PIV Measurements of Flow immediately above Woven Fabrics, 2011 PaperCon Conference

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Three-dimensional velocity fields in the single phase approach flow to a multiple layer woven forming fabric were measured using Particle Image Velocimetry (PIV). The measurements were conducted on a scale model of a forming fabric in a glycerin/water flow loop. Each strand on the paper side of the model forming fabric had a filament diameter of d=15 mm and the loop test section was 300 mm square, permitting the measurement of detailed velocity distributions over multiple strands of the fabric. The liquid viscosity and the flow speed in the loop test section were varied to achieve screen Reynolds numbers, Res, between 15 and 65. PIV measurements showed that the RMS variation of machine direction velocity is about 10% of the average Z direction velocity at a distance 0.25d above the fabric. The deviation of the Z direction velocity decreases from 15% at a plane 0.25d above the forming fabric surface to 4% at a plane 1.5d above the surface. The highest Z direction velocity is about 2.2 times of the lowest Z direction velocity at a plane 0.25d above the fabric. The Z direction velocity variation for a Reynolds number of 65 is 16% lower than that for a Reynolds number of 15. CFD simulations were done of the flow through the fabric using FLUENTTM and those simulations were consistent with the PIV measurements within 9%.