Exploring of Water Distillation by Single Solar Still Basins

The lack of potable water poses a big problem in Syria. The underground water, where exists, is usually brackish and cannot be used as it is for drinking purposes. Syria lies in high solar isolation band and the vast solar potential can be exploited to convert saline water to potable water. The most economical and easy way to accomplish this objective is using solar still. The purpose of the project is to evaluate the potential of using a solar still basin. To implement this goal three similarly solar still basins have been designed, manufactured and tested in selected day for saline water in month of November, 2010. Each solar still consists of insulated metal box with channels. Pyramidal glass covers attached to the basin at an angle (α = 45°). The three basins have divided into three models (M1, M2 and M3). Before taking the measurement of the distilled water three different amount of water used, so for the (model M1) 3 liter of water, (model M2) 6 liter and (model M3) 9 liter, to study and evaluate the effect of water depth in the basin. The average daily output was found to be (3.924) liters/day for model (M1), (3.116) liters/day for model (M2) and 2.408 liters/day for model (M3) for basin area of 1 m2 based on data of selected day.

An Experimental Investigation of the Factors Which Affect on the Performance of a Single Basin Typical Double Slope Solar Still for Water Desalination

Solar energy is very useful in the process of desalination especially for areas that suffer from a lack of clean water resources. In recent years, many people have been using solar still. Therefore the raising of the productivity and efficiency of solar still represents the most important problems that need further research. The present work aims to study the effect of preheating the water entering to still and the effect of reducing pressure inside the still on the productivity of the solar still. Therefore in present work two identical single basin typical double slope solar stills of the inner basin dimensions for each still 2 m × 1 m × 0.08 m, have been designed and fabricated with mild steel plate. One of them is conventional solar still and the other is modified with flat plate collector and vacuum pump to study the effect of preheating and vacuum on the performance of solar still. The experimental measurements are made to enhance the solar still productivity by firstly preheating the water entering the still using flat plate collector and secondly by integrating the still basin with vacuum pump. The results show that preheating the water entering the still increases the water productivity by amount about 27.7% - 29.3%. The results also show that decreasing pressure inside the still using vacuum pump improves the solar still water productivety by amount about 21.8% - 23.9%.

泄洪消力池消力墩消能特性数值模拟研究

消力墩是常用的泄洪消力池消能结构物之一,对其消能效果与结构优化研究在枢纽结构设计中具有重要作用。为此,基于描述非恒定流运动的雷诺平均(RANS)方程和描述紊流运动的Realizableκ-ε湍流模型,采用VOF自由表面追踪方法,建立了模拟大自由表面变形流体运动的数值计算模型,对坝面泄洪引起的跌坎型消力池内复杂流体运动及消力墩的消能特性进行研究。首先,对不同坝面泄洪条件下消力池内水流运动进行模拟,通过将自由液面、水流流态及底板压强分布等的模拟结果与室内实测数据进行对比,验证了模型的模拟精度和可靠性;在此基础上,模拟分析了矩形、直角梯形和T形三种典型消力墩对消力池内水流流速、液面形态及湍动能分布的影响,探讨了长、宽、高相同、几何形状不同的消力墩的消能效果。结果表明,对水流能量的耗散作用,矩形消力墩优于直角梯形消力墩、直角梯形消力墩优于T形消力墩。

趾墩-悬栅消力池水力特性分析

为了解决新疆某工程泄洪洞消力池流态紊乱、消能率低的问题,采用数值模拟方法,在设计及校核流量下,对传统消力池、悬栅消力池以及趾墩-悬栅消力池3种不同形式消力池水力特性进行系统性分析。结果表明:趾墩-悬栅联合消能工改善了消力池内水流流态,消力池发生淹没式水跃,其池内悬栅与悬栅间隙处涡量分布广泛,池内整体涡量分布比悬栅消力池分布更加均匀。在设计流量下,消能率为74.41%,相较于传统消力池消能率提高2.61%,相较于悬栅消力池消能率提高0.95%;在校核流量下,消能率为78.99%,相较于传统消力池消能率提高5.64%,相较于悬栅消力池消能率提高0.95%。

