A High Accuracy Volume Flow Rate Measurement Using Vortex Counting
Résumé
A prototype device for measuring the volume by counting vortices has been designed and realized. It consists of a quadrangular pipe section in which are placed a two-dimensional bluff body and a strain gauge force sensor. These two elements are separated from each other, unlike the majority of vortex apparatus currently available. The principle is based on the generation of a separated wake behind the bluff body. The volume measurement is done by counting vortices using a flat plate placed in the wake and attached to the beam sensor. By optimizing the geometrical arrangement, the search for a significant signal has shown that it was possible to get a quasi-periodic signal, within a good range of flow rates so that its performances are well deduced. The repeatability of the value of the digital volume is tested for a given flow and then the accuracy of the measuring device is determined. In the case of volume measurement, the constant of the device which is called digital volume (Vp ) varies with the confinement of the flow vein and with the Reynolds number. This led us to set up the reduced digital volume (Vr ) with the average speed in the contracted section downstream of the bluff body which is independent of the confinement.
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