共查询到19条相似文献,搜索用时 359 毫秒
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为提高多折回通道型同侧竖缝式鱼道的消能作用、降低竖缝流速,以利于鱼道过鱼,在设计工况下通过模型试验研究其水力特性。试验分析了设计工况下鱼道典型部位的流态、水面线分布以及竖缝表面和底部流速的沿程分布情况,总结了多折回通道型鱼道在不同通道区段竖缝流速的沿程分布规律。结果表明,设计工况下竖缝流速在通道一、三中沿程变化较小,通道二中下降稍快,流速大小均在0.7~0.9m/s的较高水平。针对竖缝流速大于过鱼喜好流速的问题,提出了加糙鱼道边壁的优化设计方案。对比优化前后的流速分布可知,边壁加糙措施有效降低了鱼道竖缝流速大小。试验研究成果可为类似工程提供借鉴。 相似文献
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竖缝式鱼道因其能够适应不同水位变化、消能效果明显、水流流态稳定等特点而逐渐引起水利工程界的重视。通过数值模拟的方法探究了池室长宽比对异侧式竖缝鱼道水力特性的影响,结果表明,池室长宽比的变化对单位体积耗散率影响较小;主流区沿程衰减率先随池室长宽比的增大而增大,后保持不变。池室长宽比越大,池室内最大流速越靠近竖缝处;不同池室长宽比,池室主流流速与池室最大流速(主流流速沿程变化最大值)比值在一定范围内。池室长宽比L/B在1.00~1.13之间,可在鱼道主流区内获得较好的水流流态、较大的回流区及较好的消能效果,有利于研究区内鱼类的洄游。 相似文献
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为研究不同湍流模型对竖缝式鱼道数值模拟的适用性和准确度,采用RNGκ-ε模型、大涡模拟(LES)模型及分离涡(DES)模型3种湍流模型对某竖缝式鱼道进行数值模拟,并对比分析了模拟的竖缝式鱼道流态特征、流速及湍动能等水力指标值与实测数据。结果表明,3种模型均可较为准确地解析鱼道池室流态特性,其中DES模型最能反映竖缝式鱼道的流态、流速分布;综合模拟成本后,RNGκ-ε模型在湍动能模拟方面较其他两个瞬时模型具有优势。因此,鱼道数值模拟在不追求较高精度流场特征的要求下,应优先选用RNGκ-ε模型。研究结果可为今后数值模拟在鱼道工程的应用提供参考。 相似文献
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为探讨台阶式溢洪道水流空化特性,结合某水库实际工程,采用水工模型试验方法,研究了不同流量条件下台阶式溢洪道的流速、压强分布和空化特性。结果表明,在溢流堰段,水流流速沿程逐渐增大,压强沿程逐渐减小,水流空化数也逐渐减小;在台阶段,流速沿程先逐渐增大,在初始掺气点达到最大值后有所下降,随后逐渐增加并趋于某一常数,压强沿程呈波浪式发展,水流空化数也呈波浪式发展;在消力池内,水流流速先逐渐减小,达到最小值后又逐渐增大,压强先逐渐增大,增大到最大值后逐渐减小,然后减小到最小值,再逐渐增大,水流空化数沿程先逐渐增大,达到最大值后逐渐减小;台阶水平面上的空化数从台阶凹角向凸角逐渐增大,竖直面上的空化数从底部向顶部逐渐减小;同时水流空化数随着流量的增加而减小。 相似文献
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根据某工程特点和过鱼要求,提出了三种不同的结构方案,采用标准三维紊流数学模型对比分析了三种方案的水力学特性,并用模型试验对数值模拟结果进行验证。对流场、过鱼适宜性空间和紊动能的分析研究表明,在单级池室中主流流速有先减小再增大的趋势,最大流速出现在长蛮石墙附近;主流两侧的低流速区紊动能范围为0~0.02m~2/s~2,能够形成紊动能较弱的鱼类休息区;同等长宽比时,增加底宽主流最大流速减小0.1~0.2m/s,低流速区面积相对增加5%~8%;同等长宽比和底宽时,鱼道出口的两级池室改为平坡,紊动能减小0.01m~2/s~2。研究结果为交错蛮石墙式仿自然鱼道在实际工程中的应用提供了参考。 相似文献
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弯道干流与支流交汇口垂线流速分布的试验研究 总被引:1,自引:0,他引:1
为了深入了解干支流汇合口水流的运动特性,通过概化模型试验,利用ADV流速仪对顺直型支流与弯曲型干流60°交汇角的汇合口区域进行了垂线流速测量,验证了试验数据的可靠性,分析了弯道干支流汇合口区域垂线流速分布特性。结果表明,随汇流比增大,交汇断面上游纵向流速减小,交汇口各断面径向流速绝对值增大,断面环流方向发生改变;汇流比较大时,交汇断面最大纵向、径向流速点出现于凹岸侧;交汇断面下游附近最大纵向、径向流速偏向弯道中心线;在交汇断面下游附近的凹岸出现水流分离区。 相似文献
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Using a novel concept, the present study experimentally investigates underlying physics pertaining to statistics of the flame front position and the flame front velocity in turbulent premixed V-shaped flames. The concept is associated with characteristics of the reactants velocity at the vicinity of the flame front, referred to as the edge velocity. The experiments are performed using simultaneous Mie scattering and Particle Image Velocimetry techniques. Three mean streamwise exit velocities of: 4.0, 6.2, and 8.6 m/s along with three fuel–air equivalence ratios of: 0.7, 0.8, and 0.9 are examined. The results show that fluctuations of the flame front position and the flame front velocity are induced by the fluctuations of the component of the edge velocity transverse to the mean flow direction. Analysis of the results show that the mean of the flame front velocity in the normal direction to the flame front is significantly dependent on the vertical distance from the flame-holder. Relatively close to the flame-holder, the mean of the flame front velocity in the direction normal to the flame front is about zero; however, it increases to values several times larger than the laminar flame speed by increasing the vertical distance from the flame-holder. 相似文献
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为获得风力机近尾流风速在垂直方向和水平方向的变化规律,提出一种测量风力机近尾流区风速的实测方法。针对某沿海滩涂风电场,采用2台搭载风速仪的无人机对近尾流区进行测量。结果表明:垂直方向,尾流和来流风速比值在1.0D~2.5D处(D为风轮直径)随着高度的增加呈先减小后增大的趋势,在轮毂中轴线处存在最小值0.53~0.68;风速比值沿轮毂中轴线呈非对称分布。0.5D处风速比值分别在上下风轮处存在2个极小值0.56和0.50。水平方向,风速比值在1.0D~3.0D处沿径向距离从左向右呈先减小后增大的趋势,在轮毂中轴线处存在最小值(0.54~0.78);风速比值沿轮毂中轴线呈对称分布,随着风轮下游距离的增加呈扩张趋势。最后给出用于A类风场风力机下游尾流风速剖面的预测公式。 相似文献
