摘要
为了完善驻留式微气泡阵列减阻的机理理论,基于有限体积方法,采用大涡模拟(LES)方法对平板及驻留微气泡阵列近壁面复杂湍流流动开展数值模拟研究,采用本征正交分解法(POD)提取 2 种模型近壁区湍流拟序结构进行对比分析.结果表明:相较于平板,驻留微气泡阵列近壁面切应力变化更加平稳,减小了约 13.7%;微气泡气/水界面的动态形变使边界层间歇性流动分离再附着,抑制低速流体上抛、高速流体下扫形成的"猝发"现象,湍流相干结构"猝发"频率减小 5.6 Hz.利用POD方法,能够有效地提取近壁面复杂湍流拟序结构的主要分布特征,微气泡的存在加强了湍流近壁区内的小尺度结构,促进流场内湍流动能的均匀分布,抑制了拟序结构的发展,体现了驻留微气泡良好的减阻特性.
Abstract
A numerical simulation study was conducted using the finite volume method and large eddy simulation(LES)method to analyze the complex turbulent flow near the wall of a flat plate and with the resident microbubble array in order to improve the theoretical mechanism of drag reduction by the resident microbubble array.The proper orthogonal decomposition(POD)method was used to extract and compare the near-wall turbulent quasi-coherent structure.Results showed that the wall shear stress of the resident microbubble array was more stable and decreased by 13.7%approximately compared with the flat plate.The dynamic deformation of the gas/liquid interface of the microbubbles caused intermittent flow separation and reattachment in the boundary layer,which suppressed the"bursting"phenomenon of low-speed fluid upcast and high-speed fluid down-sweep,leading to a 5.6 Hz reduction in the bursting frequency of turbulent coherent structures.The POD method can effectively extract the main distribution characteristics of the near-wall turbulent quasi-coherent structures.The presence of microbubbles strengthens the small-scale structure in the near-wall turbulent region,promoting a more homogeneous distribution of turbulent kinetic energy within the flow field,suppressing the development of quasi-coherent structure and demonstrating the good drag-reduction property.
基金项目
中央军委国防创新科技计划(22TQ2218TS01006)
福建省自然科学基金(2022J01058)
厦门市自然科学基金(3502220227179)
气动噪声控制重点实验室项目(2201ANCL20220105)
西藏民族大学校内科研项目(23MDY03)
NETL
NSTL
维普
万方数据