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Computational Mathematics Colloquium

Title: A Discontinuous Galerkin Conservative Level Set Method for Simulating Turbulent Atomization
Speaker(s): Olivier Desjardins
Affiliation: Department of Mechanical Engineering University of Colorado at Boulder
When: Monday,  February 14, 2011
Time: 9:30 AM  -  10:30 AM
Where: CU building, Room 656

In the context of rising environmental concerns and record-high oil prices, the need for cleaner and more efficient combustion devices becomes pressing. Thanks to the steady progress in computer power and computational fluid dynamics (CFD) methods, computational modeling of combustion systems emerges as a promising tool that can drive the design of future devices. In these systems, fuel is usually injected in liquid form. Atomization of the liquid fuel, or the process by which a coherent liquid ow disintegrates into droplets, represents one of the key challenges that remain to be tackled to make predictive simulations possible. Because atomization governs the size of the fuel droplets, and therefore their subsequent evaporation rate, it will have far-reaching repercussions on many aspects of the combustion process, for example pollutant formation. However, the inherent multi-physics and multi-scale nature of this process limits both experimental and numerical investigations. In an eff ort to improve the numerical schemes available for simulating of multiphase flow, a novel numerical method is developed to track the interface location. This method combines the excellent mass conservation properties of the accurate conservative level set (ACLS) method of Desjardins et al. [J. Comp. Physics 227 (18), 8395{8416] with a discontinuous Galerkin (DG) discretization. DG provides an arbitrarily high order representation of the level set without requiring a large stencil, resulting in a highly accurate and parallelizable method. Excellent performance is shown for a variety of test cases including Zalesak's disk rotation and deformation by a vortex field. This new approach is then applied in a detailed study of the turbulent airblast atomization of n-dodecane. Numerical predictions are compared to experimental measurements, showing the satisfactory behavior of the proposed level set scheme. In particular, the onset of break-up, most unstable wavelength, and drop size and velocity distributions are in good agreement, suggesting that the fundamental physics of air-blast atomization are well captured by the simulations.

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