In the present investigation the complex flow past a delta winglet-pair placed in a rectangular channel is studied numerically using the Large eddy Simulation (LES) approach. The Reynolds number based on the channel height and inlet velocity is 10000. A grid of 165 × 45 × 95 is used. The code is based on Marker and Cell algorithm with third order upwind scheme for the convective term. The computed results are compared with experimental data at Reynolds number of 134000. The Reynolds number in computation is lower due to limitation of computing resources but the computations are able to capture the essential features and show qualitative agreement with experimental data. Computation show that the longitudinal velocities generated by the winglet-pair disrupt the growth of boundary layer and would serve ultimately to bring about enhancement of heat transfer between fluid and neighboring surface. Many features of flow, which are difficult to measure experimentally, can be obtained from the LES study. © 2005 Begell House, Inc.