Three-Dimensional Velocity and Vorticity Measuring and Image Analysis Techniques

Book excerpt: The contents of this volume reflect to a large extent the efforts made by a group of Institutes at the ETH Zürich to develop new techniques for measurements of flows in fluids in the last decade. The motivation came from the study of tr~sport and mixing processes in natural and industrial systems. One of the characteristic properties of turbulence is its high mixing efficiency. The techniques developed are therefore suitable, although not exclusively, for turbulence measurements. They can be subdivided into point-measurements and field-measurements. The aim of the point-measurements developed is to determine the three components of the velocity and all their first derivatives with good temporal resolution and accuracy in turbulent flows. The old and weIl established method of hot-wire anemometry was used for this purpose. One of the main achievements in this context is the construction of miniature multi-wire probes. This technique was introduced to the Institute of Hydromechanics and Water Resources Management of ETH Zürich by Profs. A. Tsinober and E. Kit from Tel-Aviv University. This was made possible by the generous financial support by ETH, for which I would like to express my gratitude on this occasion. In addition, Dr. F.E. Joergensen from DANTEC contributed an example of recent developments in the hardware ofConstant Temperature Anemometry (CTA), for which I am very thankful.