The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.
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tomography based determination of permeability dupuit forchheimer coefficient and interfacial heat transfer coefficient in reticulate porous ceramics
International Journal of Heat and Fluid Flow, 2008Co-Authors: Jorg Petrasch, Aldo Steinfeld, Fabian Meier, Hansmartin FriessAbstract:Abstract A computer tomography based methodology is applied to determine the transport properties of fluid flow across porous media. A 3D Digital Representation of a 10-ppi reticulate porous ceramic (RPC) sample was generated by X-ray tomographic scans. Structural properties such as the porosity, specific interfacial surface area, pore-size distribution, mean survival time, two-point correlation function s2, and local geometry distribution of the RPC sample are directly extracted from the tomographic data. Reference solutions of the fluid flow governing equations are obtained for Re = 0.2–200 by applying finite volume direct pore-level numerical simulation (DPLS) using unstructured, body-fitted, tetrahedral mesh discretization. The permeability and the Dupuit–Forchheimer coefficient are determined from the reference solutions by DPLS, and compared to the values predicted by selected porous media flow models, namely: conduit-flow, hydraulic radius theory, drag models, mean survival time bound, s2-bound, fibrous bed correlations, and local porosity theory-based models. DPLS is further employed to determine the interfacial heat transfer coefficient and to derive a corresponding Nu-correlation, which is compared to empirical correlations.
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tomography based monte carlo determination of radiative properties of reticulate porous ceramics
Journal of Quantitative Spectroscopy & Radiative Transfer, 2007Co-Authors: Jorg Petrasch, Peter Wyss, Aldo SteinfeldAbstract:A 3D Digital Representation of a reticulate porous ceramic (RPC) sample, generated by computer tomography (CT), is employed to determine its porosity, surface-to-volume ratio, and the minimum size of a representative elementary volume (REV) for continuum domain. Subsequently, the Monte Carlo (MC) ray-tracing technique is applied to calculate the extinction coefficient and scattering phase functions based on the probabilistic distribution functions of the extinction path-length and of the directional cosine of incident radiation. The methodology and governing equations are presented for diffusely and specularly reflecting surfaces. The isotropic assumption is justified by demonstrating that the extinction coefficient is directionally independent.
Jorg Petrasch - One of the best experts on this subject based on the ideXlab platform.
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tomography based determination of permeability dupuit forchheimer coefficient and interfacial heat transfer coefficient in reticulate porous ceramics
International Journal of Heat and Fluid Flow, 2008Co-Authors: Jorg Petrasch, Aldo Steinfeld, Fabian Meier, Hansmartin FriessAbstract:Abstract A computer tomography based methodology is applied to determine the transport properties of fluid flow across porous media. A 3D Digital Representation of a 10-ppi reticulate porous ceramic (RPC) sample was generated by X-ray tomographic scans. Structural properties such as the porosity, specific interfacial surface area, pore-size distribution, mean survival time, two-point correlation function s2, and local geometry distribution of the RPC sample are directly extracted from the tomographic data. Reference solutions of the fluid flow governing equations are obtained for Re = 0.2–200 by applying finite volume direct pore-level numerical simulation (DPLS) using unstructured, body-fitted, tetrahedral mesh discretization. The permeability and the Dupuit–Forchheimer coefficient are determined from the reference solutions by DPLS, and compared to the values predicted by selected porous media flow models, namely: conduit-flow, hydraulic radius theory, drag models, mean survival time bound, s2-bound, fibrous bed correlations, and local porosity theory-based models. DPLS is further employed to determine the interfacial heat transfer coefficient and to derive a corresponding Nu-correlation, which is compared to empirical correlations.
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tomography based monte carlo determination of radiative properties of reticulate porous ceramics
Journal of Quantitative Spectroscopy & Radiative Transfer, 2007Co-Authors: Jorg Petrasch, Peter Wyss, Aldo SteinfeldAbstract:A 3D Digital Representation of a reticulate porous ceramic (RPC) sample, generated by computer tomography (CT), is employed to determine its porosity, surface-to-volume ratio, and the minimum size of a representative elementary volume (REV) for continuum domain. Subsequently, the Monte Carlo (MC) ray-tracing technique is applied to calculate the extinction coefficient and scattering phase functions based on the probabilistic distribution functions of the extinction path-length and of the directional cosine of incident radiation. The methodology and governing equations are presented for diffusely and specularly reflecting surfaces. The isotropic assumption is justified by demonstrating that the extinction coefficient is directionally independent.
