Flow Separation Dynamics in Three-Dimensional Asymmetric Diffusers

Abstract The mean and instantaneous flow separation of two different three-dimensional asymmetric diffusers is analysed using the data large-eddy simulations. geometry both under investigation based on experimental configuration Cherry et al. (Int J Heat Fluid Flow 29(3):803–811, 2008). feature similar area ratios $$\mathrm{AR}=4.8$$ AR = 4.8 $$\mathrm{AR}=4.5$$ 4.5 while exhibiting differing expansion $$\mathrm{AER}=4.5$$ AER or $$\mathrm{AER}=2.0$$ 2.0 , respectively. Reynolds number averaged inlet velocity height duct approximately $${\textit{Re}}=10{,}000$$ Re 10 , 000 . time-averaged in terms streamwise profiles size location backflow region are validated data. In general good agreement simulated results with found. Further quantification behaviour unsteadiness coefficient reveals volume portion which reversal evolves. This new approach investigates cumulative fractional occupied by throughout simulation, a power density spectra analysis their time series periodicity growth reduction phases within diffusers. dominating turbulent events responsible for formation energy-containing motions including ejection sweep examined quadrant at various locations. Finally, isourfaces Q-criterion visualise origin fate coherent structures