自由出流的拦河水闸消力池计算探讨

拦河水闸下游消力池尾坎自由出流时,其下游河床水深ht往往小于相应的临界水深hk,消力池水力计算无法满足相关水闸设计规范水力设计的要求。目前,有关自由出流拦河水闸消力池的水力计算方法尚不够完善,给工程设计带来极大的不便。在总结有关水闸下游消力池研究成果的基础上,在假设自由出流的消力池下游河床水深ht等于临界水深hk的条件下,对自由出流的消力池尾坎高度计算进行探讨,提出了相应的计算方法。研究成果得到了水力模型试验研究的验证,具有计算较方便的特点,可供类似工程设计和运行参考。

下游极低水位溢洪道消力池布置及优化研究

溢洪道消力池的消能问题是保障泄洪安全的关键,特别是极低下游河道水位给消能布置带来更大的难度.结合某高水头水库工程岸边溢洪道,采用物理模型试验的方法,分析了下游极低水位消力池布置与流态衔接方法;研究成果建立了下游河道水深、消力池池深与水跃跃后水深的控制方法,提出了优化消力池流态的工程措施.

基于等效收缩断面的渐扩折坡消力池特性研究

针对不规则渐扩折坡式消力池中的水跃初始断面和水深难以确定的问题,提出了等效收缩断面的假设,利用坎前水深计算等效断面位置和水深,将其引入到渐扩折坡式消力池的水跃消能分析中,提出渐扩折坡水跃消能公式,为渐扩折坡式消力池中的水跃消能特性评估提供依据。此外,通过物理模型试验对渐扩折坡式消力池的水力特性进行测试研究,分析折坡水跃消能的流态、临底流速、脉动压力分布和空蚀空化分布规律。结果表明,采用等效收缩断面的消能率计算公式能够对渐扩折坡式消力池的水力特性进行合理评估,水跃发生在渐扩折坡式消力池的渐扩折坡段上,能有效缩短消力池长度,减少底板空蚀空化风险,提高消能效率。

宽尾墩—跌坎消力池脉动压强试验研究

宽尾墩与跌坎消力池联合消能使跌坎消力池内的水力参数更加复杂,研究消力池底板的脉动压强特性对宽尾墩体型设计具有参考作用.基于模型试验研究5种收缩比(a=0.38;0.44;0.50;0.56;0.62)Y型宽尾墩与跌坎消力池联合消能下消力池的脉动压强特性.试验结果表明:脉动压强峰峰值可以达到设计水头的1.03~1.36倍,收缩比的减小可以削减峰峰值,消除跌坎后的负压;消力池底板脉动压强均方根沿程呈现单峰与双峰型,最大脉动压强系数出现在跌坎之后,减小收缩比使消力池主要脉动消能区域增大前移,最大脉动压强系数降低;脉动压强概率密度基本符合正态分布,存在正偏与负偏现象,水流速度偏向底板为正,偏离时为负;消力池底板脉动压强主要由10 Hz以内的低频脉动组成,随着收缩比的减小,消力池前端的脉动能量增大,后端脉动能量减小.

金沟河红山水库溢洪道下游消能工优化试验研究

水利枢纽泄洪建筑物下游的高速水流冲击下游河床致使下游河床严重冲刷及岸坡淘刷,处理不当可能危及大坝安全。针对金沟河红山水库溢洪道下游的消能问题,通过水工模型试验对溢洪道进行不同工况下的消能效果分析,提出了采用“台阶+消力池+消力坎辅助消能工”的综合消能方案,较好地解决了红山水库溢洪道泄洪消能问题,为水库工程溢洪道下游消能防冲设计提供参考。

NUMERICAL SIMULATION OF THE ENERGY DISSIPATION CHARACTERISTICS IN STILLING BASIN OF MULTI-HORIZONTAL SUBMERGED JETS

3-D numerical simulation was carried out for the water flow in a stilling basin with multi-horizontal submerged jets by using two different turbulence models, namely, the VOF RNG k-ε and Mixture RNG k-ε turbulence models. The calculated water depth, velocity profile and pressure distribution are in good agreement with the data obtained in experiments. It indicates that the numerical simulation can effectively be used to study the water flow movement and the energy dissipation mechanism. The numerical simulation results show that the turbulent kinetic energy distribution obtained by using the Mixture turbulence model covers a region about 18% larger than that calculated by using the VOF turbulence model, and is in better agreement with the actual situation. Furthermore, the Mixture turbulence model is better than the VOF turbulence model in calculating the air entrainment.

