Dr. Thomas conducts his research in the Supersonic Research Laboratory and other laboratories at the Hessert Laboratory for Aerospace Research.

Current Research

Noise Source Modeling and Control of Compressible Turbulent Jets

Unsteady flow processes associated with large-scale coherent vortical structures in the near field of the axisymmetric turbulent jet are very important in determining radiate jet noise. Details regarding the nature of the underlying source mechanisms are still incomplete. Our research is focused on the characterization, modeling and control of acoustic source mechanisms in compressible turbulent jet flows. The overall objective is the quantification of the acoustic sources in the jet and their active control via an array of phased plasma actuators at the jet lip. The proper orthogonal decomposition (POD) is applied in order to quantify the most energetic large-scale motions in the near field of the axisymmetric compressible jet.

Experimental Investigation of the Flow Field Physics of High-Lift Systems

These projects focus upon the complex viscous flow interactions involved in high lift multi-element airfoils for commercial airliners. In particular, the fundamental experiments seek to provide new insight regarding the flow field physics of slat/leading edge confluent boundary layer, wake development in pressure gradient, boundary layer relaminization and noise production in high lift systems. Passive flow control is used to enhance aerodynamic performance and for noise abatement.

Low-Order Dynamical Systems Modeling of Turbulent Shear Flows

This research is focused on the development of low-order dynamical systems models of the large-scale structures in turbulent shear flows. The modeling is based on Galerkin projections of the Navier-Stokes equations onto experimentally determine proper orthogonal decomposition eigen modes. Unresolved scales are treated as a dissipative effect on the resolved modes. The resulting models are utilized in the development of rational flow control strategies.

Active Separation Control in a Turbo-jet Low Pressure Turbine

This research involves the application of active separation control to the rotor blades of the low pressure turbine in turbojet engines. The separation control is based upon using surface mounted plasma actuators. Active separation control allows in creased blade loading and has the potential to reduce part count, weight and length of turbojet engines. This research is currently underway in cascade facility located at the Center for Physics and Control at the University of Notre Dame.

 

Selected Recent Publications

Gordeyev, S.V., and Thomas, F.O., "Coherent Structure in the Turbulent Planar Jet, Part 2. Structural Topology via POD Eigenmode Projection,"Journal of Fluid Mechanics, Vol. 460, pp. 349-380, 2002.

Gordeyev, S.V., and Thomas, F.O., "Coherent Structure in the Turbulent Planar Jet, Part 1. Extraction of Proper Orthogonal Decomposition Eigenmodes and Their Self-Similarity," Journal of Fluid Mechanics , Vol. 414, pp. 145-194, 2000.

Gordeyev, S.V., and Thomas, F.O., "Temporal Subharmonic Amplitude and Phase Behaviour in a Jet Shear Layer: Wavelet Analysis and Hamiltonian Formulation," Journal of Fluid Mechanics, Vol. 394, pp. 205-240, 1999.

Liu, X., Thomas, F.O., and Nelson, R.C., "An Experimental Investigation of the Planar Wake in Constant Pressure Gradient," Physics of Fluids, Vol. 14, No. 8, pp. 2817-2838, 2002.

Thomas, F.O., Nelson, R.C., and Liu, X., "Experimental Investigation of the Confluent Boundary Layer of a High-Lift System," AIAA Journal, Vol. 36, No. 6, pp. 978-988, 2000.

Direct comments, questions, and corrections to amedept@nd.edu