In this study, the Eulerian-Eulerian approach based on kinetic theory of granular flow (KTGF) was used to simulate the gas-solid planar opposed jets. The periodically deflecting oscillation was observed, i.e., the two opposed jets deflect off each other and swing up and down periodically. The system entropy production rate was calculated to explain this periodic oscillation for the first time. It was found that the periodic deflecting oscillation was dominated by a self-adjusting mechanism of planar opposed jets with the combined action of the pressure release and the entrainment of continuous jets. The effects of nozzle separation, initial jet Reynolds number and particle parameters on the oscillation period were analyzed. The period decreases as the jet Reynolds number or mass loading increases, but increases as the nozzle separation or the particle diameter increases. Furthermore, it is found that the residence time of particles was increased by increasing the mass loading. (c) 2013 Elsevier B.V. All rights reserved.