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

【摘要】：浸入邊界法是基于笛卡爾網(wǎng)格系統(tǒng)來計(jì)算柔性結(jié)構(gòu)體或剛性結(jié)構(gòu)體和粘性流體相互作用的一種新型數(shù)值方法。在計(jì)算復(fù)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(jì)算流體力學(xué)方法的不同和先進(jìn)性。如剛體發(fā)生大位移時(shí),對于常規(guī)的基于動網(wǎng)格技術(shù)的求解方法就提出了挑戰(zhàn),網(wǎng)格生成困難、網(wǎng)格畸形以及網(wǎng)格更新等問題頻頻出現(xiàn)。而浸入邊界法采用笛卡爾網(wǎng)格技術(shù),無需在計(jì)算過程中更新網(wǎng)格,在具有大位移的剛體運(yùn)動計(jì)算中顯現(xiàn)出優(yōu)越性。同時(shí)浸入邊界法還有算法簡單,編程容易,并行計(jì)算方便,邊界容易處理,計(jì)算效率高等很多優(yōu)勢。對于柔性結(jié)構(gòu)體和剛性結(jié)構(gòu)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(shù)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(shí)更是向模擬高雷諾數(shù)運(yùn)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(jié)合的方法進(jìn)行發(fā)展,極大地?cái)U(kuò)展了浸入邊界法的應(yīng)用范圍。 由于水輪機(jī)流道形狀和水流運(yùn)動的復(fù)雜性,使得調(diào)節(jié)控制進(jìn)入轉(zhuǎn)輪液流流量的導(dǎo)葉至關(guān)重要,導(dǎo)葉水力性能的優(yōu)劣直接影響到轉(zhuǎn)輪內(nèi)的流態(tài)從而影響水輪機(jī)的效率和穩(wěn)定性。本文根據(jù)實(shí)驗(yàn)室HLA551-LJ-43型混流式水輪機(jī)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(jī)內(nèi)重要的水力過流部件雙列葉柵進(jìn)行數(shù)值模擬,得到一些有意義的結(jié)果,對深入了解導(dǎo)水部件的運(yùn)動機(jī)理有一定的參考價(jià)值。論文共計(jì)七章,其主要研究內(nèi)容如下： (1)采用二維固定圓柱繞流算例和二維旋轉(zhuǎn)圓柱繞流算例分別去驗(yàn)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(jì)算結(jié)果同文獻(xiàn)和實(shí)驗(yàn)結(jié)果進(jìn)行對比,符合良好。 (2)根據(jù)實(shí)驗(yàn)室水輪機(jī)雙列葉柵的數(shù)據(jù)建立數(shù)值計(jì)算模型,基于反饋力浸入邊界法分析了水輪機(jī)雙列葉柵的流場分布特性以及導(dǎo)葉尾跡區(qū)各流向斷面壓力、速度和各量的不均勻指標(biāo)。 (3)通過驗(yàn)證算例證實(shí)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(jī)活動導(dǎo)葉擺動繞流后的動邊界流場進(jìn)行數(shù)值模擬,得到導(dǎo)葉繞流后的流場分布特性和渦結(jié)構(gòu)的演化過程。 (4)對水輪機(jī)活動導(dǎo)葉的減阻研究進(jìn)行初步探討,分析了在18度攻角下,導(dǎo)葉從吹流法、制造漩渦法和柔性壁面法三個(gè)方向進(jìn)行數(shù)值模擬,使用反饋力浸入邊界法結(jié)合混合有限元浸入邊界法。對比于不做特別處理的活動導(dǎo)葉進(jìn)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(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TV136.1

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