基于光斑投影3D-DIC的动态液面波高场测量方法研究

DYNAMIC LIQUID SURFACE WAVE HEIGHT FIELD MEASUREMENT METHOD BASED ON SPECKLE PROJECTION 3D-DIC

动态液面波高场测量与面型三维重建是流体力学、晃荡动力学等研究领域中的重要问题,但目前仍缺乏一种简易且高效的高精度全场测量手段.基于光斑投影和三维数字图像相关(3D digital image correlation,3DDIC)原理,提出了一种动态液面波高场的测量方法.通过液体染色和光斑投影,在液体表面形成光斑纹理,设置双目相机拍摄动态液面的散斑图像.运用交比不变性标定板及张正友标定法获得双目相机内外参矩阵,并基于反向组合高斯牛顿(inverse-compositional Guass-Newton,IC-GN)的3D-DIC算法实现动态液面波高场的高精度三维重构.进一步建立光斑投影的几何光学模型,模拟规则波液面的双目图像,开展数值模拟测量以验证本方法的理论精度,同时开展真实液面波高场的测量验证.结果表明,本方法可实现动态液面波高场的高精度全场测量,模拟液面测量的均方差为0.004 mm,真实静态液面抬升测量的均方差为0.022 mm,真实动态液面测量的均方差小于0.037 mm.本文方法具有高精度、非接触和全场测量等优势,可在实验室流体测量和相关工程场景中推广应用.

The measurement and 3D reconstruction of dynamic liquid surface wave height field is an important problem in the field of fluid mechanics and sloshing dynamics,while there remains a lack of a high-precision and effective full-field measurement method.Based on the principle of three-dimensional digital image correlation(3DDIC),this research presented a high-precision measurement method for dynamic liquid surface wave height field by using speckle projection.The approach employs liquid dyeing and speckle projecting so that the textured patterns can be formed on liquid surface,and then uses the binocular cameras to capture the dynamic speckle patterns.The stereo cameras are calibrated to obtain the internal and external parameter matrices by using Zhang’s calibration method and a cross-ratio invariance calibration plate.Subsequently,3D-DIC algorithm based on inverse-compositional GaussNewton(IC-GN)is utilized to achieve the high-precision reconstruction of dynamic liquid surface wave height field.A geometric optical model of spot projection is established to simulate binocular images of liquid surfaces of regular waves.Numerical simulation measurements were then conducted to verify the theoretical accuracy of this method.Physical experiment validations were also conducted.Results show that the proposed method can achieve highprecision and full-field measurement of dynamic liquid surfaces wave field.The root mean square(RMS)error of the method in simulated liquid surface measurement is 0.004 mm,and the maximal RMS of real static and dynamic liquid surface measurement are respectively 0.022 mm and 0.037 mm.The proposed method has the advantages of highprecision,non-contact measurement,and full-field measurement,which make it suitable for the applications in the laboratory measurements of fluent liquid or other related engineering scenarios.