Direct numerical simulation has been carried out for turbulent ow over a rectangular trailing edge at a Reynolds number of 1 £ £ 10 3 (based on the freestream quantities and the trailing-edge thickness) and ratio of boundarylayer displacement thickness to trailing-edge thickness close to unity. Two types of ow control were studied: base transpiration and secondary splitter plate. Simulation of base transpiration was performed using different slit heights and volume ow rates. It was found that even small ow rates could produce signi cant changes in overall aerodynamic performance, measured, for example, by the base pressure coef cient. It was also found that for the same volume ow rate, a greater increase in base pressure (drag reduction) was obtained by blowing slowly through a wide slit rather than quickly through a narrow slit. The effectiveness of a secondary splitter plate located on the trailing-edge centerline was investigated by varying the plate length from one to ve times the trailing-edge thickness. A signi cant increase in the base pressure coef cient (about 25%) was achieved, even with the shortest splitter plate equal to the trailing-edge thickness. The base pressure coef cient increased monotonically with the splitter plate length, and no intermediate maximum value was found.