Described are computer-related techniques for determining rotation direction of an axial fan for use in fluid flow simulations. The techniques involve receiving by a computer processing system digital data of a three dimensional representation of an axial fan having plural fan blade, determining by the computer processing system from the data of three dimensional representation of the axial fan, at least a single centerline of a single blade of the axial fan from a two dimensional projection of the axial fan, and calculating by the computer processing system based on the initial valve of fan rotation, an actual value of fan rotational direction.