本文選題：浸入邊界法 + 有限元方法��； 參考：《昆明理工大學》2014年碩士論文

【摘要】：浸入邊界法是基于笛卡爾網格系統(tǒng)來計算柔性結構體或剛性結構體和粘性流體相互作用的一種新型數值方法。在計算復雜幾何邊界、非定常移動邊界以及流固耦合這些問題上,浸入邊界法體現(xiàn)出和傳統(tǒng)計算流體力學方法的不同和先進性。如剛體發(fā)生大位移時,對于常規(guī)的基于動網格技術的求解方法就提出了挑戰(zhàn),網格生成困難、網格畸形以及網格更新等問題頻頻出現(xiàn)。而浸入邊界法采用笛卡爾網格技術,無需在計算過程中更新網格,在具有大位移的剛體運動計算中顯現(xiàn)出優(yōu)越性。同時浸入邊界法還有算法簡單,編程容易,并行計算方便,邊界容易處理,計算效率高等很多優(yōu)勢。對于柔性結構體和剛性結構體的處理,科研人員不斷提出新的處理方法,像基于能量函數的浸入邊界法、有限元離散的浸入邊界方法、離散直接力浸入邊界方法、虛擬邊界法(反饋力浸入邊界法)等。同時更是向模擬高雷諾數運動的浸入邊界法以及浸入邊界法同大渦模擬方法、格子波爾茲曼方法相結合的方法進行發(fā)展,極大地擴展了浸入邊界法的應用范圍。 由于水輪機流道形狀和水流運動的復雜性,使得調節(jié)控制進入轉輪液流流量的導葉至關重要,導葉水力性能的優(yōu)劣直接影響到轉輪內的流態(tài)從而影響水輪機的效率和穩(wěn)定性。本文根據實驗室HLA551-LJ-43型混流式水輪機的雙列葉柵建立模型,基于有限元浸入邊界方法和傳統(tǒng)的反饋力方法對水輪機內重要的水力過流部件雙列葉柵進行數值模擬,得到一些有意義的結果,對深入了解導水部件的運動機理有一定的參考價值。論文共計七章,其主要研究內容如下： (1)采用二維固定圓柱繞流算例和二維旋轉圓柱繞流算例分別去驗證反饋力浸入邊界法處理剛體繞流和動邊界問題上的可行性。計算結果同文獻和實驗結果進行對比,符合良好。 (2)根據實驗室水輪機雙列葉柵的數據建立數值計算模型,基于反饋力浸入邊界法分析了水輪機雙列葉柵的流場分布特性以及導葉尾跡區(qū)各流向斷面壓力、速度和各量的不均勻指標。 (3)通過驗證算例證實反饋力浸入邊界法處理動邊界問題的可行性,對水電站水力過渡過程中水輪機活動導葉擺動繞流后的動邊界流場進行數值模擬,得到導葉繞流后的流場分布特性和渦結構的演化過程。 (4)對水輪機活動導葉的減阻研究進行初步探討,分析了在18度攻角下,導葉從吹流法、制造漩渦法和柔性壁面法三個方向進行數值模擬,使用反饋力浸入邊界法結合混合有限元浸入邊界法。對比于不做特別處理的活動導葉進行分析,從表面渦的脫落、升力阻力來看不同的減阻形式下的流場情況。
[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.
【學位授予單位】：昆明理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TV136.1

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