Effect of Inlet Velocity on The Entrance Length of Laminar and Turbulent Flow in A Circular Pipe

Abstract

This study uses numerical simulations performed with ANSYS-FLUENT to investigate the hydrodynamic entrance length for fluid flow in a circular pipe under both laminar and turbulent conditions. The effect of inlet velocity on entrance length and pressure drop was analysed. Two physical models with diameters of 15 cm and lengths of 10 m and 13 m were employed. The numerical results were validated against theoretical predictions, showing good agreement. The results indicate that entrance length increases with inlet velocity due to the extended development of the boundary layer. For laminar flow, entrance lengths of 1.46 m, 3.85 m, and 12.54 m were observed for velocities of 1, 3, and 10 m/s, respectively, while a turbulent flow velocity of 16.6 m/s yielded an entrance length of 5.8 m. Additionally, it was found that higher inlet velocities significantly amplify pressure drop due to increased friction and energy losses