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

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 (3D-DIC), 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 Gauss-Newton (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 high-precision 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 high-precision, 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.