Hexagonal pattern instabilities in rotating Rayleigh-Bénard convection of a non-Boussinesq fluid: Experimental results

Alessio Guarino , Valerie Vidal (1)

1 IPGP - Institut de Physique du Globe de Paris

Motivated by the Küppers-Lortz instability of roll patterns in the presence of rotation, we have investigated the effects of rotation on a hexagonal pattern in Rayleigh-Bénard convection. While several theoretical models have been developed, experimental data cannot be found in the literature. In order to check the validity of the predictions and to study the effects of rotation on the behavior of the system, we present experimental results for a non-Boussinesq Rayleigh-Bénard convection with rotation about the vertical axis. Rotation introduces an additional control parameter, namely the dimensionless rotation rate Ω= 2πf d² /ν , where f is the rotation rate (in Hz), d is the thickness of the cell, and ν is the kinematic viscosity. We observe that the cell rotation induces a slow rotation of the pattern in the opposite direction (≈Ω× 10^-4 ) in the rotating frame. Moreover, it tends to destroy the convective pattern. No oscillation of the hexagonal pattern over the range of its existence (Ω⩽6) has been observed.

Domaines: Planète et Univers [physics]

Alessio Guarino, Valerie Vidal. Hexagonal pattern instabilities in rotating Rayleigh-Bénard convection of a non-Boussinesq fluid: Experimental results. Physical Review E , 2004, 69, pp. 327-345. ⟨10.1103/PhysRevE.69.066311⟩. ⟨insu-03600282⟩