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Receptivity of Hypersonic Boundary Layers to Distributed Roughness and Acoustic Disturbances
| Content Provider | Semantic Scholar |
|---|---|
| Author | Balakumar, Ponnampalam |
| Copyright Year | 2012 |
| Abstract | Boundary-layer receptivity and stability of Mach 6 flow over smooth and rough 7° half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances are considered. The effects of two-dimensional isolated and distributed roughness on the receptivity and stability are also simulated. The results show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. An isolated two-dimensional roughness element of height h/δ=1/4 did not produce any difference in the receptivity or in the stability of the boundary layer. Distributed roughness elements produced a small decrease in the receptivity coefficient and also stabilized the boundary layer by small amounts. 1.0 INTRODUCTION Transition from laminar to turbulent flow in hypersonic and supersonic boundary layers increases the skin friction and heat transfer on the vehicle. The efficient design of a vehicle depends on predicting the transition fronts accurately and delaying the transition fronts using passive or active control methods. Transition in boundary layers occurs due to the growth of disturbances inside the boundary layer. These disturbances are initiated by free stream disturbances such as acoustic, turbulence, and other impurities in the free stream and/or by the surface nonuniformities such as roughness and surface vibrations. The evolution and breakdown of the disturbances inside the boundary layer depend on the initial amplitudes of the disturbances, flow parameters such as Mach number and Reynolds number, and the geometry of the vehicle. In quiet environments with small surface nonuniformities, the initial amplitudes of the disturbances are very small and the initial evolution of the disturbances occurs due to some linear instability mechanisms. These boundarylayer instabilities may include, but are not limited to, Tollmien-Schlichting, second-mode, attachment-line, and crossflow instabilities. In noisy environments with large surface roughness, the initial perturbations are large and the evolution bypasses the linear route and enters some nonlinear processes. Transition in hypersonic boundary layers in quiet environments occurs due to the growth of unstable second mode disturbances inside the boundary layer . Numerical, experimental, and theoretical investigations have been performed to try to understand these instability modes for hypersonic boundary layers. Fedorov recently reviewed the stability characteristics of hypersonic boundary layers. In previous work, the interactions of slow and fast acoustic waves, and vorticity waves with hypersonic boundary layers over sharp and blunt flat plates, wedges, and cones were investigated. The results show that flows over geometries with sharp leading https://ntrs.nasa.gov/search.jsp?R=20120007199 2018-11-08T12:28:20+00:00Z |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120007199.pdf |
| Alternate Webpage(s) | https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130003312.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Acoustic cryptanalysis Attachments Blunt (object) Catabolism Coefficient Control theory Flow Friction Hyperacusis Instability Interaction Jaccard index Neurofibromatosis 2 Nonlinear system Numerical analysis Numerical method Retinal Cone Reynolds-averaged Navier–Stokes equations Simulation Small Turbulence Unstable Medical Device Problem Vibration - physical agent Vortex anatomical layer |
| Content Type | Text |
| Resource Type | Article |
