In internal flows, solid particles carried by the fluid could damage pipelines and fittings. Particles that are entrained in the fluid can cross streamlines and transfer a part of their momentum to the internal surface by impacts and cause local wall material degradation. Over the past decades, a wide range of models is introduced to predict particle erosion which includes empirical models, mechanistic models, and CFD which is currently the state-of-art numerical approach to simulate the erosion process. Multiphase flow under annular flow conditions adds to the complexity of the model. Although with the current computational capabilities transient CFD models are effectively applicable, this type of transient multiphase approach is not practical yet for engineering prediction of erosion especially for the large diameter applications with huge computational domains. Therefore, the presented combined approach could be utilized to obtain erosion rates for large diameter cases. Thus, an approach combining CFD and mechanistic multiphase models characterizing annular flow is developed to predict solid particle erosion. Different factors including film thickness in pipes and fittings which are affecting erosion under gas-dominated multiphase flow conditions are investigated. The results from the current approach are compared to experimental data and transient CFD simulations for annular flow in elbows showing a very good agreement with both.