Response characteristics of plunge pool slabs of Xiaxiluodu Hydropower deformation conditions

The key problem of the energy dissipation scheme of the arch dam body flood discharge and plunge pool below the dam is the stability problem of the plunge pool slab.As the protection structure of the underwater bed,the plunge pool slab bears the continuous impact of high-speed water flow.The hourly average dynamic water pressure on the slab is one of the main loads directly affecting the stability of the slab and is the main factor causing its erosion destruction.After the impoundment of the Xiluodu Hydropower Station,the measuring line of valley width in the plunge pool area has been continuously shrinking.By 2020,the cumulative shrinking value is about 80 mm.In light of the general background condition of valley shrinkage,daily inspection,annual detailed inspection,underwater inspection and drainage inspection of the plunge pool found that the plunge pool has experienced different degrees of damage,which greatly influences the long-term safety stability of the plunge pool.In this paper,the prototype observation data of flood discharge is used as the input load of pulsatingpressure,and the stress and displacement distribution of the plunge pool structure under the vibration load of flood discharge is analyzed under the condition that the stress and strain state of the plunge pool is changed under the influence of valley displacement.The results show that the stress,strain,and displacement distribution of the plunge pool are mainly caused by valley deformation,the vibration caused by flood discharge is little in influence,and the impact effect of deep hole flood discharge tongue on the plunge pool slab is weak.

折线大斜切挑坎水力特性研究

斜切挑坎多被用于泄水建筑物轴线与天然河道互成夹角的工程。然而,当下游河道过于狭窄时,斜切挑坎无法满足水流归槽及消能防冲的要求。为此,在斜切挑坎的基础上提出折线大斜切挑坎。通过模型试验的方法,测量不同折线大斜切挑坎体型在不同来流条件下,挑射水流的扩散情况和下游水垫塘内的底板压力分布,以研究折线大斜切挑坎的水力特性。结果表明:相较于传统斜切挑坎,折线大斜切挑坎既可以实现对挑流水舌水量和入水范围的灵活调整,也可以缓解水垫塘压力分布的不均匀现象。研究结果可为折线大斜切挑坎的工程设计和应用提供一定的参考。

花岗岩红壤坡面沟头高度对沟床跌穴发育过程的影响

[目的]为明确花岗岩红壤坡面沟头溯源侵蚀的关键过程及形成机制。[方法]通过设定5个沟头高度(25,50,75,100,125 cm)研究花岗岩红壤坡面沟床跌穴发育过程。[结果](1)随沟头高度增加,沟床径流雷诺数、径流剪切力、径流功率和射流参数(触底流速、射流剪切应力、瞬时动能、跌穴径流能耗)均表现为增加趋势。(2)红土层沟床形成“V”形跌穴,随流量增加跌穴形态变化增大,但只形成面积较小的跌穴。而砂土层在冲刷过程中,沟床跌穴发育较为明显,当流量增大到120 L/min后,沟床破碎化程度增加,跌穴轮廓逐渐清晰,横截面积增大。(3)通过随机森林算法和沙普利值构建并表征模型各参数的关系,红土层沟床径流的弗罗德数、径流功率、水平出射动能、雷诺数与横截面积呈负相关;砂土层沟床径流的弗罗德数和跌穴径流能耗与横截面积呈负相关。沟床跌穴侵蚀程度可用随机森林算法构建模型预测(LCCC=1.02,R_(adjusted)^(2)=0.876和0.868)。[结论]研究结果可为揭示沟头溯源侵蚀机理和沟蚀防治提供理论依据。

姚家平高拱坝水垫塘的研究与选择

高拱坝泄洪消能设施的选择与布置设计是高拱坝设计成败的关键。姚家平水利枢纽属于典型的高山峡谷地区高拱坝项目,其所在位置特殊的地形地质条件给该高拱坝的消能设施布置与设计造成了一定的难度。通过类似工程的类比分析,并结合相关的模型试验科研,得出了符合本工程特点的泄洪消能设施布置方案,明确了水垫塘的长度、厚度和与之对应的二道坝高度,可供类似工程设计参考。

旭龙水电站泄洪消能设计研究

为了研究高地震烈度区特高拱坝设计采用全坝身泄洪的可行性,以旭龙水电站特高拱坝为例,对泄洪消能布置、水力指标、坝身孔口布置方式、体型以及孔口结构抗震影响等方面进行研究和综合比选后,推荐采用全坝身3表孔加4中孔泄洪、下游反拱水垫塘消能方案。研究表明:合适的坝身孔口布置体型可保障泄洪消能安全与减轻岸坡泄洪雾化,反拱水垫塘安全性和经济性较好,孔口结构对坝体整体极限抗震性能无影响,高地震烈度区特高拱坝设计采用全坝身泄洪是可行的。研究成果可为类似工程泄洪消能建筑物设计提供参考。

