Grzegorz L. Pankanin

The vortex flowmeter: various methods of investigating phenomena

This paper is devoted to the Karman vortex shedding flowmeter?its physical fundamentals, research, design, optimization and applications. The flowmeter is currently in a stage of rapid development. Many valuable discoveries concerning the applied Karman vortex street phenomenon have been made. In this paper, various aspects of the problems concerning the vortex meter are described. Fundamental problems and their solutions are presented based on a description of the principles of operation. The most important methods of investigating the phenomena that appear in the vortex meter are described: measured signal analysis, flow field investigations using a hot-wire anemometer, flow visualization supported by image processing and numerical modelling. The most powerful achievements in these fields are also described.

Experimental and Theoretical Investigations Concerning the Influence of Stagnation Region on Karman Vortex Shedding

The paper contains an attempted explanation of the stagnation regions role in vortex shedding. The stagnation region appears in the closest neighborhood downstream of the bluff body, and is a factor which considerably influences vortex shedding. Former investigations of these phenomena in the vortex meter entitle the author to summarize yielded results and to formulate the overall conclusions concerning the mentioned problem. Analysis of the results gained due to various method applications is presented in the paper. The role of the stagnation region during the vortex shedding process is discussed.

Karman vortex street parametrization with image processing application

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.

Influence of vortex meter configuration of measure signal parameters

The problem of vortex meter optimization is considered. A new approach relies on optimization of the whole meter configuration, i.e., the bluff body geometry and the sensor location. Linearity of the meter characteristic, quality of the signal and stability of the signal period were applied as optimization criteria. The dependence of the parameters on the configuration of the meter was confirmed during the tests.<<ETX>>

Sensitivity of the stagnation region in the vortex meter to mechanical disturbances

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.