Finite Element based Numerical FLOw Simulation System / Controllable
The software FENFLOSS is developed at IHS for the simulation
of incompressible flows. It uses Reynolds-averaged Navier-Stokes-equations
on unstructured grids and can be applied to laminar and turbulent
flows. The turbulence models used are turbulent mixing length
models as well as various k-eemodels, containing nonlinear
k-e models and algebraic Reynolds stress models. Especially
for unsteady vortex flows it also contains a Very Large Eddy
Simulation (VLES) approach.
The solver works for 2D or 3D geometries, which can be fixed
or rotating and either steady or unsteady state problems.
FENFLOSS can also handle moving grids (rotor-stator-interactions).
FENFLOSS contains methods to calculate free surface flows.
It can be used on massively parallel computer platforms and
is optimized for vector processors e.g. the NEC SX series.
FENFLOSS employs a segregated solution algorithm using a
pressure correction. The parallelization takes place in the
solver (BICGstab2 including ILU pre-conditioning).
Coupling of fixed and moving grids is accomplished by using
integrated dynamic boundary conditions.
Application example: Controllable pitch propeller
Controllable pitch propellers are used to drive commercial,
civil and naval ships. As every ship is a unique copy, the
propellers are tailor-made as well. The remarkable thing is
that the blades of the propeller can be rotated around their
axis in a range of 100°, offering a flexible and efficient
operating range to the customer.
The design process aims at noise reduction and preventing
cavitation, which is a severe issue especially for naval applications.
In this example, the two propellers (manufacturer: VATech,
Ravensburg) have a diameter of 3.8 meters and consume 14 MW
of power. They produce 855 kN of thrust and weigh 6 tons each.
To obtain accurate simulation results which include transient
phenomena, the use of supercomputers is essential. In this
example, the grid consists of 2.3 million hexagonal elements.
The pictures show the two propellers with simulation results
computed on a NEC SX-6.
Uwe Wössner / Martin Becker
Institut für Strömungsmechanik und
Hydraulische Strömungsmachinen, Universität Stuttgart
NEC - High Performance Computing Europe GmbH
European HPC Technology Center