Flow Stability of Laminar Supercritical CO₂ Sudden Expansion Flow With Field Synergy Principle

Forced convection of two-dimensional supercritical CO₂ flow in plane symmetric sudden expansion duct is investigated numerically in this paper. Simulations were conducted under three wall boundary conditions, i.e., heating, cooling and isothermal, at low Reynolds numbers. Critical Reynolds numbers above which flow asymmetric occurs were examined under each condition. Results of the isothermal case agree well with previous numerical results. However, Compared with the isothermal case, smaller critical Reynolds numbers are found under both of heating and cooling conditions. In addition, the critical Reynolds numbers decrease with the increasing of heating/cooling intensity each under these two conditions. Furthermore, a new concept from the viewpoint of field synergy is introduced to illustrate this phenomenon of the reduction of flow stability.