In present study, two-dimensional numerical simulations have been carried out to investigate scour beneath a piggyback pipeline subjected to a subsea boundary layer flow using SedFoam (an open-source multi-dimensional Eulerian two-phase solver for sediment transport based on OpenFOAM). In the piggyback configuration, a small pipeline is attached on the upstream and downstream sides of a large pipeline. This form of piggyback can reduce the scour depth beneath the pipeline (Yang et al., 2019). In the solver, the turbulence Reynolds stress is resolved using a two-phase modified k-ε model. The particle stresses caused by the binary collisions and contacts are modeled by the kinetic theory for granular flow and a phenomenological frictional model, respectively. The effects of the locations of the small pipelines attached on the large pipeline on the scour and the surrounding flow field are discussed.