Sandro Wartzack - One of the best experts on this subject based on the ideXlab platform.
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Status and Prospects of Skin Model Shapes for Geometric Variations Management
Procedia CIRP, 2016Co-Authors: Benjamin Schleich, Luc Mathieu, Nabil Anwer, Sandro WartzackAbstract:Geometric part deviations, which are inevitably observed on every manufactured workpiece, have distinct effects on the assemblability as well as on the function and quality of physical artefacts. As a consequence, geometric variations management is an important issue for manufacturing companies. However, assessing the effects of form deviations already in virtual product realization remains an important challenge. This paper illustrates and summarizes the current status and development trends of the Skin Model Shape paradigm, which provides an operationalization and a Digital Representation of the Skin Model concept for modelling product shape variability and hence may serve as a comprehensive model for computer-aided variations management.
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From solid modelling to skin model shapes: Shifting paradigms in computer-aided tolerancing
Cirp Annals-manufacturing Technology, 2014Co-Authors: Nabil Anwer, Benjamin Schleich, Luc Mathieu, Sandro WartzackAbstract:Abstract Product design requires the consideration of geometric models and Representations that reflect shape deviations and support tolerance management issues. Computer-Aided Tolerancing (CAT) systems have been developed as simulation tools for modelling the effects of tolerances on Digital product simulation. However, geometric variations cannot be addressed efficiently with regard to form deviations. This paper investigates the concepts of Skin Model Shapes, which provide a finite describability and the Digital Representation of the Skin Model concept, and their unified discrete geometry Representation. New contributions to tolerance Representation and analysis are presented. Applications and perspectives for CAT systems are highlighted as well.
Noam Lior - One of the best experts on this subject based on the ideXlab platform.
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errors in thermochromic liquid crystal thermometry
Review of Scientific Instruments, 2004Co-Authors: Roland Wiberg, Noam LiorAbstract:This article experimentally investigates and assesses the errors that may be incurred in the hue-based thermochromic liquid crystal thermochromic liquid crystal (TLC) method, and their causes. The errors include response time, hysteresis, aging, surrounding illumination disturbance, direct illumination and viewing angle, amount of light into the camera, TLC thickness, Digital resolution of the image conversion system, and measurement noise. Some of the main conclusions are that: (1) The 3×8 bits Digital Representation of the red green and blue TLC color values produces a temperature measurement error of typically 1% of the TLC effective temperature range, (2) an eight-fold variation of the light intensity into the camera produced variations, which were not discernable from the Digital resolution error, (3) this temperature depends on the TLC film thickness, and (4) thicker films are less susceptible to aging and thickness nonuniformities.
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error causes and magnitudes in thermochromic liquid crystal thermometry
ASME 2003 International Mechanical Engineering Congress and Exposition, 2003Co-Authors: Roland Wiberg, Noam LiorAbstract:This paper investigates experimentally and assesses the errors that may be incurred in the hue-based thermochromic liquid crystal (TLC) method, and their causes. The errors include response time, hysteresis, aging, surrounding illumination disturbance, direct illumination and viewing angle, illumination light intensity, TLC thickness, Digital resolution of the image conversion system, and measurement noise. Some of the main conclusions are that (1) the 3×8 bits Digital Representation of the red, green and blue TLC color values produces a temperature measurement error of typically 1% of the TLC effective temperature range, (2) an 8-fold variation of the light intensity into the camera produced variations, which were not discernable from the Digital resolution error, (3) this temperature depends on the TLC film thickness, (4) thicker films are less susceptible to aging and thickness nonuniformities.Copyright © 2003 by ASME
Peter Wyss - One of the best experts on this subject based on the ideXlab platform.
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tomography based monte carlo determination of radiative properties of reticulate porous ceramics
Journal of Quantitative Spectroscopy & Radiative Transfer, 2007Co-Authors: Jorg Petrasch, Peter Wyss, Aldo SteinfeldAbstract:A 3D Digital Representation of a reticulate porous ceramic (RPC) sample, generated by computer tomography (CT), is employed to determine its porosity, surface-to-volume ratio, and the minimum size of a representative elementary volume (REV) for continuum domain. Subsequently, the Monte Carlo (MC) ray-tracing technique is applied to calculate the extinction coefficient and scattering phase functions based on the probabilistic distribution functions of the extinction path-length and of the directional cosine of incident radiation. The methodology and governing equations are presented for diffusely and specularly reflecting surfaces. The isotropic assumption is justified by demonstrating that the extinction coefficient is directionally independent.
