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Fluid Dynamics Reviews Seminar: Dennice Gayme "The Restricted Nonlinear Model: A Minimal Model..." FLUID DYNAMICS REVIEWS SEMINAR SERIES Speaker: Dr. Dennice Gayme THE RESTRICTED NONLINEAR MODEL: A MINIMAL MODEL FOR SELF-SUSTAINING TURBULENCE IN WALL BOUNDED SHEAR FLOWS March 8, 2018 | 3:00 PM | DeWalt Seminar Room, 2164 Martin Hall Abstract: Understanding wall-turbulence is crucial to enabling technological advances in a wide range of applications. However attaining the requisite knowledge has been hindered by the complexity of its mathematical description, the Navier Stokes equations. This talk describes one of a growing number of dynamical systems based models that have been proposed to address this challenge by studying important aspects of wall-turbulence in a simplified setting. The restricted nonlinear (RNL) model for wall-bounded turbulent flows is a quasi-linearization of the Navier-Stokes equations with a streamwise averaged mean flow; a choice motivated by experimental and analytical evidence of the central role of streamwise elongated coherent structures in these flows. Simulations of the RNL model at a range of Reynolds numbers are shown to support self-sustaining turbulence that naturally collapses to a minimal system supported by a small number of streamwise varying perturbations. We discuss the fact that RNL turbulence with accurate statistical features can be sustained even when the model is further restricted to a small number of appropriately selected streamwise varying modes interacting with the streamwise constant mean flow. The resulting ‘band-limited’ RNL system therefore constitutes an analytically and computationally attractive reduced order model for studying some of the key underlying mechanisms wall-turbulence. In particular, its study can inform mechanistic and control oriented models for engineering applications such as wind farm design. More info at: www.enme.umd.edu/events/fluid-dynamics-review-seminars
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