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Experimental study of boundary layer flow over three dimensional arrays of embedded cavities.

机译：嵌入式空腔三维阵列上边界层流动的实验研究。

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It is well known that proper surface patterning on a flat plate can decrease drag. Whether it be the dimples on a golf ball or riblets on a flat plate, there are many proven ways to alter a smooth surface to decrease drag.;Continuing the previous research related to biomimetic models of shark skin, this research focuses on finding similar, but simpler, geometries that could lead to a decrease in drag. This experiment studies an array of embedded hexagonal cavities on a flat plate in a water tunnel facility. The flow over the modified flat plate generates vortices in the cavities which cause a partial slip condition that can alter boundary layer flow.;Fluorescent dye in the cavities was illuminated with a UV lamp to capture images of the flow inside the cavities. Digital particle image velocimetry, which uses a laser to illuminate particles in the flow and captures images with a high speed camera, was used to measure the velocity flow field over the cavities. The flow fields were analyzed for the purpose of studying velocity profiles above the cavities, measuring partial slip velocities, calculating momentum thicknesses and shape factors, as well as determining the difference in boundary layer characteristics of the hexagonal cavities at two different orientations. Finally, the Reynolds stresses over the hexagonal cavities were compared to those over the flat plate under turbulent conditions to attempt to discern the effect of orientation on turbulence augmentation.;The results show that the hexagonal cavities cause the boundary layer to transition to turbulence sooner than the flow over a flat plate. Also, in a turbulent flow, the cavities bring higher momentum fluid closer to the wall compared to the flat plate case, which is a proven requirement for the prevention of boundary layer separation. The results also suggested a decrease in the cavity circulation at the downstream portion of the model; confirming this trend should be a focus of future work. If this result is indeed confirmed, only applying this pattern to local regions of incipient separation may prove to be most effective.
机译：众所周知，在平板上进行适当的表面构图可以减少阻力。无论是高尔夫球上的酒窝还是平板上的肋骨，都有许多行之有效的方法来改变光滑表面以减少阻力。;继续先前与鲨鱼皮仿生模型相关的研究，本研究着重于寻找相似之处，但更简单的几何形状可能会导致阻力减小。该实验研究了水隧道设施中平板上嵌入的六角形空腔的阵列。改性平板上的流动会在空腔中产生涡旋，从而引起局部滑移状态，从而改变边界层的流动。用紫外线灯照射空腔中的荧光染料以捕获空腔内部流动的图像。数字粒子图像测速技术使用激光照射流中的粒子并使用高速相机捕获图像，用于测量腔体上的速度流场。分析流场的目的是研究空腔上方的速度分布，测量部分滑移速度，计算动量厚度和形状因子，以及确定在两个不同方向上六角形空腔的边界层特性的差异。最后，在湍流条件下，将六角形腔上的雷诺应力与平板上的雷诺应力进行比较，以试图辨别取向对湍流增强的影响。在平板上的流动。而且，在湍流中，与平板壳体相比，空腔使较高的动量流体更靠近壁，这是防止边界层分离的公认要求。结果还表明模型下游部分的空腔循环减少。确认这种趋势应该是未来工作的重点。如果确实确认了该结果，则仅将这种模式应用于初期分离的局部区域可能被证明是最有效的。

著录项

  • 作者

    Melnick, Michael Blake.;

  • 作者单位

    The University of Alabama.;

  • 授予单位 The University of Alabama.;
  • 学科 Engineering Aerospace.
  • 学位 M.S.
  • 年度 2009
  • 页码 83 p.
  • 总页数 83
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 航空、航天技术的研究与探索;
  • 关键词

  • 入库时间 2022-08-17 11:38:27

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