Effects of Pore Geometry on Intrafloc Flow

Abstract

Large pores in wastewater sludge floe control intrafloc advective flow. Such pores, probed using fluorescence in situ hybridization (FISH) and the confocal laser scanning microscope (CLSM) technique, exhibited zigzagging with a non-circular cross-section and fractal-like boundary. Simplification of the complicated pore structure was needed before modeling could be conducted. This work demonstrated, using numerical simulation, how the roughness of the pore boundary, the pore zigzaggedness, and the shape of the pore cross-section affected the flow field and the associated pressure drop in a simulated pore. Simulation revealed that the pore zigzaggedness changed the direction of main-stream flow in pore mostly affected the pressure drop. The “main” boundary irregularity was also found to be an important geometric parameter. Over a wide range of aspect ratios, the non-circular (elliptic) had cross-section only a mild effect on the advective flow. Correctly allocating the centroids of pores in order to reveal their zigzaggedness is necessary to adequately model advective flow through floe pores.