Particle image velocimetry measurements of vortex structures in stilling basin of multi-horizontal submerged jets

Measurements of turbulent flow fields in a stilling basin of multi-horizontal submerged jets were made with the single- camera Particle Image Velocimetry （PIV）. The particle images were captured, processed, and subsequently used to characterize the flow in terms of the 2-D velocity and vorticity distributions. This study shows that the maximum close-to-bed velocity in the stilling basin is approximately reduced by 60%, comparing to the jet velocity at the outlet of orifices. The jet velocity is distributed evenly at the latter half of the stilling basin and the time-averaged velocity of the cross section is reduced by 77%-85%, comparing to the jet velocity at the outlet of orifices. These results show that the vortices with horizontal axes are continuously repeated during the form-merge-split-disappear process. The vertical vortices are continuously formed and disappeared, they appear randomly near the slab and intermittently reach the slab of the stilling basin. The range of these vortices is small. Vortices with horizontal axes and ver- tical vortices do not coincide in space and the vortices with horizontal axes only affect the position of the tail of the vertical vortices attached to the slab of the stilling basin.

悬栅消力池压强特性研究及优化

为了解决悬栅消力池由于时均压强过大产生底板失稳及悬栅压强破坏的问题,采用数值模拟的方法,在设计及校核流量下,对4种不同布置形式悬栅消力池内水位差及压强场进行研究,并在稳水效果较好的方案4基础上提出趾墩-悬栅联合及圆化悬栅2种消力池优化方案。结果表明,趾墩-悬栅联合优化方案相较于方案4在设计及校核流量下,底板时均压强最大分别降低63%、50%,有效降低了消力池内悬栅上表面C与下表面D之间的时均压强差值∣Δp2∣;圆化悬栅优化方案可使悬栅处总压强分布更加均匀,避免悬栅局部破坏。故针对有压强要求的大流量悬栅消力池,建议选择趾墩-悬栅联合辅助消能工消能方式。

Experimental investigation of the optimization of stilling basin with shallowwater cushion used for low Froude number energy dissipation

Energy dissipations induced by the hydraulic jump and the trajectory jet are the most widely known as the two dissipation modes at the downstream of flood discharging structures, which are often considered quite different even contradictory. However, such two energy dissipators can be used jointly and harmonically. In this paper, a new type of stilling basin with a shallow-water cushion and a triangular bottom deflector is proposed based on two different scale physical model tests of the flood discharging tunnel No.2 of Luding hydropower project. The experimental results show that the flow regime of the hydraulic jump in the presented stilling basin with bottom deflector enjoys a good and stable performance within a large range of flow rates and the energy dissipation rate is considerably high as compared to the conventional stilling basin even at a low Froude number. The results also indicate that the stilling basin with triangular bottom deflector has a better performance in improving the potential cavitation erosion according to the analysis of the pressure and the cavitation number compared to the trapezoidal one. The proposed new type of shallow-cushion stilling basin with a shallow-water cushion can be applied in similar energy dissipation projects with low Froude number and large range of flow rates.

超校核洪水对某重力坝泄洪水力特性的影响研究

跌坎底流消力池在保证较高消能率的前提下,能够有效降低临底流速,因此,在多个高坝工程中得到应用。梯级水库群中设防标准较低的挡水坝一旦遭遇巨型地震或超标准洪水,存在溃坝风险,而溃坝洪峰流量一般会超过下游重力坝的校核流量。为了预测超校核洪水对重力坝跌坎底流消力池泄洪消能的影响,通过物理模型试验研究了重力坝在设计、校核洪水及超校核洪水泄洪时典型水力学参数的变化情况。结果表明:随着洪水流量增大,溢流坝面掺气空腔长度呈现先减小后趋于稳定的规律,反弧段脉动压强值和消力池前段纵向压强梯度都明显增加,尾坎下游平均波高增大,总消能率有一定的减小。研究结果可为重力坝枢纽工程设计及预防超标洪水提供参考。

REDUCTION OF STILLING BASIN LENGTH WITH TALL END SILL

Experiments were conducted to characterize forced hydraulic jumps in stilling basins for enforced cases due to tail water level or dam site arrangement and construction. The case with a single tall sill was simulated in a horizontal flume downstream of a sluice gate. Results of experiments are compared with the classical hydraulic jump, and significant effect of tall sill on dissipation of energy in shorter distance was confirmed. Furthermore, the generated jumps were classified based on the ratio of sill height to basin length, and a simple design criterion was proposed to estimate the basin length for a desired jump and particular inflow.

