The profile-linear average velocity for the transition in pipes based on the method of LES

The ultrasonic flowmeter has been widely used in the industrial flow measurement. The flow measurement accuracy depends on the relationship of the profile-linear average velocity. But this relationship of the transition zone is not available at present.In this paper, the characteristics of transition flow with specific Re number in pipes are researched. The k-ɛ model and LES(Large Eddy Simulation) model are respectively used to calculate the flow field of the transition zone, and the experiment results show that the LES model is more effective than the k-ɛ model. The relationship of the profile-linear average velocity for the transition zone in pipes is obtained by the calculated results of the LES model and it is proved that there is a big error using the tradition relationship based on the turbulence flow to calculate the profile-linear average velocity relationship of the transition flow. The research results of this paper can improve the measurement accuracy of ultrasonic flowmeters and provide theoretical basis for the research on the whole transition flow.