基于非均匀查询窗口PIV技术的湍流边界层特性实验研究

The experimental study on the characteristics of turbulent boundary layer based on the PIV technology of non-uniform interrogation window

粒子图像测速技术以及互相关图像查询算法在湍流边界层测量中应用广泛,而均匀查询窗口(Interrogation Window,IW)较强的空间平均作用提高了IW对速度数据的尺度敏感性。根据量纲为一的速度的相对不确定度构造与局部平均速度相适应的非均匀IW模型,结合图像变形技术,形成IW法向尺寸随法向位置或速度梯度变化的IW布局。利用DNS槽道流对该方法的性能进行评估,通过Reθ=355,440,538的平板湍流边界层PIV实验,对比不同IW方法的湍流边界层特性结果差异。结果表明:相比于均匀IW方法结果,非均匀IW方法有效提高了近壁面的空间分辨率和位移精度,获得了准确的湍流统计量信息,识别出了更完整的涡结构并提升了湍流结构中含能结构的能量获取能力。非均匀IW在边界层测量中表现出了更好的性能,这对于充分的解析边界层至关重要。

Particle image velocity(PIV)measurement and the cross-correlation algorithm are widely used in turbulent boundary layer measurements.The strong spatial averaging effect of the interrogation window(IW)enhances that the IW is sensitive to the scale of the velocity data.According to the relative uncertainty of the dimensionless velocity,a non-uniform IW model adapted for the local average velocity is constructed.Combined with image deformation technology,IW layout with IW normal size varying from the normal position or velocity gradient is formed.The performance of the method is assessed using images of DNS channel flow.Through the PIV experiment of plate turbulent boundary layer at Reθ=355~538,the characteristic discrepancies of the turbulent boundary layer are compared between different IW methods.Results indicate that the non-uniform IW method effectively improves the spatial resolution and displacement precision near the wall,and obtains more accurate turbulence statistics results.In addition,the more complete vortex structure is identified and the energy acquisition ability of the energetic structure containing in the turbulent structure is improved.Non-uniform IW shows better performance in boundary layer measurements,which is essential for adequate analysis of the boundary layer.