AN ALTERNATIVE APPROACH TOWARDS INVESTIGATING STABILITY AND TRANSITION
Abstract
Prediction of boundary layer transition from laminar to turbulent flow is critical to the design of hypersonic vehicles, for example, space planes and re-entry capsules, as instability and eventual transition to turbulent flow can lead to high levels of drag and heat loads which, in turn, can be detrimental to performance and safety of the vehicle. As is well known, prior to transition, the laminar boundary layer goes through an instability regime and the type of instability affects the eventual transition and its location. As a typical hypersonic vehicle covers both continuum and near non-continuum regimes such as merged layer and slip flow in its flight trajectory, methods to calculate stability and transition must be able to handle all these flow regimes. Presently, computations based on Navier-Stokes solvers are the principal tools for this purpose with appropriate correction factors to account for rarefaction effects. Recently, hybrid techniques using both CFD and Direct Simulation Monte Carlo (DSMC) are being tried to predict transitional and turbulent flows to deal with high altitude flows. In this project, we propose a new approach – the Fokker-Planck method which is also a particle based technique like the DSMC but much less computationally intensive and hence much less expensive. The method has shown excellent agreement with DSMC data at higher Knudsen number end and with Navier-Stokes flows at the lower Knudsen number end. The technique has been shown to be quite effective in computing simple flows such as hypersonic flow around a cylinder and a wedge. Its use to study stability and transition as proposed here is, however, new.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2023
- Source ID
- FA23862210136
Entities
People
- S. L. Gai
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of New South Wales