Analysis of the dependence of the Strouhal number in the measurement equation for vortex sonic flowmeters

The article describes a study of the Strouhal number in a wide range of flow measurement at different temperatures of the medium. It is established that the value of the Strouhal number is not constant over the entire range of measurement and has significant non-linearity at low flow. With the use of quality indicators was done choosing the best mathematical model describing the dependence of the Strouhal number of the flow rate at different temperatures. A comparison of the chosen mathematical model conversion function with the currently used in mass production flow was done. Description of Strouhal number in the form of non-linear functions, depending on the frequency of vortex shedding and fluid temperature, can significantly reduce the measurement error at low flow. We proposed a method for adapting a nonlinear conversion function of the investigated flow for meters with a large diameter flow section.