ABOUT SELECTING THE VORTEX FLOWMETER OPTIMAL BLUFF BODY SHAPE

Vortex flow meters are becoming more widespread in many industries. This is due to the simplicity and reliability of the flow transducer, the scale linearity, the frequency measuring signal presence, low requirements for alignment and ensuring the straight sections length at the installation site, etc. Among the vortex measuring instruments, the most common are instruments with a bluff body. Such flow meters operation principle is based on measuring the vortex stripping frequency behind a streamlined body installed in the flow. In this case, the metrological characteristics are determined by the bluff body shape. Therefore, the search for the optimal sensing element shape and the hydraulic channel configuration of the flow meter as a whole remains an actual issue. The paper proposes an algorithm for solving this issue according to the criteria of the measured flow rates maximum range and the interaction efficiency of the bluff body with the measured medium flow. The first criterion value is determined from the condition that the Strouhal’s number remains unchanged; the second criterion is based on the estimation of the measured medium pressure drop and the measurement error. To realize the algorithm, simulation modeling is used in the Ansys Fluent fluid simulation software, which uses computational fluid dynamics methods. Modeling carried out for three shapes of the bluff body: a cylinder, a prism with a triangular section, a prism with a trapezoidal section, which made it possible to choose a sensitive element for further solving the multi-parameter optimization problem. Geometric features of the selected sensitive element shape, the limits of their change and boundary values are grounded. The simulation made it possible to estimate the measured flow rates range and pressure losses, as well as to determine the vortex stripping frequency, measurement error and efficiency factor for the investigated geometric model. To further improve the instrument metrological parameters, the authors proposed to supplement the primary transducer geometric model with gradual contraction and diffuser sections. These sections parameters are selected from the conditions of a continuous flow and the maximum measured flow rates range with a minimum pressure loss. The obtained results confirmed the strategy proposed by the authors. The further research prospect is to carry out simulation studies of the flow meter hydraulic channel proposed configuration for different measured media.