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基于边界层转捩后阶段的高精度直接数值模拟结果,发现流向条纹结构的低速条纹的演化过程中存在不连续现象,以及随高速条纹的发展会出现称之为"高速斑"的新特性. 通过详细剖析边界层转捩过程中的复杂涡系结构以及上喷下扫流动现象,证实流向高低速条纹新特性与流场涡系结构的演化过程紧密相关.
关键词:
流向条纹
边界层
转捩
直接数值模拟 相似文献
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三维扰动波的非平行边界层稳定性研究 总被引:2,自引:0,他引:2
导出了三维扰动波的原始变量形式的抛物化稳定性方程(PSE),研究了三维空间模态TS波的非平行边界层稳定性问题.采用了法向四阶紧致格式,以提高计算精度.通过给出不会导致奇性的坐标变换、修改外边界条件以及克服平行流初始值的瞬态影响和推进步长的限制,保证了计算的数值稳定.用补全元素带状矩阵法求解块三对角矩阵,大大提高了速度.计算结果清楚地显示了三维扰动波的演化过程和非平行性对边界层稳定性的影响,特别是,观察到非平行性对三维扰动波的影响,有时会使其稳定性出现逆转的现象.还研究了逆压梯度的作用.算例的结果与其他结果符合良好. 相似文献
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用Navier-Stokes方程直接数值模拟平板边界层流动中湍斑的形成和演化过程.发展了模拟湍斑的高精度、高分辨率的高效计算方法,包括推出四阶时间分裂法以提高精度;提出三维耦合差分方法,用于关于压力的泊松方程和关于速度的亥姆霍兹方程的空间离散,建立其四阶三维耦合中心差分格式;并采用四阶紧致迎风差分格式,避免了一般四阶中心差分格式不适用于边界邻域的困难和提高了分辨率;精心地处理各种边界条件,以保持精度和稳定.该方法适用于包含边界邻域的整个区域内的湍斑模拟.通过模拟平板边界层流动中湍斑的复杂演化过程,显示了湍斑的基本特征. 相似文献
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The three-dimensional H-type nonlinear evolution process for the problem of boundary layer stability is studied by using a newly developed method called parabolic stability equations (PSE). The key initial conditions for sub-harmonic disturbances are obtained by means of the secondaryinstability theory. The initial solutions of two-dimensional harmonic waves are expressed in Landau expansions. The numerical techniques developed in this paper, including the higher order spectrum method and the more effective algebraic mapping for dealing with the problem of an infinite region, increase the numerical accuracy and the rate of convergence greatly. With the predictor-corrector approach in the marching procedure, the normalization, which is very important for PSE method, is satisfied and the stability of the numerical calculation can be assured. The effects of different pressure gradients, including the favorable and adverse pressure gradients of the basic flow, on the “H-type“ evolution are studied in detail. The results of the three-dimensional nonlinear “H-type“ evolution are given accurately and show good agreement with the data of the experiment and the results of the DNS from the curves of the amplitude variation, disturbance velocity profile and the evolution of velocity. 相似文献
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Nonlinear evolution analysis of T-S disturbance wave at finite amplitude in nonparallel boundary layers 总被引:1,自引:1,他引:0
IntroductionNonlinearstabilityprobleminnonparallelboundarylayersneedsmainlyconsidertheevolutionofunstabilityT_Swaveandinteractionbetweenwavesofdifferentfrequencies.Itisveryimportanttosimulateaccuratelyspatialevolutionroleofdisturbanceinboundarylayers,… 相似文献
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Formation and evolution of secondary streamwise vortices in the compressible transitional boundary layers over a flat plate
are studied using a direct numerical simulation method with high-order accuracy and highly effective non-reflecting characteristic
boundary conditions. Generation and development processes of the secondary streamwise vortices in the complicated transitional
boundary flow are clearly analyzed based on the of numerical results, and the effects on the formation of the ring-like vortex
that is vital to the boundary layer transition are explored. A new mechanism forming the ring-like vortex through the mutual
effect of the primary and secondary streamwise vortices is expressed. 相似文献