Aspect ratio and combined installation in fluidic oscillator-crossflow interactions

Abstract

This paper describes a computational study of fluidic oscillator-crossflow interactions. Fluidic oscillators are high potential active flow control devices, which offer promise for cooling and flow separation. Previous experimental studies have investigated the internal/external flow fields of fluidic oscillators. This improved the understanding of three-dimensional flow fields; however, this has been limited to single aspect ratio nozzles in single variable installations. Research has not analyzed the effects of varying both oscillator parameters and installation conditions. Therefore, the present aim is to enhance flow field understanding by examining three aspect ratio (AR) nozzles in default perpendicular condition and in a “skewed incline” configuration (β = 60°, α = 75°). An unsteady Reynolds averaged Navier Stokes model was validated with prior experimental data and then used to evaluate time-averaged and time-accurate flow fields at three different blowing ratios. Strouhal number analysis uncovers the effectiveness of parametric changes. Internal flow fields are presented, identifying key differences and similarities. External flow field analysis in regard to spreading angles 55°–65° observes greater wall-normal penetration for lower AR oscillators with improved spanwise penetration for larger AR's. The combined installation produces stronger primary vortices, improving penetration along the wall, while inclination keeps vortices close to the wall. Oscillator effectiveness is dependent on the application.