In the pseudo-shock of duct flow, the static pressure at the wall surface increases gradually along the duct. This phenomenon has been explained by the well known Crocco's shockless model. His model, however, has some problems as follows : (1) It cannot present the distribution of various quantities related to the distance along the duct and the length of the pseudo-shock, since all the quantities are calculated as the functions of the ratio of the flow rate of the dissipative low velocity region to the total flow rate. (2) There is a discrepancy of velocities between the high and low speed regions at the final section of pseudo-shock. In order to correct these defects, a diffusion model for pseudo-shock has been presented in this paper by reforming his shockless model. The theoretical values of the length of pseudo-shock and the pressure distribution along the duct obtained by this model are able to explain the experimental data by the authors and other researchers quantitatively. Closer agreements are obtained in the case of higher Mach number at the initial section.
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IKUI et al. (1974) studied this question.