【作者】 史万里；

【导师】 张堃元； 葛宁；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2012， 博士

【摘要】 湍流是一种极为复杂的流动状态，直至现在，人们对湍流机理的认识尚不完善，仍在探索之中。湍流问题又是在工程技术中经常涉及到的重要难题，如何精确数值模拟湍流的复杂流场，成了湍流研究的一个重要目标。近些年发展起来的大涡模拟方法受到人们特别关注，本文采用该方法进行了航空燃气涡轮相关的湍流流场的精确数值模拟与拟序结构的机理性研究，这是与发动机性能的提高密切相关的，其研究工作是具有重要的理论意义和工程应用价值。文中发展了高精度、高效率的可压缩流大涡模拟算法，主要包括：1）导出可压缩流大涡模拟控制方程和无需近壁修正的动态亚格子模型，并在大涡模拟算法中引进计算低马赫数的先进预处理技术，扩展了可压缩流大涡模拟算法的应用范围。2）在数值解法中，为了确保空间离散数值通量的高精度，对流项采用六阶WENOSYM格式离散、粘性项采用六阶紧致格式离散，并导出了紧致格式的相应系数；为了简化隐式迭代的矩阵形式，提出应用预处理之后的简化Roe Jacobians矩阵形式，推动了隐式预处理技术在工程中的应用。3）为了更好的给定适用于壁湍流大涡模拟的进口扰动，采用一种先进的合成涡方法，经过计算检验，确认其仅需很短的计算域就可以得到完全发展湍流，为大涡模拟在工程上应用提供了适用的进口边界条件。深入进行了相关的湍流边界层流场拟序结构及流动特性研究，主要包括：1）分析了平板槽道湍流边界层内层的拟序结构。把计算得到的拟序结构特征参数与Cantwell B. J.的平壁湍流边界层拟序结构参数做了对比，以及将流场统计平均值与经验公式及DNS解作对比，得到了基本一致的结果；对于计算中发现的两种发卡涡包结构，经与实验结果对比，证实了其结构的合理性；在对拟序涡结构时空演化研究中，详细地展示出单侧涡腿的发卡涡的形成过程。上述对平壁湍流中发卡涡研究中的新成果，尚未见诸其他文献。2）探讨了横向射流场中的发卡涡结构及射流脉冲控制发卡涡结构的优化气膜冷却方法。通过对稳定工况平板横向射流场的大涡模拟数值解的研究，分析了流场中典型的发卡涡对于射流场的影响，及发卡涡的发展演化过程，在此基础上结合其他文献的研究成果，从控制发卡涡的角度提出了射流进口方波脉冲控制优化气膜冷却的方法，并对不同脉冲频率下的射流场进行了大涡模拟计算分析，初步得到了方波脉冲使得发卡涡间歇出现，无发卡涡的间歇区间与射流出口脉冲波的“波谷”相对应的结论。此间歇区间的提出可以为今后涡轮气膜冷却设计提供一种新的思路。3）展示了无气膜冷却和带气膜冷却的MT1涡轮导叶流场中不同转捩模式的拟序结构形态。通过对流场大涡数值模拟的研究，展示了叶片吸力面无气膜射流时激波诱导下分离转捩过程和湍流中的发卡涡无序且密集的分布形态，文中称此形态为发卡涡“森林”，研究了位于涡轮导叶不同位置的气膜射流在叶片表面产生的射流拟序结构的形态，显示了逆转捩过程影响下的涡拉伸结构。展示上述转捩过程的近壁涡结构形态，这种在高压涡轮的研究中还是第一次。显然，本文进行的大涡模拟算法与湍流拟序结构的研究是密切相关的，高精度、高效率的可压缩流大涡模拟算法为湍流拟序结构的研究提供了技术支持，而槽道湍流、横向射流及涡轮导叶壁面流场的拟序结构和机理的研究为大涡模拟在涡轮中的实际应用提供了研究基础和理论依据。更多还原

