Temporal acceleration of a turbulent channel flow
Temporal acceleration of a turbulent channel flow
复制标题
DOI：
10.1017/jfm.2017.753
复制
发表时间：
2018-01-25
影响因子：
3.7
通讯作者：
Pokrajac, D.
中科院分区：
文献类型：
--
作者：
Mathur, A.;Gorji, S.;Pokrajac, D.
我们报告新的实验室实验的流量加速从最初的湍流状态下打开的阀门，连同大涡模拟的实验和扩展的斯托克斯第一问题的解决方案的早期阶段的流动。结果表明，瞬态流动非常类似于叠加在原始稳定湍流上的加速层流。加速的主要后果是从壁面开始的边界层的暂时增长，逐渐导致强烈的不稳定性，从而引起转捩。这扩展了以前的直接数值模拟的瞬态流后，近一步的流量增加的结果。在这种解释中，初始湍流不是产生的瞬态流的主要特征，但可以被视为噪声，其演变受到边界层发展的强烈影响。我们观察到自发出现的湍流斑点和不连续性的速度信号在时间和空间，揭示丰富的细节的过渡过程中，包括流向和壁正常的波动速度之间的鲜明对比。
We report new laboratory experiments of a flow accelerating from an initially turbulent state following the opening of a valve, together with large eddy simulations of the experiments and extended Stokes first problem solutions for the early stages of the flow. The results show that the transient flow closely resembles an accelerating laminar flow superimposed on the original steady turbulent flow. The primary consequence of the acceleration is the temporal growth of a boundary layer from the wall, gradually leading to a strong instability causing transition. This extends the findings of previous direct numerical simulations of transient flow following a near-step increase in flow rate. In this interpretation, the initial turbulence is not the primary characteristic of the resulting transient flow, but can be regarded as noise, the evolution of which is strongly influenced by the development of the boundary layer. We observe the spontaneous appearance of turbulent spots and discontinuities in the velocity signals in time and space, revealing rich detail of the transition process, including a striking contrast between streamwise and wall-normal fluctuating velocities.