Long-term thermal two- and three-dimensional analysis of roller compacted concrete dams supported by monitoring verification

2010 ◽  
Vol 37 (4) ◽  
pp. 600-610 ◽  
Author(s):  
Vladan Kuzmanovic ◽  
Ljubodrag Savic ◽  
John Stefanakos
Keyword(s):  
Thermal Analysis ◽  
Boundary Conditions ◽  
Thermal Field ◽  
Numerical Models ◽  
Three Dimensional ◽  
Roller Compacted Concrete ◽  
Rcc Dam ◽  
Field Investigations ◽  
Good Agreement

This paper presents two-dimensional (2D) and three-dimensional (3D) numerical models for unsteady phased thermal analysis of RCC dams. The time evolution of a thermal field has been modeled using the actual dam shape, RCC technology and the adequate description of material properties. Model calibration and verification has been done based on the field investigations of the Platanovryssi dam, the highest RCC dam in Europe. The results of a long-term thermal analysis, with actual initial and boundary conditions, have shown a good agreement with the observed temperatures. The influence of relevant parameters on the thermal field of RCC dams has been analyzed. It is concluded that the 2D model is appropriate for the thermal phased analysis, and that the boundary conditions and the mixture properties are the most influential on the RCC dam thermal behavior.

scholarly journals Edge Cooling of a Fuel Cell during Aerial Missions by Ambient Air

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1432
Author(s):  
Lev Zakhvatkin ◽  
Alex Schechter ◽  
Eilam Buri ◽  
Idit Avrahami
Keyword(s):  
Fuel Cell ◽  
Numerical Model ◽  
Wind Tunnel ◽  
Boundary Conditions ◽  
Air Temperature ◽  
Numerical Models ◽  
Heat Removal ◽  
Ambient Air ◽  
Experimental Setup ◽  
Good Agreement

During aerial missions of fuel-cell (FC) powered drones, the option of FC edge cooling may improve FC performance and durability. Here we describe an edge cooling approach for fixed-wing FC-powered drones by removing FC heat using the ambient air during flight. A set of experiments in a wind tunnel and numerical simulations were performed to examine the efficiency of FC edge cooling at various flight altitudes and cruise speeds. The experiments were used to validate the numerical model and prove the feasibility of the proposed method. The first simulation duplicated the geometry of the experimental setup and boundary conditions. The calculated temperatures of the stack were in good agreement with those of the experiments (within ±2 °C error). After validation, numerical models of a drone’s fuselage in ambient air with different radiator locations and at different flight speeds (10–30 m/s) and altitudes (up to 5 km) were examined. It was concluded that onboard FC edge cooling by ambient air may be applicable for velocities higher than 10 m/s. Despite the low pressure, density, and Cp of air at high altitudes, heat removal is significantly increased with altitude at all power and velocity conditions due to lower air temperature.

Magma system pressurisation and long-term surface deformation at Soufrière Hills Volcano, Montserrat

2021 ◽  
Author(s):  
James Hickey ◽  
Karen Pascal ◽  
Matthew Head ◽  
Jo Gottsmann ◽  
Nico Fournier ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Numerical Models ◽  
Three Dimensional ◽  
Magmatic System ◽  
System Pressure ◽  
Digital Elevation ◽  
Elevation Model ◽  
Magma System ◽  
Continuous Gps

