An excessive computational time is required to perform accurate numerical simulations for flow kinematics in a FRP processing, e.g., one week. In contrast, when the eco-strategy of numerical solution proposed here is used, it would take a so much shorter computational time, less than 10 minutes. The predictions will be also useful for the practical purpose in a fiber composite processing, thus the numerical solution strategy would have some potential. Furthermore, it is well known that the addition of slender particles to a Newtonian liquid can drastically change the flow kinematics even at very low concentrations. Why does such a phenomenon occur ? Estimation of flow energy consumption makes it clear that slender particle dispersion can flow through a complex geometry by smaller energy consumption owing to a change in its flow kinematics. In particular, contribution of extensional deformation to flow energy saving becomes dominant. It is, therefore, concluded that slender particle dispersions are so smart.