The vortex shedding on the bluff body located in a flowing fluid is the physical basis of the vortex flow meter. The
phenomenon is very complicated and - up to now - has not entirely been recognized. New effects have been found in the
course of laboratory investigations of the phenomenon. As it appears, even a slight mechanical disturbance of the area just
downstream of the bluff body can cause considerable changes of the frequency of the vortex shedding. This effect in both
gases and liquids was experimentally confirmed.
Considerations concerned the problem pointed out in the title of the article are presented. Results of laboratory investigations of the vortex shedding phenomenon, with application of various research methods are described. During the tests the specific discoveries of the phenomenon properties were made. In the article the problems and threats related to the numerical simulation of von Karman vortex street phenomenon are discussed. Conditions of successful numerical simulation are specified.
The karman vortex street phenomenon is applied in the vortex flowmeter. Application of various methods of investigations is necessary in the course of getting increased knowledge of the phenomenon. Flow visualization being the leading method of aero- and hydrodynamic phenomena investigations enables qualitative evaluation in micro-scale. Due to the image processing application in analysis of flow visualization pictures, calculation of geometrical parameters of the Karman vortex street is feasible. So, the quantitative information is obtained. The worked out methodology of investigations as well as designed software for analysis of vortex street pictures are described in the paper. The results of the carried out laboratory tests are reported. Flow visualization has been carried out on the especially designed laboratory tests are reported. Flow visualization has been carried out on the especially designed laboratory stand. The visualized flow has been recorded on the magnetic tape and then processed into set of consecutive frames. Four groups of frames of similar vortex development phases have been put on the image processing procedure. Distances between adjoining vortices have been calculated. On the basis of obtained results it can be stated, that in spite of probabilistic nature of the investigated phenomenon strengthened by the applied research method (flow visualization), the proposed method enables quantitative determination of Karman vortex street parameters.
Conference Committee Involvement (1)
Photonics Applications in Industry and Research IV