Abstract: After the validation of CFD method with Carroll’s experimental data, the characteristics of shock train in two dimensional bends with constant area are numerically studied in this paper, on which the influence of coming Mach number and coming boundary layer thickness are also obtained. The investigation is focused on the structure and length of the shock train, the static pressure distribution along the wall, the Mach number and total pressure recovery at the exit section and the back pressure process of the duct with comparison of the straight duct. Results show that a duct with appropriate curvature can improve the symmetry of the flow pattern and shorten the shock train at high coming Mach number (e.g. Ma₀=2.45). The use of the bend can suppress the fluctuation of the Mach number at the exit caused by the change of the back pressure. Because the gap of total pressure recovery of the straight duct and the bend duct is obvious at a low back pressure (Ma_e>1) and noteless at a high back pressure(Ma_e<1), a bend duct with high curvature is recommended for a ramjet to shorten the axial length of the duct. The existing empirical correlation based on straight duct can not predict well the length of shock train in bend duct due to their distinct difference in shock train length.

Key words: bend duct, shock train, inlet, isolator, ramjet, scramjet