scholarly journals Development and Validation of Numerical Models for Evaluation of Foam-Vacuum Insulation Panel Composite Boards, Including Edge Effects

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2228 ◽  
Author(s):  
Kaushik Biswas
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Numerical Models ◽  
Small Scale ◽  
Minimization Method ◽  
Element Analysis ◽  
Vacuum Insulation ◽  
Experimental Parameters ◽  
Development And Validation ◽  
Vacuum Insulation Panel

A combined finite element analysis (FEA) and experimental validation approach to estimating effective edge conductivities of vacuum insulation panels (VIPs) embedded in foam-VIP composites is presented. The edge conductivities were estimated by comparing the simulation results with measurements of small-scale (0.61 × 0.61 m) foam-VIP composites and using an error minimization method. The two composites contained multiple VIPs that were butt-jointed with each other in one composite and separated by foam insulation in the other. Edge conductivities were estimated by considering the neighboring materials, i.e., whether the VIPs were adjacent to other VIPs or foam insulation. Models incorporating the edge conductivities were then used to simulate additional small- and large-scale (2.44 × 1.22 m) composites for validation and evaluation of the overall thermal transmission properties. The simulations used either the same boundary conditions as the experiments or used the experimental parameters to define the appropriate boundary conditions.

scholarly journals CHALLENGES OF BOUNDARY CONDITIONS IN OPEN OCEAN MODELS

2020 ◽  
pp. 52
Author(s):  
Judith Herold ◽  
Eric Lemont ◽  
Stuart Bettington ◽  
Edward Couriel
Keyword(s):  
Environmental Impact ◽  
Boundary Conditions ◽  
Large Scale ◽  
Numerical Models ◽  
Open Ocean ◽  
Small Scale ◽  
Ocean Models ◽  
Support Engineering ◽  
Ocean Boundary ◽  
Professional Judgement

The development and calibration of coastal numerical models to support engineering design and environmental impact studies is a challenging process and one that requires professional judgement and continual assessment of all aspects of the model makeup. Fundamental to the integrity of the model are appropriate boundary conditions and quality observational data for calibration. Open ocean boundary conditions are typically the most complex and important aspect of a model build. They represent the influence of dynamics occurring beyond the model extent, bridging large-scale dynamics to the small-scale processes in the model. This study discusses the challenges of open ocean boundaries and how we utilised data to achieve an effective model.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/evL7f_17wZg

Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

2000 ◽  
Vol 663 ◽  
Author(s):  
J. Samper ◽  
R. Juncosa ◽  
V. Navarro ◽  
J. Delgado ◽  
L. Montenegro ◽  
...  
Keyword(s):  
Large Scale ◽  
Reference Model ◽  
Numerical Models ◽  
Full Scale ◽  
Small Scale ◽  
Model Parameters ◽  
In Situ Test ◽  
Wide Range ◽  
Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

A fully distributed unstructured Navier-Stokes solver for large-scale aeroelasticity computations

2001 ◽  
Vol 105 (1050) ◽  
pp. 419-426 ◽  
Author(s):  
G. Barakos ◽  
M. Vahdati ◽  
A.I. Sayma ◽  
C. Bréard ◽  
M. Imregun
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Navier Stokes ◽  
Multiple Data ◽  
Computational Mesh ◽  
Blade Row ◽  
Scale Modelling ◽  
Modelling Methodology ◽  
Speed Up ◽  
Development And Validation

Abstract This paper presents the development and validation of a parallel unsteady flow and aeroelasticity code for large-scale numerical models used in turbo machinery applications. The work is based on an existing unstructured Navier-Stokes solver developed over the past ten years by the Aeroelasticity Research Group at Imperial College Vibration University Technology Centre. The single-process multiple-data paradigm was adopted for the parallelisation of the solver and several validation cases were considered. The computational mesh was divided into several sub-sections using a domain decomposition technique. The performance and numerical accuracy of the parallel solver was validated across several computer platforms for various problem sizes. In cases where the solution could be obtained on a single CPU, the serial and parallel versions of the code were found to produce identical results. Studies on up to 32 CPUs showed varying levels of parallelisation efficiency, an almost linear speed-up being obtained in some cases. Finally, an industrial configuration, a 17 blade row turbine with a 47 million point mesh, was discussed to illustrate the potential of the proposed large-scale modelling methodology.

scholarly journals A Computational Workflow for Flow and Transport in Fractured Porous Media Based on a Hierarchical Nonlinear Discrete Fracture Modeling Approach

