Dynamic flow characteristics influenced by impinging shear layer mode in a rectangular tube with a closed side branch

Abstract

The pipeline with a closed side branch is a typical structure in nuclear systems; the shear layer flow and deep cavity in this structure can lead to a complex flow-acoustic coupling, which may result in severe vibration and noise. To clarify the shear layer flow characteristics in this typical structure filled with water, the numerical strategy is established by employing the localized dynamic k-equation large eddy simulation model. Then, the statistical and instantaneous characteristics of the fluid field are analyzed, respectively. The dynamic vortex evolution process is presented by time–frequency domain analysis. Also, the phase relationship of pressure in shear layer is adopted to investigate the formation process of the shear layer mode. The results verify that the pressure fluctuation near the downstream corner is the sound source as the vortex impacts the wall periodically. The convection effect and disturbance intensity effect are separated for the first time through the control of the kinematic viscosity. The results show that the convection velocity influences the vortex shedding frequency (VSF) by changing the vortex moving speed. Also, changes in the disturbance intensity and branch length rectify the VSF by changing the phase relationship of impinging shear layer mode. Finally, a suppressing method of shifting the VSF is put forward by modifying the disturbance only.