Fluid motion in ultrasonic flowmeter cavities

The ultrasonic flow meter is a newcomer among flow meters for measuring lar ge quantities of natural gas. It has notable advantages compared to traditi onal meters. The ultrasonic flow meter is much more compact and has a wider dynamic range for flow measurements than the orifice plate meter, When man ufactured the ultrasonic sensors are often set back fr om the pipe wall in a cavity. When the fluid flows past the cavities, a secondary flow of vorti ces with characteristic size equal to the cavity width is established insid e the cavities, The aim of this study has been to investigate the influence of this secondary flow on the accuracy of the ultrasonic flowmeter. Both m easurements and numerical simulations of the cavity flow have been conducte d, it has been found from the present work, that the influence of the flow in the cavities on the measurements increases nonlinearly with the pipe pow rate.