HYDRODYNAMIC SMOOTHING IN THE SHEET FORMING PROCESS

We present a series of experiments performed to evaluate a family of s tochastic models designed to detect and quantify any cooperative hydro dynamic effects during a paper forming process. The smoothing paramete r, s, ranges from 0 for no correlation between successive layers to 1 for the case of perfect infilling of earlier voids. For laboratory han dsheets formed over a range of grammages and crowding numbers, we find s to be positive in all cases, confirming that the smoothing phenomen on exists. Handsheets formed at crowding numbers close to 1 exhibit va riability, at the 1 mm scale, decaying from over 10 times random at 4 g m(-2) to approximately random above 50 g m(-2). We conclude that sub stantial hydrodynamic smoothing does occur though it is insufficient t o overcome the opposing effect of flocculation.