Severe slugging occurs at pipe-riser systems. The phenomenon is highly undesirable and can have influence on production and damage process equipment. A one-dimensional model is developed in order to simulate the severe slugging phenomenon. The model is developed to the open source program OpenFOAM. The model is tested and all relevant OpenFOAM coding is presented. The model was found capable of capturing physical behavior such as static pressure, friction, and buoyancy. The model is not capable of simulating severe slugging, but future work is proposed in order to achieve this.