Investigation of flow features around shallow round cavities subject to subsonic grazing flow
Résumé
The focus of this work is the study of the asymmetric mean flow which can appear inside shallow cavities of circular planform, and for which limited experimental data is available. To this end, the behaviour of cylindrical cavities in grazing flow is investigated numerically, for varying ratios of diameter to depth. Large-eddy simulations (LESs) of cylindrical cavities of diameter D = 10 cm and depths H ranging from 1 to 10 cm, grazed by a flow at a Mach number 0.25, are reported. The diameter-based Reynolds number of these cavityflows is 600 000. The incoming boundary layer, of thickness δ/D = 0.17, is numerically tripped, in order to reach a highly disturbed state upstream of the cavity. Numerical flow results are compared to experimental findings obtained for similar configurations, and mean flow dependence on the ratio H/D is shown to be correctly reproduced. For cavities of depth greater than 0.7 times their diameter, a symmetric mean flow is obtained, as expected. For shallower cavities, of depth between 0.4 and 0.7 times the diameter, an asymmetric mean flow regime is observed, as previously described in a few experimental papers. Over a small range of depths, from 0.2 to 0.4 times the diameter, very low frequency flow unsteadiness or switching is found. Based on the LES results, a detailed description of these different flow patterns, in terms of both steady and unsteady aspects, is proposed. This description both confirms and adds to the relatively small amount of experimental data available for shallow cylindrical cavityflows.
Origine : Fichiers éditeurs autorisés sur une archive ouverte
Loading...