Impact of Roughness on the Emptying Time of a Tank: Experimental and Numerical Analysis

Abstract

This study investigates the hydrodynamic influence of surface roughness on the discharge time of free-surface tanks through a combined experimental and numerical approach. The research evaluates the mechanisms by which varying roughness magnitudes alter flow resistance, turbulence modulation, and energy dissipation during the drainage process. Experimental data were obtained from a tank with controlled roughness parameters, providing validation for Computational Fluid Dynamics (CFD) simulations performed using ANSYS FLUENT. The Volume of Fluid (VOF) method was employed to resolve the multiphase flow dynamics. Results indicate a distinct inverse correlation between surface roughness and emptying time. Specifically, the introduction of surface roughness (5–15 mm) reduced discharge duration by up to 4.67%, with the most pronounced efficiency gains observed within the lower roughness interval (0–6 mm). This phenomenon is attributed to the modification of near-wall flow structures and the reduction of laminar flow resistance. The study validates the accuracy of the numerical framework in predicting complex fluid behaviors and underscores the critical role of surface roughness optimization in enhancing the design and operational efficiency of hydraulic systems.