The most important feature of Vehicular Ad hoc Networks (VANETs) is the high mobility of nodes, which makes the mobility model one of the most important parameters that should be carefully selected when evaluating any protocol. To correctly and faithfully evaluate protocols in a simulation study, the model should be as realistic as possible. Vehicles communicating wirelessly play an important role in the simulation of Vehicular Ad Hoc Networks (VANETs). In this paper, one of the main mobility modeling approach is discussed to the extent that it can help to understand models formulation and integration strategies with network simulators. This approach is called as flow mobility modeling. It is put into the discussion and elaborated in such way it clarifies basics of flow modeling and its impact. It also finds a different ways of modeling and implementation into existing traffic simulators viz. SUMO, VISSIM etc.