某高砾石土心墙堆石坝平面有限元应力应变分析

本文介绍了某高砾石粘土心墙堆石坝平面有限元应力应变分析,对两种坝型采用不同本构模型进行了分析比较,特别对防渗心墙的拱效应、抗水力劈裂性能及砼防渗墙应力进行了深入的分析研究,并对水力劈裂的判断标准进行了讨论。结果表明两种坝型均是可行的,心墙抗水力劈裂的能力是有保障的,防渗墙的应力有廊道的较大。这些结论对设计方案的确定有一定的指导意义。     

泵及装置原型与模型水力特性换算方法

对国内外多种泵及装置原型、模型水力特性换算方法研究所取得的进展进行了回顾,主要内容包括具有奠基意义的Moody效率换算公式,考虑比尺效应的原型、模型泵及装置效率的换算方法,以及原型、模型泵能量性能参数的换算方法。详细介绍了我国学者在这方面的研究成果,并对现有不同换算方法进行了简要的评述,指出缺乏高精度完整可靠的水泵装置原型测试数据,是目前制约水力特性换算方法深入研究的重要原因,将数值模拟与理论分析和试验研究相结合,可望取得突破性的进展。     

Comparison of the influences of vegetation stem parameters on hydraulic variables and sediment transport capacity

The hydraulic variables (Hv) and sediment transport capacity (Tc) of overland flow have changed immensely due to large-scale revegetation. However, research comparing the influences of stem parameters (diameter, cover, and arrangement) on Hv and Tc is limited. The objectives of this study were to explore and compare the influences of stem parameters on Hv and Tc. Data on three treatment groups with varying stem diameters, covers, arrangements, flow discharges and slopes were collected in this study. With increasing stem diameter, Hv and Tc increased; Hv included the Reynolds and Froude numbers, flow velocity (v), shear stress (τ), stream power (Ω), and unit stream power (ω). However, the trend of the Darcy-Weisbach friction coefficient (f) was opposite. Hv and Tc were significantly influenced by stem diameter and cover. The effect of stem diameter on Hv and Tc was greater than the effects of cover and arrangement. Stem cover as a variable could not be used to adequately estimate the Tc when there were various stem diameters. A new exponential equation involving stem cover and stem diameter was demonstrated to be an appropriate predictor of Tc. Stem diameter and arrangement had no obvious influence on the relationship between Tc and v, and v as an indicator could explain the effect of stem parameters on Hv and Tc. This result could illustrate why the variables, including v, were able to predict Tc under vegetation stem and litter cover.     

液压锤误操作时液压冲击和噪声的研究

利用功率键合图法，分析了液压锤的功率流向，分配及转换关系，绘制了打击工况的功率键合图，建立了数学模型，并研究了液压锤误操作时产生液压冲击及噪声的机理。结合实例，阐述了液压锤的最佳操作规程，建议打击能量程序化。     

Multi-criteria site selection and hydraulic modeling of green flood retention measures in a highly urbanized basin in Costa Rica

Green flood retention measures (GFRMs) are nature-based solutions applied to. mitigate floods by slowing and storing floodwater. This study employed a hydraulic, model developed in HEC-RAS to analyze the effects of GFRMs in the Quebrada Seca-Burío basin in Costa Rica. A multi-criteria methodology was developed to select. suitable sites for implementing the measures. A baseline representing the status quo, scenarios with individually assessed measures implemented at different sites, and a scenario with all measures combined were compared concerning their flood retention. potential. Twelve suitable sites capable of providing multiple socio-ecological benefits. were identified, of which three were implemented in the model to evaluate their. hydraulic performance. The results indicate that all scenarios are effective in reducing. peak flow, volume, and inundation areas, but to varying degrees. The combination of. all measures presented the most effective results, with peak flow reductions of 5.6 –15.3% and flood volume reductions of 3.6 – 9.9%.     

水轮泵相似律的研究

为了解决水轮泵设计中的模型换算设计方法,以及利用模型水轮泵的水力性能换算出比其大得多的同轴型和非同轴型(含传动装置)真机水轮泵的水力性能,进行了水轮泵相似律的研究。在水轮机和水泵相似理论的基础上,推导出水轮泵在相似工况下各个基本工作参数模拟换算的关系式,为水轮泵的设计和验收工作提供了一种方便而可靠的方法。     

Potential of roots and shoots of Napier grass for arresting soil erosion and runoff of mollisols soils of Himalayas

In this study, a soil filled Hydraulic Tilting Flume (HTF) was used as a test plot under simulated rainfall conditions. This flume was filled with mollisols soils (sandy loam in texture) collected from tarai region of Himalayas. The effects of root and shoot characteristics of Napier grass in terms of leaf area index (LAI), shoot length (SL), number of leaves (NL), number of tillers (NT), shoot biomass (SB), root density (RD), root length (RL), root biomass (RB), and total biomass (TB) were investigated on runoff and sediment outflow at 90, 120 and 150 days after planting (DAP). Four simulated rainfall intensities namely 4.0, 6.5, 8.3 and 9.4 cm/h over three land slopes of 1, 2 and 3% were selected. Runoff samples collected from whole plant plot and only root plot were analyzed for runoff and sediment outflow. Findings revealed that Napier grasses were very effective to reduce runoff and sediment outflow and its efficacy increased with the extended growth stages. The reduction in runoff and sediment outflow at 90, 120 and 150 DAP was obtained as 56% and 85%, 68% and 90%, and 74% and 96%, respectively, as compared to bare plot conditions. It was observed that the comparative contribution of shoots in runoff rate reduction was higher than the roots. On the contrary, the root part of the plant showed more contribution in sediment rate reduction as compared to the shoot part. Step wise regression was attempted for the selection of effective input parameters to establish authentic runoff and sediment outflow models. Power form of multiple non-linear regression (MNLR) showed very satisfactory results for predicting runoff and sediment outflow with coefficient of determination (R²) as 97.4% and 99.0%, respectively, root mean square error (RMSE) as 38.8 cc/m²/min and 0.126 g/m²/min, respectively, and coefficient of efficiency (CE) as 93.9% and 96.7%, respectively, during testing period.