Coherent features in the sensitivity field of a planar mixing layer

Abstract

Coherency in the topology of the instantaneous sensitivity fields of the planar mixing layer was captured using the sensitivity equation method ͑SEM͒. In the SEM approach, the partial differential equations governing the evolution of the sensitivity coefficients are derived, discretized, and solved directly, in the present work, using an unsteady finite-volume-based fractional-step algorithm. This allows the investigation of parameter-dependence without performing parametric studies. The present results, from numerical simulations run at Re ␦ 0 = 200 and Pr= 0.71, provide a means to examine how and to what extent perturbations in the Reynolds/Prandtl number locally alter the structure of the flow. Specifically, a two-blade pattern appears as a dominant feature in the sensitivity solution and highlights the physical mechanism leading to vortex thickness growth and enhanced molecular mixing with increasing Re ␦ 0 and Pr. An expression describing the sensitivity of vortex thickness to changes in Re ␦ 0 is also derived and validated using the concept of "nearby" flows.

A Parallel Computational–Statistical Framework for Simulation of Turbulence: Applications to Data-Driven Fractional Modeling

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Anomalous Features in Internal Cylinder Flow Instabilities subject to Uncertain Rotational Effects

“…Given the discussion on the generation and evolution of the coherent vortices, and our quantitative/qualitative study on the emergence of strong non-Gaussian statistical behavior for velocity and vorticity fluctuations, one can argue that such statistics are closely tied to and in other words, the direct result of generation and growth of coherent vortical structures due to the effect of the rotational symmetry-breaking factors. In prior studies, such connection was investigated and partially addressed in the contexts of planar mixing and free shear layers [90][91][92] , subgrid-scale (SGS) motions and their nonlocal modeling for homogeneous and wall-bounded turbulent flows 93,94 , boundary layer flows 95,96 , and turbulent flows interacting with wavy-like moving/actuated surfaces (with application to reduction and control of flow separation) 97,98 .…”

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