Effect of porous surfaces on compressible boundary layers perturbed by free-stream disturbances
Abstract
The objective of the proposed work is to study pre-transitional compressible boundary layers theoreticaly and numerically, and to investigate the effects of porous surfaces on the generation and growth of boundary layer disturbances induced by free-stream turbulence with the aim of delaying transition to turbulence. Thanks to our theoretical and numerical approach, we will be able to study the influence of these passive control surfaces on Klebanoff modes, Tollmien-Schlichting waves, and unsteady Gortler vortices. All these disturbances are generated by free-stream turbulence in compressible boundary layers and they all contribute to initiate the breakdown of the laminar boundary layer to turbulence. Therefore, the attenuation of the intensity of these perturbations is bound to lead to a delay of transition. The use of a passive surface is particularly attractive because no energy is input into the system. Furthermore, the flow control is also interesting because it is aimed at disturbances that are developing on the laminar viscous layer, and therefore they are still of low intensity. It would be much more difficult to act on these disturbances once the turbulent regimes has already ensued. The methodology is based on a blend of asymptotic and perturbation methods and numerical techniques. Inspired by experimental results, the compressible Navier- Stokes equations are simplified ina rigorous manner in order to retrieve only the relevant physical terms. This allows the equations to be simplified, the cost of their numerical computation to drop considerably, and to extract the essential physical mechanism responsible for the formation of these disturbances by free-stream turbulence and for the attenuation through the porous surface.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 23, 2016
- Source ID
- FA95501510248
Entities
People
- Pierre Riccó
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Sheffield Department of Psychology