<p>Soufrière Hills Volcano (SHV) is an andesitic dome-building volcano on the island of Montserrat (British West Indies). SHV began its current, and anomalously long, eruption in 1995, but eruptive activity has been intermittent with phases of lava extrusion separated by periods of relative quiescence. The current pause in eruption started in February 2010 and is the longest yet recorded, 10 years and 11 months at the time of writing (January 2021). Continuous GPS measurements show island-wide inflation from 2010 onwards, with the rate of inflation slowly decreasing with time. However, the length of the eruptive pause raises questions as to whether there have been significant changes to the magmatic system and/or the eruption at SHV might have ended. To assess the behaviour and evolution of the SHV magmatic system since 2010 and the relation to ongoing hazard assessment, we analyse the continuous GPS temporal deformation trends using a suite of geodetic numerical models. Our models incorporate a temperature-dependent viscoelastic rheology, topography derived from a Digital Elevation Model and three-dimensional variations in mechanical properties derived from seismic tomography. The models are driven using one of four possible time-dependent source functions, to simulate differences in the temporal evolution of the magmatic system. The results show that the observed deformation data requires a temporal source function whereby the magmatic system pressure is increasing with time. A viscoelastic crustal response cannot explain the long-term deformation trends alone. The nature of the source pressurisation is unclear, and could be due, for example, to one or a combination of, magma supply, degassing/volatile influx, or overturning within a transcrustal magmatic system. Continued pressurisation within the magmatic system highlights the need for sustained vigilance in the monitoring and management of the volcano and its surroundings.</p>

Numerical Simulation of Impeller–Volute Interaction in Centrifugal Compressors

1999 ◽  
Vol 121 (3) ◽  
pp. 603-608 ◽  
Author(s):  
K. Hillewaert ◽  
R. A. Van den Braembussche
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Flow Calculation ◽  
Total Temperature ◽  
Temperature And Pressure ◽  
Good Agreement

A numerical procedure to predict the impeller–volute interaction in a single-stage centrifugal compressor is presented. The method couples a three-dimensional unsteady flow calculation in the impeller with a three-dimensional time-averaged flow calculation in the volute through an iterative updating of the boundary conditions on the interface of both calculation domains. The method has been used to calculate the flow in a compressor with an external volute at off-design operation. Computed circumferential variations of flow angles, total temperature, and pressure are shown and compared with measurements. The good agreement between the predictions and measurements confirms the validity of the approach.

Finite element analysis for precision cold forging of helical gear using recurrent boundary conditions

1998 ◽  
Vol 212 (3) ◽  
pp. 231-240 ◽  
Author(s):  
Y B Park ◽  
D Y Yang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Helical Gear ◽  
Cold Forging ◽  
Rigid Plastic ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Good Agreement

In metal forming, there are problems with recurrent geometric characteristics without explicitly prescribed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear (which is industrially useful and geometrically complicated) has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. The three-dimensional deformed pattern by the finite element analysis is shown, and the forging load is compared with the experimental load. The profiles of the free surface of the workpiece show good agreement between the computation and the experiment.

scholarly journals LARGE-WAVE SIMULATION OF TURBULENT FLOW INDUCED BY WAVE PROPAGATION AND BREAKING OVER CONSTANT SLOPE BED

2012 ◽  
Vol 1 (33) ◽  
pp. 65
Author(s):  
Gerasimos Kolokythas ◽  
Aggelos Dimakopoulos ◽  
Athanassios Dimas
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Wave Breaking ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Surface Boundary ◽  
Large Wave ◽  
Wave Simulation ◽  
Constant Slope ◽  
Good Agreement

In the present study, the three-dimensional, incompressible, turbulent, free-surface flow, developing by the propagation of nonlinear breaking waves over a rigid bed of constant slope, is numerically simulated. The main objective is to investigate the process of spilling wave breaking and the characteristics of the developing undertow current employing the large-wave simulation (LWS) method. According to LWS methodology, large velocity and free-surface scales are fully resolved, and subgrid scales are treated by an eddy viscosity model, similar to large-eddy simulation (LES) methodology. The simulations are based on the numerical solution of the unsteady, three-dimensional, Navier-Stokes equations subject to the fully-nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow boundary conditions. The case of incoming second-order Stokes waves, normal to the shore, with wavelength to inflow depth ratio λ/dΙ = 6.6, wave steepness H/λ = 0.025, bed slope tanβ = 1/35 and Reynolds number (based on inflow water depth) Red = 250,000 is investigated. The predictions of the LWS model for the incipient wave breaking parameters - breaking depth and height - are in very good agreement with published experimental measurements. Profiles of the time-averaged horizontal velocity in the surf zone are also in good agreement with the corresponding measured ones, verifying the ability of the model to capture adequately the undertow current.

