Vortex flow consists of a flow tube, in which bluff body is located middle of the pipe. This body is a kind of obstruction which disturbs the flow.
Downstream from the bluff body, a mechanical sensor which register the tiniest pressure differences in the flowing fluid. if the fluid is not flowing, no vertices are formed. as soon as the fluid starts to flow and reaches certain flow rate vertices gradually appear down stream of the bluff body. these vertices are detached either side if the bluff body, and are carried away by flowing fluid.
Zones of the high and low pressure now appear down stream a phenomenon called ” KARMAN” vertex street. These difference in pressure match exactly the passing frequency of vertices.
Pipe born vibrations , pressure surges, temperature shocks whatsoever no effect on the measurement. The distance between two consecutive vertices correspond to defined volume of flow. total flow can be calculated by counting the vertices that pass.
In certain applications, the velocity is too low, this can be overcome by reducing the cross sectional area. Which doesn’t effect measuring accuracy. one more sensor , the temperature probe installed to calculate the temperature compensation.