Loading...

Receptivity of High-Speed Flows over Blunt Noses using Spectral Methods

Najafi, Mehdi | 2014

629 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45965 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hejranfar, Kazem; Esfahanian, Vahid
  7. Abstract:
  8. The receptivity, transition and stability mechanisms of supersonic and hypersonic boundary layers to freestream disturbances are one of the most complex studies in fluid mechanics. It is well known that turbulent flows generate much higher shear forces on the surface of vehicles and hence much higher viscous heating rates than a laminar flow would at the same flight conditions. Therefore, the accurate prediction of boundary layer behavior is a critical part of the aerodynamic design of high-speed vehicles and thermal protection systems. Formation of a bow shock in front of the vehicle makes the receptivity of flow-field more complex than and different from those of low-speed subsonics. Since experimental and analytical methods fall into trouble according to cost and theoretical limitations, high-order numerical methods are able to surmount with providing the highest level of details for such studies. A collocation spectral method with shock-fitting technique is developed to inspect the inviscid/viscous blunt body problem. The dual combination of the outflow boundary is inspected and remedies are introduced to obtain the most accurate basic steady flow against several verifications and validations. Computing the steady high-speed flow over a cylinder accurately, freestream disturbances of the most importance in such regimes, i.e, fast and slow acoustic waves are introduced in front of the bow shock to investigate how freestream disturbances interact with the shock, penetrate the boundary layer and ultimately induce boundary-layer disturbances. The effects of incident wave frequency and type on the receptivity of inviscid and viscous flow-field are studied in detail. It is shown that there are two different inviscid and viscous mechanisms responsible for the receptivity. Since the basic flow-field is nonlinear, decomposition of the mechanisms in such flows is quite a difficult task
  9. Keywords:
  10. Compressible Flow ; Spectral Method ; Supersonic Flow ; Shock Fitting Method ; Receptivity Analysis

 Digital Object List

 Bookmark

No TOC