I am doing multiphase simultion in a 2 D axisymetric geometry in Ansys fluent. My purpose was to obtain air water slug flow without phase change in miniature channel. I have attached both my geometry file and contours of volume fraction of air after complete solution.

had it been a channel with single inlet we would have calculated average pressure at inlet and outlet and thus get pressure drop for the channel.

but in fluent post processing I am able to get AREA AVG PRESSURE FOR AIR INLET AND AREA AVG PRESSURE FOR WATER INLET.

HOW DO I CALCULATE PRESSURE DROP FOR ENTIRE CHANNEL?

I AM ALSO ATTACHING PRESSURE CONTOURS.

MOREVER I HAVE USED MIXTURE MODEL WHICH DOES NOT HAVE PROPER LIQUID GAS INTERFACE.