In recent years, hydrocyclones have been studied to improve their performance. This study aimed to evaluate the modification of the feed duct of a hydrocyclone from circular to square and rectangular using 3D CFD simulations under single-phase to assess the flow hydrodynamics. The simulations suggest that a non-circular feed duct provided small changes in Euler numbers (Eu), suggesting improvements in the classification efficiency. As indicated in the simulations, experimental tests performed with circular duct and square feed duct hydrocyclones, using a diluted aqueous quartzite suspension (1% v/v), provided increases of 7.6% and 12.5% in the underflow-tothroughput ratio and Euler number, respectively, and a 32% decrease in the cut size diameter for the square feed duct compared to standard hydrocydone. Therefore, a simple change in the shape of the hydrocydone feed duct improves the solids separation performance of equipment previously designed for high separation efficiency. (C) 2020 Elsevier B.V. All rights reserved.