Abstract
The past ten years have seen remarkable developments in flow measurement technology. There is a tendency, however, for the actual phenomena to remain as black boxes, which adds to the importance of flow visualization technologies. This article presents a survey of recent developments and trends in flow visualization technologies, focusing on double pulse ruby laser hologranhic interferometry and laser speckle velocimetry, which are of particular relevance to a deeper understanding of flow behavior in microgravity conditions. While conventional laser flow measurement does not easily lend itself to the study of flow behavior in the dynamic stage, the use of a double pulse ruby laser in holographic interferometry allows visualization of microscopic flow displacement in the dynamic stage, thus being a powerful new instrument for real-time quantative analysis of Marangoni convection phenomena. Furthermore, laser speckle velocimetry and its applications to flow measuremnt in a broad range of velocities are also addressed.
