基于浸入边界法研究水轮机双列叶栅绕流特性

发布时间：2018-06-20 18:36

本文选题：浸入边界法 + 有限元方法　；参考：《昆明理工大学》2014年硕士论文

【摘要】：浸入边界法是基于笛卡尔网格系统来计算柔性结构体或刚性结构体和粘性流体相互作用的一种新型数值方法。在计算复杂几何边界、非定常移动边界以及流固耦合这些问题上,浸入边界法体现出和传统计算流体力学方法的不同和先进性。如刚体发生大位移时,对于常规的基于动网格技术的求解方法就提出了挑战,网格生成困难、网格畸形以及网格更新等问题频频出现。而浸入边界法采用笛卡尔网格技术,无需在计算过程中更新网格,在具有大位移的刚体运动计算中显现出优越性。同时浸入边界法还有算法简单,编程容易,并行计算方便,边界容易处理,计算效率高等很多优势。对于柔性结构体和刚性结构体的处理,科研人员不断提出新的处理方法,像基于能量函数的浸入边界法、有限元离散的浸入边界方法、离散直接力浸入边界方法、虚拟边界法(反馈力浸入边界法)等。同时更是向模拟高雷诺数运动的浸入边界法以及浸入边界法同大涡模拟方法、格子波尔兹曼方法相结合的方法进行发展,极大地扩展了浸入边界法的应用范围。由于水轮机流道形状和水流运动的复杂性,使得调节控制进入转轮液流流量的导叶至关重要,导叶水力性能的优劣直接影响到转轮内的流态从而影响水轮机的效率和稳定性。本文根据实验室HLA551-LJ-43型混流式水轮机的双列叶栅建立模型,基于有限元浸入边界方法和传统的反馈力方法对水轮机内重要的水力过流部件双列叶栅进行数值模拟,得到一些有意义的结果,对深入了解导水部件的运动机理有一定的参考价值。论文共计七章,其主要研究内容如下： (1)采用二维固定圆柱绕流算例和二维旋转圆柱绕流算例分别去验证反馈力浸入边界法处理刚体绕流和动边界问题上的可行性。计算结果同文献和实验结果进行对比,符合良好。 (2)根据实验室水轮机双列叶栅的数据建立数值计算模型,基于反馈力浸入边界法分析了水轮机双列叶栅的流场分布特性以及导叶尾迹区各流向断面压力、速度和各量的不均匀指标。 (3)通过验证算例证实反馈力浸入边界法处理动边界问题的可行性,对水电站水力过渡过程中水轮机活动导叶摆动绕流后的动边界流场进行数值模拟,得到导叶绕流后的流场分布特性和涡结构的演化过程。 (4)对水轮机活动导叶的减阻研究进行初步探讨,分析了在18度攻角下,导叶从吹流法、制造漩涡法和柔性壁面法三个方向进行数值模拟,使用反馈力浸入边界法结合混合有限元浸入边界法。对比于不做特别处理的活动导叶进行分析,从表面涡的脱落、升力阻力来看不同的减阻形式下的流场情况。
[Abstract]:The immersion boundary method is a new numerical method to calculate the interaction between flexible or rigid structure and viscous fluid based on Cartesian grid system. In the calculation of complex geometry boundary, unsteady moving boundary and fluid-solid coupling, the immersion boundary method is different and advanced than the traditional computational fluid dynamics method. For example, when rigid body has large displacement, it is a challenge to the conventional solution method based on moving mesh technology, such as the difficulty of mesh generation, mesh malformation and mesh renewal. However, the immersion boundary method uses Cartesian mesh technology, which does not need to update the grid in the calculation process, so it shows its superiority in the calculation of rigid body motion with large displacement. At the same time, immersion boundary method has many advantages, such as simple algorithm, easy programming, convenient parallel computation, easy boundary processing, high computational efficiency and so on. For the treatment of flexible and rigid structures, researchers have been proposing new methods, such as the immersion boundary method based on energy function, the discrete immersion boundary method of finite element method, and the discrete direct force immersion boundary method. Virtual boundary method (feedback force immersion boundary method) and so on. At the same time, the immersion boundary method, the large eddy simulation method and the lattice Boltzmann method are developed to simulate the movement of high Reynolds number, which greatly extend the scope of application of the immersion boundary method. Because of the complexity of runner shape and flow movement, it is very important to regulate and control the flow into the runner. The hydraulic performance of the guide vane has a direct impact on the flow state in the runner, thus affecting the efficiency and stability of the turbine. In this paper, based on the model of double-row cascade of HLA551-LJ-43 Francis turbine in laboratory, the numerical simulation is carried out based on the finite element immersion boundary method and the traditional feedback force method. Some meaningful results are obtained, which is valuable for further understanding the motion mechanism of the water-conducting components. There are seven chapters in this paper. The main contents are as follows: 1) the feasibility of the feedback force immersion boundary method in dealing with the flow around rigid body and moving boundary is verified by two dimensional fixed cylinder flow examples and two dimensional rotating cylinder flow cases respectively. The calculated results are in good agreement with the literature and experimental results. Based on the feedback force immersion boundary method, the flow field distribution characteristics of the turbine double-row cascade and the flow direction cross-section pressure in the guide vane wake region are analyzed. The inhomogeneity index of velocity and quantity. 3) the feasibility of the feedback force immersion boundary method in solving the moving boundary problem is verified by an example. The dynamic boundary flow field around the turbine guide vane is numerically simulated during the hydraulic transition of hydropower station. The characteristics of flow field distribution and the evolution process of vortex structure after flow around the guide vane are obtained. The numerical simulation is carried out in three directions of the vortex manufacturing method and the flexible wall method. The feedback force immersion boundary method combined with the hybrid finite element immersion boundary method is used. Compared with the moving guide vane without special treatment, the flow field under different drag reduction forms can be seen from the surface vortex shedding and lift resistance.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV136.1

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