Methods of digital close-range photogrammetry allow for manifold real 3-D measurements in dynamic processes. Based on the acquisition of multi-camera digital image sequences, image analysis with subpixel accuracy image measurement operators, photogrammetric multi-image matching and point determination techniques, strict geometric modeling of complex environments and thorough system calibration techniques, time-resolved accurate 3-D coordinates of a large number of objects in a scene can be determined fully automatically. The paper will first give a short review on basic principles of digital photogrammetry and discuss the application and accuracy potential. After that, practical examples will be given from several breadboard experiments conducted in the frame of the ESA Technological Research and Development Programme to show the applicability of the technique to typical experiments in the field of fluid physics. These experiments focus on the investigation of experiments on Marangoni convection; they include the determination of 3-D velocity fields near a hanging drop within a fluid matrix and the observation of the tangential tension on the boundary surface by measuring changes in shape and/or position of liquid bodies like drops, bubbles or liquid columns in a fluid matrix.
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|Published - Feb 2002