In this paper, we propose a kind of buoyancy-driven flow leading to unstably stratified homogeneous (USH) turbulence. This approach is developed in the context of incompressible Navier–Stokes equations under Boussinesq approximation. We show that USH turbulence is a valuable tool for understanding and modeling turbulent mixing induced by Rayleigh-Taylor (RT) instability. It is a much simpler configuration than “RT turbulence” which is in fact inhomogeneous. Thus, it gives insights in the basic mechanisms of buoyancy-driven turbulence, namely the interplay between buoyancy production, nonlinearities and dissipation. Besides, despite their differences both types of turbulence share very similar features for the large scale characteristics as well as for the inertial range spectrum structure.