Amplified Frequencies in the Proximal Region of a Circular Jet
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Earlier Large Eddy Simulations (LES) of the proximal region of the spatially developing jet, using a dynamic subgrid scale (SGS) model, showed that it was possible to capture the transition from laminar to turbulent flow, Olsson and Fuchs (1996). This work is focused on the amplification of certain frequencies in the proximal region of the jet. Frequency amplification is studied for different inlet disturbances and Reynolds numbers using a dynamic SGS-model. The disturbances correspond to perturbations used in experimental studies by Crow and Champagne (1971) and Longmire and Eaton (1992). The results of the dynamic models are compared with the results of a simulation without any explicit SGS-model. The numerical accuracy is studied using LES with different spatial resolutions. The validity of the LES assumption is assured by resolving the Taylor micro-length scales which implies spatial resolution within the inertial sub-range. The dynamic SGS-model employs artificial bounds of the SGS-model parameter instead of the commonly used spatial averaging. This is done to exclude unphysical values of the model parameter and to enhance numerical stability.
KeywordsReynolds Number Fundamental Frequency Large Eddy Simulation Vortex Ring Strouhal Number
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