Assessment and application of wavelet-based optical flow velocimetry (wOFV) to wall-bounded turbulent flows.
Assessment and application of wavelet-based optical flow velocimetry (wOFV) to wall-bounded turbulent flows.
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DOI：
10.1007/s00348-023-03594-y
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发表时间：
2023
影响因子：
2.4
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中科院分区：
文献类型：
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基于小波的光流测速（wOFV）算法在提取高精度和高分辨率的速度场的示踪粒子图像在有壁湍流的性能进行了评估。首先使用从湍流边界层的通道流DNS生成的合成粒子图像来评估wOFV。wOFV的正则化参数（）的敏感性进行量化，并将结果进行比较，基于互相关的PIV。对合成粒子图像的结果表明，根据分析的边界层区域，对欠正则化或过正则化的敏感性不同。尽管如此，对合成数据的测试表明，wOFV在矢量精度方面可以在很大范围内略优于PIV。wOFV在解决粘性子层和获得壁面剪应力的高精度估计从而使边界层变量归一化方面比PIV显示出明显的优势。wOFV也适用于发展中的湍流边界层的实验数据。总体而言，wOFV显示与PIV和PIV + PTV联合方法具有良好的一致性。然而，wOFV能够成功地解决壁面剪切应力，并正确地将边界层流向速度归一化为壁面单位，其中PIV和PIV + PTV显示出较大的偏差。湍流速度波动的分析揭示了PIV在壁附近的虚假结果，导致粘性子层区域中显着夸大和非物理湍流强度。PIV + PTV在这方面仅显示出微小的改善。wOFV没有表现出同样的效果，这表明它在捕捉边界附近的小尺度湍流运动时更准确。wOFV增强的矢量分辨率使瞬时导数量和复杂的流动结构的估计得到改善，比其他测速方法更接近壁面，更准确。这些方面表明，在可以使用物理原理验证的合理范围内，wOFV可以在解决物理边界附近发生的湍流运动的诊断能力方面提供改进。
The performance of a wavelet-based optical flow velocimetry (wOFV) algorithm in extracting high accuracy and high-resolution velocity fields from tracer particle images in wall-bounded turbulent flows is assessed. wOFV is first evaluated using synthetic particle images generated from a channel flow DNS of a turbulent boundary layer. The sensitivity of wOFV to the regularization parameter () is quantified and results are compared to cross-correlation-based PIV. Results on synthetic particle images indicated different sensitivity to under-regularization or over-regularization depending on which region of the boundary layer is being analyzed. Nonetheless, tests on synthetic data revealed that wOFV can modestly outperform PIV in vector accuracy across a broad range. wOFV showed clear advantages over PIV in resolving the viscous sublayer and obtaining highly accurate estimates of the wall shear stress and thus normalizing boundary layer variables. wOFV was also applied to experimental data of a developing turbulent boundary layer. Overall, wOFV revealed good agreement with both PIV and a combined PIV + PTV method. However, wOFV was able to successfully resolve the wall shear stress and correctly normalize the boundary layer streamwise velocity to wall units where PIV and PIV + PTV showed larger deviations. Analysis of the turbulent velocity fluctuations revealed spurious results for PIV in close proximity to the wall, leading to significantly exaggerated and non-physical turbulence intensity in the viscous sublayer region. PIV + PTV showed only a minor improvement in this aspect. wOFV did not exhibit this same effect, revealing that it is more accurate in capturing small-scale turbulent motion in the vicinity of boundaries. The enhanced vector resolution of wOFV enabled improved estimation of instantaneous derivative quantities and intricate flow structure both closer to the wall and more accurately than the other velocimetry methods. These aspects show that, within a reasonable range that can be verified using physical principles, wOFV can provide improvements in diagnostics capability in resolving turbulent motion occurring in the vicinity of physical boundaries.
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影响因子：
22.7
作者：
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通讯作者：
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