  We present the results of the first application in the naval architecture
field of a methodology based on active subspaces properties for parameters
space reduction. The physical problem considered is the one of the simulation
of the hydrodynamic flow past the hull of a ship advancing in calm water. Such
problem is extremely relevant at the preliminary stages of the ship design,
when several flow simulations are typically carried out by the engineers to
assess the dependence of the hull total resistance on the geometrical
parameters of the hull, and others related with flows and hull properties.
Given the high number of geometric and physical parameters which might affect
the total ship drag, the main idea of this work is to employ the active
subspaces properties to identify possible lower dimensional structures in the
parameter space. Thus, a fully automated procedure has been implemented to
produce several small shape perturbations of an original hull CAD geometry, in
order to exploit the resulting shapes to run high fidelity flow simulations
with different structural and physical parameters as well, and then collect
data for the active subspaces analysis. The free form deformation procedure
used to morph the hull shapes, the high fidelity solver based on potential flow
theory with fully nonlinear free surface treatment, and the active subspaces
analysis tool employed in this work have all been developed and integrated
within SISSA math- Lab as open source tools. The contribution will also discuss
several details of the implementation of such tools, as well as the results of
their application to the selected target engineering problem.
