Gypsum Slurry Flow during Deposition on the Belt under a Roller*

1. This study investigates the spreading on a moving belt under rollers of foam-containing gypsum slurries. Particle Image Velocimetry (PIV) based on seeding particles located on the free surface of an opaque material is used to measure the surface velocity field of the gypsum slurry flow in 3D based on the direction of roller rotation, its speed, and the foam content in the slurry. In particular, PIV is applied using coffee particles as tracers to analyze the opaque flow of the gypsum slurry, which is not typical for the standard applications of PIV. The slurry surface flow is observed in detail from the top and in side view. This method allows us to accurately determine the effect of the high pressure area below the roller on slurry spreading. The theoretically predicted changes in the slurry width (Plog and Yarin 2023) and the observed ones here are in reasonable agreement, indicating a high degree of reliability for the developed theory and the experimental method.