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6667
Author(s):  
Wenjuan Zhang ◽  
Waleed Diab ◽  
Hadi Hajibeygi ◽  
Mohammed Al Kobaisi
Keyword(s):  
Boundary Condition ◽  
Porous Media ◽  
Boundary Conditions ◽  
Large Scale ◽  
Fractured Porous Media ◽  
Small Scale ◽  
Flow And Transport ◽  
Fracture Length ◽  
Discrete Fracture ◽  
Computational Workflow

Modeling flow and transport in fractured porous media has been a topic of intensive research for a number of energy- and environment-related industries. The presence of multiscale fractures makes it an extremely challenging task to resolve accurately and efficiently the flow dynamics at both the local and global scales. To tackle this challenge, we developed a computational workflow that adopts a two-level hierarchical strategy based on fracture length partitioning. This was achieved by specifying a partition length to split the discrete fracture network (DFN) into small-scale fractures and large-scale fractures. Flow-based numerical upscaling was then employed to homogenize the small-scale fractures and the porous matrix into an equivalent/effective single medium, whereas the large-scale fractures were modeled explicitly. As the effective medium properties can be fully tensorial, the developed hierarchical framework constructed the discrete systems for the explicit fracture–matrix sub-domains using the nonlinear two-point flux approximation (NTPFA) scheme. This led to a significant reduction of grid orientation effects, thus developing a robust, applicable, and field-relevant framework. To assess the efficacy of the proposed hierarchical workflow, several numerical simulations were carried out to systematically analyze the effects of the homogenized explicit cutoff length scale, as well as the fracture length and orientation distributions. The effect of different boundary conditions, namely, the constant pressure drop boundary condition and the linear pressure boundary condition, for the numerical upscaling on the accuracy of the workflow was investigated. The results show that when the partition length is much larger than the characteristic length of the grid block, and when the DFN has a predominant orientation that is often the case in practical simulations, the workflow employing linear pressure boundary conditions for numerical upscaling give closer results to the full-model reference solutions. Our findings shed new light on the development of meaningful computational frameworks for highly fractured, heterogeneous geological media where fractures are present at multiple scales.

scholarly journals A highly flexible laboratory setup to demonstrate granular flow characteristics

2020 ◽  
Vol 104 (2) ◽  
pp. 1581-1596
Author(s):  
Thomas Heinze
Keyword(s):  
Granular Flow ◽  
Large Scale ◽  
Numerical Models ◽  
Low Cost ◽  
Experimental Investigations ◽  
Small Scale ◽  
Local Pressure ◽  
Slope Length ◽  
Runout Distance ◽  
Laboratory Setup

Abstract Dynamics of snow avalanches or landslides can be described by rapid granular flow. Experimental investigations of granular flow at laboratory scale are often required to analyze flow behaviour and to develop adequate mathematical and numerical models. Most investigations use image-based analysis, and additional sensors such as pressure gauges are not always possible. Testing various scenarios and parameter variations such as different obstacle shapes and positions as well as basal topography and friction usually requires either the construction of a new laboratory setups for each test or a cumbersome reconstruction. In this work, a highly flexible and modular laboratory setup is presented based on LEGO bricks. The flexibility of the model is demonstrated, and possible extensions for future laboratory tests are outlined. The setup is able to reproduce published laboratory experiments addressing current scientific research topics, such as overflow of a rigid reflector, flow on a bumpy surface and against a rigid wall using standard image-based analysis. This makes the setup applicable for quick scenario testing, e.g. for hypothesis testing or for low-cost testing prior to large-scale experiments, and it can contribute to the validation of external results and to benchmarks of numerical models. Small-scale laboratory setups are also very useful for demonstration purposes such as education and public outreach, both crucial in the context of natural hazards. The presented setup enables variation of parameters such as of slope length, channel width, height and shape, inclination, bed friction, obstacle position and shape, as well as density, composition, amount and grain size of flowing mass. Observable quantities are flow type, flow height, flow path and flow velocity, as well as runout distance, size and shape of the deposited material. Additional sensors allow further quantitative assessments, such as local pressure values.

