
Mathematical and Numerical Modeling in Maritime Geomechanics
Directory of Open Access Journals (Sweden)
Miguel Martín Stickle
20120401
Full Text Available A theoretical and numerical framework to model the foundation of marine offshore structures is presented. The theoretical model is composed by a system of partial differential equations describing coupling between seabed solid skeleton and pore fluids (water, air, oil,... combined with a system of ordinary differential equations describing the specific constitutive relation of the seabed soil skeleton. Once the theoretical model is described, the finite element numerical procedure to achieve an approximate solution of the overning equations is outlined. In order to validate the proposed theoretical and numerical framework the seaward tilt mechanism induced by the action of breaking waves over a vertical breakwater is numerically reproduced. The results numerically attained are in agreement with the main conclusions drawn from the literature associated with this failure mechanism.

Numerical modeling of ICF plasmas
Energy Technology Data Exchange (ETDEWEB)
Dahlburg, J.P.; Gardner, J.H.; Schmitt, A.J.; Colombant, D.; Klapisch, M.; Phillips, L.
19990701
Radiation transport hydrodynamics codes play an important role in the design and development of ignitionregime and highgain direct drive Inertial Confinement Fusion (ICF) pellets. In this concept, laser light is used to symmetrically implode a spherical pellet to sufficiently high densities and temperatures to achieve thermonuclear fusion. This requires a very symmetric illumination and a stable hydrodynamic implosion. Simulations of the dynamics of both planar and spherical targets are being performed to provide better understanding of how to control the RayleighTaylor (RT) instability, using the 1, 2 and 3dimensional laser matter interaction (LMI) code FAST. To benchmark FAST, and the Super Transition Array material opacities used in the pellet design simulations, comparisons are being made with experimental data obtained in planar LMI experiments on the Naval Research Laboratory Nike KrF laser. One of the major efforts is to understand the behavior of the RT instability in planar laseraccelerated targets. Since this is one of the primary obstacles to successful ICF, experimental comparison is not only providing for code benchmarking, but will also lead to a better understanding of how to control this basic instability. Code benchmarking is also being performed using data from Nike opacity experiments, and from equation of state experiments in ICFrelevant regimes. In this talk they present an overview of FAST and a comparison of simulation results with data from ongoing laboratory experiments.

Numerical modeling of ICF plasmas
International Nuclear Information System (INIS)
Dahlburg, J.P.; Gardner, J.H.; Schmitt, A.J.; Colombant, D.; Klapisch, M.; Phillips, L.
19990101
Radiation transport hydrodynamics codes play an important role in the design and development of ignitionregime and highgain direct drive Inertial Confinement Fusion (ICF) pellets. In this concept, laser light is used to symmetrically implode a spherical pellet to sufficiently high densities and temperatures to achieve thermonuclear fusion. This requires a very symmetric illumination and a stable hydrodynamic implosion. Simulations of the dynamics of both planar and spherical targets are being performed to provide better understanding of how to control the RayleighTaylor (RT) instability, using the 1, 2 and 3dimensional laser matter interaction (LMI) code FAST. To benchmark FAST, and the Super Transition Array material opacities used in the pellet design simulations, comparisons are being made with experimental data obtained in planar LMI experiments on the Naval Research Laboratory Nike KrF laser. One of the major efforts is to understand the behavior of the RT instability in planar laseraccelerated targets. Since this is one of the primary obstacles to successful ICF, experimental comparison is not only providing for code benchmarking, but will also lead to a better understanding of how to control this basic instability. Code benchmarking is also being performed using data from Nike opacity experiments, and from equation of state experiments in ICFrelevant regimes. In this talk they present an overview of FAST and a comparison of simulation results with data from ongoing laboratory experiments

