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 the object zone and a system based on the method. The method steps are: a) Obtaining a dataset containing all the cells or points satisfying one of the conditions of four Region-based vortex detection criteria (the Q-criterion, the Kinematic vorticity number, the Δ-criterion, the λ2-criterion); b) Obtaining a new dataset containing all the cells or points of the previous dataset satisfying one of the conditions mentioned in step a) not selected previously; c) Repeating the step b) until all the conditions mentioned in step a) have been selected in step b).