Energy spectrum of Buoyancy-driven Flows

الأصل · EN

Using high-resolution direct numerical simulation and arguments based on the kinetic energy flux Πᵤ, we demonstrate that for stably stratified flows, the kinetic energy spectrum Eᵤ(k) k⁻¹¹/⁵, the entropy spectrum Eθ(k) k⁻⁷/⁵, and Πᵤ(k) k⁻⁴/⁵ (Bolgiano-Obukhov scaling). This scaling is due to the depletion of kinetic energy because of buoyancy. For weaker buoyancy in stratified flows, Eᵤ(k) follows Kolmgorov's spectrum with a constant energy flux. We also argue that for Rayleigh Bénard convection, the Bolgiano-Obukhov scaling will not hold for the bulk flow due to the positive energy supply by buoyancy and non-decreasing Πᵤ(k).