Numerical investigation of upstream cylinder flow and characterization of forming fabrics

Artikel i vetenskaplig tidskrift, 2019

In this work, the fundamentals of upstream flow over cylinders and forming fabrics are investigated, and measures for characterization of fabrics are proposed. Two-dimensional flow over one cylinder, two cylinders, and one and two rows of cylinders, are analysed numerically. By studying different configurations and various Reynolds numbers, the upstream flow features are characterized. It is concluded that cylinders have a short range of upstream flow impact, shortest for rows of cylinders with small spacings. For Re∈[10,80], the Reynolds number dependency is weak. It is shown that a downstream row positioned in tandem has negligible impact on the upstream flow, while a displaced second row influences the upstream flow if the spacing in the first row is larger than one diameter. The pressure drop required to drive the flow over the cylinders depends non-linearly on the porosity of the configuration. Flow measures of the upstream flow are proposed, which in addition to the volume flow per area are used to characterize fabric flow properties. The conclusions from the cylinder study also hold for industrial fabrics, and it can be explained how properties of the fabric influence the final paper. The wave-length of flow periodicity is studied in relation to drainage marking. This study demonstrates that simulations can greatly improve pure experimental-based fabric characterization.