Measurement of three-dimensional velocity field of an opaque material (foamed gypsum slurry) flowing under a roller is explored using a PIV surface-tracking technique employoing two types of software. The foamed slurry was deposited on a moving belt pulling it under a rotating roller. The case of the water-to-stucco ratio (WSR) of 75 was studied at 0.19 wt%, and 1.86 wt% of foam added. The cases of roller co-rotation with the belt, no rotation, and counter-rotation were explored. The effect of the added foam on widening of the slurry layer on a roller was also studied. Particle Image Velocimetry (PIV) was used to measure the surface velocity flow field in both top and side views. A significant rejection flow of slurry before the roller was observed in some cases, with its severity varying with the roller’s rotating direction, its angular speed, as well as the foam content. One of the main aims of the present work is in the comparison of two PIV software: PIVlab (Matlab source, Germany) and PIVware (provided by TUDelft).

An experimental setup was designed and built to explore the spreading of a slurry layer during deposition on a moving belt before a rotating roller. The case of the water-to-stucco ratio of 75 was studied. The roller could be at rest (no rotation) or in co-rotation and counter-rotation compared to the directional motion of the spreading plastic belt (parchment paper). The widening of the slurry layer was measured and compared with the predictions of the theory developed previously by the present group, and the predicted maximum width reasonably agreed with the experimental observations. Particle image velocimetry was used to measure the velocity field at the surface of the slurry layer in top and side views. A flow pattern was observed before the slurry bypassed under the roller, in the domain where variations in entrainment led to different surface profiles. Depending on the roller's rotating direction and speed, the slurry was either more effectively drawn under the roller, forming a mild ridge, or less effectively entrained, resulting in a pronounced ridge.