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Interaction of a bursting phenomena with a row of longitudinal vortices

爆裂现象与一排纵向涡流的相互作用

基本信息

批准号：
63550137
负责人：
OSAKA Hideo
金额：
$ 1.22万
依托单位：
Department of Engineering, Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

Measurement was made on the mean flow field in the planar turbulent boundary layer to investigate the interaction process between controlled trailing vortices released from tiny airfoils arranged side by side in the free stream and the turbulent boundary layer without pressure gradient. Five cases for arrangements spacing between neighboring airfoils and the arrangement height of longitudinal vortex arrays at the same attack angle alpha=8ﾟ were studied in this report. Measurements of mean and fluctuating velocities were performed by a hot wire anemometer with a linearizer and wall shear stress were measured by a Preston tube with Patel's constant.At first, the streamwise pathes of longitudinal vortex core center were examined. In the case of L/S<greater than or equal>1, where L is the spanwise distance between two airfoils and S is the airfoil span, pathes of vortices descend and embedded in the boundary layer with streamwise distance, while in the other case of L/S<1 the streamwise vo … More rtice monotonously continue to ascend and never interact so strong and move downstream along the outside of boundary layer. Secondary currents generated by the longitudinal vortices showed that the boundary layer was thickened markedly in the center section between the neighboring airfoils and that in the midspan of airfoil the boundary layer was thinned. Even in the present three-dimensional flow field, logarithmic velocity law was valid. However, the logarithmic region profiles were different depending on the local spanwiseNext, the ensemble averaged patterns obtained from the VITA technique showed that the ejection process was intensively affected by the secondary currents caused by the longitudinal vortices and that the magnitude and the mean periods of those ejection process were emphasized compared with the two-dimensional flow. Hence, the generation of the turbulence was stressed. In addition, the events contributing to the Reynolds shear stress were measured using the four quadrant method. The longitudinal vortices in the free stream had direct effects upon the turbulent structure at the boundary layer edge in the ratio of the fractional contributions to the Reynolds shear stress. The fractional contributions to the Reynolds shear stress of both the ejection and sweep events increased near y/delta =0.4 where the inner layer structure strongly interacted with the outer layer. Less

对平板湍流边界层内的平均流场进行了测量，研究了自由流中并排小翼型释放的受控尾涡与无压力梯度湍流边界层的相互作用过程。本文研究了在相同攻角α =8 °时，相邻翼型的布置间距和纵向涡列的布置高度的五种情况。用热线风速仪测量了平均速度和脉动速度，用普雷斯顿管测量了壁面切应力。在L/S = <greater than or equal>1（L为翼型展向间距，S为翼型展向间距）的情况下，涡的路径随流向距离的增加而下降并嵌入边界层中，而在L/S<1的情况下，流向涡的路径随流向距离的增加而下降并嵌入边界层中。 ...更多信息边界层继续单调上升，相互作用不强，沿边界层外侧沿着向下游移动。纵向涡产生的二次流表明，在相邻翼型之间的中心区域边界层明显增厚，而在翼型的中跨区域边界层变薄。即使在目前的三维流场中，对数速度定律也是有效的。然而，对数区域的轮廓是不同的，取决于当地展向其次，从VITA技术得到的系综平均图案表明，强烈的喷射过程中所造成的纵向涡的二次流的影响，并强调这些喷射过程的大小和平均周期相比，二维流。因此，强调了湍流的产生。此外，使用四象限法测量了对雷诺剪应力有贡献的事件。自由流中的纵向涡对边界层边缘的湍流结构有直接的影响，其贡献率与雷诺切应力之比也是如此。在y/delta =0.4附近，喷射和扫掠事件对雷诺剪切应力的分数贡献增加，其中内层结构与外层强烈相互作用。少