Oppositely, the modified Rayleigh number is larger than the critical modified Rayleigh number that ABT 724 means the width to be enlarged. The width becomes wider, and more surrounding fluids ought to be allowed to flow into the plates via the inlet. However, the effect of the buoyancy force on the suction of surrounding fluids is concentrated in the region close to the left heated wall and becomes weak in the region away from the heated left wall. Besides, along the heated wall the buoyancy force becomes stronger in the upward direction that results in the upward velocities of the fluids close to the heated left wall being continuously accelerated. Meanwhile, the slow fluids away from the heated left wall are pulled by the upward fluids and gradually close to the heated left wall that leads the space close to the right wall to be vacant. Accompanied with the increment of the distance away from the inlet, the fluids are uninterruptedly accelerated along the heated left wall and flow out of the plates finally. At androecium situation, the total mass flow rate via the inlet is not only less than the critical mass flow rate induced by the buoyancy force, but also concentrated along the heated left wall. In order to supplement the quantity of the shortage of mass flow rate between the critical mass flow rate and total mass flow rate, some surrounding fluids close to the right wall of the outlet are compulsively sucked into the plates. Consequently, both the upward and downward mass flow rates inevitably impinge on mutually at a certain location in the plates. Accompanied with the increment of the modified Rayleigh number, the Ra∗ = 1.04 × 104 behaviors of the impingement are drastic and become an unsteady flow reversal. As a result, the mass flow rate via the outlet flowing into the plates increases with the increment of the modified Rayleigh number.