Examinando por Autor "Steeb, Holger"
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Ítem Determining the limits of geometrical tortuosity from seepage flow calculations in porous media(WILEY-VCH Verlag, 2014) Uribe, David; Osorno, María; Sivanesapillai, Rakulan; Steeb, Holger; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAERecent investigations have found a distinct correlation of effective properties of porous media to sigmoidal functions, where one axis is the Reynolds number Re and the other is the effective property dependent of Re, Θ = S (Re) -- One of these properties is tortuosity -- At very low Re (seepage flow), there is a characteristic value of tortuosity, and it is the upper horizontal asymptote of the sigmoidal function -- With higher values of Re (transient flow) the tortuosity value decreases, until a lower asymptote is reached (turbulent flow) -- Estimations of this parameter have been limited to the low Reynolds regime in the study of porous media -- The current state of the art presents different numerical measurements of tortuosity, such as skeletization, centroid binding, and arc length of streamlines -- These are solutions for the low Re regime. So far, for high Re, only the arc length of stream lines has been used to calculate tortuosity -- The present approach involves the simulation of fluid flow in large domains and high Re, which requires numerous resources, and often presents convergence problems -- In response to this, we propose a geometrical method to estimate the limit of tortuosity of porous media at Re → ∞, from the streamlines calculated at low Re limit -- We test our method by calculating the tortuosity limits in a fibrous porous media, and comparing the estimated values with numerical benchmark results -- Ongoing work includes the geometric estimation of different intrinsic properties of porous mediaÍtem Estimation of large domain Al foam permeability by Finite Difference methods(WILEY-VCH Verlag, 2013) Osorno, María; Steeb, Holger; Uribe, David; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEClassical methods to calculate permeability of porous media have been proposed mainly for high density (e.g. granular) materials -- These methods present shortcomings in high porosity, i.e. high permeability media (e.g. metallic foams) -- While for dense materials permeability seems to be a function of bulk properties and occupancy averaged over the volume, for highly porous materials these parameters fail to predict it -- Several authors have attacked the problem by solving the Navier-Stokes equations for the pressure and velocity of a liquid flowing through a small domain (Ωs) of aluminium foam and by comparing the numerical results with experimental values (prediction error approx. 9%) -- In this article, we present calculations for much larger domains (ΩL) using the Finite Difference (FD) method, solving also for the pressure and velocity of a viscous liquid flowing through the Packed Spheres scenario -- The ratio Vol(ΩL)/Vol(Ωs) is around 103 -- The comparison of our results with the Packed Spheres example yields a prediction error of 5% for the intrinsic permeability -- Additionally, numerical permeability calculations have been performed for Al foam samples -- Our geometric modelling of the porous domain stems from 3D X-ray tomography, yielding voxel information, which is particularly appropriate for FD -- Ongoing work concerns the reduction in computing times of the FD method, consideration of other materials and fluids, and comparison with experimental dataÍtem Geometry simplification for modeling of porous materials(2015) Ruíz, Óscar E.; Cadavid, Esteban; Osorno, María C.; Uribe, David; Steeb, Holger; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEPorous and lattice materials have become everpresent in applications such as medicine, aerospace, design, manufacturing, art, entertainment, robotics, material handling, etc -- However, their application is impeded by the uncertainty of their mechanical properties (elongation, torsion, compression moduli, etc.) -- Computational Mechanics of poorus materials is also hindered by the massive geometric data sets that they entail, if their full geometric representations are used -- In response to these limitations, this article presents a truss simplification of a porous material --This simplified representation is usable in computer simulations, instead of the full triangle- or freeform-based Boundary Representations (B-Rep), which produce intractable problems -- This article presents the simplification methodology, along with results of estimation of the stress - strain response of porous material (in this