The presence of large-scale coherent structures can significantly impact the dynamics of a turbulent flow field and the behaviour of a flame stabilized in that flow. The goal of this study is to analyse how increasing free-stream turbulence can change the response of the flow to longitudinal acoustic excitation of varying amplitudes. We study the flow in the wake of a cylindrical bluff body at both non-reacting and reacting conditions, as the presence of a flame can significantly alter the global stability of the flow. The frequency of longitudinal acoustic excitation is set to match the natural frequency of anti-symmetric vortex shedding for this configuration and we vary the free-stream turbulence using perforated plates upstream of the bluff body. The results show that varying the level of free-stream turbulence can influence not only the amplitude of the coherent flow response, but also the symmetry of vortex shedding in the presence of longitudinal acoustic excitation. Increasing the turbulence intensity can fundamentally change the structure of the time-averaged flow and can directly impact the coherent flow response in two ways. First, increasing turbulence intensity can enhance the amplitude of the natural anti-symmetric vortex shedding mode in the wake. Second, increasing turbulence intensity weakens the symmetric response of the flow to the longitudinal acoustic excitation. In the non-reacting and reacting conditions, both symmetric and anti-symmetric modes are present and are characterized using a spectral proper orthogonal decomposition. We see evidence of interaction between the symmetric and anti-symmetric modes, which leads to an interference pattern in the coherent vorticity response in the shear layers. We conclude by presenting a conceptual model for the influence that turbulence has on these flows.
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Large Eddy Simulation of a Turbulent Wake behind a Body of Revolution at ReD=5000
This study is concerned with the numerical investigation of a three-dimensional wake behind a body of revolution via Large-eddy Simulations. Large-eddy Simulations with the Reynolds number $Re_D=5000$ based on the bluff body diameter is performed using a high-order spectral-element solver Nek5000. The focus of the study is on characterizing the wake asymmetries and time-dependent behavior observed in previous experimental studies with similar bluff body models. The time-dependent history of the wake meandering and rotating behavior will be presented.
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- Award ID(s):
- 1707075
- NSF-PAR ID:
- 10112474
- Publisher / Repository:
- AIAA Aviation Forum and Exposition
- Date Published:
- Journal Name:
- AIAA Aviation Forum and Exposition, Dallas, TX, June 2019
- Format(s):
- Medium: X
- Location:
- Dallas, TX
- Sponsoring Org:
- National Science Foundation
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