Structure of Periodic Flows through a Channel with a Suddenly Expanded and Contracted Part  

作　　者：Takuya Masuda Toshio Tagawa Miah Md. Ashraful Alam Yasutaka Hayamizu Takuya Masuda;Toshio Tagawa;Miah Md. Ashraful Alam;Yasutaka Hayamizu(Department of Integrated Engineering, National Institute of Technology, Yonago College, Tottori, Japan;Department of Aeronautics and Astronautics, Tokyo Metropolitan University, Tokyo, Japan;Department of Mechanical Engineering for Transportation, Faculty of Engineering, Osaka Sangyo University, Osaka, Japan)

机构地区：[1]Department of Integrated Engineering, National Institute of Technology, Yonago College, Tottori, Japan [2]Department of Aeronautics and Astronautics, Tokyo Metropolitan University, Tokyo, Japan [3]Department of Mechanical Engineering for Transportation, Faculty of Engineering, Osaka Sangyo University, Osaka, Japan

出　　处：《Open Journal of Fluid Dynamics》2023年第S1期232-249,共18页流体动力学（英文）

摘　　要：With respect to flows in a two-dimensional sudden expansion and contraction channel having a pair of cavities, numerical simulation was performed by imposing inlet/outlet boundary conditions giving a velocity distribution to the inlet. Periodic flows have been reproduced, which have a discrete spectrum about frequency. A fundamental wave occupies most part of the disturbance components, but higher harmonic waves are also included. The disturbance is excited by Kelvin-Helmholtz instability in a cavity section, where only the fundamental wave is generated. A wavenumber is regulated by a channel length under a periodic boundary condition, but there is no restriction in a main flow direction under the inlet/outlet boundary conditions, and therefore, some wavenumbers can occur. Therefore, an arbitrary frequency component of disturbance is a synthesized wave composed of various wave numbers. There are two kinds of components constituting this synthesized wave: a maximum of a velocity distribution is near a wall and in the center of the channel, which are called as wall mode and central mode in linear stability analysis of the plane Poiseuille flow. The synthesized wave composed of some modes shows a tendency to lower wavenumbers at the center of the channel.With respect to flows in a two-dimensional sudden expansion and contraction channel having a pair of cavities, numerical simulation was performed by imposing inlet/outlet boundary conditions giving a velocity distribution to the inlet. Periodic flows have been reproduced, which have a discrete spectrum about frequency. A fundamental wave occupies most part of the disturbance components, but higher harmonic waves are also included. The disturbance is excited by Kelvin-Helmholtz instability in a cavity section, where only the fundamental wave is generated. A wavenumber is regulated by a channel length under a periodic boundary condition, but there is no restriction in a main flow direction under the inlet/outlet boundary conditions, and therefore, some wavenumbers can occur. Therefore, an arbitrary frequency component of disturbance is a synthesized wave composed of various wave numbers. There are two kinds of components constituting this synthesized wave: a maximum of a velocity distribution is near a wall and in the center of the channel, which are called as wall mode and central mode in linear stability analysis of the plane Poiseuille flow. The synthesized wave composed of some modes shows a tendency to lower wavenumbers at the center of the channel.

关 键 词：Frequency Spectrum HARMONIC Wave Number Phase Velocity SUPERPOSITION Eigenfunction Profile 

分 类 号：O35[理学—流体力学]