The streamline modeling is a design methodology of fair free-form surfaces where the tangent vectors are specified/manipulated to generate/deform them instead of the control points of the traditional surface representations. Creations and deformations of complex 3D free-form shapes generally require a large amounts of labours and costs. Therefore in this paper we propose a new modeling technique based on dynamics of fluid flow in order to create and deform high-quality surfaces more intuitively with less number of parameters based on the streamline modeling. We construct a flow field based on the potential flow, then calculate tangent vectors in the flow field that are required for streamline modeling. Streamlines are generated by numerically integrating the tangent vectors, then the surface is represented as a set of streamlines. The deformations of the surface is performed by changing of the flow field. We have developed a prototype design system using our new modeling technique.