Generation of inflow perturbations and its influence on wake stability

Jinan, P. (2023) Generation of inflow perturbations and its influence on wake stability. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (Ms dissertation of Jinan P (18MS186)) Thesis_18MS186.pdf - Submitted Version Restricted to Repository staff only Download (5MB)

Abstract

High Reynolds number flows exhibit distinct dynamic behaviours in both twodimensional (2D) and three-dimensional (3D) domains. However, studying turbulence characteristics in 2D domains, which tend to deviate from turbulence, presents challenges in accurately predicting the behaviour of originally 3D flow problems. This research focuses on exploring novel methods to predict the behaviour of 3D flows within a 2D domain. The main objective is to provide a ”turbulent-like” inflow condition to a Direct Navier-Stokes simulation and investigate its impact on the wake dynamics. The flow over a flat plate normal to the free stream is studied for Reynolds numbers ranging from 28 to 35 for low Reynolds number flows, and at Reynolds number 1200 for a high Reynolds number case. For low Reynolds number flows, temporal instability is observed beyond Reynolds number 28, contrary to previous reports suggesting transition between Reynolds numbers 30-35. By introducing dynamically fluctuating inflow conditions, instabilities are induced in the originally stable Reynolds number 28 case, even with a turbulence intensity of 0.5%. However, in the high Reynolds number case, the turbulent inflow does not significantly affect the flow behaviour in the 2D domain. The behaviour of the introduced inflow turbulence can be altered by modifying the spot function and the time-space span of the turbulent spot. Keywords:

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