A computer-aided method suitable for assisting in the design of an object zone such as a CROR engine of an aircraft subjected to high vorticity and/or low static pressure fields when moving inside a flow field by providing suitable seed points for constructing vortex core lines in a fluid data model of the environment of said object zone and a system based in said method. The method steps are: a) Obtaining a dataset of candidate seeds containing all the cells or points satisfying a condition of the pressure gradient in the direction of the flow or a condition of the drag friction coefficient at the solid boundaries; b) Updating the previous dataset of candidate seeds with all the cells or points satisfying the equation not used for obtaining the dataset in step a).