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首页> 外文期刊>International Journal of Heat and Fluid Flow >Unsteady wall pressure field of a model A-pillar conical vortex
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Unsteady wall pressure field of a model A-pillar conical vortex

机译：A柱圆锥形涡旋的非定常壁压力场

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The spatio-temporal properties of the unsteady wall pressure field of a model A-pillar conical vortex are studied in this paper by combining 2 component LDV measurements and multi-point pressure measurements using off-set microphones. The model body has sharp edges. Detailed LDV measurements are presented and discussed in the vortex region. The fluctuating velocities are the signature of both an unsteady behaviour of the organised vortical structure interacting with the wall and of finer scale turbulence carried by the unsteady flow. A spectral analysis of the fluctuating pressure under the vortex core is used to analyse the link between the temporal and spatial scales of the unsteady aerodynamics and the wall pressure field. We show that the conical vortex is a guide for the velocity perturbations and that their hydrodynamic pressure footprint is transported at the measured mean axial velocity in a local reference frame aligned with the vortex core. Two distinct peaks of coherence can then be associated with perturbations having (ⅰ) a length scale of the order of the full length of the conical structure; (ⅱ) a length scale of the order of the width of the structure. These perturbations may correspond to a global meandering of the structure (low frequency contribution) and to large scale perturbations generated during the rolling-up of the unsteady vortex sheet. Notably, the energy containing higher frequency parts of the PSD are only weakly correlated when distant sensors are considered. The three distinct contributions extracted here have a significant impact as far as Cp' is concerned and should be transmitted in very different ways by the car structure because the frequency and length scale range is very distinct.
机译：通过结合2分量LDV测量和使用偏移传声器的多点压力测量，研究了模型A柱圆锥形涡旋的非恒定壁压力场的时空特性。模型主体具有锋利的边缘。详细的LDV测量在涡流区域中进行了讨论。波动的速度既是与壁相互作用的有组织的涡旋结构的非稳态行为的标志，也是非稳态流动所产生的更细尺度的湍流的标志。涡流核心下脉动压力的频谱分析用于分析非定常空气动力学的时空尺度与壁面压力场之间的联系。我们显示出圆锥形涡旋是速度扰动的指南，并且它们的流体动压足迹在与涡旋核对准的局部参考系中以测得的平均轴向速度传输。然后可以将两个不同的相干峰与扰动相关联，扰动的长度尺度为圆锥结构全长的数量级。 （ⅱ）长度比例尺，该长度比例尺为结构的宽度。这些扰动可能对应于结构的整体曲折（低频贡献），并且对应于不稳定涡流片卷起期间产生的大规模扰动。值得注意的是，当考虑到远距离传感器时，包含PSD的高频部分的能量仅弱相关。就频率Cp'而言，这里提取的三个不同的贡献具有重大影响，并且由于频率和长度比例范围非常不同，因此汽车结构应以非常不同的方式进行传输。

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