The influence of flattened flow profiles to the airflow velocity measurement by ultrasound

Abstract

It is shown that the methods, usually used for evaluation of the influence of flow profiles, are not sufficiently accurate. Especially, when flow velocity is measured by ultrasound and flow profiles are flattened by special form convergent nozzle. It is proposed to evaluate the influence of flattening of airflow profile on the results of flow velocity measurement. On the basis of measurement of flow profiles by static Pitot tubes is proposed to use the hyperbolic tangent for description of flow velocity profiles in the measuring round channel. For evaluation of change of hyperbolic tangent, which corresponds the change of flattened flow profile across measuring round channel, is proposed to use flow profile flattening factor. The dependences of flow flattening and flow velocity distribution correction factors on flow velocity in the measuring channel are presented. It is shown, that the accuracy of flow velocity measurement by ultrasound may be increased after the evaluation of flow flattening factor as well as of flow velocity distribution correction factor.