An aftertreatment system for treating constituents of an exhaust gas produced by an engine, comprising: a housing; a selective catalytic reduction (SCR) system disposed within the housing; a reductant injector disposed on a sidewall of the housing upstream of the SCR system and configured to insert a reductant into the exhaust gas; and a vortex generator disposed in the housing, the vortex generator comprising at least one deflector disposed on a surface within the housing, the at least one deflector configured to generate vortices in a portion of the exhaust gas flow flowing over the at least one deflector such that the portion of the exhaust gas remains attached to the surface at a downstream location of the surface.