Using ansys fluent udf for numerical study of the movement of the rollers of a downhole positive displacement pump

In order to improve the design and increase the technical characteristics of pump and compressor equipment, computational modeling of fluid dynamics is used. Numerical research techniques of positive displacement machines are quite diverse and are widely used for vane and gerotor pumps. The roller rotary pump considered in this work is used for oil production in the sidetracks of oil wells. The difference in the design is the use of rollers as partitions separating the working chambers of the pump. The authors of the article propose a method for studying the movement of rollers in the Ansys (Fluent) software package, and related issues of creating userdefined functions (UDF) to describe reciprocating motion using the macro DEFINE_CG_MOTION (name, dt, vel, omega, time, dtime). It is shown that the result of calculating the movement speed in ansys fluent differs from the graph of the given function. A sine law is substantiated to describe the speed of movement of the roller’s center of mass. The method for determining the coefficients in a sinusoidal dependence is described and it is shown how these coefficients affect the movement of the roller. The results obtained in the study can be used when performing verification of analytical calculation methods with finite element modeling data using UDF Ansys, and will also help young researchers understand the writing of UDF DEFINE_CG_MOTION. Keywords: fuel and energy complex; oil and gas industry; well equipment; volumetric pump; Computational Fluid Dynamics (CFD); numerical simulation; moving mesh; User Define Function (UDF).