Experimental modelling and CFD simulation of air/water flow in a horizontal channel

For the investigation of air/water slug flow, a horizontal channel with rectangular cross-section was build at Forschungszentrum Rossendorf. The channel allows the investigation of air/water co- and counter current flows under atmospheric pressure, especially the slug behaviour. Optical measurements were performed with a high-speed camera, and were complemented by simultaneous dynamical pressure measurements.

CFD simulation of the stratified co-current flow was performed using the code CFX-5 applying the two fluid model with the free surface option. The grid contains 400000 control volumes. The tubulence was modeled separately for each phase using the k, w-turbulence model. The results show wave formation up to slug development with closure of the whole channel cross section, where the slug is propagating towards the outlet of the channel with an increasing speed compared to the water velocity and an increase of the pressure level in the channel after the slug front.

The qualitative slug formation in the CFX calculation is in good agreement with the experiment, while the calculated pressure distribution shows higher peak values than the measured one.