Dynamics of turbulent mixing of two miscible fluids driven by Faraday instability under the influence of rotation

  • Singh, Narinder (Indian Institute of Technology Kanpur, India)
  • Pal, Anikesh (Indian Institute of Technology Kanpur, India)

Please login to view abstract download link

Direct numerical simulations are performed to investigate the influence of rotation on the turbulent mixing driven by Faraday instability in two miscible fluids of small contrasting density subjected to periodic vertical vibrations. It is found that at lower forcing amplitudes (F), rotation stabilizes the flow and delays the onset of the sub-harmonic instability responsible for turbulent mixing. However, the effect of rotation in stabilizing the flow diminishes with an increase in F. The instability saturates for (f/ω) < 0.5, where f is the Coriolis frequency and ω is the forcing frequency, and the mixing zone size asymptotes, whereas for (f/ω) ≥ 0.5 the instability does not saturate and the mixing zone size keeps growing. At lower forcing amplitudes, the turbulent kinetic energy (TKE) increases with an increase in the Coriolis frequency till (f/ω) < 0.5 owing to the triggering of more sub-harmonic instabilities as compared to the without rotation case. When (f/ω) ≥ 0.5, the effect of rotation is strong enough to suppress turbulence. Although small, the TKE for (f/ω) ≥ 0.5 sustains owing to the continued triggering of the sub-harmonic instability, resulting in continuous turbulent mixing. At higher F and (f/ω) < 0.5, the sub-harmonic instabilities onset from the beginning of periodic forcing and saturate quickly due to the shorter sub-harmonic instability phase. The instabilities do not have enough time to evolve and intensify turbulence. Therefore, turbulence is less intense and short-lived than at lower F. An interesting finding is an increase in TKE after an initial decrease for (f/ω) ≥ 0.5 due to the continuous triggering of the sub-harmonic instabilities resulting in continuous turbulent mixing.