An active cooling substrate (ACS) is a microelectro mechanical system (MEMS) device which implements the synthetic jet concept into printed wiring board (PWB) to enhance thermal management. This paper presents a numerical approach to solve the synthetic jet fluid mechanics and heat transfer problem. Fluent, a computational fluid dynamics (CFD) package, is utilized to perform the three-dimensional (3-D), unsteady, and double precision simulations. The large eddy simulation (LES) is selected as the turbulence model. The simulation results are consistent with the experimental data. A numerical predictive model is developed for future designs of synthetic jet based active cooling substrates. (c) 2006 Elsevier Ltd. All rights reserved.