Ph.D. Defense

Dhruv Purushotham

(Advisor: Prof. Joseph Oefelein)

"Direct and Large-Eddy Simulations of Spatially Evolving Supercritical Turbulent Shear Layers"

Thursday, April 18

12:30 p.m.

Montgomery Knight Building 317

Abstract

The physics of supercritical combustion is now increasingly relevant to the development and deployment of next-generation gas turbine power platforms. Computational methods can be employed in conjunction with experiments to facilitate efficient design of these systems. The increasing availability of powerful computing platforms enables the use of high-fidelity techniques such as large-eddy simulation (LES) in lieu of the more accessible Reynolds-Averaged Navier-Stokes (RANS) approximation. However, even the LES technique suffers from the classical closure problem of turbulence, and the accuracy of a given calculation is closely coupled to the performance of the subfilter models selected to close the governing system of equations and the filter cutoff scale selected. Subfilter closures historically developed and employed for LES have been well validated to treat atmospheric pressure flows of ideal gases, however their performance within the supercritical regime cannot be taken for granted. Thermophysical nonlinearities near the critical point stress existing closures and their performance under these conditions is largely unclear. The extension of this argument to multi-component settings adds further uncertainty. The research in this dissertation aims to address a judiciously selected subset of these concerns through a multi-faceted approach based on the joint application of the direct numerical simulation (DNS) and LES techniques. Outcomes of the research include novel insight regarding supercritical mixing at the selected operating conditions from both a theoretical and numerical perspective. Further insights regarding subfilter model performance in an a priori sense are also garnered, as well as the aggregate performance of LES calculations at a variety of grid resolutions at the selected operating conditions.
 

Committee
•Prof. Joseph Oefelein – School of Aerospace Engineering (advisor)
•Prof. Adam Steinberg – School of Aerospace Engineering
•Prof. Jerry Seitzman – School of Aerospace Engineering
•Prof. Devesh Ranjan – School of Mechanical Engineering
•Dr. Ramanan Sankaran – Oak Ridge National Laboratory