  We investigate the statistical properties of Rayleigh-Taylor turbulence in a
convective cell of high aspect ratio, in which one transverse side is much
smaller that the others. We show that the scale of confinement determines the
Bolgiano scale of the system, which in the late stage of the evolution is
characterized by the Kolmogorov-Obukhov and the Bolgiano-Obukhov phenomenology
at small and large scales, respectively. The coexistence of these regimes is
associated to a three to two-dimensional transition of the system which occurs
when the width of the turbulent mixing layer becomes larger that the scale of
confinement.
