The main contribution of the study is the introduction of the new dimensionless number Na.

Could you clarify if the model performs well for angles less than -30 degrees to vertical downward flow? Also, it is recommended to discuss further how using other correlations could affect the proposed model's accuracy.

Very good work and showed a detailed comparison between all available models. The proposed model showed more accurate prediction than the available ones
In figure 6 the box of Start /Data lecture isn’t it “vs” the slip velocity which is unknown, why input.
In the same box what is E exactly? you wrote Tol=0.001 thenE=100 then you defined E as the difference between the old and new HLS why start with E=100 ?
A new correlation for the liquid slug holdup HLs has been proposed in the paper "Novel Correlations for the Liquid Holdup in a Gas-Liquid Slug Flow" published in Geoenergy Science and Engineering in 2024. Can you compare it with other correlations?