and f. Increasing the specific mass leads to both an increase of the pressure drop and of the critical velocity. Experimental data on particles of similar size that are available in the Literature [4,12] are also plotted in this figure. Please note that they have been collected in pipes of smaller diameters. The shape of the present curves is very similar to previously reported works, particularly when presented in a dimensionless form (k vs. Vmix /V0 in Fig. 4 f).
Please nonetheless notice that the single-phase flow pressure drop coefficients are different (black solid line, blue and red dashed linesin Fig. 4f)