Graduate Seminar in Fluid Mechanics 530.807

September 15, 2017 @ 3:00 pm – 4:00 pm
316 Hodson Hall

3:00 p.m. Presentation

Large Eddy Simulation Including Population Dynamics Model for Polydisperse Droplet Evolution in Turbulence

 Presented by ADITYA KANDASWAMY AIYER (Adviser: Prof. Meneveau)

Previous studies have shown that dispersion patterns of oil droplets in the ocean following a deep sea oil spill depend critically on droplet diameter. Hence predicting the evolution of the droplet size distribution is of critical importance for predicting macroscopic features of dispersion in the ocean. We adopt a population dynamics model of polydisperse droplet distributions for use in LES. We generalize a breakup model from Reynolds averaging approaches to LES in which the breakup is modeled as due to bombardment of droplets by turbulent eddies of various sizes. The breakage rate is expressed as an integral of a collision frequency times a breakage efficiency over all eddy sizes.An empirical fit to the integral is proposed in order to avoid having to recalculate the integral at every LES grid point and time step. The fit is tested by comparison with various stirred tank experiments. As a flow application for LES we consider a jet of bubbles and large droplets injected at the bottom of the tank. The advected velocity and concentration fields of the droplets are described using an Eulerian approach. We study the change of the oil droplet distribution due to breakup caused by interaction of turbulence with the oil droplets.

Acknowledgement: This research was made possible by a grant from the Gulf of Mexico Research Initiative.

3:25 p.m. Presentation

Flow-Induced Flutter of Multiple Inverted Flags for Improved Energy Harvesting

 Presented by AARON RIPS (Adviser: Prof. Mittal)

Multi-inverted flag configurations undergoing flow-induced flutter have been studied using a coupled fluid-structure interaction solver. Both tandem and side-by-side configurations are examined to better understand the dynamics and energy harvesting potential of these systems, and to identify configurations that enhance energy harvesting. Parametric sweeps over the separation distance demonstrate a rich variety of coupling modes and system dynamics. A number of operational regimes have been identified for this two-flag system and correlated to the vortex dynamics. Simulations indicate that the coupling between flags can be used to enhance overall energy harvesting potential.

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