Models for the forces acting on bubbles in comparison with experimental data for vertical pipe flow

As a consequence of the averaging process constitutive models for the interaction between the phases are required in the multi-fluid modelling. For the simulation of bubbly flows this concerns models for the forces acting on bubbles. Detailed experimental data for vertical pipe flow, obtained by an advanced wire-mesh sensor, were used to assess such models for a wide range of combinations of superficial velocities. A simplified one-dimensional model, which considers a number of bubble classes is used for the prediction of radial gas fraction profiles from a given (measured) bubble size distribution. A comparison of these profiles with the measurements allows the evaluation of the models for the non-drag forces. In contrast to common CFD codes the simplified model also allows to consider the extension of the bubbles. This is important, if large bubbles or slugs occur. A good agreement is achieved for liquid superficial velocities up to 1 m/s using the lift- and wall force models from Tomiyama and the Favre averaged drag model for the turbulent dispersion force. For larger liquid superficial velocities an intermediate peak occur in the measured radial gas fraction profile, which cannot be reproduced by the available models.