In the late 60’s of the last century, the well-preserved remains of two medieval ships were discovered in Nin (Croatia), in the inner Nin lagoon. In the next few decades, the remains were raised from the sea, conserved, partly reconstructed, and studied by nautical archaeologists, who analysed the ship to estimate its original dimensions and topology, resulting in three different sets of hull lines with slight variations in width, length, and shape.

Nin 1 lacks a traditional keel and instead features a stem, providing structural integrity to the bow and making the ship better suited for shallow waters which makes it unconventional when hydrodynamic calculations are considered, as there are no empirical methods for calculating such a ship’s resistance in a fast and reliable way. In this research, CFD is employed to precisely evaluate all three versions of Nin 1, aiming to identify the most efficient form among them, which is likely to be the original design. Three ship models are generated, based on each set of lines, and subjected to the same examined scenarios, i.e., sailing through calm water in the velocity range between 0.5 and 7 kn. The turbulence phenomenon is also analysed by applying the adequate turbulence model while respecting the appropriate mesh size. By applying the CFD method, each component of resistance is determined so that the effects of different hull forms and appendage dimensions are visible separately.