Small-scale universal features captured normally in many turbulent flows have been reviewed in Rayleigh-Bénard convection. Namely, dynamical Lagrangian representations of the velocity gradient tensor invariants have displayed the so-called “tearing drop” spiraling feature within the bulk region. Furthermore, essential common aspects as the asymmetric alignment of vorticity with the vortex-stretching vector, and the preferential alignment between vorticity and the intermediate eigenvector of the rate-of-strain tensor have been observed in that scope. Further and in more appropriate implement, we have performed a similar dynamical study of flow topology pertained to the traceless part of the gradient velocity-times-temperature tensor. The new invariants are related basically with the small-scale dynamics associated with the evolution of thermal plumes and buoyant production. We find that a self-amplification of velocity derivatives developed at harder turbulent flow supports indirectly the local effects of vortex-stretching generation. Moreover, the averaged evolution of the new invariants have revealed a converging change towards two skew-symmetric origins at Rayleigh number equals to 1e8 but one zero-valued origin at 1e10.

Peer Reviewed