scholarly journals Hydro- and morphodynamics in curved river reaches – recent results and directions for future research

2013 ◽  
Vol 37 ◽  
pp. 19-25 ◽  
Author(s):  
K. Blanckaert ◽  
G. Constantinescu ◽  
W. Uijttewaal ◽  
Q. Chen
Keyword(s):  
Sediment Transport ◽  
Secondary Flow ◽  
Large Scale ◽  
Numerical Models ◽  
Three Dimensional ◽  
Future Research ◽  
Turbulence Structures ◽  
Outer Bank ◽  
Flow Processes

Abstract. Curved river reaches were investigated as an example of river configurations where three-dimensional processes prevail. Similar processes occur, for example, in confluences and bifurcations, or near hydraulic structures such as bridge piers and abutments. Some important processes were investigated in detail in the laboratory, simulated numerically by means of eddy-resolving techniques, and finally parameterized in long-term and large-scale morphodynamic models. Investigated flow processes include secondary flow, large-scale coherent turbulence structures, shear layers and flow separation at the convex inner bank. Secondary flow causes a redistribution of the flow and a transverse inclination of the riverbed, which favour erosion of the outer bank and meander migration. Secondary flow generates vertical velocities that impinge on the riverbed, and are known to increase the erosive capacity of the flow. Large-scale turbulent coherent structures also increase the sediment entrainment and transport capacity. Both processes are not accounted for in sediment transport formulae, which leads to an underestimation of the bend scour and the erosion of the outer bank. Eddy-resolving numerical models are computationally too expensive to be implemented in long-term and large-scale morphodynamic models. But they provide insight in the flow processes and broaden the investigated parameter space. Results from laboratory experiments and eddy-resolving numerical models were at the basis of the development of a new parameterization without curvature restrictions of secondary flow effects, which is applicable in long-term and large-scale morphodynamic models. It also led to the development of a new engineering technique to modify the flow and the bed morphology by means of an air-bubble screen. The rising air bubbles generate secondary flow, which redistributes the patterns of flow, boundary shear stress and sediment transport.

The Use of Advanced Transient Structural Codes to Study Interior Gun Dynamics

1991 ◽  
Author(s):  
Stephen Wilkerson
Keyword(s):  
Kinetic Energy ◽  
Boundary Conditions ◽  
Numerical Models ◽  
Three Dimensional ◽  
Numerical Results ◽  
Numerical Techniques ◽  
Modeling Process ◽  
Numerical Studies ◽  
Areas Of Concern

Abstract Three-dimensional numerical models used to analyze the in-bore dynamics of kinetic energy projectiles are presented. The intricate modeling process, boundary conditions, and assumptions used in the analysis are given. Numerical results are analyzed and presented to show the importance of three-dimensional numerical studies. Finally possible areas of concern and future improvements in the numerical techniques used are reviewed.

Finite Element Thermal Analysis for Microscale Laser Joining of Nanoscale Coatings of Titanium on Glass/Polyimide System

2009 ◽  
Author(s):  
Mohammed S. Mayeed ◽  
Nusrat J. Lubna ◽  
Gregory W. Auner ◽  
Golam M. Newaz ◽  
Rahul Patwa ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Dissimilar Materials ◽  
Fe Model ◽  
Element Analysis ◽  
Laser Joining ◽  
Bonded Joint ◽  
Laser Heat Source

