Global Transient Growth Mechanisms in High-Speed Flows with Application to the Elliptic Cone
Abstract
It is proposed to create the world-first theoretical framework for the analysis of non-modal (transient growth) global linear instability mechanisms in flows with multiple inhomogeneous spatial directions in the supersonic and hypersonic regimes. Subsequently, the tools generated will be applied to unravel presently unexplored instability mechanisms on the elliptic cone at supersonic and hypersonic speeds. In incompressible boundary layer flows, the laminar-turbulent transition scenario based on short-time (transient) algebraic growth of non-modal perturbations, typically streamwise aligned streaks, is well-known to constitute a path to transition alternative to the modal scenario based on exponential amplification of Tollmien- Schlichting waves and crossflow eigenmodes at subcritical Reynolds numbers. Under certain flow conditions, the transient growth scenario can altogether bypass that based on modal amplification, rendering the modal/exponential decay irrelevant. In other situations, optimal perturbations growing algebraically at early times transform into modal perturbations that eventually grow exponentially. Non-modal perturbations growing algebraically are also known to modify the underlying base state, which can then undergo laminar-turbulent flow transition on account of exponentially amplifying secondary disturbances. In all, it can be safely asserted that no linear instability analysis is complete until both the algebraic, short-time non-modal transient-growth and the exponential, asymptotic/long-time modal linear instability mechanisms have been examined and fully understood as precursors to laminar-turbulent flow transition.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 23, 2016
- Source ID
- FA95501510387
Entities
People
- Vassilios Theofilis
Organizations
- Air Force Office of Scientific Research
- United States Air Force