Intermittent flow generation by means of cavitation nozzles

Cavitation is a well-known phenomenon in the world of fluid mechanics. The use of cavitating Venturi nozzles, so-called Cavitation nozzles, as a flow control element is, however, novel. The aim of the investigations on intermittent flow generation by cavitation nozzles is to verify if this technology is applicable for realistic testing of flowmeters. The equipment that was used was integrated into an existing test rig. Firstly, the nozzles are characterized individually. This provided a flow stability of an average scatter of 0.0015 % of the current flow amplitude, which was not achieved with other methods so far. The opening and closing of the nozzles within a few milliseconds by means of pneumatic stamps enables the realization of intermittent flow sequences with a repeatability of up to +/- 0.07 %. Due to the almost additive behavior of the nozzles (+/- 0.1 %), the volume flow of nozzle pairs is approximately the sum of the volume flows of the individual nozzles. Two different flow sequences were created by the cavitation nozzle apparatus and the response of two flowmeters to intermittent operation was observed. The studies presented show that the use of cavitation nozzles makes it possible to test and evaluate flowmeters with the required accuracy under realistic conditions - which previously was not possible. Cavitation nozzles could thus pave the way for test procedures that come closest to real conditions in flow measurements.