24-10-2012, 01:04 PM
Facility Unsteadiness Research
ABSTRACT
This report summarizes work that was performed in fiscal years 2002 through 2004 on or related to the ‘Facility
Unsteadiness Research’ project sponsored by the Air Force Office of Scientific Research (AFOSR). Many ground test facilities
experience some form of flow unsteadiness at various points in their operational envelope. This unsteadiness can at times cause
significant problems in the quality of data obtained, the structural integrity of the facility, or both. Conventional simulation
techniques, which do quite well for steady-state simulation, have been found to be deficient in many cases when applied to
unsteady flows. The current project attempts to address these problems. This work has focused on three areas: building up the
computational infrastructure of a production CFD code to be able to tackle large scale unsteady problems, developing a
rigorous code verification capability in order to ensure continued reliability of the results in the face of extensive code
modification, and the running of test cases leading toward the ultimate objective of being able to simulate full scale facilities.
The Detached Eddy Simulation model and the hybrid model of Nichols and Nelson were found to offer improved results over
conventional turbulence models for unsteady flows. The Method of Manufactured Solutions was employed to verify several
of the numerical methods available in the Wind-US code. The algorithm improvements to the Wind-US code have now made
it possible to begin to model large ground test facilities and resolve medium and large-scale instabilities within them.