The prediction of the resistance of a ship is, together with the propeller performance
prediction, part of the key aspects during the design process of a ship, as it partly ensures the
quality of the power-prediction. Body fitted structured grids for ship simulations can be rather
challenging and time consuming to build, especially when dealing with appended ship geometries.
For this reason, unstructured hexahedral trimmed grids are more and more used. Such grids can
be build by various CFD package such as CD-Adapcos Star CCM+, NUMECAs Hexpress grid
generator or OpenFOAMSs SnappyHexMesh. Although their use is increasing or even already
adopted, the numerical uncertainty of these simulations seems to be a well-kept secret.
In the study presented, an attempt at quantifying the numerical uncertainty of the resistance
for the combination of the RANS Solver ReFRESCO  with grids generated using the commercial
package Hexpress is made. The studied case is the flow around the bare-hull KVLCC2
at model scale Reynolds number. Extensive verification and validation on the same test case
has already been published for the combination of ReFRESCO and structured grids by Pereira
et al. .
For more information contact Pierre Crepier