论文标题
雷诺数超过100,000的持续层流流量
Persistent Laminar Flow at Reynolds Numbers Exceeding 100,000
论文作者
论文摘要
从层流到湍流的过渡的准确预测仍然是尚未解决的挑战,尽管它对于理解各种环境,生物学和工业现象的重要性。超过一个世纪以来的一致努力旨在对奥斯本·雷诺兹(Osborne Reynolds)进行定量的机制解释,即对管道流量过渡到湍流的过渡的良性观察,通常发生在惯性和粘性动力学之比(同名的reynolds数字)中,这些研究是在这些研究中的临时序列。值高达100,000。但是,在70多年来,在任何类似的流程配置中尚未超过这种创纪录的层流雷诺数,因为它需要使用在炸弹避难所内容纳的管道长度进行的管道长度进行实验,以消除环境干扰。在这里,我们展示了一个台式喷射流,该台式流量表现出持续的层流流,超出了雷诺数为116,000,仅受到当前设施的最大流量产生能力的限制。射流形状和流动速度计的高速摄影证实了流动的层流性质,即使在设施设计中非理想化引起的可见环境流动障碍的情况下也是如此。射流内速度曲线的空间演化,随着下游距离的增加接近“顶帽”形状,似乎促进了层流流的持久性。这些结果表明存在一个可访问的流动状态,其中可能在任意高雷诺数的数字下可以规避湍流。
Accurate prediction of the transition from laminar flow to turbulence remains an unresolved challenge despite its importance for understanding a variety of environmental, biological, and industrial phenomena. Well over a century of concerted effort has aimed toward a quantitative, mechanistic explanation of Osborne Reynolds' seminal observation of transition to turbulence in pipe flow, typically occurring when the ratio of inertial and viscous fluid dynamic forces -- the eponymous Reynolds number -- is approximately 2000. These studies have been confounded by subsequent observations that the Reynolds number at which transition occurs can be delayed to values as high as 100,000. This record-high laminar Reynolds number has not been exceeded in any similar flow configuration for more than 70 years, however, as it required experiments to be conducted using pipe lengths of up to 18 meters housed within a bomb shelter to eliminate ambient disturbances to the flow. Here, we demonstrate a benchtop jet flow that exhibits persistent laminar flow beyond a Reynolds number of 116,000, a value limited only by the maximum flow-generating capacity of the current facility. High-speed videography of the jet shape and flow velocimetry within the jet confirm the laminar nature of the flow, even in the presence of visible ambient flow disturbances arising from non-idealities in the facility design. The measured spatial evolution of the velocity profile within the jet, approaching a "top hat" shape with increasing downstream distance, appears to promote persistence of the laminar flow. These results suggest the existence of an empirically accessible flow regime in which turbulence might be circumvented at arbitrarily high Reynolds numbers.