论文标题
在自由表面的接近度中，球的横向流动引起的振动：数值研究
Transverse flow-induced vibrations of a sphere in the proximity of a free surface: A numerical study
论文作者
论文摘要
我们介绍了一项关于在亚临界雷诺数下游离表面附近的弹性安装的球体的横向流动诱导振动（FIV）的数值研究。首先，我们验证并分析了完全淹没球的模式过渡和运动轨迹，并在各个方向上自由振动雷诺数，最高$ 30 \，000 $。接下来，研究了三个归一化的沉浸式比率（$ h^*= h/d $的三个值，其中$ h $是距球顶的距离，$ H^*= 1 $（$ h^*= 1 $ sperners $ sperface），$ h $是$ h^*note $ sperface，$ h $是$ h^*触摸自由表面）和$ h^*= -0.25 $（球形刺穿了自由表面）。在锁定范围内，我们观察到$ h^*= 0 $在$ h^*= 1 $的情况下，幅度响应显着降低。发现涡度通量由于自由表面边界而扩散，并且自由表面充当能量水槽，从而导致横向力和振幅响应的降低。当球体以$ h^*= -0.25 $刺穿自由表面时，发现锁定状态下的幅度响应大于所有研究的淹没案例，最大峰值峰值幅度为$ \ sim2d $。我们发现，穿孔球与空气水接口的相互作用会导致相对较大的表面变形，并对涡旋脱落和振动频率的同步产生重大影响。流向涡度的增加会导致相对较大的横向力以$ h^*= -0.25 $以$ H^*= -0.25 $，从而导致每个周期的正能传递更大，以维持大振幅振动。最后，我们研究了FIV响应对质量比的敏感性，$ m^*$，而Froude编号（$ fr $）在锁定状态下。
We present a numerical study on the transverse flow-induced vibration (FIV) of an elastically mounted sphere in the vicinity of a free surface at subcritical Reynolds numbers. To begin, We verify and analyze the mode transitions and the motion trajectories of a fully submerged sphere vibrating freely in all directions for the Reynolds number up to $30\,000$. Next, the response dynamics of a transversely vibrating sphere is studied for three values of normalized immersion ratio ($h^*=h/D$, where $h$ is the distance from the top of the sphere to undisturbed free-surface level and $D$ is the sphere diameter), at $h^*=1$ (fully submerged sphere with no free-surface effect), $h^*=0$ (where the top of the sphere touches the free surface) and $h^*=-0.25$ (where the sphere pierces the free surface). At the lock-in range, we observe that the amplitude response at $h^*=0$ is decreased significantly compared to the case at $h^*=1$. It is found that the vorticity flux is diffused due to the free-surface boundary and the free surface acts as a sink of energy that leads to a reduction in the transverse force and amplitude response. When the sphere pierces the free surface at $h^*=-0.25$, the amplitude response at the lock-in state is found to be greater than all the submerged cases studied with the maximum peak-to-peak amplitude of $\sim2D$. We find that the interaction of the piercing sphere with the air-water interface causes a relatively large surface deformation and has a significant impact on the synchronization of the vortex shedding and the vibration frequency. Increased streamwise vorticity gives rise to a relatively larger transverse force to the piercing sphere at $h^*=-0.25$, resulting in greater positive energy transfer per cycle to sustain the large-amplitude vibration. Lasty, we study the sensitivity of FIV response on the mass ratio, $m^*$, and Froude number, $Fr$, at the lock-in state.
