Abstract
When pressurized with a fluid, the sweeping jet actuator (SWJA) emits a self-induced and self-sustained temporally continuous, but spatially oscillating bi-stable jet at the outlet. The SWJA adds up local momentum using the Coanda extension without any moving parts and, therefore, can be a promising tool for suppressing aerodynamic flow separation. However, the SWJA needs to be integrated into curved aerodynamic surfaces with an angle. The present study focuses on investigating the effects of various exit nozzle geometries on the flow field. The geometric parameters considered were the exit nozzle angle, diffuser arm length, and curvature. The working fluid was air, and the mass flow rate was 0.015 lb/s. A set of time-dependent flow fields was computed using a two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulation. The time history of pressure was recorded inside the upper and lower feedback channels. The jet oscillation frequency was obtained by employing the fast Fourier transform (FFT) for all datasets. The results were compared against the baseline case and data available in the literature. The results showed that external geometric variations at the nozzle exit had a negligible impact on the oscillation frequency. However, there were notable effects on the pressure and velocity distribution in the flow field, indicating that the actuator had sensitivity towards the geometric variation of the exit nozzle—the wider the exit nozzle, the lower the downstream velocity. Notably, we observed that the mean velocity at the exit nozzle downstream for the curvature case was 40.3% higher than the reference SWJA.
Highlights
The fluidic oscillator has been studied experimentally earlier to understand the model better, as well as contribute to developing the numerical setup
The geometric modifications were based on the critical dimension; the exit nozzle throat and the variation of the parameters were analyzed after that location
Based on the mean velocity ratio (η% = Vcase /VBaseline ∗ 100) obtained at a downstream (x/h = 5) location, we evaluated the efficiency of the respective geometry [7,25]
Summary
The fluidic oscillator has been studied experimentally earlier to understand the model better, as well as contribute to developing the numerical setup. A computational study for the characterization of the jet oscillation of the actuator was conducted by Furkan et al [7] by varying the mass flow rate from incompressible to subsonic compressible flow This 3D URANS model with a stable mesh structure was proven to be a cost-effective alternative for SWJA performance analysis. Experimental analysis by Ostermann et al [19] explained the time-resolved flow field created by a fluidic actuator on a spatially oscillating jet by changing different parameters such as the velocity ratio, installation angle, and Strouhal number. Another experimental analysis [20] was carried out by Park et al to investigate the effect of the internal geometric parameters of the oscillators on the sweeping jet oscillation distribution. This analysis gives a direction for improving the actuator design effectively in the future
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