M. Corelli Grappadelli, S. Asaro, R. Radespiel, C. Badrya
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引用次数: 0
Abstract
Laminar boundary layer suction has significant potential for reducing aircraft drag, thereby diminishing its environmental impact. This study presents wind tunnel experiments conducted on a flat plate to examine the effectiveness of laminar boundary layer suction in delaying the transition and compares the measured data with the \(e^n\) method based on linear stability theory (LST). The experiments, performed over a range of freestream velocities from 15 to 50 m/s, comprised infrared thermography, pressure measurements, and hot-wire anemometry. The boundary layer suction is implemented through interchangeable suction boxes mounted on the flat plate, with two types of suction surfaces tested, featuring hole diameters of 120 and \(60\,\upmu \hbox {m}\) and a constant porosity of 0.9%. The study examines the influence of various parameters on transition, as the intensity of the suction coefficient, particularly at elevated values, as well as the impact of the micro-holes diameter, the chordwise distribution of the suction velocity and the freestream Reynolds number. A discrepancy between the experimentally measured transition location and the predictions from LST is observed. To identify the origin of this deviation, boundary layer measurements are taken on the porous surface while varying both the suction coefficient and its spatial distribution. A particular flow disturbance near the porous surface, amplified by the suction intensity, is identified, leading to increased velocity fluctuations in the near-wall measurement points. The difference depends on both the suction coefficient and the suction velocity distribution. For this reason, a configuration is investigated in which only the first and last of the four suction chambers are used to aspirate the boundary layer. It is observed that the flow disturbances are significantly reduced, and the boundary layer predictions align more closely with the experimental data.
层流边界层吸力具有显著的降低飞机阻力的潜力，从而减少其对环境的影响。本文通过在平板上进行风洞实验，检验了层流边界层吸力对延迟过渡的有效性，并将实测数据与基于线性稳定理论（LST）的\(e^n\)方法进行了比较。实验在15到50米/秒的自由流速度范围内进行，包括红外热成像、压力测量和热线风速测量。边界层吸力是通过安装在平板上的可互换吸力盒来实现的，测试了两种吸力面，孔径分别为120和\(60\,\upmu \hbox {m}\)，孔隙率恒定为0.9%. The study examines the influence of various parameters on transition, as the intensity of the suction coefficient, particularly at elevated values, as well as the impact of the micro-holes diameter, the chordwise distribution of the suction velocity and the freestream Reynolds number. A discrepancy between the experimentally measured transition location and the predictions from LST is observed. To identify the origin of this deviation, boundary layer measurements are taken on the porous surface while varying both the suction coefficient and its spatial distribution. A particular flow disturbance near the porous surface, amplified by the suction intensity, is identified, leading to increased velocity fluctuations in the near-wall measurement points. The difference depends on both the suction coefficient and the suction velocity distribution. For this reason, a configuration is investigated in which only the first and last of the four suction chambers are used to aspirate the boundary layer. It is observed that the flow disturbances are significantly reduced, and the boundary layer predictions align more closely with the experimental data.
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.
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