Modular visualization environments (MVEs) are commonly used in many disciplines including fluid science. However, it is difficult for scientists and engineers, who are not necessarily visualization experts, to make full use of many built-in modules on the basis of their usability and interdependency for constructing optimal visualization workflows. In this paper, we present a novel MVE, called goal-oriented application design guidance for modular visualization environments/flow visualization (GADGET/FV), that is designed and built on an ontological framework to assist users to design their flow visualization workflows. The system relies primarily on an extended Wehrend Matrix that allows users to specify their goals and requirements, and to search the knowledge-base for appropriate visualization workflows on their behalf. In addition, users can browse successful examples maintained in a case repository to facilitate their workflow design further; this concept is referred to as "design by example." In this paper, examples of three practical fluid analyses have been presented to illustrate the usefulness of a prototype system. Furthermore, the extensibility of the system to handle large-scale datasets has also been discussed.