高重力坝防冲建筑物体型参数对水力特性的影响

高重力坝防冲建筑物体型参数的选取决定了泄洪消能水流的水力特性,从而影响水电站的安全运行。采用水工模型试验的方法,研究了防冲建筑物体型参数对水流的水力特性影响规律。研究结果表明:水垫塘长度的减小,使塘内淹没冲击射流的扩散空间减小、冲击区的紊动增强,导致塘内底板时均压强谷值减小、脉动压强均方根峰值增大、底板安全风险增大;二级消力池池长的减小,使出池临底流速增大、下游冲刷风险增大;二道坝高度的降低,导致水垫塘底板沿程时均压强减小、脉动压力均方根峰值增大、底板安全风险增大,同时导致二级消力池内水跃收缩断面水深增加、跃首区临底流速降低、紊动强度降低、脉动压力均方根峰值减小,但出池临底流速增大。

A new type of plunge pool―Multi-horizontal submerged jets

Based on the understanding of the mechanism of energy dissipation,a new type of plunge pool is presented with the advantages of high rate of energy dissipation,low impact pressure,and small close-to-bed velocity on the soleplate of the plunge pool.The first advantage owes to enlarged shearing energy dissipation areas in the plunge pool,while the other two are caused by the jet that enters in a nearly horizontal level to keep the soleplate from being scoured directly.All of the above arrangements make this new type of energy dissipator distinct from the underflow energy dissipation.Through experiments on the physical model,the authors found that the water flow maintained stable and submerged in horizontal direction when the flow was narrow in horizontal but thick in vertical direction.However,the wide flat nappe was ready to submerge or float as the downstream water level rised or dropped.The entire flow fields of multi-horizontal submerged jets into plunge pool were also numerically simulated.The numerical results of water surface curve,close-to-bed velocity and floor pressure agree well with the experimental data.The flow pattern in the plunge pool was analyzed after combining the laboratory data and numerical simulation.

EXPERIMENTAL RESEARCH ON CHARACTERISTICS OF HYDRODYNAMIC PRESSURE SPREADING IN THE BASE GAP OF ARCH INVERTED PLUNGE POOL

A detailed experimental research on characteristics of the hydrodynamicpressure spreading in the base gap of the arch inverted plunge pool was carried out. The features ofthe distributon of its ampitudes and spectral density and its characteristics in time domain fortwo conditions, i. e. , (1) a through gap and (2) a blind gap were given. The influence of the dampat the joint opening upon the hydrodynamic pressure inside the gap was also investigated.Accordingly, the stabilization mechanism of the arch invert plunge pool was worked out.

Safety evaluation and the static-dynamic coupling analysis of counter-arched slab in plunge pool

The stability of plunge pool slab of drainage structure is crucial to energy dissipation,but the working conditions of counter-arched slab are very complex and its stress procedure is considerably nonlinear and coupling.Therefore,a nonlinear static and dynamic coupling method to analyze the counter-arched slab configuration is put forward,which can reflect the coupling of dynamic loads,slab,anchor bars,groundwork and abutment as well as the dynamic procedure of instability.Various nonlinear factors and static-dynamic coupling are taken into consideration,and the working conditions,stress mechanism,dynamic instability procedure and influential instability factors are revealed.The proposed method thus provides a comprehensive safety evaluation method of plunge pool,which further pro-vides an important theoretical basis for engineering design of counter-arched slab in plunge pool.

NUMERICAL SIMULATION OF 3-D TURBULENT FLOWS OF PLUNGE POOL AND ENERGY DISSIPATION ANALYSIS

A 3-D numerical model for simulating the complicated turbulent flows was developed and the code was made. A numerical calculation of the plunge pool of Laxiwa project in China was carried on. Those 3-D distributions of velocity,pressure on bottom wall,turbulence kinetic energy and turbulence energy dissipation rate are revealed in detail and the detailed flow patterns of plunge pool were shown. By studying on the characteristics of turbulent diffusion and energy dissipation,the calculated results show that the major turbulence and energy dissipation are taken place near the axis of water jet. The calculated results also indicated that the calculated maximum impact pressures on the bottom wall of the plunge pool have a good agreement with those obtained by physical hydraulic model test.

Experimental investigation of submerged impinging jets in a plunge pool downstream of large dams

Submerged impinging jets in a plunge pool downstream of large dams are experimentally investigated in details. By use of the hot\|film anemometer, the velocity field in the plunge pool produced by middle orifices of 1∶400 scale Xiluodu spillway model is measured. The diffusive characteristics and energy dissipation mechanism of the submerged impinging jet in the plunge pool are analyzed.

