摘要
采用谱方法求解柱坐标系下三维不可压缩流Navier-Stokes方程,直接数值模拟了不同半径比下的同心旋转圆筒间的Taylor-Couette(TC)湍流问题.由于TC湍流是由大尺度Taylor涡和湍流随机脉动的叠加而成,采用周向平均成功识别了TC湍流中的大尺度Taylor涡,并将其诱导的脉动流动与湍流随机脉动分离开来,对比分析了不同半径比下大尺度Taylor涡对脉动强度和湍动能的贡献;同时,通过计算雷诺应力输运方程,研究了半径比对湍动能生成、耗散和再分配等动力学特性的影响.计算结果表明,在小半径比的宽槽TC湍流中,Taylor涡诱导的脉动流相对较弱,湍流随机脉动更为强烈,其对湍流统计特性的影响占优;在大半径比的窄槽TC湍流中,流体脉动特性主要源于Taylor涡的贡献;另外,随着半径比的增大,近外壁面附近流体沿周向剪切作用增强,流场表现出类似于平板Couette流的流动特性.
Direct numerical simulations （DNS ） using the spectral method to solve the three-dimensional incompressible Navier-Stokes equations in cylindrical coordinates were performed to study the influence of radius ratio on the turbulent Taylor-Couette （TC） flows between two rotating concentric cylinders .As the TC flows are well accepted as imposition of turbulence fluctuations on the organized large-scale Taylor vortices （TV ） ,averaging along the azimuthal direction and in time was used to separate the large-scale TVs from the TC flow and thus divide the turbulent motions into the TVs-induced and the randomly fluctuating parts . The contributions to the velocity fluctuation intensities and turbulent kinetic energy coming from the TVs-induced and turbulent fluctuating motions , were examined for different radius ratios .Moreover ,the budget equations of Reynolds stresses were calculated to elucidate the influence of radius ratio on the dynamical features of turbulence energy production ,dissipation and redistribution .It was demonstrated that for a narrow-gap TC flow with a low radius ratio ,the relatively stronger random fluctuating motions have great contributions to the statistics ,as compared to the TVs-induced fluctuations which ,however , becomes dominant in a wide-gap TC flow with a high radius ratio . Additionally , increasing radius ratios leads to an increase in the shear rates of mean flow in the near outer wall region . As a consequence ,the TC flow with a high radius ratio behaves in a similar fashion to the planar Couette flow .
基金
国家自然科学基金(11272306)资助
