Influence of Mean Shear on Fiber Flocs, 2001 Engineering / Finishing & Converting Conference Proceedings

H. Henry, V. Tang, P. E. Sullivan, M. Aberg, D. C. S. Kuhn--The fiber suspension delivered by the headbox to the forming section strongly affects the structure of the resulting paper. In this study, the turbulence statistics of (a) a fiber/mineral oil suspension past a grid, (b) water flow past a two-dimensional obstacle and (c) water flow past a three-dimensional obstacle are measured with Particle Image Velocimetry. These high shear flow geometries were chosen due to their similarity to step diffusers used in headboxes and due to the relevance of the induced complex fiber - fluid interactions to many other fiber suspension flows. The fiber addition to the mineral oil results in a dampening of the velocity fluctuations downstream of the grids and the turbulence intensity of the fiber suspension was organized and the variations were of larger scale as compared to the pure oil measurements. Numerical and experimental comparisons of the high shear flow of water past a cubical obstacle show a significant difference in predicted shear.