This paper revisits the particle flow system, a time-based computational tool, which has received a lot of attention from the early pioneers of digital architecture. The use of particle flow systems in architecture enables designers to materialize what they term as site forces which can later be formalized into a building. The methods offered by various designers for using particle flow systems in architecture have kept the discourse purely formal by focusing on the exterior and neglecting the interior. This paper offers a different way of using and conceptualizing particle flow systems in architecture. Shifting the emphasis from the formal, the paper aims to show the potential of using particle flow systems as a parametric model for exploring the spatial organization of an architectural program. This paper also illustrates the application of the proposed computational model, i.e., the particle flow system, by using a case study - the design of a high-rise building in downtown Tel Aviv, Israel.