Abstract:

The large eddy simulation (LES) method was used to study the vortex characteristics in impinging stream reactor, and the fluid flow characteristics in the impact area were analyzed. The distribution of flow field velocity, vorticity magnitude and the average plane vortex energy was studied by changing inlet velocity and nozzle spacing. The flow regime, vortex evolution process and vortex core form were analyzed. The vortex striking near the stagnation point in the reactor had small size and high pulsation. With the increased of impact distance, the fluid velocity magnitude gradually decreased and the influence range of vortex became larger. The average vorticity magnitude and the average vortex plane energy first increased and then decreased with the increased of inlet velocity. The vortex evolution process and the flow regime in the reactor were analyzed based on Q criterion. According to the vortex evolution process of radial jet, the evolution period of vortex on both sides of radial jet was obtained, which was between 0.15 s and 0.20 s. The vortex structures in the impact zone were horseshoe vortex and ribbed vortex, and there was a vortex ring at the outlet. The research results provide a theoretical reference for the in-depth analysis of the fluid motion law of the impingement flow reactor and optimization of the reactor.

Key words: impinging stream, numerical simulation, turbulent flow, vortex structure, flow regime, fluid mechanics

摘要：

利用大涡模拟（LES）方法研究了撞击流反应器内流场涡特性，分析撞击区域流体流动特征。改变进口速度、喷嘴间距，讨论流场速度、涡量和平面涡能量分布规律，并分析了流场流型、涡演化过程和涡核形式。在反应器内靠近撞击驻点的涡尺寸小、脉动性高，随着撞击距离的增加，流体速度逐渐减小，涡影响范围变大。平均涡量和平均涡能量随进口速度的增加，先增加后减小。结合Q判据分析了反应器内涡的演化过程和流体流型。根据径向射流涡的演变过程，得到径向射流两侧涡演化的周期，在0.15~0.20 s之间。撞击区的涡结构主要为马蹄涡和肋状涡，在出口位置存在涡环。研究结果为深入分析撞击流反应器流体运动规律和优化反应器提供了理论参考。

关键词: 撞击流, 数值模拟, 湍流, 涡结构, 流型, 流体力学