Vortex Tubes, Spirals and the Large-Eddy Simulation of Turbulence

California Institute Of Technology, Pasadena CA

Investigators

Abstract

ABSTRACT PROPOSAL NO.: CTS-0227881 PRINCIPAL INVESTIGATORS: DALE I. PULLIN INSTITUTION: CALIFORNIA INSTITUTE OF TECHNOLOGY VORTEX TUBES, SPIRALS AND THE LARGE-EDDY SIMULATION OF TURBULENCE This study aims to further develop the idea of the stretched vortex as the fundamental element for both the modeling of the fine-scales of turbulence and for the building of structure-based subgrid-scale models for the Large-Eddy Simulation (LES) of turbulent flows. The challenge is to develop a unified description of the small-scale dynamics and their effect on the larger scales in realistic turbulent flow at large Reynolds numbers. This modeling approach will be applied to the construction of a special subgrid scale model for the near-wall region of turbulent flow, to the LES of trailing vortices and to the study of velocity-scalar correlations in turbulent mixing. The research to be conducted will include: (1) development and testing of a special subgrid-scale model for the near-wall region of wall-bounded turbulent flows. A quantitative description of this process is developed based on the distortion/winding of the local mean spanwise shear by a nearly longitudinal sublayer vortex. (2) LES of complex unsteady flows with high large-scale strain, such as the turbulent trailing vortex at high Reynolds number. This involves the evolution of a highly anisotropic, unsteady flow with mean streamline curvature that is subject to strong internal large-scale rotation and strain. The proposed LES will use realistic initial conditions combined with a model for the production, inside the vortex core, of axial flow generated by an induced axial pressure gradient. (3) application of the stretched-spiral-vortex model of turbulence small scales to the analysis of velocity-scalar correlations in homogeneous turbulence in the presence of a mean scalar gradient. These application areas are chosen because they represent, respectively, important problems in the modeling, computation, and analysis of turbulent flows at large Reynolds numbers.