This paper explores the possibility of developing a high capacity (similar to100 lpm) liquid/liquid separation system based on low-capacity (<1 lpm) and low-pressure drop (<1 kPa) hydrocyclone separators. Direct numerical simulations of swirling flows within a 5-mm diameter hydrocyclone show that local centrifugal accelerations larger than 3g develop near the vortex finder within small hydrocyclones and, thereby, support the idea of using a bundle of very small hydrocyclones for downhole oil and water separation or for solvent recovery in extraction processes. (C) 2004 Elsevier Ltd. All rights reserved.