandering” Effects on the Diffusion of Continuous Dye Plumes in Coastal Currents

Experimental data on the diffusion of fluorescent dye plumes were obtained in the nearshore zone of the Great Lakes. The transport and diffusion of continuous dye plumes may be studied either in a frame of reference moving with the centre of gravity of the plume or in a frame of reference fixed to the stationary source. Conventionally, the former is referred to as “relative” diffusion and the latter as “absolute” diffisuion. The inter-link between the two concepts is explained by the random movements of the centre of gravity of the diffusing dye plume usually referred to as the “meandering”.In the past, experimental data from continuous dye plumes in coastal currents have been used to study “relative” diffusion, neglecting the random movements of the centre of gravity. In reality, however, “meandering” appears to be a more efficient agency than “relative” diffusion from the practical point of view of dispersing effluents over larger volume of the water body.In the present analysis, particular attention is given to delineate the two component physical processes of “relative” diffusion and “meandering” diffusion, by extended sampling of the dye plume to cover time scales of both the processes. Calculated horizontal eddy diffusivity K_y in “absolute” diffusion is greater by a factor of 2 as compared to “relative” diffusion. Very high peak/mean concentration ratios observed as the centre of the plume are a direct result of “meandering” due to large scale turbulent eddies.     

浅水型同流污水排放近区稀释特性

用三维湍流模式结合混合有限分析法对浅水型同流情况下污水排放的近区稀释特性进行了数值计算，与Ｐａｒｒ和ＭｃＧｕｉｒｋ的试验资料进行了对比，两者吻合较好，进而给出了温度和速度的沿程变化规律以及浮力射流的分叉现象。     

Tracking River Plumes with Volatile Halocarbon Contaminants: The Niagara River—Lake Ontario Example

The concentrations of six predominant volatile halocarbon contaminants CCl₄, total and industrial CHCl₃, CHBrCl₂, CH₂Cl₂, CFCl₃, and C₂Cl₄ in epi- and hypolimnetic lake waters are used to demonstrate tributary plumes and nearshore currents on the Lake Ontario/Niagara River example. The relative speed and sensitivity of the analysis for volatile halocarbons provides for a synoptic view of the major currents at the time of sampling. For example, the individual distributions of several contaminants indicate the existence of a Niagara River surface water plume in northerly direction for approximately 8 km into the lake. In contrast, the predominantly east-west isostats of the contaminant concentrations in the hypolimnetic water indicate little direct influence by the Niagara River and show the existence of other contaminant sources in these areas.     

The Impact of Surface Heat Flux and Wind on Thermal Stratification in Portage Lake,Michigan

Portage Lake is situated near the center of the Keweenaw Peninsula and is connected to Lake Superior via lengthy (> 7 km) navigation channels. Using moored thermistor records and meteorological data, we examine how changes in lake stratification are related to surface winds and heat flux. Frequent episodes of full water column mixing are observed throughout the summer. Convective mixing through surface cooling appears to be an important agent responsible for these events, as all occur during cold air outbreaks and when the net heat flux is directed out of the lake (negative). However, wind-induced mixing is also implicated in contributing to some vertical mixing events, as evidenced by two events initiated during a period of strong winds and declining, but not yet negative, heat fluxes. Our analysis indicates that each time the water column restratifies, it tends to become more susceptible to convectively-driven overturn during cold air outbreaks. This tendency is quantified by the estimated time over which surface cooling due to a specified set of conditions, characteristic of a cold air outbreak, would reduce the temperature contrast between the upper and lower layers by half. This time declines by more than an order of magnitude for successive restratification events observed in the summer of 1999. Our analysis also reveals successive formation and dissolution of a diurnal surface mixed layer in an otherwise homogeneous water column during a 10-day period of August 1999. This is attributed to the combination of relatively light winds and negative daily net heat fluxes.     

