Spatial and Temporal Structures of Turbulence Transition Process of Natural-Convection Boundary Layer Developed along a Vertical Heated Plate at High Temperature

Abstract

We performed a large-eddy simulation for a natural convection boundary layer along a vertical plate heated at high temperature, which gave the turbulence transition with the significant non-Boussinesq effects. An open source CFD code, Fire FOAM, was used to consider the density fluctuation effects directly and the one-equation model was applied to estimate SGS components. The spatial distributions of statistics with Reynolds decomposition clearly showed the transition at Grz ≅ 10⁹; this critical Gr number agreed with that in the boundary layer without non-Boussinesq effects. The non-Boussinesq effects were definitive in the amplification process of fluctuations, i.e., the density fluctuations primarily generated the velocity fluctuations with reduction in correlation with temperature fluctuations.