Monitoring of dimple formation in honeycomb sandwich structures using distributed fiber optic sensors

2020 ◽  
pp. 109963622093582
Author(s):  
Juho T Siivola ◽  
Shu Minakuchi ◽  
Tadahito Mizutani ◽  
Kazuya Kitamoto ◽  
Nobuo Takeda
Keyword(s):  
Optical Fibers ◽  
Large Scale ◽  
Sandwich Structures ◽  
Beam Theory ◽  
Small Scale ◽  
Element Analysis ◽  
Thermal Expansion Coefficients ◽  
Honeycomb Sandwich ◽  
The Face ◽  
And Performance

Dimpling in the composite face sheets of honeycomb sandwich structures due to mismatch in the thermal expansion coefficients of the constituent materials was studied with emphasis on its monitoring and prediction. Strain distributions along optical fibers embedded in the face sheet were monitored during manufacturing. Dimple formation and in-plane strain distributions in the face sheets were studied using finite element analysis, and an analytical model based on the beam theory was constructed to predict the dimple depths from the strain data. A system using twin optical fiber sensors was proposed to accurately measure the dimpling-induced strains. The usability and performance of the system was evaluated using small scale specimens and finally on a more realistic large-scale specimen. The system could measure the strain changes due to dimpling of the face sheets and provided decent prediction of the dimple depth distribution along the sandwich panels.

Small-Scale FE Modelling for the Analysis of Flexible Risers

2015 ◽  
Author(s):  
M. T. Rahmati ◽  
G. Alfano ◽  
H. Bahai
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Small Scale ◽  
Fe Model ◽  
Fe Modelling ◽  
Sequential Approach ◽  
Multi Scale ◽  
Flexible Risers

Flexible risers which are used for transporting oil and gas between the seabed and surface in ultra-deep waters have a very complex internal structure. Therefore, accurate modeling of their behaviour is a great challenge for the oil and gas industry. Constitutive laws based on beam models which allow the large-scale dynamics of pipes to be related to the behaviour of its internal components can be used for multi-scale analysis of flexible risers. An integral part of these models is the small-scale FE model chosen and the detailed implementation of the boundary conditions. The small scale FE analyses are typically carried out on models of up to a few meters length. The computational requirements of these methods limit their applications for only multi-scale structural analysis based on a sequential approach. For nested multi-scale approaches (i.e. the so called FE2 method) and for multi-scale multi-physic analyses, e.g. fluid structure interaction modeling of flexible risers, more efficient methods are required. The emphasis of the present work is on a highly efficient small-scale modelling method for flexible risers. By applying periodic boundary conditions, only a small fraction of a flexible pipe is used for detailed analysis. The computational model is firstly described. Then, the capability of the method in capturing the detailed nonlinear effects and the great advantage in terms of significant CPU time saving entailed by this method are demonstrated. For proof of concept the approach is applied on a simplified 3-layer pipe made of inner and outer polymer layers and an intermediate armour layer made of 40 steel tendons.

scholarly journals Decomposition technique for contributions to groundwater heads from inside and outside of an arbitrary boundary: Application to Guantao County, North China Plain

2019 ◽  
Author(s):  
Ning Li ◽  
Wolfgang Kinzelbach ◽  
Haitao Li ◽  
Wenpeng Li ◽  
Fei Chen
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Soil Column ◽  
Scale Model ◽  
Small Scale ◽  
Decomposition Technique ◽  
Arbitrary Boundary ◽  
Groundwater Head ◽  
Administrative Unit ◽  
Small Models

Abstract. To assess the efficiency of groundwater management of an administrative unit, we propose to decompose the groundwater head changes within an administrative unit into inside and outside contributions by using numerical models. Guantao County of Hebei Province, China, serves as an example to demonstrate the decomposition technique. The groundwater flow model of Guantao was constructed using observed heads as prescribed head boundary conditions. The model was coupled with Hydrus 1D, to calculate the groundwater recharge distribution in time reflecting the delay and damping effects of the soil column on seepage at the surface. The model was calibrated by adjusting parameters such as hydraulic conductivities, recharge infiltration ratios and specific yields. The calibrated parameters are then used in a large model with a boundary at large distance from Guantao administrative boundary to determine the groundwater head changes due to inside drivers. The differences of the two models on the Guantao boundary serve as the specified head values on the boundary for a small scale model, which is used to calculate the groundwater head imposed by outside drivers. To eliminate inconsistencies caused by the different types of boundary conditions of large and small models, the groundwater head changes due to inside drivers must be updated. The results indicate that the groundwater head changes in the centre and south of Guantao County are influenced equally by both inside and outside contributions, while in the north outside contributions have the stronger impact. The sensitivity analysis shows that the groundwater head changes and their decomposition are much more sensitive to infiltration ratios than to the aquifer parameters. The parameters within Guantao have a certain influence on the net groundwater head changes while the parameters outside of Guantao have only an influence on the decomposition.

