585 research outputs found
A new generation 99 line Matlab code for compliance Topology Optimization and its extension to 3D
Compact and efficient Matlab implementations of compliance Topology
Optimization (TO) for 2D and 3D continua are given, consisting of 99 and 125
lines respectively. On discretizations ranging from to
elements, the 2D version, named top99neo, shows speedups from
2.55 to 5.5 times compared to the well-known top88 code (Andreassen-etal 2011).
The 3D version, named top3D125, is the most compact and efficient Matlab
implementation for 3D TO to date, showing a speedup of 1.9 times compared to
the code of Amir-etal 2014, on a discretization with elements.
For both codes, improvements are due to much more efficient procedures for the
assembly and implementation of filters and shortcuts in the design update step.
The use of an acceleration strategy, yielding major cuts in the overall
computational time, is also discussed, stressing its easy integration within
the basic codes.Comment: 17 pages, 8 Figures, 4 Table
Revisiting topology optimization with buckling constraints
We review some features of topology optimization with a lower bound on the
critical load factor, as computed by linearized buckling analysis. The change
of the optimized design, the competition between stiffness and stability
requirements and the activation of several buckling modes, depending on the
value of such lower bound, are studied. We also discuss some specific issues
which are of particular interest for this problem, as the use of non-conforming
finite elements for the analysis, the use of inconsistent sensitivities in the
optimization and the replacement of the single eigenvalue constraints with an
aggregated measure. We discuss the influence of these practices on the
optimization result, giving some recommendations.Comment: 15 pages, 12 figures, 2 table
Topological Insulators by Topology Optimization
An acoustic topological insulator (TI) is synthesized using topology
optimization, a free material inverse design method. The TI appears
spontaneously from the optimization process without imposing requirements on
the existence of pseudo spin-1/2 states at the TI interface edge, or the Chern
number of the topological phases. The resulting TI is passive; consisting of
acoustically hard members placed in an air background and has an operational
bandwidth of 12.5\% showing high transmission. Further analysis
demonstrates confinement of more than 99\% of the total field intensity in the
TI within at most six lattice constants from the TI interface. The proposed
design hereby outperforms a reference from recent literature regarding energy
transmission, field confinement and operational bandwidth.Comment: 6 pages, 5 figure
A "poor man's" approach for high-resolution three-dimensional topology optimization of natural convection problems
This paper treats topology optimization of natural convection problems. A
simplified model is suggested to describe the flow of an incompressible fluid
in steady state conditions, similar to Darcy's law for fluid flow in porous
media. The equations for the fluid flow are coupled to the thermal
convection-diffusion equation through the Boussinesq approximation. The coupled
non-linear system of equations is discretized with stabilized finite elements
and solved in a parallel framework that allows for the optimization of high
resolution three-dimensional problems. A density-based topology optimization
approach is used, where a two-material interpolation scheme is applied to both
the permeability and conductivity of the distributed material. Due to the
simplified model, the proposed methodology allows for a significant reduction
of the computational effort required in the optimization. At the same time, it
is significantly more accurate than even simpler models that rely on convection
boundary conditions based on Newton's law of cooling. The methodology discussed
herein is applied to the optimization-based design of three-dimensional heat
sinks. The final designs are formally compared with results of previous work
obtained from solving the full set of Navier-Stokes equations. The results are
compared in terms of performance of the optimized designs and computational
cost. The computational time is shown to be decreased to around 5-20% in terms
of core-hours, allowing for the possibility of generating an optimized design
during the workday on a small computational cluster and overnight on a high-end
desktop
Designing Photonic Topological Insulators with Quantum-Spin-Hall Edge States using Topology Optimization
Designing photonic topological insulators is highly non-trivial because it
requires inversion of band symmetries around the band gap, which was so far
done using intuition combined with meticulous trial and error. Here we take a
completely different approach: we consider the design of photonic topological
insulators as an inverse design problem and use topology optimization to
maximize the transmission through an edge mode with a sharp bend. Two design
domains composed of two different, but initially identical,
C-symmetric unit cells define the geometrical design problem.
Remarkably, the optimization results in a photonic topological insulator
reminiscent of the shrink-and-grow approach to quantum-spin-Hall photonic
topological insulators but with notable differences in the topology of the
crystal as well as qualitatively different band structures and with
significantly improved performance as gauged by the band-gap sizes, which are
at least 50 \% larger than previous designs. Furthermore, we find a directional
beta factor exceeding 99 \%, and very low losses for sharp bends. Our approach
allows for the introduction of fabrication limitations by design and opens an
avenue towards designing PTIs with hitherto unexplored symmetry constraints.Comment: 7 pages, 5 figure
On the implementation and effectiveness of morphological close-open and open-close filters for topology optimization
© 2016, Springer-Verlag Berlin Heidelberg. This note reconsiders the morphological close-open and open-close filters for topology optimization introduced in an earlier paper (Sigmund Struct Multidiscip Optim 33(4–5):401–424 (2007)). Close-open and open-close filters are defined as the sequential application of four dilation or erosion filters. In the original paper, these filters were proposed in order to provide length scale control in both the solid and the void phase. However, it was concluded that the filters were not useful in practice due to the computational cost of the sensitivity analysis. In this note, it is shown that the computational cost is much lower if the sensitivity analysis for each erosion or dilation step is performed sequentially. Unfortunately, it is also found that the close-open and open-close filters do not have the expected effect in terms of length scale control: each close or open operation ruins the effect of the preceding filters, resulting in a design with a minimum length scale in either the solid phase or the void phase, but not both.status: publishe
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