Comparison of predictions (closed symbols) of swells in the parison against the experimental data (open symbols) as functions of average extrusion velocity v_ave under the extrusion conditions in Table 4; (a) diameter swell, and (b) thickness swell. The dotted lines indicate the linear fit of the experimental data of equation (13) for diameter swell and equation (14) for thickness swell, respectively. The simulation data are for the die diameter of 400 mm and the flow rate of 400 kg/h at the constant stroke of 18, 20, 25, 30, 35, and 40%.