Abstract: In order to deeply understand the motion mechanism of bubbles in turbulent flows, instantaneous forces exerting on bubbles in a channel turbulence flow with a low Reynolds number were analyzed in details with the Euler-Lagrange one-way method. The liquid-phase turbulence field was computed with direct numerical simulations (DNS) in Euler reference frame, and instantaneous forces on bubbles were solved with Newtonian motion equations including drag, shear lift, pressure gradient, virtual mass, gravity (i.e., buoyant) and inertia forces in Lagrange reference frame. The present investigations showed that forces acting on bubbles depended simultaneously on the gravity direction, the flow direction of liquid and the bubble place in the wall-normal direction. The instantaneous force components controlling bubble motions changed with bubbles location and motion direction. Comparatively speaking, the component of the shear lift force perpendicular to gravity had an important influence on the bubble motion in the region near walls. The wall-normal component of the pressure gradient force was dominant for bubble motions in the region away from walls. The drag force components was very important for bubble motions in the whole channel region, and the virtual mass force played a dominant role in bubble motions in all regions except one near the walls for the vertical channel.

Key words: Euler-Lagrange model, one-way, direct numerical simulations, bubbles, force analysis

摘要： 为了深入理解气泡在湍流场内的运动机制,使用欧拉-拉格朗日单向耦合数值方法,详细分析了气泡在低雷诺数槽道湍流场内的瞬态受力情况;其中液相湍流速度场采用直接数值模拟方法求解,气泡的瞬态受力由牛顿运动方程计算;计算时,考虑了相间阻力、剪切升力、压力梯度力、虚拟质量力、重力对气泡运动的影响。目前的计算结果表明:气泡所受的瞬态作用力分量同时取决于重力作用方向、液相流向以及气泡所处的法向位置;不同方向上、不同位置处影响气泡运动的主要作用力分量是不同的;相比较而言,与重力方向垂直的剪切升力分量在近壁面区域为影响气泡运动的主要作用力,压力梯度力的法向分量在近壁面区域之外为影响气泡运动的主要作用力,相间阻力分量在整个槽道区域内均为影响气泡运动的主要作用力,除了竖直槽道近壁面处之外、虚拟质量力也均为影响气泡运动的主要作用力。

关键词: 欧拉-拉格朗日模型, 单向耦合, 直接数值模拟, 气泡, 受力分析