Numerical modelling of reflood processes
International Nuclear Information System (INIS)
Glynn, D.R.; Rhodes, N.; Tatchell, D.G.
19830101
The use of a detailed computer model to investigate the effects of grid size and the choice of walltofluid heattransfer correlations on the predictions obtained for reflooding of a vertical heated channel is described. The model employs equations for the momentum and enthalpy of vapour and liquid and hence accounts for both thermal nonequilibrium and slip between the phases. Empirical correlations are used to calculate interphase and walltofluid friction and heattransfer as functions of flow regime and local conditions. The empirical formulae have remained fixed with the exception of the walltofluid heattransfer correlations. These have been varied according to the practices adopted in other computer codes used to model reflood, namely REFLUX, RELAP and TRAC. Calculations have been performed to predict the CSNI standard problem number 7, and the results are compared with experiment. It is shown that the results are substantially gridindependent, and that the choice of correlation has a significant influence on the general flow behaviour, the rate of quenching and on the maximum cladding temperature predicted by the model. It is concluded that good predictions of reflooding rates can be obtained with particular correlation sets. (author)

Understanding Etna flank instability through numerical models
Science.gov (United States)
Apuani, Tiziana; Corazzato, Claudia; Merri, Andrea; Tibaldi, Alessandro
20130201
As many active volcanoes, Mount Etna shows clear evidence of flank instability, and different mechanisms were suggested to explain this flank dynamics, based on the recorded deformation pattern and character. Shallow and deep deformations, mainly associated with both eruptive and seismic events, are concentrated along recognised fracture and fault systems, mobilising the eastern and southeastern flank of the volcano. Several interacting causes were postulated to control the phenomenon, including gravity force, magma ascent along the feeding system, and a very complex local and/or regional tectonic activity. Nevertheless, the complexity of such dynamics is still an open subject of research and being the volcano flanks heavily urbanised, the comprehension of the gravitative dynamics is a major issue for public safety and civil protection. The present research explores the effects of the main geological features (in particular the role of the subetnean clays, interposed between the ApennineMaghrebian flysch and the volcanic products) and the role of weakness zones, identified by fracture and fault systems, on the slope instability process. The effects of magma intrusions are also investigated. The problem is addressed by integrating field data, laboratory tests and numerical modelling. A bi and tridimensional stressstrain analysis was performed by a finite difference numerical code (FLAC and FLAC3D), mainly aimed at evaluating the relationship among geological features, volcanotectonic structures and magmatic activity in controlling the deformation processes. The analyses are well supported by dedicated structuralmechanical field surveys, which allowed to estimate the rock mass strength and deformability parameters. To take into account the uncertainties which inevitably occur in a so complicated model, many efforts were done in performing a sensitivity analysis along a WNWESE section crossing the volcano summit and the Valle del Bove depression. This was

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study
Science.gov (United States)
Moriarty, Julia M.; Harris, Courtney K.; Fennel, Katja; Friedrichs, Marjorie A. M.; Xu, Kehui; Rabouille, Christophe
20170401
Observations indicate that resuspension and associated fluxes of organic material and porewater between the seabed and overlying water can alter biogeochemical dynamics in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabedwatercolumn interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; fluxes of this material between the seabed and the water column via erosion, deposition, and diffusion at the sedimentwater interface; and biogeochemical reactions within the seabed. A onedimensional version of HydroBioSed was then implemented for the Rhône subaqueous delta in France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a 2month period that included three resuspension events; also, the supply of organic matter, oxygen, and nutrients to the model was held constant in time. Consistent with time series observations from the Rhône Delta, model results showed that erosion increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabedwater interface. This enhanced supply of oxygen to the seabed, as well as resuspensioninduced increases in ammonium availability in surficial sediments, allowed seabed oxygen consumption to increase via nitrification. This increase in nitrification compensated for the decrease in seabed oxygen consumption due to aerobic remineralization that occurred as organic matter was entrained into the water

A numerical model of aerosol scavenging
International Nuclear Information System (INIS)
Bradley, M.M.; Molenkamp, C.R.
19911001
Using a threedimensional numerical cloud/smokeplume model, we have simulated the burning of a large, midlatitude city following a nuclear exchange. The model includes 18 dynamic and microphysical equations that predict the firedriven airflow, cloud processes, and smokecloud interactions. In the simulation, the intense heating from the burning city produces a firestorm with updraft velocities exceeding 60 m/s. Within 15 minutes of ignition, the smoke plume penetrates the tropopause. The updraft triggers a cumulonimbus cloud that produces significant quantities of ice, snow, and hail. These solid hydrometeors, as well as cloud droplets and rain, interact with the smoke particles from the fire. At the end of the onehour simulation, over 20% of the smoke is in slowly falling snowflakes. If the snow reaches the ground before the flakes completely sublimate (or melt and then evaporate), then only approximately 50% of the smoke will survive the scavenging processes and remain in the atmosphere to affect the global climate

