2 research outputs found
Energy spectrum of buoyancy-driven turbulence
Using high-resolution direct numerical simulation and arguments based on the
kinetic energy flux , we demonstrate that for stably stratified flows,
the kinetic energy spectrum , the entropy spectrum
, and , consistent with the
Bolgiano-Obukhov scaling. This scaling arises due to the conversion of kinetic
energy to the potential energy by buoyancy. For weaker buoyancy, this
conversion is weak, hence follows Kolmogorov's spectrum with a
constant energy flux. For Rayleigh B\'{e}nard convection, we show that the
energy supply rate by buoyancy is positive, which leads to an increasing
with , thus ruling out Bolgiano-Obukhov scaling for the
convective turbulence. Our numerical results show that convective turbulence
for unit Prandt number exhibits a constant and for a narrow band of wavenumbers.Comment: arXiv admin note: text overlap with arXiv:1404.214
Phenomenology of buoyancy-driven turbulence: Recent results
In this paper, we review the recent developments in the field of
buoyancy-driven turbulence. Scaling and numerical arguments show that the
stably-stratified turbulence with moderate stratification has kinetic energy
spectrum and the kinetic energy flux , which is called Bolgiano-Obukhov scaling. The energy flux for the
Rayleigh-B\'{e}nard convection (RBC) however is approximately constant in the
inertial range that results in Kolmorogorv's spectrum ()
for the kinetic energy. The phenomenology of RBC should apply to other flows
where the buoyancy feeds the kinetic energy, e.g. bubbly turbulence and
fully-developed Rayleigh Taylor instability. This paper also covers several
models that predict the Reynolds and Nusselt numbers of RBC. Recent works show
that the viscous dissipation rate of RBC scales as ,
where is the Rayleigh number