An efficient shape parametrisation by free-form deformation enhanced by active subspace for hull hydrodynamic ship design problems
in open source environment
In this contribution, we present the results of the application
of a parameter space reduction methodology based on active subspaces to
the hull hydrodynamic design problem. Several parametric deformations
of an initial hull shape are considered to assess the influence of the
shape parameters considered on the hull total drag. The hull resistance
is typically computed by means of numerical simulations of the
hydrodynamic flow past the ship. Given the high number of parameters
involved - which might result in a high number of time consuming
hydrodynamic simulations - assessing whether the parameters space can
be reduced would lead to considerable computational cost reduction.
Thus, the main idea of this work is to employ the active subspaces to
identify possible lower dimensional structures in the parameter space,
or to verify the parameter distribution in the position of the control
points. To this end, a fully automated procedure has been implemented
to produce several small shape perturbations of an original hull CAD
geometry which are then used to carry out high-fidelity flow
simulations and collect data for the active subspaces analysis. To
achieve full automation of the open source pipeline described, both the
free form deformation methodology employed for the hull perturbations
and the solver based on unsteady potential flow theory, with fully
nonlinear free surface treatment, are directly interfaced with CAD data
structures and operate using IGES vendor-neutral file formats as input
files. The computational cost of the fluid dynamic simulations is
further reduced through the application of dynamic mode decomposition
to reconstruct the steady state total drag value given only few initial
snapshots of the simulation. The active subspaces analysis is here
applied to the geometry of the DTMB-5415 naval combatant hull, which is
which is a common benchmark in ship hydrodynamics simulations
