提高大坝安全性能的一种方法——溢洪道维修案例分析(英文)

瑞典新的洪水设计及大坝安全指南对全国水库大坝的安全提出了更高的要求。指南对每一条河流情况进行了复核并找到了较好的解决方案,即储水和提高溢洪道泄洪能力相结合的方案。为了符合指南的要求,瑞典全国上下都在实施一个大坝安全计划,对大量的水库大坝提高其安全性能,以满足更高的洪水设计(及其它方面)的要求。技术方案包括大坝加固、溢洪道泄洪能力提升和临时储水设施。Stenkullafor 水库大坝设有一个 2 闸控制的敞开式溢洪道。该水库修改后的设计洪水将比现有溢洪道泄洪能力提高 40%。根据成本效益分析,提高溢洪道泄流能力的主要措施是降低其中一个闸门顶高程,以适应需要提高的泄洪能力。通过水工模型试验,一方面优化溢洪道顶部轮廓,另一方面降低溢洪道顶部改造和新闸门的成本。溢洪道右侧闸门底高程降低 4.3 m,并新安装一扇更高的闸门。现在,大坝的安全性能已得到提高。对水工模型试验和施工时的洪水风险,施工过程及其遇到的困难进行了介绍,并对坝体加固、上游坡新的侵蚀防护、下游消能及下游行洪渠道等工程措施进行了描述。

Air-vent layouts and water-air flow behaviors of a wide spillway aerator

A spillway aerator should guarantee favorable flow conditions in the coupled water-air system even if the aerator is unconventionally wide. Eight air-vent configurations are devised and incorporated into a 35-m wide chute aerator for a generalized study. Computational fluid dynamics(CFD) simulations are performed to explore their effects on water-jet and air-cavity features. The Re-normalisation group(RNG) k-ε turbulence model and the two-fluid model are combined to predict the two-phase flow field. The results demonstrate appreciable influences of the vent layouts on the water-air flow. The air vents stir the air motion and re-distribute the cavity air pressure. Once the vent layout is modified, reciprocal adjustments exist between the jet behavior and air-pressure field in the cavity, thus leading to considerable differences in air-flow rate, jet-trajectory length, vent air-flow distribution across the chute, etc. The large width plays a discernable role in affecting the aerated flow. Telling differences exist between the near-wall region and the central part of the chute. To improve the duct pressure propagation, a gradual augment of the vent area should be assigned towards the chute center. Relative to single-slot vents across the flow, the layouts with segregated vents gain by comparison. A designer should see to it that a vented aerator operates satisfactorily for a given range of flow discharges.

Characterization of Hydraulic Behaviours of Coarse Rock Materials in a Large Permeameter

The hydraulic behaviour of a rock material structure is a major feature for its design and safety assess- ment. Similar to all other physical problems, in order to enclose the governing equations systems and achieve a solution, the hydraulic characteristics of these materials need to be determined experimentally and implemented then into adopted thermo-dynamical models. This paper covers the process of the design, construction and operation of an experimental rig built for this specific purpose. Using the constructed large-scale permeameter, tests have been conducted. The non-linear hydraulic behaviour of various mate- rials under extreme turbulent conditions, where Reynolds number reaches unprecedented values, has not been studied before. Preliminary results are presented and discussed.

Air-core characteristics in a swirling tunnel flow

A cost-effective technique to dissipate the energy in hydropower systems is the formation of a swirling flow within a tunnel.In such flows,an air core with a significant cross section usually occurs.To reveal the air-core features in the horizontal tunnel of a high-head shaft spillway,laboratory tests,numerical modeling,and prototype observations are performed,to examine issues such as the formation of the air core,the interjacent air motion,the air-carrying capacity,and the scale effects.It is shown that the shape of the air core varies greatly in the axial and radial directions along the tunnel and that the center of the core deviates from the axis of the tunnel.The motion of the air within the core is caused by the combined action of the water entrainment on the inner surface of the swirling flow and the axial pressure difference in the air core.The aeration process can be divided into five processes with respect to the changes of the gate openings.A theoretical expression is established for the air-carrying capacity of the swirling flow.The vacuum degree is the similarity condition of the air-carrying capacity of the swirling flow between the model and prototype tests based on the Froude law of the similitude,and this similarity condition is verified by both the model and prototype results.This work provides a reference for the application of the swirling flows in horizontal hydropower tunnels.

背景墙张目

背景墙,也叫主墙,或者主题墙。这些看似背道而驰的说法,正道出了这个室内装饰元素之既主亦陪衬的身份。我们姑且称之为背景墙吧,因为它更多衬托空间气质的效能,而并无生活实际不可或缺的意义。其实背景墙我国古代就有,大到皇宫殿宇里迎门正墙上由绘画、匾额、对联等元素组成的"主墙",小到民间堂屋正中一幅年画配一双对联等。这种型制的墙面更适合叫主墙,它是室内空间气度、气势甚至风水转承的载体。今天我们要说的是具体室内装饰所要注重的背景墙。

我们只是老了,又不是死了——银发经济下银发营销的缺失

最近,《乘风破浪的姐姐》捧红了王心凌,红到一帮大叔大爷们用脚投票,让芒果超媒的股价在翻绿的大盘中独自走高。而在众多社交媒体上,亦真亦假的大叔们追捧昔日甜心教主的内容中,有一句评论非常触动我,这句话就是“我们只是老了,又不是死了”。环顾四周,有一个现象已经非常普遍,就是四五十岁的中老年人,甚或是更年长一些的老年人,其实在各类场合尤其是数字社交媒体上表现非常活跃,且受到大批年轻人的追捧。