2021/04/04 by P. R. Kumar, Kumar, Purushotam, S. P. Vanka +1
Engineering · #Fluid Dynamics and Heat Transfer #Fluid Dynamics Simulations and Interactions #Fluid Dynamics and Mixing
paper · pdf · doi:10.48550/arxiv.2104.01636
In this paper, we present the results of a numerical study of air-water\nturbulent bubbly flow in a periodic vertical square duct. The study is\nconducted using a novel numerical technique which leverages Volume of Fluid\nmethod for interface capturing and Sharp Surface Force method for accurate\nrepresentation of the surface tension forces. A three-dimensional geometry\nconstruction method is employed during solution of interface equation which\ngives absolute conservation of mass and sharp interface between gas and liquid\nphases. The entire algorithm has been implemented on a data parallel mode on\nmultiple graphics processing units (GPU) taking advantage of the large number\nof available cores.\n We have studied the dynamics of a swarm of spherical bubbles co-flowing with\nthe upward turbulent flow and compared results with an unladen turbulent flow.\nThe frictional Reynolds number of the unladen Re\τ is 360, which is\nsufficient to sustain a turbulent flow. We observe the turbulence-driven\nsecondary flows in the mean flow, with complex instantaneous turbulent vortical\nstructures. The interaction of these secondary flows with the upwards rising\nbubbles is very complex and leads to significant changes in the instantaneous\nand time-averaged flow field.\n We present the results of mean void fraction distribution, mean velocities,\nlongitudinal and transverse turbulence intensities along the wall, corner\nbisector, and wall bisector. A peak in the void fraction distribution near the\nwalls is observed representing the migration of bubbles to a preferred section\nof the duct. The effects of turbulence-driven secondary flows and instantaneous\nlarge eddies on preferential concentration of the bubbles are discussed. The\ndispersed bubbles are seen to break the long elongated turbulent structures\ncommonly observed in the unladen turbulent flow.\n