Wake survey of vortices shed from two co-rotating vortex generators in boundary layer developed on a flat plate was performed in low-speed wind tunnel. The two vortex generators were arranged in lateral direction on the plate at 20 deg angle of attack and the spacing of the models was varied as the control parameter in order to assess the interference in the wake flow. Five-holes pitot tube was used to visualize the distributions of velocity vector, total pressure loss and vorticity in a measurement plane which was set at 10c downstream of the models, where $c$ was chord length of the vortex generator. Drag coefficient was also estimated by the wake measurement. It was shown that two vortices shed from the models existed respectively when the spacing was large. The strength of Vortex A was always superior to that of Vortex B. Where Vortex A was defined by the vortex that was located in the upwash region generated by the other vortex (i.e. Vortex B). Note the vortex B was located in the downwash region generated by the other vortex (Vortex A). As the spacing between those two vortices A and B was decreased, two vortices were gradually dissipated. However, dissipation was more significant on Vortex B. The two vortices subsequently merged into a single vortex.