Effects of plunge pool configuration on downstream passage survival of juvenile blueback herring

Anadromous alosines are widespread throughout the Northern Hemisphere.Juveniles of this clade are notoriously fragile animals that are at high risk of injury and death associated with passage at hydroelectric facilities.Although turbine mortality is a common concern,conditions encountered when bypassed around these routes may also be hazardous.Downstream bypass structures typically discharge into plunge pools,which are highly turbulent and may cause mechanical injury.We subjected live,actively migrating juvenile blueback herring to a suite of realistic plunge pool conditions(3 m drop,pool depth of 60-180 cm,and discharge of 0.28-1.70 m^(3)/s)and monitored them for≥96 h.Survival was generally higher than expected(>80%in all cases).However,both plunge pool volume and total discharge affected survival with elevated discharge and shallow conditions associated with increased mortality.Mortality was often delayed:rates remained elevated throughout the monitoring period,indicating that survival studies based on shorter periods underestimate total mortality.

反拱型水垫塘底板结构的稳定性研究

在研究反拱型水垫塘底板上整体水动力荷载特征的基础上,针对反拱底板的结构受力特点,提出了“随机拱”分析模型,对反拱型水垫塘底板结构局部和整体的稳定性进行了定量分析,从板块极限平衡角度给出了反拱型底板优于平底板的量化指标。

水垫塘三元流态及消能特征的数值和实验研究

采用数值模拟和实验测试相结合的方法对水利工程中高拱坝泄洪水垫塘三元流场进行研究．获得了详细的流态特征，得到了水垫塘三元典型流态概化图．研究了水垫塘消能特性，并据此将塘内水体划分为剪切消能区、撞击消能区和混掺消能区．计算和实验所得的速度场及底板最大冲击动压相比较，二者基本一致．

射流掺气对水垫塘及坑底压强影响的实验研究

通过对射流掺气与不掺气时,水垫塘底板及冲坑底部脉动压强的对比试验,研究了掺气对水垫塘及冲坑底部压强特性的影响。结果表明:在冲坑未形成前,掺气使水垫塘底板上射流冲击区的脉动压强增加;无论是否掺气,滞点时均压强的量纲一分布遵从相同的规律,底板量纲一时均压强分布存在很好的自模性,且与气体冲击射流的压强分布具有相同的规律。冲坑形成后,掺气不再明显增大冲坑底部的脉动压强,掺气后,坑底脉动压强没有明显的变化。

水垫塘底板缝隙中脉动压力传播特性

高坎下游泄洪常常采用水垫塘消能 ,挑跌水流可能对塘底产生巨大的冲击。如果底板止水破坏 ,冲击压力在缝隙中形成强烈的脉动压力是底板失稳破坏的重要因素。利用瞬变流理论 ,揭示了底板缝隙中脉动压力形成条件和传播特性 。

悬栅消力池消能特性的试验研究

悬栅消力池是在新疆喀什河吉林台一级水电站引水隧洞水力学模型试验中提出的一种新型的消能工型式。通过试验研究,进一步分析悬栅消力池的消能特性,加栅前后消力池内水深及消力池下游明流洞内涌浪的变化。试验结果表明:同一工况下,悬栅的设置,破坏了水跃的结构,使水流内部结构经历剧烈的改变和再调整,消耗大量的机械能。消能率整体提高,最大提高幅度为15.10%,最高消能率达95.14%。加栅后消力池内水深及消力池下游明流洞内涌浪高度都有明显消减。

多股水平淹没射流水垫塘流场数值模拟

水垫塘三维流场的研究是深入研究消能机理的基础 ,多股水平淹没射流水垫塘作为一种新的消力池型式 ,其水垫塘内水流流态特征是研究者最为关心的问题之一 ,本文对向家坝多股水平淹没射流水垫塘的三维流场进行了数值模拟 ,将计算的消力池底板压强及流速与实测结果进行了对比 ,计算值与实测值吻合较好 ,计算的消力池内三维流场与实验中观察到的流态及理论分析结果吻合很好 ,结合流场特性分析了试验和计算中发现的中孔射流冲击点比表孔射流冲击点更远的原因 ,分析了中孔之间不存在稳定的、明显的、贯穿的“马蹄涡”及其原因。

水垫塘内冲击射流特证及其对岩石河床的冲刷

本文详细地分析了水垫塘内淹没冲击射流的基本特征，针对不同性质的流动区域，首次提出采用不同的岩块起动判别条件．

水垫塘三维紊流数值模拟及消能分析

开发了能模拟复杂紊流的三维数学模型，编制了大型计算程序，针对拉西瓦水垫塘进行了数值模拟，揭示了水垫塘内速度、压力、紊动能及其耗散率的三维分布规律。获得了详细的水垫塘流态特性。研究了水流紊动扩散及消能特性，反映出紊动和消能大量地发生在射流轴线附近，计算所得的底板最大冲击动压与实验值进行了比较，二者符合良好。