In recent years, additive manufacturing vat polymerization has received more attention and industrial applications such as injection molding inserts produced with the polymerization process has increased their marked share. For most industrial applications, strength and stiffness are crucial factors to a successful implementation of cured photopolymer thermosets. Hence, fiber-reinforced polymers have recently been introduced to vat polymerization processes. In this research contribution, to understand the behavior and especially orientation of short fibers, a further understanding of the flow characteristics, velocity profile, pressure distribution and viscosity of the liquid photopolymer during the manufacturing process are investigated. A vat polymerization machine consisting of a resin vat and a moving build plate was simulated using the fluid flow module of Comsol Multiphysics™. A moving mesh with hyper-elastic behavior was utilized to simulate the flow of the photopolymer during the lifting of the build plate after a successful curing of a single layer. The velocity profile can thereafter be used to estimate a prediction for position and orientation of the short fibers added to the liquid photopolymer resin. The prediction can be used to identify potential clusters or misalignment of fibers and in the future allow for optimization of the machine design and manufacturing process.