Understanding Hypersonic Transition Mechanisms through Interactions Between Hydrodynamic, Acoustic and Thermal Modes
Abstract
Hypersonic weapons offer substantial advantages to the Navy, not only as a ship-based asset fortime-critical targets, but also as a"" defense against anti-ship threats. Among the many problemsassociated with hypersonic flight, one of great consequence is transitio""n to turbulence, becauseof its significant implication for drag and heat loads. Decades of research have revealed the phenomenology""of some key processes, but many of the underlying mechanisms remain obscure. Thehypersonic transition parameter space, and thus hy""personic transition scenarios, are much richerthan at lower speeds: in addition to the Reynolds number and the disturbance field, t""he Machnumber and thermal conditions play influential roles. Although the terminology varies, the phenomenologyis often discussed"" in terms of various transition modes such as Tollmien-Schlichting,Mack, 2-D/oblique and resonant interactions among others, each o"f which is modulated by theabove parameters. The description of these transition modes implicitly or explicitly refers to theirKov"asznay-type fluid-thermodynamic (FT) components i.e., hydrodynamic (vortical), acoustic andthermal (entropic) modes. However, studi""es have neither explicitly connected transition and FTmodes, nor have they explained the phenomenology in terms of basic energy exc""hange mechanismsthat modulate FT modes. The goal of the proposed work is to provide this connection, thuspresenting the phenomena"" in a more effective manner. Of the many phenomena, we focus attentionon two primary events: synchronization of the slow and fast d"iscrete modes and fundamentalresonant interactions in the non-linear regime. We select a comprehensive set of four benchmarkDirect" Numerical Simulation cases, covering flat plate, wedge and cone configurations, differentdisturbance environments, Mach numbers an""d wall thermal conditions. For each, we will examinethe evolving form and spectral content of all FT modes as well as their energy"" sources andsinks. For this, we will use the newly-rediscovered Doak~s method, which places no limitations(such as linearity) on t"he flow and naturally yields an equation for total fluctuating enthalpy (TFE)that identifies intermodal energy transfer through vor"ticity interactions, shear, viscous and thermaleffects. The evolution of form and spectral content of crucial FT mode components in" resonantinteractions and the global behavior of the most rapidly growing modes in non-stationary situationswill be identified with spectral decomposition techniques. Intermittent events will be isolatedwith non-Fourier techniques and cross-correlated with the flow variables to elucidate their connectionto coherent structures. In addition to improving our understanding of hypersonic trans"ition,the results aid in the evolution of more comprehensive predictive theories, as well as conceptualadvancement of better, phys""ics-based, strategies for control.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712528
Entities
People
- Datta V. Gaitonde
Organizations
- Office of Naval Research
- Ohio State University
- United States Navy