Abstract
In the flow through porous media such as screens the structure of the screen affects the upstream flow field. This is relevant for filtration and deposition processes where the local filtrate deposition rate depends on the upstream flow field, while deposition also alters this flow field over time. Here, we investigate the flow through forming fabrics that retain pulp fibers during the papermaking process, while the liquid phase passes through. The associated drainage velocity through the fabric has a significant impact on the quality of the finished product. Microparticle image velocimetry (micro-PIV) was used to measure the drainage velocity distribution upstream of two different fabrics. To make measurements at the scale of the forming fabric filaments, an experimental micro-PIV procedure was developed to permit velocity measurements several millimeters into the fluid stream with a depth of correlation of \(28\,\upmu \hbox {m}\) and an in-plane resolution of \(40 \,\upmu \hbox {m} \times 40 \,\upmu \hbox {m}\). For the single phase flow of water, the experiments show the existence of a highly variable drainage velocity field upstream of both fabrics. The normalized standard deviation (NSD) of the velocity fields decays exponentially with distance upstream of the fabric. The decay constant is on the order of one filament diameter at moderate Reynolds numbers \((Re=52-140)\). At a constant freestream velocity, the deposition of a small number of wood fibers onto a fabric results in a higher NSD than that of the bare fabric. This is believed to be due to partial obstruction of some holes in the fabric, which leads to higher velocities through unobstructed holes. Once about 5 g per square meter of fiber has been deposited onto the fabric, the velocity field above the fabric with adhering fiber mat becomes uncorrelated with the velocity field through the bare fabric.
Similar content being viewed by others
References
Adrian, R.J., Olsen, M.G.: Out-of-focus effects on particle image visibility and correlation in microscopic particle image velocimetry. Exp. Fluids S166–S174 (2000)
Bourdon, C.J., Olsen, M.G., Gorby, A.D.: Power-filter technique for modifying depth of correlation in microPIV experiments. Experiments in Fluids 37, 263–271 (2004)
Dalpke, B., Kerekes, R.J., Green, S.I.: Modelling Jet Impingement and the Initial Drainage Zone in Roll Forming. J. Pulp Paper Sci 30(3), 65 (2004)
Danby, R.: The impact of forming fabric structures on print quality. Pulp & Paper Canada 95(1), 48–51 (1994)
Danby, R., Plouffe, P.: Print quality improvement through forming fabric design changes. Pulp & Paper Canada 101(9), 66–69 (2000)
Green, S., Wang, Z., Waung, T., Vakil, A.: Simulations of the flow through woven fabrics. Computer & Fluids 37, 1148–1156 (2008)
Gui, L., Wereley, S.T., Lee, S.Y.: Digital Filters for Reducing Background Noise in Micro PIV Measurements. In 11th international symposium on the application of laser techniques to fluid mechanics, Lisbon. (2002)
Honkanen, M., Nobach, H.: Background extraction from double frame PIV images. Exp Fluids 38, 348 (2005)
Huang, Z.: Numerical simulations of flow through model paper machine forming fabrics, M.A.Sc Thesis, The University of British Columbia. (2003)
Huang, Z., Olson, J., Kerekes, R., Green, S.: Numerical simulation of the flow around rows of cylinders. Computers & Fluids 35, 485 (2006)
Lindken, R., Rossi, M., Grobe, S., Westerweel, J.: Micro-Particle Image Velocimetry: Recent Developments, applications, and guidelines. Lab on a chip 9(17), 2551–2567 (2009)
Nguyen, C.V., Fouras, A., Carberry, J.: Improvement of measurement accuracy in micro PIV by image overlapping. Experiments in Fluids 49, 701–712 (2010)
Olsen, M.G., Adrian, R.J. Out of focus effects on particle image visibility and correlation in microscopic particle image velocimetry. Experiments in Fluids S166–S174. (2000)
Peng, H., Green, S.I.: PIV measurements of flow through forming fabrics. Nordic Pulp and Paper Research Journal 27(4), 783–789 (2011)
Saleh, S., Thovert, J.F., Adler, P.M.: Flow along porous media by particle image velocimetry. AIChE Journal 39, 1765–1776 (1993)
Scarano, F., Rirthmuller, M.: Iterative multigrid approach in PIV image processing with discrete window offset. Exp Fluids 26(6), 513–523 (1999)
Scarano, F., Rirthmuller, M.: Advances in iterative multigrid PIV image processing. Exp Fluids 29(7), S051–S060 (2000)
Serles, A., Green, S.I.: Forming fabric weave-scale variations in paper filler content. Tappi Journal 12(11), 9–18 (2013)
Vakil, A., Green, S.I.: Two-dimensional circular cylinders in tandem at moderate Reynolds numbers. ASME Journal of Fluids Engineering 135(7), 1–9 (2013)
Vakil, A., Olyaei, A., Green, S.I.: Three-dimensional geometry and flow field modeling of forming fabrics. Nordic Pulp and Paper Research Journal 24(3), 342–350 (2009)
Acknowledgments
The authors thank AstenJohnson Inc. and NSERC for their financial support. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Singh, F., Stoeber, B. & Green, S.I. Micro-PIV Measurement of Flow Upstream of Papermaking Forming Fabrics. Transp Porous Med 107, 435–448 (2015). https://doi.org/10.1007/s11242-014-0447-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11242-014-0447-8