时间演化分形流场的直接数值模拟  

Direct numerical simulation of temporally evolving fractal-generated turbulence

作　　者：石均 邱颖宁[1] 周毅 SHI Jun;QIU Ying-ning;ZHOU Yi(School of Energy and Power Engineering,Nanjing University of Science and Technology,Nanjing 210094,China)

机构地区：[1]南京理工大学能源与动力工程学院,江苏南京210094

出　　处：《浙江大学学报（工学版）》2022年第8期1606-1621,共16页Journal of Zhejiang University：Engineering Science

基　　金：国家重点研发计划政府间国际科技新合作重点专项(2019YFE0104800)。

摘　　要：为了研究分形网格湍流中小尺度结构的运动规律,在具有高分辨率的空间网格中,开展分形流场时间演化的直接数值模拟,并通过模拟具有相同阻塞率的规则流场进行对比研究.通过给流场中注入合适的能量扰动,促使2类流场从层流初始状态向湍流状态过渡.数值模拟结果表明,与规则流场相比,分形流场受到初始条件影响的持续时间更久,同时在时间演化的初期,分形流场产生的动能更小,但分形流场在衰减期的大尺度运动起到强化湍流的作用,导致其产生的动能更大、湍流强度更高,有利于实现对流场的被动控制.分形流场和规则流场均在截断波数kM≈20时满足能量与耗散水平相等,但有别于能量级串过程中能量传输与耗散的平衡.当流场达到统计均匀后,规则流场衰减符合Saffman湍流特征的规律.The direct numerical simulation of temporal evolution of fractal flow field was performed in a high resolution spatial grid to study the characteristics of small scale motions in fractal-generated turbulence.An additional numerical simulation of regular-generated turbulence with the same blockage ratio was also performed for comparison.Random disturbances with appropriate energy distribution were imposed for a quick transition of the two types of flow fields from the laminar initial state to the turbulent state.Numerical results indicated that the fractal-generated turbulence can be significantly affected by the initial velocity conditions for a long time.And in the early stage of the temporally evolution,the kinetic energy generated by the fractal-generated turbulence was smaller,but the large-scale motions of the fractal-generated turbulence in the decay period played an important role in turbulence evolution,resulting in a larger kinetic energy level and a higher turbulence intensity compared with regular-generated turbulence.This observation contributes to the possible passive control of the fractal-generated turbulence.Both fractal-generated and regular-generated turbulence reached the same level of energy and dissipation at the wave number kM≈20,but it was different from the balance of energy transmission and dissipation in energy cascade process.Furthermore,when the regular-generated turbulence became statistically homogenous,the energy decay law was more or less consistent with the Saffman turbulence.

关 键 词：时间演化 分形网格湍流 直接数值模拟 能量级串 湍流控制 

分 类 号：O357.51[理学—流体力学]