New aspects of the arrangement and geometry of bluff bodies in ultrasonic vortex flow meters

Conventional vortex flow meters mostly are working with pressure sensors for the detection of vortex frequency behind bluff bodies. Big sizes of bluff bodies are necessary to generate large structures to be detected by pressure sensors with their poor sensitivity. Ultrasound is very sensitive on turbulences in the flow. Therefore the size of bluff bodies can be reduced drastically resulting in neglectable pressure losses behind the bluff body. Experiments have shown that opposite to bluff body arrangements used up to now a triangular shape e.g. should be turned around 180° with the lip facing to the inflow. Various shapes of bluff bodies have been tested. Best results could be obtained with threaded control rods. The sensitivity and accuracy of ultrasound measurements could be increased by the factor 12 in comparison to conventional flow meters using pressure sensors.