Flow features of a new fluidic oscillator using time-resolved PIV measurement and 3D numerical simulation

Abstract

The current study measures the instantaneous velocity field inside and outside a new designed fluidic oscillator using planar time-resolved PIV technique on its symmetry plane in a water tank. The instantaneous velocity field showed that the interaction of four vortices with the jet was the main reason of jet oscillation inside the main chamber. Threedimensional transient numerical solutions were also carried out using Ansys-Fluent 2020R2 software. Four turbulence models (k-ε, k-ε RNG, k-ω, and k-ω SST) were used for these numerical solutions, which their results were then compared with the PIV results, qualitatively and quantitatively. The comparison showed that the k-ε and k-ω SST models were better for simulating the flow of the new oscillator. However, both models over-predicted the jet spreading angle and oscillation frequency compared to the PIV results. A similar PIV measurement was accomplished outside the conventional oscillator to compare the timeaveraged velocity fields of the new and conventional oscillators. The comparison showed that the amplitude and frequency of the new oscillator were, respectively, lower and higher than those of the conventional one. The time-averaged velocity and momentum flux outside the new oscillator was significantly higher than for the conventional one. Abbreviations A Throat area (m 2 ) D Throat height (m) D h Hydraulic diameter (m) Fr Oscillation frequency (1/s) f Oscillation frequency (1/s) H Domain height outside the oscillator (m) rate k Turbulence kinetic energy (m 2 /s 2

Jet Oscillations and Mixing in Fluidic Oscillators: Influence of Geometric Configuration and Scale

“…It was reported that k –ε was in good agreement with the experimental data. On other hand Nili-Ahmadabadi jet oscillation frequency was obtained by k –ε, RNG k –ε, k –ω, and SST k –ω with frequency obtained by PIV. It was reported that k –ε and SST k –ω overpredicted the jet oscillation frequency.…”

“…The model equations for other turbulence models are given in Table S2 of the Supporting Information. Additional information on these equations can be found in any standard textbook − and Ansys Fluent theory guide …”

“…experimentally studied the effect of the ratio of the width of the inlet, mixing chamber and outlet on the jet oscillation frequency. Nili-Ahmadabadhi introduced a new design for an oscillator and compared 3 different turbulence models with PIV, and it was observed that both k –ε and SST k –ω models overpredicted the jet oscillation frequency measured with PIV. Hossain et al presented the effect of the FO’s exit nozzle on the flow field and the subsequent impingement heat transfer.…”