Presence of sand particles within production fluids can lead to serious erosion and erosion-corrosion damage to production facilities. Sand particles behavior in multiphase flows is complicated and as a result erosion mechanism in such flows is complex as well. The current work focuses on sand erosion modeling in ascending vertical slug/churn multiphase flow. Two steps were taken toward modeling of erosion. First at different superficial gas and liquid velocities upward slug/churn flow was studied. Different interfacial structures within flow which carry sand particles were recognized and velocity of those structures was evaluated. Second several erosion experiments were carried out to study effects of sand particle size liquid viscosity and superficial gas velocity on erosion rate in a standard 3-in elbow. Finally results from mentioned steps were used for erosion modeling.