Woldesemayat and Ghajar
General Description
The correlation for twophase flow by Woldesemayat and Ghajar (2007)^{1} is based on an extensive review of void fraction/liquid hold up correlations with associated data sets. 68 correlations with a total of 2845 underlying data points were used in the study. The authors arrived at six correlations having the best accuracy, in which one of them is selected and modified to make its predictions the most accurate overall of those reviewed.
The modified correlation is
where
Pressure Gradient Calculations
The authors are only reviewing liquidholdup correlations, and do not discuss pressuredrop calculations. Therefore, it is up to the reader to decide which properties to use for pressuregradient calculations. The following properties are suggested here
Density in the gravity gradient \(\rho_g=\rho_s\)
Density in the friction gradient \(\rho_f=\rho_s\)
Density in the acceleration gradient \(\rho_a=\rho_s\)
Friction factor \(f_D\) is calculated with \(N_{Re}=\rho_sv_md_h/\mu_s\)

Melkamu A. Woldesemayat and Afshin J. Ghajar. Comparison of void fraction correlations for different flow patterns in horizontal and upward inclined pipes. International Journal of Multiphase Flow, 33:347–370, 2007. doi:10.1016/j.ijmultiphaseflow.2006.09.004. ↩