Finite element thermal analysis and comparison with experiments of microscale laser joining of biocompatible materials, polyimide (PI) and nanoscale coating of titanium (Ti) on glass (Gl), is vital for the long-term application of bio-implants and important for the applications of nanoscale solid coatings. In this study, a comprehensive three dimensional (3D) transient simulation for thermal analysis of transmission laser micro-joining of dissimilar materials has been performed by using the finite element (FE) code ABAQUS, along with a moving Gaussian laser heat source. The laser beam (wavelength of 1100 nm and diameter of 0.2 mm), moving at an optimized velocity (100 mm/min), passes through the transparent PI, gets absorbed by the absorbing Ti, and eventually melts the PI to form the bond. The laser bonded joint area is 6.5 mm long on three different Ti coating thicknesses of 400, 200 and 50 nms on Gl surface. Non-uniform mixed meshes have been used and optimized to formulate the 3D FE model and ensure very refined meshing around the bond area. During the microscale laser heating finite element modeling shows widths of PI surface experiencing temperatures above the glass transition temperature are similar to the widths of bonds observed in experiments for coating thicknesses of 400 and 200 nms of Ti on Gl. However, for the case of 50 nm coating bond width using finite element analysis cannot produce and is lower than the bond width observed experimentally.

scholarly journals Regional atmospheric composition modeling with CHIMERE

2013 ◽  
Vol 6 (1) ◽  
pp. 203-329 ◽  
Author(s):  
L. Menut ◽  
B. Bessagnet ◽  
D. Khvorostyanov ◽  
M. Beekmann ◽  
A. Colette ◽  
...  
Keyword(s):  
Air Quality ◽  
Forest Fires ◽  
Numerical Models ◽  
Regional Scale ◽  
Three Dimensional ◽  
Volcanic Eruptions ◽  
Atmospheric Composition ◽  
Meteorological Model ◽  
Wide Range

Abstract. Tropospheric trace gas and aerosol pollutants have adverse effects on health, environment and climate. In order to quantify and mitigate such effects, a wide range of processes leading to the formation and transport of pollutants must be considered, understood and represented in numerical models. Regional scale pollution episodes result from the combination of several factors: high emissions (from anthropogenic or natural sources), stagnant meteorological conditions, velocity and efficiency of the chemistry and the deposition. All these processes are highly variable in time and space, and their relative importance to the pollutants budgets can be quantified within a chemistry-transport models (CTM). The offline CTM CHIMERE model uses meteorological model fields and emissions fluxes and calculates deterministically their behavior in the troposphere. The calculated three-dimensional fields of chemical concentrations can be compared to measurements to analyze past periods or used to make air quality forecasts and CHIMERE has enabled a fine understanding of pollutants transport during numerous measurements campaigns. It is a part of the PREVAIR french national forecast platform, delivering pollutant concentrations up to three days in advance. The model also allows scenario studies and long term simulations for pollution trends. The modelling of photochemical air pollution has reached a good level of maturity, and the latest projects involving CHIMERE now aim at increasing our understanding of pollution impact on health at the urban scale or at the other end of the spectrum for long term air quality and climate change interlinkage studies, quantifying the emissions and transport of pollen, but also, at a larger scale, analyzing the transport of pollutants plumes emitted by volcanic eruptions and forest fires.

3D Simulation and Experimental Validation of an Electrically-Excited Flow in a Folded Microchannel

2006 ◽  
Author(s):  
Dominik P. J. Barz ◽  
Hamid Farangis Zadeh ◽  
Peter Ehrhard
Keyword(s):  
Mathematical Model ◽  
Finite Elements ◽  
Flow Field ◽  
Boundary Conditions ◽  
Experimental Validation ◽  
Three Dimensional ◽  
Numerical Treatment ◽  
Matching Procedure ◽  
Asymptotic Matching ◽  
Good Agreement

We investigate the flow field in a folded microchannel, which serves as an essential part of an electrically-excited micromixer. A mathematical model that allows for the numerical treatment of the channel core is developed. The boundary conditions at the walls are implemented by means of an asymptotic matching procedure. Three-dimensional finite-elements simulations are performed and verified against experiments. The comparison shows good agreement.

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