Modified diffusion model of pseudo-shock waves considering upstream boundary layers

Experiments were performed to investigate the effects of the upstream boundary layer on pseudo-shock waves, by varying the Mach number and boundary layer thickness upstream of the pseudo-shock. A new flow model is presented in which both the effects of the upstream boundary layer and wall friction are taken into account. The configuration and axial static pressure distribution of the pseudo-shock were found to depend on both the upstream Mach number at the center of the duct and the ratio of the displacement thickness to the equivalent diameter. An experimental formula of the dimensionless length of the pseudo-shock L/D was obtained in terms of the mean Mach number in the supersonic region just upstream of the pseudo-shock and the ratio of the mass flow rate in the subsonic region to the total mass flow rate. The calculated values of axial static pressure distributions within the pseudo-shock and the static and total pressure ratios across the pseudo-shock were found to agree better with experimental values than did previous flow models.