Table 2. Polynomial Fitting Expressions of Gas Holdup and D₃₂.

polynomial	formula	correlation index
quadratic	y = 1.057 74 – 1.6292x + 1.119 69x2	0.7699
cubic	y = 2.530 41 – 10.619 03x + 18.408 01x2 – 10.445 04x3	0.8518
quartic	y = −2.409 39 + 31.039 06x – 108.967x2 + 156.5266x3 – 78.9773x4	0.9255
quintic	y = −12.7142 + 136.279 04x – 527.084 11x2 + 964.3064x3 – 838.380 78x4 + 278.231 04x5	0.9324