【Abstract】 Turbulence is a kind of very complex flow. Up until now, people on the understanding of themechanism of turbulence is not perfect, still in the exploration. Turbulence in the engineeringtechnology question also often involves the important problem. How accurate numerical simulation ofturbulence complex flow field, the turbulent research become into one of the most important goals. Inrecent years the development of Large Eddy Simulation method is special attention by people. In thisarticle, Large Eddy Simulation was used to carry out the accurate numerical simulation of turbulentflow field and the Basic theory research of Coherent structure，which turbulent flow field has closerelations with air gas turbine，and the improvement of the performance of the engine is closely relatedto its research work. It is has important theoretical significance and application value.Compressible flow Large Eddy Simulation algorithm with high precision and high efficiencywas developed in the paper, its content mainly includes：1) The governing Equations of the non-dimensional Large Eddy Simulation and dynamicsub-grid scale model specific form of this article is derived in the general curvilinear coordinatesystem. Then the preconditioned algorithm is used in the code to expand the scope of the program’scalculation, so that it can calculation of transonic flows and low-Mach number flows, such as the flowfield of turbine vane with the film cooling.2) The finite volume methods take advantage of the integral form of the governing equation toachieve a algebraic discrete approximation for numerical calculations. In order to ensure generatednumber the discrete error did not exceed the influence of the sub-grid scale model, the numerical fluxwas calculated by six order precision WENOSYM scheme and Compact scheme. The WENOSYMscheme was adopted on calculation of the Convection flux. The Compact scheme was adopted oncalculation of the viscous flux and the specific coefficient was deduced.In this paper, the implicit Newton iteration scheme was used for temporal discretization. Thenthe analytical S-W Jacobians formula and simplify Roe Jacobians formula of implicit Jacobiansmatrix was deduced. The engineering practicability of Roe Jacobians matrix was confirmed. Thiswork makes a good evolution for the implicit method.3) In the process of computation, a given imported disturbance in the boundary layer is using asynthetic vortex approach. The computation result shows that the flow in calculation domaindeveloped turbulence after a short development section. The application of the approach is theengineering application of positive preparation. The turbulent boundary layers fields related to Coherent structure and the flow characteristicswere further research in the paper. Its content mainly includes:1）Coherent structure in the inner layer of the flat channel turbulent boundary layer is analyzed.Solution of the flow field statistical average was compared with the empirical formula and DNS result,and the characteristic parameters of large eddy coherent structures was compared with Cantwell’sparameters. The results of comparison were very well. The two kinds of hairpin vortex packetstructures of the calculated results were compared with experimental results to confirm its structure.Studying the temporal evolution process of coherent vortex structures, the hairpin vortices withunilateral vortex leg formation process was discussed. This conclusion of the hairpin vortices in theflat-wall turbulence is still not seen in the literature.2）Hairpin vortex structure of the Jet into Cross-flow and the method of Pulsation optimizing filmcooling efficiency was discussed. On the research of the flat basis, the flow field of the Jet inCross-flow that was applied in the gas turbine film cooling is studied. Through the analysis of thestructure and development of the hairpin vortices in flow field, the flow’s characteristics of the Jet inCross-flow were learned. Then combined with the literatures, the idea that the hairpin vortices in themain body of jet are control by the pulsed jet is proposed. Through the analysis of the pulsed jet flowfield simulation results, the initial conclusions are that the pulsation controls the intermittent existenceof the hairpin vortices’ group and the interval between the hairpin vortices’ groups corresponding tothe frequency of pulsation.3）Coherent structure form In the transition process on flow filed of MT1turbine vane is to show.Flow fields of the MT1turbine guide vane with film cooling and without film cooling were simulated.Without film cooling, coherent structures of shock-induced separated flow transition were showed onthe suction side of the blade. With film cooling, the forms of coherent structures that was produced byfilm cooling jet in different locations on blade surface were researched, and the influence thatcurvature of wall surface has an effect on jet’s structures were discussed, and the vortex stretching byinfluence of reverse transition were shown.Obviously, in this paper the Large Eddy Simulation algorithm and to the research of theturbulence’s Coherent structure are closely related. The Large eddy simulation Algorithm providestechnical support for the research of Coherent structure, and the research provides researchfoundation and the theoretical basis for the practical application of the LES in flow field of turbinevane, that the research is related with flow field of flat，the Jet into Cross-flow，and the turbine vane.更多还原