Abstract
Direct numerical simulations of natural convection in differentially heated vertical channel are conducted with Boussinesq approximation. The discritization of computation is carried out with a spectral method for three directions. Rayleigh number (Ra) which is defined with the channel width and the temperature difference between both walls, is 5.4 × 104. We extract the large-scale structures by using Snapshot POD (Proper Orthogonal Decomposition) and trace the time evolution of the structures. The formation and the breakdown of the large-scale streaky structures are observed sequentially in one cycle, suggesting that the regeneration process of the large scale flow is similar to the case of a minimal plane Couette flow. Also it is found that the strong down-wash event, due to the large scale vortical flow, play a key role for the heat transfer on the wall.
