Momentum flux coefficient effect on vertical two-phase flows: Numerical method comparison

The governing equations of two-phase flows have a safe operating range, and exceeding this range can negatively impact the results. To extend this safe range, one key strategy is to incorporate the momentum flux coefficient into the governing equations. This paper introduces the application of the momentum flux coefficient to no-pressure or free-pressure model equations for the first time, specifically evaluating its performance in downward co-current two-phase flows through numerical methods. A new and improved version of the no-pressure model is also presented. Findings suggest that the force approach method yields more accurate results compared to other methods, whereas the Richmeier method produces unrealistic outcomes at discontinuities. A comparison between the standard and the developed no-pressure models reveals that the latter does not prevent nonphysical mutations and even exacerbates their occurrence. However, the developed no-pressure model successfully reduces numerical distribution production.