High accuracy measurement of magnification for monocular PIV

A method to reduce uncertainty in the measurement of magnification for monocular particle image velocimetry (PIV) experiments is proposed. The technique is based on the optical calibration of the imaging system and a proper identification of the laser sheet location in the physical space with the aid of a second camera in stereoscopic arrangement. A preliminary run can be performed to locate the laser sheet position and orientation with respect to the optical axis of the camera by using the well-established technique for the disparity map correction in stereographic PIV. The proposed method reduces the uncertainty in measuring the local magnification due to undetermined depth position of the laser sheet, misalignment of the sheet and optical aberrations. It eliminates the need for a high-precision alignment mechanism, and the calibration can be performed outside of the test section.