STOCHASTIC LORENZ-MODEL FOR PERIODICALLY DRIVEN RAYLEIGH-BENARD-CONVECTION

The order-disorder transition observed in periodically driven Rayleigh -Benard convection is studied by extending the generalized Lorenz mode l introduced by Ahlers, Hohenberg, and Lucke [Phys; Rev, A 32, 3493 (1 985)] to include the effects of thermal noise. It is shown that this s tochastic Lorenz model predicts. for thermal noise intensities, an ord er-disorder transition Line much closer to the experimental values tha n the prediction of previous models. This result makes clear that a dy namical description allowing for inertial effects is needed to account for the behavior of systems dynamically forced to cross an instabilit y threshold.