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A numerical simulation of the temporally developing flow through a generic scramjet combustor duct is presented for stagnation conditions typical of flight at Mach 13. The particular focus is to examine the startup transients and to determine the time required for certain flow parameters to become established. The calculations were made with a Navier-Stokes solver SPARK with temporally relaxing inflow conditions derived from the operation of the T4 shock tunnel at the University of Queensland in Australia. The generic combustor geometry includes the injection of hydrogen fuel from the base of a centrally located strut. The flow was assumed laminar and fuel combustion was not included. The establishment process is presented for viscous parameters in the boundary layer and for parameters related to the fuel-air mixing.transient flow case, QV/fe / = fuel mass fraction f R = fuel mass fraction that is reactable G s = characteristic flow time k = thermal conductivity L c = characteristic length M = Mach number m R = mass flow ratio P = static pressure Pr = Prandtl number P s = stagnation or nozzle supply pressure Re = Reynolds number T = temperature T aw = adiabatic wall temperature t = time U c = characteristic velocity u = local velocity ;c, y = longitudinal and transverse coordinates y w = location of upper wall boundary, 0.02357 m 8 = boundary-layer thickness 8* = displacement thickness r\ m = mixing efficiency parameter 0 = momentum thickness p = mass density r e = establishment time 4> = fuel equivalence ratio boundary-layer edge conditions inflow plane conditions normalized values wall values Subscripts e = in = TV w = RIntroduction ESEARCH related to the operation of a scramjet engine at conditions corresponding to flight at. speeds above