126 research outputs found
Numerical modelling of granular cargo on bulk carriers in seaway
This paper outlines the development of a numerical model for granular cargo
on bulk carriers. In order to study the vessel behaviour including the motion of the load,
a monolithic approach is chosen to model the fully coupled problem. The formulation of the
granular material therefore has to be fully Eulerian. A nonlinear elastic solid phase is
implemented in the Finite Volume solver FreSCo+ following the approach of Richter et. al [19] and
Sugyiama et. al [22]. The method is then verified with the help of different
Fluid-Structure interaction test cases
GPU-accelerated large-eddy simulation of ship-ice interactions
This paper reports on the applicability of the Lattice Boltzmann based
free surface flow solver elbe to the simulation of complex ship-ice interactions in marine
engineering. In order to model the dynamics of these colliding rigid multi-body systems, elbe is
coupled to the ODE physics engine. First, basic validations of the ODE collision and friction
models are presented, particularly focusing on interacting triangle meshes that later will serve to
describe the ice floes. Then, the basic methodology and initial validation of the fluid-structure
coupling of elbe and ODE is presented. Finally, performance is addressed: As elbe uses
graphics processing units (GPUs) to accelerate the numerical calculations, the coupled numerical
tool allows for investigations of ship-ice interactions
in very competitive computational time and on off-the-shelf desktop hardware
A next-generation CFD tool for large-eddy simulations on the desktop
Dive deep into the fascinating world of real-time computational fluid dynam-
ics. We present details of our GPU-accelerated flow solver for the simulation of non-linear
violent flows in marine and coastal engineering. The solver, the efficient lattice boltzmann
environment elbe, is accelerated with recent NVIDIA graphics hardware and allows for
three-dimensional simulations of complex flows in or near real-time. Details of the very ef-
ficient numerical back end, the pre- and postprocessing tools and the integrated OpenGL visualizer
tool will be discussed. Moreover, several applications with marine relevance demonstrate
that elbe can be considered as prototype for next-generation CFD tools for
simulation-based design (SBD) and interactive flow field monitoring on commodity
hardware
Parametric-adjoint approach for the efficient optimization of flow-exposed geometries
Today, the optimization of ship hulls and appendages, including energy-saving
devices, is typically undertaken by means of coupling parametric modelling (variable
geometry) and Computational Fluid Dynamics (CFD). A relatively new approach is based on
parameter-free solutions, solving the adjoint RANS equations for selected objective functions (like
drag and lift). Combining parametric and parameter-free solutions is an emerging
technique that helps to effectively optimize shapes without leaving the CAD domain of the model,
making it easier to integrate in the overall design process.
On the basis of the Computer Aided Engineering (CAE) software CAESES, a parametric- adjoint
approach will be presented. The approach is built on concatenating so-called “design velocities”
and “adjoint shape sensitivities”. Design velocities yield regions of influence from a pure
geometric point of view within a given parametric model. Meanwhile, adjoint shape sensitivities
show where and how changes of the surface affect the objective. Overlaying the surface
distributions of both the design velocities and the adjoint shape sensitivities result in so-called
“parametric sensitivities.” These help to understand the importance of all parameters wi hin the
chosen model.
This approach will be demonstrated on a practical hull form optimization example
A Scalable Algorithm for Shape Optimization with Geometric Constraints in Banach Spaces
This work develops an algorithm for PDE-constrained shape optimization based
on Lipschitz transformations. Building on previous work in this field, the
-Laplace operator is utilized to approximate a descent method for Lipschitz
shapes. In particular, it is shown how geometric constraints are
algorithmically incorporated avoiding penalty terms by assigning them to the
subproblem of finding a suitable descent direction. A special focus is placed
on the scalability of the proposed methods for large scale parallel computers
via the application of multigrid solvers. The preservation of mesh quality
under large deformations, where shape singularities have to be smoothed or
generated within the optimization process, is also discussed. It is shown that
the interaction of hierarchically refined grids and shape optimization can be
realized by the choice of appropriate descent directions. The performance of
the proposed methods is demonstrated for energy dissipation minimization in
fluid dynamics applications
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