Experimental hydrodynamic study of the Qiantang River tidal bore

To study the hydrodynamics of tidal bore, a physical modeling study is carried out in a rectangular flume with considerations of the tidal bore heights, the propagation speeds, the tidal current velocities, the front steepness, and the bore shapes. After the validation with the field observations, the experimental results are analyzed, and it is shown that: (1) the greater initial ebb velocity or the larger initial water depth impedes the tidal bore propagation, (2) the maximum bore height appears at an initial ebb velocity in the range of 0.5 m/s-1.5 m/s, (3) when the Froude number exceeds 1.2, an undular bore appears, after it exceeds 1.3, a breaking bore occurs, and after it exceeds 1.7, the bore is broken.     

Experimental study of simple flumes with trapezoidal contraction

There are different devices available for measuring the flow discharge. Static measuring devices such as weirs and flumes (without any moving parts) play a significant role in discharge measurement in open channels. Many researchers have focused on application of flumes in irrigation networks. This investigation set out to study the flow discharge through a trapezoidal cut-throated flume (TCTF). The flume is simply constructed by placing two triangular plates on either side of a rectangular open channel to form a trapezoidal throat. The channel cross section is rectangular while throat cross section of the flume is trapezoidal. The proposed flume is simple, low-cost, easy to install and does not require high maintenance. The present study was designed to determine the effect of different variables on the flume discharge. For this, an experimental study was carried out under free outflow conditions and under upstream subcritical flow regime to formulate the flume discharge. Three models are defined for flume discharge relation based on the Buckingham's theorem of dimensional analysis, and then calibrated using the experimental data collected during this study. The first discharge model has an average error of 1.81%, while the second and third improved models have average errors of 0.96% and 1.44% respectively. To reliably estimate the flume discharge, free-flow and submerged-flow conditions should be distinguished. For this, suitable equations with an average error less than 2.23% were presented to estimate the submergence threshold. The results of this study indicate that while the downstream wall slope influences the submergence threshold, the flume discharge is not influenced by this variable. The proposed models are simple and accurate and present appropriate estimation of discharge for flows through the TCTFs. The findings of this study will be of interest for practical hydraulic engineers.     

天然挺水植物明渠三维紊流特性研究

以天然挺水植物茭草、芦苇、水葱及模拟植物PVC管为试验材料并种植于大结构混凝土明渠中,研究其在流量及种植密度相同条件下明渠中水流的三维时均流速、脉动强度及雷诺切应力的分布特点。结果表明,明渠水流流速垂线更符合抛物线分布;天然挺水植物之间、天然挺水植物与PVC管间的时均流速分布相差较大,难以用一种分布模式描述;含挺水植物水流紊流特性表现出明显的各向异性;紊动强度与植物的生长形态及柔韧性密切相关;除水葱外,芦苇、茭草及PVC管的雷诺切应力-ρu′zu′x基本接近;相比天然挺水植物PVC管对水流切应力-ρu′yu′z影响最为显著;切应力-ρu′xu′y垂线分布于相对水深0.5处出现极值,总体呈ε形状。     

超大跨径变截面钢筋混凝土拱式渡槽抗震分析

结合跨径200m的超大跨径变截面拱式渡槽的结构设计方案,通过建立有限元模型,对渡槽进行了动力特性和地震响应分析。结果表明,设计方案拱轴系数的取值合理,拱脚偏心弯矩引起的拉应力在允许范围内;变截面的做法增大了拱脚截面刚度,增强了拱圈的稳定性,有效地减小了起控制作用的拱脚处的轴向拉应力,可满足渡槽抗震要求。     

南水北调渡槽侧壁温度场计算及保温材料应用分析

南水北调中线工程大型渡槽槽身混凝土温度变幅较大，温度应力的影响显著，设计中考虑在混凝土外侧增设保温板以使混凝土温度变幅降低。通过对渡槽设置保温板前后的的混凝土内温度场进行了数值计算，结果表明，加设聚苯保温板后混凝土表面温度基本保持不变，降低了结构的温度应力，有利结构安全。     

带异形块体海堤越浪的数值模拟

该文在FLUENT软件平台上，发展了数值消波-造波技术，通过在动量方程里添加多孔介质源项，建立了带有多孔介质模型的二维数值波浪水槽。应用该数值波浪水槽，数值模拟了在斜坡堤坡面上铺设异形块体情况下的越浪过程，给出了越浪量。为了率定异形块体的等效惯性阻力系数，进行了典型工况的物理模型实验，给出了在斜坡堤坡面上不同位置处铺设一层异形块体情况下多孔介质模型的等效阻力系数。     

船舶上滩的影响因素及动水特性试验

在急流滩地形概化了的试验水槽中，进行了多种水力条件下的船模上滩试验．试验结果表明，滩段的水面比降、水流速度及船舶水深吃水比是船舶上滩的主要影响因素．     

Experimental study on rectangular cut-throated flume: Effects of flume walls slopes and channel longitudinal slope

This research conducted to study the flow through a rectangular cut-throated flume (RCTF). The flume is simply formed by placing two vertical triangular prisms (two vertical folded plates) on either side of a rectangular open channel. Both channel and flume cross-sections are rectangular. The investigated flume is inexpensive, easy to install and does not require high maintenance. A wide experimental investigation, carried out under free outflow conditions and under upstream subcritical flow regime to investigate the effects of the channel longitudinal slope, the flume throat width, and slopes of upstream and downstream flume walls on the stage-discharge relationship. The stage-discharge relationships were deduced by applying the dimensional analysis and were calibrated using the data of this study. The proposed stage-discharge equation for horizontal channel has an average absolute relative error of 2.97% with the relative errors restricted in the range of ±10%, and 80% of the data points are in the error range of ±5%. The proposed stage-discharge equation for sloping channel has an average absolute relative error of 3.97% with the relative errors restricted in the range of ±10%, and 66% of the data points are in the error range of ±5%. The measurements indicate that slopes of upstream and downstream walls affect the stage-discharge relationship of the CTFs only in sloping channels and flow discharge is not influenced by the flume walls slopes in a horizontal channel. The proposed unified stage-discharge equation for both horizontal and sloping channels has an average absolute relative error of 3.38% with the relative errors restricted in the range of ±10%, and 74% of the data points are in the error range of ±5%. The proposed stage-discharge model demonstrates favorable accurate and convenient estimation of discharge for flows through the CTFs.     

游泳水槽的气泡运动规律及去除方法研究

游泳水槽作为一个先进的工具，可有效地提高竞技游泳水平。目前游泳水槽建造技术尤其是对水流的控制技术已趋于成熟，但水槽内的气泡将会影响对运动员技术动作观测和图象解析，并对运动员游泳姿态测试、分析和改进带来困难。本文通过对游泳水槽结构及水槽中水流流动状况分析得到了气泡产生的主要原因，并研究了气泡运动的规律，提出了减少气泡产生的合理方法以及去除气泡的合理设计，为现有的游泳水槽改进提供良好方案，为今后自主设计先进的游泳训练用水槽提供技术支撑。