NUMERICAL ANALYSIS OF FLUID FLOW AND PRESSURE DISTRIBUTION IN A PIPE UNDER ISOTHERMAL CONDITIONS

This study proposes a numerical method for investigating the isothermal state of an elementary section of a pipe with a given inlet pressure, outlet mass flow rate, and known initial distributions of mass flow and pressure. A quasi-one-dimensional model reflects the linear relationship between fluid density and pressure, considering the quadratic resistance law and the volumetric compressibility coefficient of the fluid. The governing equations and conditions were modified through the introduction of dimensionless variables and opposing wave propagation. To solve the nonlinear equations of moving waves, a first-order accuracy scheme and an anti-flow scheme were applied. The nonlinear boundary condition was satisfied with high accuracy using the Newton’s iteration method. The study identifies the characteristics of the transition process to a new operating regime of the linear pipe section, where the mass flow rate, pressure, and velocity are represented by multi-joint curves. The results show the influence of sharp boundary condition changes on the system's response and provide a detailed analysis of the flow's behavior.