Investigation of similarity criterion for gas flow field based on physical properties

An investigation of a new similarity criterion for gas flow field is conducted theoretically and numerically. The criterion is derived theoretically based on physical properties. It solves the problem of conflict between the similarity requirements, and can make two flow fields completely similar. Two theoretical analysis methods, the formulation analysis and dimensionless analysis methods, are used for the derivation, and the conclusions are coincident. The criterion would be helpful for the experimental study of complex phenomena influenced by all parameters of the flow field, such as thermo-convection and flow separation. Based on kinetic theory, similarity relationships of aerodynamic pressure and heat flux on solid surface between two similar flow fields are presented. Simulations of nitrogen flow over a sphere and a third-scale model are performed to validate the criterion with the Computational Fluid Dynamics (CFD) method. Supersonic flow without gravity, subsonic flow without gravity and subsonic flow with gravity are used in the simulation. The calculation results are in good agreement with the theoretical results.