论文标题
壁构成的湍流控制：动作/状态的统计表征
Wall-bounded turbulence control: statistical characterisation of actions/states
论文作者
论文摘要
本文报告了使用湍流流量的蒙特卡洛实验的结果。提出了不同的动作，改变了局部体积力的大小，持续时间和符号，该局部体积力在一个小的雷诺（$re_τ= 165 $）上运行在一个小的计算域中，该局部体积力的作用在湍流通道流的一个壁附近。评估每个动作的效果，比较有或没有动作的流动的演变，以收集每个动作的1700多次重复的统计数据。对结果的分析表明，小/短螺纹同样有可能增加或减少皮肤摩擦阻力，而与强迫的符号无关（即朝着或远离墙壁）。当强迫的大小或持续时间增加时，增加皮肤摩擦的可能性也是如此。然后，进行“先验”分析，在动作之前评估流动状态，这是在一个涡流转换时间内导致皮肤摩擦减少的动作。所得的速度，壁剪应力和壁压的磁场与反对控制策略一致，在这种策略中，强迫在墙附近的垂直运动。最后，评估了由压力或壁剪应力传感器触发的致动性能的初步分析（即“后验”分析）。我们的结果表明，至少对于此处使用的传感器和阈值的初步定义，墙壁剪切传感器触发的驱动似乎比触发的驱动更有效。
The present paper reports the results of a Monte Carlo experiment using a turbulent channel flow. Different actions are proposed, varying the size, duration and sign of a localised volumetric force that acts near one wall of a turbulent channel flow, running at a small Reynolds ($Re_τ=165$) in a small computational domain. The effect of each action is evaluated comparing the evolution of the flow with and without the action, gathering statistics over 1700 repetitions of the experiment for each action. The analysis of the results show that small/short forcings are equally likely to increase or decrease the skin friction drag, independently of the sign of the forcing (i.e., towards or away from the wall). When the size or the duration of the forcing increases, so does the probability of increasing the skin friction. Then, an "a priori" analysis is performed, evaluating the state of the flow just before the action, conditioned to actions that result in a decrease of the skin friction over a period of one eddy turn-over time. The resulting fields of velocity, wall shear stresses and wall pressure are consistent with an opposition control strategy, where the forcing is opposing the vertical motions near the wall. Finally, a preliminary analysis of the performance of actuation triggered by pressure or wall shear stresses sensors is evaluated (i.e., "a posteriori" analysis). Our results show that the actuation triggered by a wall shear sensor seems to be more effective than the actuation triggered by a wall pressure sensor, at least for the preliminary definitions of sensors and thresholds used here.