case, Aluminum) -- Our methodology presents itself as a possible alternative in contrast with impossible processing when full data is used -- Follow up work is needed in using the truss methodology for calculating macro-scaleequivalent Young or Poisson moduli, with applications on mechanical designÍtem Microscale Investigations of High Frequency Wave Propagation Through Highly Porous Media(Gesellschaft für Angewandte Mathematik und Mechanik (GAMM), 2012-12-03) Uribe, David; Saenger, Erik; Jänicke, Ralf; Steeb, Holger; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEÍtem Microscale investigations of highfrequency wave propagation through highly porous media(WILEY-VCH Verlag, 2012-12-03) Uribe, David; Saenger, Erik; Jänicke, Ralf; Steeb, Holger; Ruíz, Oscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEWave propagation in highly porous materials has a well established theoretical background -- Still there are parameters which require complex laboratory experimentation in order to find numerical values -- This paper presents an effective method to calculate the tortuosity of aluminum foam using numerical simulations -- The work flow begins with the acquisition of the foam geometry by means of a micro-CT scanner and further image segmentation and analysis -- The elastodynamic wave propagation equation is solved using a velocity-stress rotated staggered finite-difference technique -- The effective wave velocities are calculated and using the fluid and, aluminum effective properties, the tortuosity is determinedÍtem Numerical analysis of wave propagation in fluid-filled deformable tubes(Gesellschaft für Angewandte Mathematik und Mechanik (GAMM), 2013-11-29) Uribe, David; Steeb, Holger; Saenger, Erik H.; Kurzeja, Patrick; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEÍtem Numerical analysis of wave propagation in fluid-filled deformable tubes(WILEY-VCH Verlag, 2013-11-29) Uribe, David; Steeb, Holger; Saenger, Erik H.; Kurzeja, Patrick; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThe theory of Biot describing wave propagation in fluid saturated porous media is a good effective approximation of a wave induced in a fluid-filled deformable tube -- Nonetheless, it has been found that Biot’s theory has shortcomings in predicting the fast P-wave velocities and the amount of intrinsic attenuation -- These problems arises when complex mechanical interactions of the solid phase and the fluid phase in the micro-scale are not taken into account -- In contrast, the approach proposed by Bernabe does take into account micro-scopic interaction between phases and therefore poses an interesting alternative to Biot’s theory -- A Wave propagating in a deformable tube saturated with a viscous fluid is a simplified model of a porous material, and therefore the study of this geometry is of great interest -- By using this geometry, the results of analytical and numerical results have an easier interpretation and therefore can be compared straightforward -- Using a Finite Difference viscoelastic wave propagation code, the transient response was simulated -- The wave source was modified with different characteristic frequencies in order to gain information of the dispersion relation -- It was found that the P-wave velocities of the simulations at sub-critical frequencies closely match those of Bernabe’s solution, but at over-critical frequencies they come closer to Biot’s solutionÍtem Relaxed loading conditions for higher order homogenisation approaches(Gesellschaft für Angewandte Mathematik und Mechanik (GAMM), 2011-01-01) Jänicke, Ralf; Uribe, David; Ruiz, Oscar Eduardo; Steeb, Holger; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThe present paper deals with the formul at ion of mi n imal loading conditions for the applicatio n of numerical homogenisa-tion techniques, namely th e FE2methodology. Based on the set of volume averaging rules connecting the het ero geneous microÍtem Relaxed loading conditions for higher order homogenisation approaches(WILEY-VCH Verlag, 2011-12-09) Jänicke, Ralf; Uribe, David; Ruíz, Óscar E.; Steeb, Holger; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThe present paper deals with the formulation of minimal loading conditions for the application of numerical homogenisation techniques, namely the FE methodology -- Based on the set of volume averaging rules connecting the heterogeneous micro and the homogeneous macro scale, the minimal constraints on the deformation of a micro volume are derived for a classical Cauchy as well as for a micromorphic overall continuum theory -- For both cases, numerical studies are included highlighting the main aspects of the proposed procedure