An Investigation of the Effects of Layer Thickness on the Fracture Behavior of Layered NiAl/V Composites

1999 ◽  
Vol 121 (4) ◽  
pp. 453-459 ◽  
Author(s):  
M. Li ◽  
R. Wang ◽  
N. Katsube ◽  
W. O. Soboyejo
Keyword(s):  
Finite Element ◽  
Layer Thickness ◽  
Large Scale ◽  
Small Scale ◽  
Pure Mode ◽  
Crack Bridging ◽  
Maximum Shear Strain ◽  
Element Analysis ◽  
Scale Bridging ◽  
Vanadium Layer

The effects of vanadium layer thickness (100, 200 and 400 μm) on the resistance-curve behavior of NiAl/V, microlaminates are examined in this paper. The fracture resistance of the NiAl microlaminates reinforced with 20 vol.% of vanadium layers is shown to increase with increasing vanadium layer thickness. The improved fracture toughness (from an NiAl matrix toughness of 6˜.6MPam to a steady-state toughness of 1˜5MPam obtained from finite element analysis) is associated with crack bridging and the interactions of cracks with vanadium layers. The reinitiation of cracks in adjacent NiAl layers is modeled using finite element methods and the reinitiation is shown to occur as a result of strain concentrations at the interface between the adjacent NiAl layers and vanadium layers. The deviation of the reinitiated cracks from the pure mode I direction is shown to occur in the direction of maximum shear strain. Toughening due to crack bridging is also modeled using large-scale bridging models. The intrinsic toughness levels of the microlaminates are also inferred by extrapolating the large scale bridging models to arbitrarily large specimen widths. The extrapolations also show that the small-scale bridging intrinsic toughness increases with increasing vanadium layer thickness.

Interpreting magmatic processes from accessory phases: titanite—a small-scale recorder of large-scale processes

2000 ◽  
Vol 91 (1-2) ◽  
pp. 257-267 ◽  
Author(s):  
Philip Piccoli ◽  
Philip Candela ◽  
Mark Rivers
Keyword(s):  
Sierra Nevada ◽  
Large Scale ◽  
Functional Dependence ◽  
Trace Element Analysis ◽  
Quartz Diorite ◽  
Small Scale ◽  
Element Analysis ◽  
General Behaviour ◽  
Rock Composition ◽  
Intrusive Suite

In this study we examined variations in ore and other trace-metal concentrations in titanite, a ubiquitous product of magmatic (and subsequent sub-solidus) crystallisation in oxidised silicic magmas. Accessory titanite occurs in the Tuolumne Intrusive Suite (TIS), Sierra Nevada Batholith, as euhedral to anhedral, poikilitic, or interstitial grains. Zoned crystals of titanite were analysed by electron microprobe and synchrotron X-ray fluorescence for major and trace elements. Backscatter electron images reveal zoning, with bright areas correlating positively with total REE concentrations. REE concentrations generally decrease toward the edge of titanite crystals; however, some crystals are reversely zoned, and others exhibit oscillatory or patchy zoning; some grains contain discrete anhedral cores. Most elements in magmatic titanite decrease in concentration towards crystal rims, independent of host rock composition.At least one major reduction event in the magma chamber(s) transiently stabilised ilmenite, now present only as inclusions in titanite, and resulted in a reduction in the REE concentration in titanite. We suggest the hypothesis that the reduction in the REE concentration in these zones is due to the diminished activity of the (REE)Fe3+Ca−1Ti−1exchange component; however, the scatter in the data, together with the operation of other exchange vectors for Fe and Al, did not allow us to test this hypothesis herein. Secondary (i.e. sub solidus, hydrothermal) titanite can be recognised on the basis of its chemistry, sometimes by its anhedral form, and by its position as an alteration rim around primary magmatic phases; however, secondary titanite growth on primary titanite crystals may be harder to discern. Secondary titanite rims on magnetite contain higher Cr, Zr and Mo, and lower REE, relative to magmatic titanite. U/Th ratios increase toward the rim of most titanite grains; however, Th decreases in concentration from core to rim. This is due, most likely, to complications resulting from the coupled substitutions necessary for replacement of Ca by tetravalent Th; factors of this sort are commonly overlooked in trace element analysis.The analysed titanites are from rocks of the normally zoned TIS which ranges in87Sr/86Sri, from 0·7059 (tonalite and quartz-diorite) to 0·7066 (granite). Many element ratios in the titanites exhibit little to no functional dependence on87Sr/86Sri. However, log Mo/W increases with increasing87Sr/86Sri, of the host unit from the equigranular quartz-diorite and tonalite, to the interior granodiorites, possibly reflecting the greater crustal contribution to the interior, more felsic units. Neither Mo nor W increase significantly from core to rim in titanite. If these trends are indicative of the general behaviour of these elements duringin-situfractionation, then these data suggest that Mo and W are not strongly incompatible, and indeed may behave compatibly, in some titaniteand magnetite-bearing granodioritic magmas.

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