Woldesemayat and Ghajar [30] emerge

Woldesemayat and Ghajar [30] emerged to be the best correlation in this range of 0.5 < a 6 0.75 by predicting 80.2% and 97.6% of the points within ±10% and ±20% error bands, respectively. The quantitative performance of Woldesemayat and Ghajar [30] in comparison to other top performing correlations is reported in Table 4. For both
orientations superior performance of the Nicklin et al. [23] correlation was anticipated since it was devised for the slug regime, i.e. approximately for the void fraction range of 0.25 < a 6 0.75.