Curvature effects on a bluff-body wake

Abstract

This paper prioritizes advancing the understanding of curvature effects on bluff-body wakes to address the possible influence of wake and vorticity dynamics of non-reacting flows inside curved combustors. First, large eddy simulation of a non-reacting flow is carried out in a well-defined triangular bluff-body geometry with no curvature effect. Then, curvature is introduced to the flow field by curving the walls of the combustor. As the curvature increases, the symmetry of the flow field breaks by diverting toward the combustor's convex side. Higher turbulence generation is achieved in the near-wake region, reaching the trailing edge of the bluff body. The dominant mechanism in the near-wake region is found to be the hydrodynamic instabilities rather than the curvature effect. Along the lower shear layer, the coherent structures have appeared as more twisted and non-organized with augmented curvature. The structures along the upper shear layer showed well-organized and quasi-two-dimensional behavior. Curvature-induced Taylor–Görtler instability causes streamwise-elongated vortices to form along the combustor walls, and middle and far-wake regions. These elongated structures are found to be the result of vortex stretching/tilting due to curvature. Stretching/tilting are observed in the recirculation region for all configurations. However, the strengths of those motions are highly altered as the curvature increases, referring to higher turbulent activities near the bluff-body trailing edge. The lower shear layer is governed by the streamwise and wall-normal stretching of vortices in curved configurations. This characteristic seemed as the governing vorticity mechanism for the unstable behavior of the lower shear layer.