Alessandro Mariotti, Gianmarco Lunghi, Elena Pasqualetto, Maria Vittoria Salvetti
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引用次数: 0
Abstract
The paper describes the first experimental study on the application of small contoured grooves in boat-tailed bodies characterized by vortex shedding. In particular, we experimentally investigate the flow-separation delay and drag-reducing performance of spanwise-extruded and spanwise-discontinuous grooves. For this purpose, we consider groove geometries similar to those proposed and numerically investigated by Mariotti et al. (Eur J Mech B/Fluids 74:351–362, 2019) and Pasqualetto et al. (Fluids 7:121, 2022a). The Reynolds number, based on the freestream velocity and the model crossflow dimension, is \(\mathrm Re=9.6\cdot 10^4\). In addition to serving as an experimental confirmation of previous numerical studies, an important difference is that the present experiments were conducted with a freestream turbulence intensity of 0.9%, whereas the simulations were carried out with a freestream without turbulence. This extends the applicability of this flow control device to a situation closer to real-world or industrial applications. In the experiments, we measure pressure-drag variations for different configurations and flow correlations in the spanwise direction through pressure and hot-wire measurements. The results confirm the good performance of the grooves as passive flow-control devices and the capability of grooves to delay flow separation even in a turbulent freestream. The experiments elucidate the physical mechanism leading to the enhanced performance, specifically the reduction of friction losses due to the local recirculation embedded in the groove region. However, the experiments reveal a different behavior in terms of vortex shedding correlation in the spanwise direction with the introduction of grooves of different spanwise extents. Interestingly, the spanwise-extruded grooves exhibit a weaker increase in spanwise correlation of vortex shedding in experiments compared to simulations. This difference is likely due to the presence of freestream turbulence in the wind tunnel, which is absent in simulations. As expected, the introduction of the spanwise-discontinuous groove reduces vortex shedding correlation. Consequently, in experiments the adoption of spanwise-discontinuous grooves yields fewer benefits than those previously found numerically.
本文首次对小轮廓槽在具有涡落特性的船尾体中的应用进行了实验研究。特别地,我们实验研究了跨向挤压和跨向不连续凹槽的流动分离延迟和减阻性能。为此,我们考虑了类似于Mariotti等人(Eur J Mech B/Fluids 74:351-362, 2019)和Pasqualetto等人(fluid 7:21 1,2022 a)提出和数值研究的沟槽几何形状。基于自由流速度和模型横流尺寸的雷诺数为\(\mathrm Re=9.6\cdot 10^4\)。除了作为以往数值研究的实验证实外,一个重要的区别是,本实验是在自由流湍流强度为0.9的情况下进行的%, whereas the simulations were carried out with a freestream without turbulence. This extends the applicability of this flow control device to a situation closer to real-world or industrial applications. In the experiments, we measure pressure-drag variations for different configurations and flow correlations in the spanwise direction through pressure and hot-wire measurements. The results confirm the good performance of the grooves as passive flow-control devices and the capability of grooves to delay flow separation even in a turbulent freestream. The experiments elucidate the physical mechanism leading to the enhanced performance, specifically the reduction of friction losses due to the local recirculation embedded in the groove region. However, the experiments reveal a different behavior in terms of vortex shedding correlation in the spanwise direction with the introduction of grooves of different spanwise extents. Interestingly, the spanwise-extruded grooves exhibit a weaker increase in spanwise correlation of vortex shedding in experiments compared to simulations. This difference is likely due to the presence of freestream turbulence in the wind tunnel, which is absent in simulations. As expected, the introduction of the spanwise-discontinuous groove reduces vortex shedding correlation. Consequently, in experiments the adoption of spanwise-discontinuous grooves yields fewer benefits than those previously found numerically.
期刊介绍:
Experiments in Fluids examines the advancement, extension, and improvement of new techniques of flow measurement. The journal also publishes contributions that employ existing experimental techniques to gain an understanding of the underlying flow physics in the areas of turbulence, aerodynamics, hydrodynamics, convective heat transfer, combustion, turbomachinery, multi-phase flows, and chemical, biological and geological flows. In addition, readers will find papers that report on investigations combining experimental and analytical/numerical approaches.