排序方式: 共有77条查询结果,搜索用时 15 毫秒
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1引言分离流在本质上是粘性流动和非粘性流动互相干扰的一类复杂流动,绕流中的分离现象往往使水力机械叶片水力损失急剧增加、效率下降,形成的压力脉动还将造成水力机械的振动山。尾水管涡带的形成和分离密切相关,是造成水力机械在部分负荷时机组振动和出力摆动的主要根源[‘j,在偏离最优工况时,叶片内的分离流动将十分严重。本文结合某电站机组出现的振动问题,求解Navier-Stokes的二维方程组,对导叶分离流场进行了分析。2控制微分方程组设导叶内流动为二维不可压粘性流动,控制微分方程组的守恒形式为:。、。分别为。,y两方向… 相似文献
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水轮机蜗壳和固定导叶内部三维紊流流场数值研究 总被引:15,自引:2,他引:13
1引言用数值方法研究蜗壳和固定导叶内部流场是改进和优化蜗壳和固定导叶设计的一个重要手段。早期的数值研究大多基于势流理论[1~2],随着计算机技术和计算流体动力学的迅速发展,蜗壳和固定导叶内部三维紊流的数值分析已经成为可能t’-’]。本文以三峡水轮机组内部流动的研究为背景,基于N-S方程和标准的k一。紊流模型,采用贴体座标和交错网格系统,用SIMPLEC算法对三峡模型机组蜗壳和固定导叶内部的流动进行数值模拟,提出设计工况时蜗壳和固定导叶内三维素流数值模拟计算结果,为改进蜗壳和固定导叶设计提供了一些有益的参考资… 相似文献
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The dense solid-phase governing equations for two-phase flows are obtained by using the kinetic theory of gas molecules. Assuming that the solid-phase velocity distributions obey the Maxwell equations, the collision term for particles under dense two-phase flow conditions is also derived. In comparison with the governing equations of a dilute two-phase flow, the solid-particle‘s governing equations are developed for a dense turbulent solid-liquid flow by adopting some relevant terms from the dilute two-phase governing equations. Based on Cauchy-Helmholtz theorem and Smagorinsky model, a second-order dynamic sub-grid-scale (SGS) model, in which the sub-grid-scale stress is a function of both the strain-rate tensor and the rotation-rate tensor, is proposed to model the two-phase governing equations by applying dimension analyses. Applying the SIMPLEC algorithm and staggering grid system to the two-phase discretized governing equations and employing the slip boundary conditions on the walls, the velocity and pressure fields, and the volumetric concentration are calculated. The simulation results are in a fairly good agreement with experimental data in two operating cases in a conduit with a rectangular cross-section and these comparisons imply that these models are practical. 相似文献
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本文采用SST k-ω湍流模型对环形压水室离心泵和螺旋形压水室离心泵进行了数值模拟,比较了两种泵在设计与非设计工况运行时叶轮所受的径向力,并对两种泵的压力沿叶轮出口分布进行了分析。分析结果发现,当运行在设计工况时,两泵的叶轮受力表现出周期性,螺旋形压水室离心泵的叶轮所受到的径向力相对更大,这是由于受到压水室自身设计和隔舌的影响,使螺旋形压水室离心泵的压力沿叶轮出口分布更加不均匀,从而导致径向力增大。此外,与设计工况相比,两泵在非设计工况运行时叶轮所受径向力更大,且在小流量时所受径向力的周期性与设计工况相比发生显著变化。 相似文献