大型多槽式矩形渡槽结构静力分析

根据大型多槽式矩型渡槽槽身结构及其受力特点,采用结构力学法使复杂的空间结构分离成相互联系的两个平面问题:横向计算时,横梁底部弹性支承在各纵梁上,根据力法位移协调理论,给出了双槽式和三槽式渡槽横向结构弹性支承反力的计算公式,并依此求得结构的横向受力与弹性支承反力;以弹性反力作为荷载,反向作用于纵梁上,从而进行纵向梁的受力分析。通过三维实体有限元软件(MIDAS)对某大型三槽式渡槽单跨槽身整体进行了建模分析,并将结构力学法和有限元法计算所得结果进行了比较分析,验证了方法的合理性和公式的准确性。利用其进行渡槽结构计算,能满足工程设计的精度要求。     

碾压混凝土坝上游面设短缝对温度应力的影响

1 引言 广西壮族自治区百色水利枢纽工程主坝为碾压混凝土重力坝,坝顶高程234.00m,顶宽10m,最大坝高130m,坝底宽约100m。坝体除基础垫层混凝土为R_(28)=20MPa的常态混凝土外,其余均为碾压混凝土。坝体上游面防渗体采用R_(180)=20MPa碾压混凝土,下游面164.00～220.00m高程设6m厚的R_(180)=20MPa的碾压混凝土,其余部位均为R_(180)=15MPa的碾压混凝土。根据枢纽布置要求和经过多方案比较,最后确定大坝横缝间距为27m,经计算分析,坝体上游面沿坝轴线方向拉应力仍然比较大。因此,为了优化设计,提出坝体上游面设短缝方案。本文采用三维有限元浮动网格法,按照设计施工进度安排和碾压混凝土浇筑温度,对坝段上游面设短缝和不设短缝方案分别进行了仿真计算。结果表明,坝段上游面设3m深短缝后,可以大大减小坝体上游面及附近的拉应力。     

矩形容器内流体晃动的数值模拟

本文应用ＭＡＣ方法对矩形容器内一层和两层流体由水平激振所引发的晃动进行了数值模拟。计算取与容器固联的坐标系，视激振加速度为质量力，计算结果在流场的形态等方面与实验观测基本一致。     

矩形明渠消力池水跃的水头损失研究

为了研究沿程水头损失与局部水头损失的变化规律,根据沿程水头损失的基本定义,推求矩形明渠消力池水跃区沿程水头损失与床面阻力系数、水跃共轭水深比、跃前断面宽高比及跃前断面水深的理论关系,提出了矩形明渠水跃区沿程水头损失及其系数和局部水头损失系数的理论公式,给出了沿程水头损失系数、局部水头损失系数和总水头损失系数的简单拟合公...     

大型矩形渡槽全程动态跟踪分析

采用大型有限元软件ANSYS,以双洎河矩形渡槽为研究对象,对其整体结构在施工期与运营期的应力、位移情况进行了分析,得出了槽身混凝土材料在不同受力阶段的力学行为变化规律,为今后类似渡槽的设计和施工提供了理论依据。     

矩形渠槽水面线的解析近似算法

采用常规的分段求和法完成矩形断面明渠水面线计算,不但存在误差累积且计算工作量大、效率低。依据优化拟合理论,以标准剩余差最小为目标函数,在工程适用参数范围内,经拟合计算获得了由一个简化通用算式替代原积分中的不可积函数,不但实现了由差分逐断面推算改为直接完成求解,且由于正、负拟合误差的相互抵消,使最终计算成果的精度进一步提高。利用该近似公式完成矩形断面明渠水面线计算,可使求解过程大大简化,工作效率明显提高,具有实用推广意义。     

矩形明渠边界平均剪切应力变化规律研究

针对棱柱型矩形明渠的特点 ,在分析均匀流运动机理的基础上 ,认为水流可以分为河床作用部分和岸壁作用部分 ,各部分分别作均匀流运动。在分析水体能量消耗的物理模式的基础上 ,提出了面积分割的补充关系。对于河床和岸壁糙率相同的情况 ,利用静力平衡条件和水流连续方程 ,可推得水流槽底、岸壁剪应力的计算关系式。对关系式的讨论表明 ,公式结构合理 ,能反映明渠水流的特点。对已有水槽试验资料进行的分析表明本文提出的计算关系式较好地描述水流的实际情况 ,比已有的公式更简便可靠。     

矩形断面收缩水深的简化计算法

针对目前矩形断面收缩水深计算方法存在的计算繁复、结果精度不高等问题,经过对矩形断面收缩水深基本方程的进一步整理,引入幂级数展开并经适当简化,获得了形式较为简单的迭代初值函数,经一次迭代后通过数学方法推求出了表达形式简单、容易记忆、计算简捷、便于实际应用、成果精度可靠的近似计算公式,通过精度分析及计算举例表明,在工程实用范围内(即0<α≤0.4,α为无量纲水深),计算相对误差小于0.54%,具有较好的应用推广价值。