The inertial effect of a feed stream entering into the center of a coating die with a rectangular channel was studied using the spectral element method. The fluid momentum impinging on the opposite wall causes a rise of pressure approaching one velocity head. The pressure at the slot entrance at the top of the channel, directly above the impingement point, is less than at impingement point. This pressure difference increases with the size of the channel (or distance from the impingement point). Having the feed entrance in the furthest position from the slot entrance, along the bottom of the channel, results in a minimum pressure rise at the slot entrance directly above the impingement point. Because of this higher pressure, there is a velocity spike at the slot entrance above the impingement point. However, this spike was completely damped out over the length of the 50-mm long slot that was examined. The pressure rise in the channel due to the momentum of the flow down the channel is another inertial effect, and it appears to be less than the conservative estimate of two velocity heads. In the one case where applicable data could be obtained it was 1.5 velocity heads.
Daniel R. Gugliotti, Edgar B. Gutoff, Andrew Tangborn, "Computational Fluid Dynamics Studies of Some Inertial Effects in Coating Die Design" in Journal of Imaging Science and Technology, 1999, pp 127 - 133, https://doi.org/10.2352/J.ImagingSci.Technol.1999.43.2.art00006