2,638 research outputs found
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 symmetric nodal conservative finite element method for the Darcy equation
This work introduces and analyzes novel stable Petrov-Galerkin EnrichedMethods (PGEM) for the Darcy problem based on the simplest but unstable continuous P1/P0 pair. Stability is recovered inside a Petrov-Galerkin framework where element-wise dependent residual functions, named multi-scale functions, enrich both velocity and pressure trial spaces. Unlike the velocity test space that is augmented with bubble-like functions, multi-scale functions correct edge residuals as well. The multi-scale functions turn out to be the well-known lowest order Raviart-Thomas basis functions for the velocity and discontinuous quadratics polynomial functions for the pressure. The enrichment strategy suggests the way to recover the local mass conservation property for nodal-based interpolation spaces. We prove that the method and its symmetric version are well-posed and achieve optimal error estimates in natural norms. Numerical validations confirm claimed theoretical results
Nanoflows through disordered media: a joint Lattice Boltzmann and Molecular Dynamics investigation
We investigate nanoflows through dilute disordered media by means of joint
lattice Boltzmann (LB) and molecular dynamics (MD) simulations -- when the size
of the obstacles is comparable to the size of the flowing particles -- for
randomly located spheres and for a correlated particle-gel. In both cases at
sufficiently low solid fraction, , LB and MD provide similar values
of the permeability. However, for , MD shows that molecular size
effects lead to a decrease of the permeability, as compared to the
Navier-Stokes predictions. For gels, the simulations highlights a surplus of
permeability, which can be accommodated within a rescaling of the effective
radius of the gel monomers.Comment: 4 pages, 4 figure
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