CAMERA CALIBRATION FOR STEREO P.I.V. WITH A FRONT-REAR CAMERA ARRANGEMENT. APPLICATION TO OPEN-CHANNEL FLOW.

Abstract

We perform high-resolution stereo P.I.V. at 15 Hz in a cross-stream plane in the lower half of a smooth-bed open channel flow at Re_τ=u_τh/v=300. This paper describes technical details of our system, concentrating on questions of calibration and validation. We demonstrate theoretically and experimentally that the pinhole model may by applied without modification to a Scheimpflug camera, and present a calibration target designed for Willert's “front-and-rear” stereo camera arrangement. A cross-check on the two horizontal components of instantaneous velocity vectors, using a third camera viewing from below with beam illumination (rather than sheet illumination), gives good agreement with results from stereo P.I.V.