510 research outputs found
Large scale three-dimensional topology optimisation of heat sinks cooled by natural convection
This work presents the application of density-based topology optimisation to
the design of three-dimensional heat sinks cooled by natural convection. The
governing equations are the steady-state incompressible Navier-Stokes equations
coupled to the thermal convection-diffusion equation through the Bousinessq
approximation. The fully coupled non-linear multiphysics system is solved using
stabilised trilinear equal-order finite elements in a parallel framework
allowing for the optimisation of large scale problems with order of 40-330
million state degrees of freedom. The flow is assumed to be laminar and several
optimised designs are presented for Grashof numbers between and .
Interestingly, it is observed that the number of branches in the optimised
design increases with increasing Grashof numbers, which is opposite to
two-dimensional optimised designs.Comment: Submitted (18th of August 2015
A "poor man's" approach to topology optimization of natural convection problems
Topology optimization of natural convection problems is computationally
expensive, due to the large number of degrees of freedom (DOFs) in the model
and its two-way coupled nature. Herein, a method is presented to reduce the
computational effort by use of a reduced-order model governed by simplified
physics. The proposed method models the fluid flow using a potential flow
model, which introduces an additional fluid property. This material property
currently requires tuning of the model by comparison to numerical Navier-Stokes
based solutions. Topology optimization based on the reduced-order model is
shown to provide qualitatively similar designs, as those obtained using a full
Navier-Stokes based model. The number of DOFs is reduced by 50% in two
dimensions and the computational complexity is evaluated to be approximately
12.5% of the full model. We further compare to optimized designs obtained
utilizing Newton's convection law.Comment: Preprint version. Please refer to final version in Structural
Multidisciplinary Optimization https://doi.org/10.1007/s00158-019-02215-
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
Topology optimisation of natural convection problems
This paper demonstrates the application of the density-based topology
optimisation approach for the design of heat sinks and micropumps based on
natural convection effects. The problems are modelled under the assumptions of
steady-state laminar flow using the incompressible Navier-Stokes equations
coupled to the convection-diffusion equation through the Boussinesq
approximation. In order to facilitate topology optimisation, the Brinkman
approach is taken to penalise velocities inside the solid domain and the
effective thermal conductivity is interpolated in order to accommodate
differences in thermal conductivity of the solid and fluid phases. The
governing equations are discretised using stabilised finite elements and
topology optimisation is performed for two different problems using discrete
adjoint sensitivity analysis. The study shows that topology optimisation is a
viable approach for designing heat sink geometries cooled by natural convection
and micropumps powered by natural convection.Comment: Submitted to the 'International Journal for Numerical Methods in
Fluids' on 28th of August 2013 - currently under revie
Performance assessment of density and level-set topology optimisation methods for 3D heatsink design
In this paper, two most prevalent topological optimisation approaches namely Density and Level set method are applied to a three dimensional heatsink design problem. The relative performance of the two approaches are compared in terms of design quality, robustness and computational speed. The work is original as for the first time it demonstrates the relative advantages and disadvantages for each method when applied to a practical engineering problem. It is additionally novel in that it presents the design of a convectively cooled heatsink by solving full thermo-fluid equations for two different solid-fluid material sets. Further, results are validated using a separate CFD study with the optimised designs are compared against a standard pin-fin based heatsink design. The results show that the Density method demonstrates better performance in terms of robustness and computational speed, while Level-set method yields a better quality design
Topology Optimization of a Pseudo 3D Thermofluid Heat Sink Model
This paper investigates the application of density-based topology optimization to the design of air-cooled forced convection heat sinks. To reduce the computational burden that is associated with a full 3D optimization, a pseudo 3D optimization model comprising a 2D modeled conducting metal base layer and a thermally coupled 2D modeled thermofluid design layer is used. Symmetry conditions perpendicular to the flow direction are applied to generate periodic heat sink designs. The optimization objective is to minimize the heat sink heat transfer resistance for a fixed pressure drop over the heat sink and a fixed heat production rate in the base plate. Optimized designs are presented and the resulting fin geometry is discussed from a thermal engineering point of view and compared to fin shapes resulting from a pressure drop minimization objective. Parametric studies are conducted to analyze the influence of the pressure drop on the heat sink heat transfer resistance. To quantify the influence of the assumptions made in the pseudo 3D optimization model, validation simulations with a body-fitted mesh in 2D and 3D are conducted. A good agreement between optimization model and validation simulations is found, confirming the physical validity of the utilized optimization model. Two topology optimized designs are exemplarily benchmarked against a size optimized parallel fin heat sink and an up to 13.6% lower thermal resistance is found to be realized by the topology optimization
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