NUMERICAL AND EXPERIMENTAL INVESTIGATION INTO POROUS SQUEEZE FILMS

The paper presents a numerical and experimental investigation into por ous squeeze films with a view to application in the printing process. The experimental programme was carried out using targets having differ ent permeability and this work confirmed the dominance of hydrodynamic behaviour associated with the thick film and porous medium flow when the film becomes thin. The numerical model has been implemented via th e finite element method and the prediction shows good overall agreemen t with the data obtained from the experimental investigation. In perfo rming sensitivity calculations, for the physical parameters of practic al interest, it was found that the inclusion of slip velocity affects the film thickness decay, but only by a small amount. When the model w as applied to the parameters of the actual printing process, it was de monstrated that the volume flowrate of the ink dot which penetrates in to the paper and which spreads on it can be obtained from the model, b ut the penetration component is negligible. In comparing predicted and measured dot gain, initial film thickness was found to be a dominant parameter and the most likely cause of the discrepancy between measure d and predicted values. (C) 1998 Elsevier Science Ltd. All rights rese rved.