To maintain the indoor air quality, it is critical to remove indoor contaminant by ventilation system with effective air distribution. This paper presents a new air distribution model termed as vortex flow model by using the principle of column vortex. The flow field characteristics and transient contaminant movement in vortex flow model are numerically investigated in a ventilated cavity under an isothermal condition, and comparisons are made with traditional bottom-supply flow model. The results show that the contaminant diffusion in vortex flow model are greatly restricted by the column vortex, which leads to smaller diffusion range in occupied zone than that of bottom-supply flow model. Meanwhile, it needs less response time for the vortex flow model to remove the contaminant in occupied zone. Furthermore, the vortex flow model exhibits higher ventilation effectiveness of contaminant removal than that of bottom supply flow model for different ventilation flow rates. The studies in the paper are beneficial to the future research and design of this air distribution system. (C) 2017 Elsevier Ltd. All rights reserved.