Dissertation Defense: Loosely Coupled Time Integration of Fluid-Thermal-Structural Interactions in Hypersonic Flows

Brent Miller, PhD Candidate, Aerospace Engineering

All dates for this event occur in the past.

E525 Scott Lab
E525 Scott Lab
201 W. 19th Ave.
Columbus, OH 43210
United States

Committee: Dr. Jack McNamara, Chair (AE)

Dr. Datta Gaitonde (AE)

Dr. Sandip Mazumder (ME)

Dr. Manoj Srinivasan (ME)

Thomas Eason

S. Michael Spottswood

Abstract:

The United States Air Force's objective to develop reusable hypersonic cruise vehicles requires analysis capability that can capture the coupled, highly-nonlinear interactions between the fluid flow, structural mechanics, and structural heat transfer. Analysis can no longer be performed only at specific flight conditions. Due to the path dependence of the structural response and long term evolution of the thermal state, analysis is required over significant portions of the flight trajectory. The fluid, structural, and thermal physics operate at disparate time scales, requiring capability to capture the smaller time scales of the fluid and structure, over the longer time scales of the thermal response. Thus, integrating models together in a time-accurate manner must be done as efficiently as possible to capture the coupled interactions at all scales with a reasonable computational expense. The goal of this research is to develop time integration procedures for fluid-thermal-structural analysis efficiently and accurately. Separate fluid, thermal, and structural solvers are "loosely" coupled together so that each solver communicates with each other just once per time step, with emphasis on maintaining the time accuracy of the individual solvers. Coupling schemes for both time-accurate and quasi-steady flow models are considered. The schemes rely on extrapolation-based fluid load predictors to maintain accuracy, and allow for subcycling, in which each solver is marched at different time steps. The developed coupling procedures are compared to several other schemes, including a basic one that does not use the predictors, and a subiteration-based strongly coupled scheme. Response predictions of multiple configurations of a panel in two dimensional hypersonic flow are performed. Using second order implicit time integrators for the individual solvers, the predictor-based and strongly coupled schemes are demonstrated to retain the second order accuracy with and without subcycling, while the others reduced to first order. Simulations are performed for a stable response and the unstable flutter response of a panel, and the responses between the coupling schemes are compared. The predictor-based schemes are found to be the least computationally expensive, and show good agreement with the more robust strongly coupled schemes. Finally, a long time-record response of the panel using time-accurate CFD is performed and compared to the response using approximate quasi-steady fluid models.