Development of an Asymptotically-Reduced, Multiscale Model of Turbulent Boundary Layer Dynamics at Extreme Reynolds Numbers

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1437851Chini, Gregory The goal of the proposed study is to use a combination of theory and unique experiments to develop a new approach to modeling turbulent flows in the boundary layer. The capacity to understand, predict, and control turbulent boundary layer dynamics is important for a multitude of technological applications and scientifically important processes. Turbulence is prevalent in the world we live in and in the industry. Success in this research could impact any industrial process that involves turbulent flow, with consequent societal benefits in the form of new products, improved energy efficiency, quieter systems, etc. Problems related to geophysical and astrophysical flows could also be approached in a new, more accurate way. The educational plan involves the participation of both graduate and undergraduate students.The main goal of the proposed research is to develop a multiscale Partial Differential Equation (PDE) model of turbulent boundary layer dynamics through the integrated useof high Reynolds number (Re) asymptotics and well-resolved high-Re experiments. By its very nature, the model development process will elucidate the so-called "inner/outer" interaction, as these are linked to boundary layer evolution as Re tends to infinity. In addition, numerical solutions of the multiscale PDEs promise to be less costly than direct numerical simulations (DNS) of the primitive Navier?Stokes (NS) equations from which they are derived, thereby enabling simulations in otherwise inaccessible parameter regimes. The proposed model will be distinct from other recent efforts, because the model retains a first principles foundation, with no reliance on system inputs or phenomenological assumptions. The multiscale analysis on which the model is based brings together recent advances in the asymptotic analysis of turbulent geophysical flows, of "exact coherent structures" in high-Re shear flows, and of the mean dynamics in canonical turbulent wall-flows. The target model is a closed multiscale PDE system that is self-consistently and systematically simplified relative to the primitive NS equations. This critical scaling information is only accessible through well-resolved, high-Re experiments. In this regard, the Univ. of New Hampshire Flow Physics Facility (FPF), which is the world's largest flow physics quality boundary layer wind tunnel, allows high-resolution measurements of velocity and vorticity at extreme Reynolds numbers.