消力池尾坎坡度对池内波浪特性影响的试验研究

本文基于波浪理论,通过水工模型不同尾坎坡度条件下常规式消力池和跌坎式消力池的波浪特性的研究,结果表明:消力池平均波高随尾坎坡度的增大而减小,尾坎坡度对跌坎式消力池波高的影响更大,但平均周期与尾坎坡度没有呈现出明显的规律;通过对试验数据的分析,得到了不同特征波高间的换算关系,得出了常规式消力池和跌坎式消力池的相对特征波高H1/100/h2的经验计算式;同时还发现出池波浪特性σw/h2与尾坎坡度i存在较好的线性关系。

深溪沟水电站泄洪闸消力池水力特性三维数值模拟研究

采用三维水气二相流数学模型,对深溪沟水电站现体型泄洪闸消力池在三个特征泄洪工况下的水力特性进行了数值模拟仿真计算研究,得到了泄洪流态、流场以及压强分布、紊动能和紊动能耗散率分布情况。计算结果显示,泄洪闸底板与进入消力池1:4斜坡之间的连接圆弧底板,由于半径偏小,存在稳定的较大负压,处于水跃区的闸墩——鱼背型尾墩圆弧两侧存在震荡波动型负压,负压临近区域出现空蚀破坏的可能性较大,数值模拟计算结果为分析判断泄洪闸流道、墩尾以及消力池底板的破坏原因提供了新的思路,为工程整改和制定工程的安全措施提供了理论依据,可供类似工程借鉴参考。

不求导加速迭代法在消力池深度计算中的应用

消力池深度计算是底流消能工消能防冲计算的重要内容之一,出池河床无水状态在泄水建筑物运行之前实际存在。为了解决消力池深度计算的困难,构造池深差方程,介绍了不求导加速迭代法(弦截法)计算收缩断面水深的步骤,进而求得消力池深度。结果表明:消力池深度计算值最大对应的下游水深为ht=φ^(’-2/3)h_(k)。研究成果对消力池设计具有重要意义。

大扩散角二级消力池对三元水流的调整影响

针对闸下翼墙每侧扩散角为12°时,中低水位期单级消力池出池流速横向分布易不均匀的问题,基于物理模型试验,研究了二级消力池布置时出池流速横向分布变化规律。结果表明,随着下游水位降低,第二级消力池尾坎左右岸处的出池流速呈减小—增大—减小—增大四个阶段变化,各阶段的起始水位高低和水位区间大小与来流弗劳德数Fr密切相关,来流Fr越小,第二级消力池内水跃横向扩散主流的能力越强,受到第一级消力池两侧回流的干扰越小,阶段二的水位区间范围越大,且更适应中低水位;下游水位越接近阶段二的终止水位,第二级消力池尾坎两端流速越大,出池流速横向分布越均匀;Fr相同时,第二级消力池调整水流作用在低水位时更显著,消能率更大。该成果可供闸下消能设计和闸门运行管理参考。

EXPERIMENTAL STUDIES ON FREQUENCY CHARACTERISTICS OF THE FLUCTUATING PRESSURE ACTING ON THE APRON OF STILLING BASINS WITH LOW FROUDE NUMBER

Using four types of stilling basin models,this paper studies frequency characteris- tics of the fluctuating pressure acting on the stilling basin apron when Froude number is not greater than 4.5.The testing results show that the frequency of fluctuating pressure,f_s in the ranges of 0. 4Hz≤f_s≤1.1Hz.0.2Hz≤f_s≤2.5Hz and 0.4Hz≤f_s≤3.3Hz.can be used as the design frequency corresponding to three patterns of hydraulic jump.The reliability of f_s for three jump patterns is all nearly equal to 90%.