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用激光多普勒测速仪对旋流器产生的强湍流有自由射流的速度场和湍流场进行了实验研究。实验结果表明,这种旋流器十分有利于中心回流区的形成,射流的平均速度分布沿轴向快速地衰减,有旋自由射流呈现湍流各向异性,特别是在回流区域中,本文对流场中湍流动量传递的方向进行了讨论。 相似文献
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Wind tunnel investigation on the effect of the turbine tower on wind turbines wake symmetry
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In wind farms, the wake of the upstream turbines becomes the inflow for the downstream machines. Ideally, the turbine wake is a stable vortex system. In reality, because of factors like background turbulence, mean flow shear, and tower‐wake interaction, the wake velocity deficit is not symmetric and is displaced away from its mean position. The irregular velocity profile leads to a decreased efficiency and increased blade stress levels for the downstream turbines. The object of this work is the experimental investigation of the effect of the wind turbine tower on the symmetry and displacement of the wake velocity deficit induced by one and two in‐line model wind turbines (,D= 0.9 m). The results of the experiments, performed in the closed‐loop wind tunnel of the Norwegian University of Science and Technology in Trondheim (Norway), showed that the wake of the single turbine expanded more in the horizontal direction (side‐wall normal) than in the vertical (floor normal) direction and that the center of the wake vortex had a tendency to move toward the wind tunnel floor as it was advected downstream from the rotor. The wake of the turbine tandem showed a similar behavior, with a larger degree of non‐symmetry. The analysis of the cross‐stream velocity profiles revealed that the non‐symmetries were caused by a different cross‐stream momentum transport in the top‐tip and bottom‐tip region, induced by the turbine tower wake. In fact, when a second additional turbine tower, mirroring the original one, was installed above the turbine nacelle, the wake recovered its symmetric structure. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Chemically reacting magnetohydrodynamic radiative flow of convective free stream nanofluid through a stretching cylinder using Buongiorno's model is discussed. The behavior of Brownian motion and thermophoresis is also appropriate. By adopting the similarity transformation, the partial differential equation is diminished into a first-order ordinary differential equation (ODE). Since transformed equations are highly nonlinear these ODEs are solved by using mathematical simulation. The shooting procedure has been adopted to resolve converted equations along the attendant Runge–Kutta–Fehlberg technique. The reason behind the present work is to research the effects of different parameters of fluid, namely, magnetic parameter, free stream velocity, Brownian motion, thermophoresis, chemical reaction, heat radiation, Lewis number on nanoparticle concentration, temperature, and velocity distribution. The impact of significantly participating parameters on velocity, concentration, and temperature distribution is distinguished with appropriate physical significance. The convergence of solutions for temperature, velocity, and concentration profiles is studied carefully. The measured challenges of nanofluids are scale-up capacity, increase in nanofluid viscosity, nanoparticle dispersion, and nanofluid cost. It is observed that nanoparticle temperature rises for more value of Brownian motion parameter while it declines for higher Lewis number. The current study in the cylindrical region is related to novel free stream flow in the presence of chemical reactions along with convective conditions which find applications in electronic systems like microprocessors and in a wide variety of industries and in the field of biotechnology. The current research helps control the transport phenomena, helping production companies to find the quality of the desired product. 相似文献