Large numerical simulations of turbulent rotating flows
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چکیده
Scientific context Rotation, as measured by the Rossby number (the ratio of the rotation period to the eddy turn over time) is present in astroand geophysics. For example, the high Reynolds number large scales of atmospheric and oceanic flows are affected by the rotation of the Earth; the Rossby number Ro = U0/[L0Ω] for mid-latitude atmospheric synoptic scales is Ro ≈ 0.1 whereas in the solar convective zone, Ro ≈ 0.1-1 (with U0, L0 characteristic velocity and scale, and Ω the rotation rate). For rapid rotation, significant progress has been made in the past by developing resonant wave theory, two-point spectral closures, and weak turbulence: at low Ro, the flow is considered as a superposition of inertial waves with a short period, and the evolution of the system for long times is derived considering the effect of resonant triad interactions. However, at high Reynolds number Re, small scales are excited with a characteristic timescale proportional to the eddy turnover time, that decreases as the scales become smaller. Therefore the approximations made in such theories (small Ro) can break down at sufficiently small scales. We thus resorted to long-time high-resolution direct numerical simulations (DNS) to explore rotating flows at high Reynolds number in the presence of helical forcing and down to Ro ≈ 0.03. The corresponding non-helical case with a Taylor-Green forcing instead of an ABC Beltrami forcing is reported in (1).
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تاریخ انتشار 2009