论文标题
Bose-Einstein冷凝物中移动障碍物的涡流脱落频率
Vortex shedding frequency of a moving obstacle in a Bose-Einstein condensate
论文作者
论文摘要
我们使用可移动的渗透高斯障碍物实验研究了高度植入的玻色子凝结物中的周期性涡流脱落动力学。脱落频率$ f_v $是根据障碍速度$ v $的函数测量的，其特征是$ f_v = a（v-v_c）$的线性关系，$ v_c $是关键速度。比例常数$ a $在障碍强度降低时线性降低，而$ v_c $接近声音的速度。当障碍物大小增加时，$ A $和$ V_C $都会减少。进一步研究了关键的涡流脱落，以解决振荡的障碍物，并发现与测量的$ f_v $一致。当障碍物的最大速度超过$ v_c $，但其振荡振幅不足以产生涡旋偶极子时，我们观察到涡流是在捕获的冷凝物的低密度边界区域中产生的，这归因于振动障碍物的声子发射。最后，我们在超级流体的普遍脱落动力学的背景下，讨论了$ a $与Strouhal数字的可能的渐近关联。
We experimentally investigate the periodic vortex shedding dynamics in a highly oblate Bose-Einstein condensate using a moving penetrable Gaussian obstacle. The shedding frequency $f_v$ is measured as a function of the obstacle velocity $v$ and characterized by a linear relationship of $f_v=a(v-v_c)$ with $v_c$ being the critical velocity. The proportionality constant $a$ is linearly decreased with a decrease in the obstacle strength, whereas $v_c$ approaches the speed of sound. When the obstacle size increases, both $a$ and $v_c$ are decreased. The critical vortex shedding is further investigated for an oscillating obstacle and found to be consistent with the measured $f_v$. When the obstacle's maximum velocity exceeds $v_c$ but its oscillation amplitude is not large enough to create a vortex dipole, we observe that vortices are generated in the low-density boundary region of the trapped condensate, which is attributed to the phonon emission from the oscillating obstacle. Finally, we discuss a possible asymptotic association of $a$ with the Strouhal number in the context of universal shedding dynamics of a superfluid.
