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In this paper, we present the results of a numerical study of air-waterturbulent bubbly flow in a periodic vertical square duct. The study isconducted using a novel numerical technique which leverages Volume of Fluidmethod for interface capturing and Sharp Surface Force method for accuraterepresentation of the surface tension forces. A three-dimensional geometryconstruction method is employed during solution of interface equation whichgives absolute conservation of mass and sharp interface between gas and liquidphases. The entire algorithm has been implemented on a data parallel mode onmultiple graphics processing units (GPU) taking advantage of the large numberof available cores.  We have studied the dynamics of a swarm of spherical bubbles co-flowing withthe upward turbulent flow and compared results with an unladen turbulent flow.The frictional Reynolds number of the unladen $Re_{\tau}$ is 360, which issufficient to sustain a turbulent flow. We observe the turbulence-drivensecondary flows in the mean flow, with complex instantaneous turbulent vorticalstructures. The interaction of these secondary flows with the upwards risingbubbles is very complex and leads to significant changes in the instantaneousand time-averaged flow field.  We present the results of mean void fraction distribution, mean velocities,longitudinal and transverse turbulence intensities along the wall, cornerbisector, and wall bisector. A peak in the void fraction distribution near thewalls is observed representing the migration of bubbles to a preferred sectionof the duct. The effects of turbulence-driven secondary flows and instantaneouslarge eddies on preferential concentration of the bubbles are discussed. Thedispersed bubbles are seen to break the long elongated turbulent structurescommonly observed in the unladen turbulent flow.

Large Scale GPU Based Simulations of Turbulent Bubbly Flow in a Square Duct