Study of intertial effects in coating die design using computational fluid dynamics

摘要

The inertial effect of the feed stream entering entering though the center of an infinite cavity slot coating die with a rectangular channel was studied using NEKTON, a computational fluid dyanics package. The momentum of the entering fluid impining on the opposite wall casues a pressure rise approaching one velocity head. The pressure at the slot entrance, which is aligned with the top of the channel, and directly above the point of impingement, is less than at the point of impingement. This difference inceases with size of the channel and the distance from the impingement point; therfore, having the feed entrance in the precommended position (towards the bottom of the channel), results in a lesser pressure rise at the slot entrance. Due to this higher pressure at the slot entrance, there is a velocity splike at this lcoation, but it is completely damped out over the length of the 5 cm slot. The pressure rise in the channel due to the momentum of the flow down the channel appears to be less than the expected two velocity heads, and may be only 1.5 velocity heads.