Abstract:
It is critically important to generate turbulent fluctuating inflow boundary conditions for numerical simulation in solving hypersonic turbulent boundary layers. A high-order finite-difference method was applied to investigate the inflow generation methods. Turbulent inflow boundary conditions are broadly classified into natural transition methods, recycling/rescaling-based methods, and synthetic turbulence generators. To investigate the feasibility of inflow generation methods at high Mach number, the simulation of a Mach 6 boundary layer over an isothermal flat plate was carried out. The validity and limitations of different inflow boundary conditions were also discussed. Several feasible methods were studied in great detail including natural transition from laminar to turbulent flows, bypass transition induced by wavy wall configuration, and turbulence generation via reintroducing the flow field obtained from temporal developing turbulent flow. The limitation of the recycling/rescaling method was also proposed in hypersonic flow condition. By analyzing the flow filed and statistical results, we summarized and discussed the advantages and drawbacks about these inflow generation approaches, and further assessed these methods. Compared with natural transition method, bypass transition method and reintroducing method can promote transition to turbulent flow field efficiently. But turbulent field has better quality generated by natural transition route. The paper can be a reference of imposing an inflow boundary condition for wall bounded turbulent flows at high Mach number.