Abstract
The lattice Boltzmann method was adopted to study the oscillating characteristics of double diffusive natural convection in square cavities with Soret and Dufour effects. The inner heating cylinder with high concentration was located at the center of the cavity and the 4 surrounding walls were assumed to be at low concentrations and temperatures. The impacts of buoyancy ratio B<sub>r</sub>(2.0≤B<sub>r</sub>≤10.0), Soret number S<sub>r</sub>(-0.6≤S<sub>r</sub>≤0.0) and Dufour number D<sub>f</sub>(-0.6≤D<sub>f</sub>≤0.0) on the oscillating characteristics in the cavity were analyzed with the time history method and the power spectrum method. The results show that the flow state is steady at S<sub>r</sub>=0.0 and D<sub>f</sub>=0.0. With decreasing S<sub>r</sub>and D<sub>f</sub> from 0.0 to -0.6, the state of double diffusive natural convection turns into the periodic state and in turn the aperiodic oscillatory state gradually. Moreover, the positive buoyancy ratio enhances the oscillating characteristics.
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