Active Control Strategies for Compressible and Multiphase Flows

Speaker: Mahesh Natarajan, National Renewable Energy Laboratory (NREL)
December 15, 2020

Presentation

Abstract

The focus of the talk is on active flow control for single and multi-phase, compressible flows. For single-phase flows, a novel method has been developed to design a linear feedback control system that utilizes the information contained within the forward and adjoint global modes of the baseflow obtained from DNS/LES. Regions of the flow-field with high dynamical sensitivity are identified, and an optimization procedure determines effective actuator locations. The efficacy of the method is demonstrated with two different flow control problems — flow stabilization in a Mach 0.65 diffuser, and the control of noise radiated by a turbulent Mach 0.9 jet. For multi-phase flows, the focus is on the control of primary atomization in sprays. An all-Mach multiphase flow algorithm that was developed in [1] is integrated into AMReX — a framework for massively parallel, block-structured adaptive mesh refinement applications [2]. Simulations are performed to investigate the dynamics of spray breakup of a water jet in the presence of transverse, standing acoustic waves. The compressible flow equations are solved, and the multiphase treatment uses an unsplit, volume-of-fluid (VOF) approach with a piecewise linear interface calculation (PLIC) for the interface reconstruction.

[1] O. Desjardins, M. Natarajan, M. Kuhn, “Numerical Study of Liquid Jet Atomization in Supersonic Crossflows, ”ILASS-Americas 29th Annual Conference on Liquid Atomization and Spray Systems, Atlanta, GA, May 2017.

[2] Weiqun Zhang, Ann Almgren, Vince Beckner, John Bell, Johannes Blaschke, Cy Chan, Marcus Day, Brian Friesen, Kevin Gott, Daniel Graves, Max Katz, Andrew Myers, Tan Nguyen, Andrew Nonaka, Michele Rosso, Samuel Williams, and Michael Zingale. AMReX: a framework for block-structured adaptive mesh refinement. Journal of Open Source Software, 4(37):1370, May 2019. doi: 10.21105/joss.01370.

Biography

Mahesh Natarajan is currently a researcher in the High-Performance Algorithms and Complex Fluids (HPACF) group at the National Renewable Energy Laboratory (NREL) at Golden, Colorado. He received his Bachelor's degree in Mechanical Engineering from the University of Calicut in 2007, and Master's in Aerospace Engineering from the Indian Institute of Science in 2009. He completed his Ph.D. from the Department of Aerospace Engineering at the University of Illinois at Urbana-Champaign in 2017 and was a postdoctoral researcher in the Department of Mechanical and Aerospace Engineering at Cornell University before joining NREL in 2019.

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