Research objectives and content
This proposal develops the study of laminar/turbulent bypass transition of sheared fluid flows. The proposed analysis methods come from both the physics community (hydrodynamic stability theory), and the engineering ones for turbulence (Rapid Distorsion Theory, Statistical modelling, Numerical Simulations). The transition processes and physical mechanisms will be studied in a series of simple sheared flows, such as plane Poiseuille, Couette, or Blasius boundary layer flows. Hypotheses for simple physical schemes will be tested by ways of numerical simulations, for which the most interesting parameters will be picked with the help of preliminar linear and weakly non linear analyses. In view of recent results, the fluid instabilities that ultimately lead to turbulence will be sought as arising from global perturbations, with specific shapes and amplitudes, so that they mimic the primary algebraic instability that appears due to the mean velocity gradients. External factors such as solid body rotation, and more complex flow geometries (curved walls) will be considered. The final goals of the project will be a highly improved knowledge of transitiors mechanisms, refined techniques for the prediction of flow transition, and strategies for controlling it either by passive or rctive methods Impact in industb is expecte from this latter point of view
Training content (objective, benefit and expected impact)
As an important part of this proposal, F. Godeferd will be trained to powerful up to date hydrodynamics stability analysis methods and asymptotic mathematical techniques, that will complement his initial training on numerical simulations and statistical modelling methods for studying turbulent flows. Stability analyses for studying transition are rather unknown to the laboratory of F. Godeferd in Lyon, and will have a significant impact on the actual flow simulation methods developed in Lyon.