Numerical Modelling of Seismic Slope Stability
Science.gov (United States)
Bourdeau, Céline; Havenith, HansBalder; Fleurisson, JeanAlain; Grandjean, Gilles
Earthquake groundmotions recorded worldwide have shown that many morphological and geological structures (topography, sedimentary basin) are prone to amplify the seismic shaking (San Fernando, 1971 [Davis and West 1973] Irpinia, 1980 [Del Pezzo et al. 1983]). This phenomenon, called site effects, was again recently observed in El Salvador when, on the 13th of January 2001, the country was struck by a M = 7.6 earthquake. Indeed, while horizontal accelerations on a rock site at Berlin, 80 km from the epicentre, did not exceed 0.23 g, they reached 0.6 g at Armenia, 110 km from the epicentre. Armenia is located on a small hill underlaid by a few meters thick pyroclastic deposits. Both the local topography and the presence of surface layers are likely to have caused the observed amplification effects, which are supposed to have contributed to the triggering of some of the hundreds of landslides related to this seismic event (Murphy et al. 2002). In order to better characterize the way site effects may influence the triggering of landslides along slopes, 2D numerical elastic and elastoplastic models were developed. Various geometrical, geological and seismic conditions were analysed and the dynamic behaviour of the slope under these con ditions was studied in terms of creation and location of a sliding surface. Preliminary results suggest that the size of modelled slope failures is dependent on site effects.

Numerical Modelling of the Dynamic Response of HighSpeed Railway Bridges Considering VehicleStructure and StructureSoilStructure Interaction
DEFF Research Database (Denmark)
Bucinskas, Paulius; Agapii, L.; Sneideris, J.
20150101
is idealized as a multidegreeoffreedom system, modelled with two layers of springdashpot suspension systems. Coupling the vehicle system and railway track is realized through interaction forces between the wheels and the rail, where the irregularities of the track are implemented as a random stationary......The aim of this paper is the dynamic analysis of a multisupport bridge structure exposed to highspeed railway traffic. The proposed computational model has a unified approach for simultaneously accounting for the bridge structure response, soil response and forces induced by the vehicle....... The bridge structure is modelled in three dimensions based on the finite element method using twonoded threedimensional beam elements. The track structure is composed of three layers: rail, sleepers and deck which are connected through springdashpot systems. The vehicle travelling along a bridge...

Recent advances in numerical modeling of detonations
Energy Technology Data Exchange (ETDEWEB)
Mader, C.L.
19861201
Three lectures were presented on recent advances in numerical modeling detonations entitled (1) Jet Initiation and Penetration of Explosives; (2) Explosive Desensitization by Preshocking; (3) Inert MetalLoaded Explosives.

A numerical reference model for themomechanical subduction
DEFF Research Database (Denmark)
Quinquis, Matthieu; Chemia, Zurab; Tosi, Nicola
20100101
Building an advanced numerical model of subduction requires choosing values for various geometrical parameters and material properties, among others, the initial lithosphere thicknesses, representative lithological types and their mechanical and thermal properties, rheologies, initial temperature...

Other relevant numerical modelling papers
International Nuclear Information System (INIS)
Chartier, M.
19890101
The ocean modelling is a rapidly evolving science and a large number of results have been published. Several categories of papers are of particular interest for this review: the papers published by the international atomic institutions, such as the NEA (for the CRESP or Subseabed Programs), the IAEA (for example the Safety Series, the Technical Report Series or the TECDOC), and the ICRP, and the papers concerned by more fundamental research, which are published in specific scientific literature. This paper aims to list some of the most relevant publications for the CRESP purposes. It means by no way to be exhaustive, but informative on the incontestable progress recently achieved in that field. One should note that some of these papers are so recent that their final version has not yet been published

Numerical models of groundwater flow and transport
International Nuclear Information System (INIS)
Konikow, L.F.
19960101
This chapter reviews the stateoftheart in deterministic modeling of groundwater flow and transport processes, which can be used for interpretation of isotope data through groundwater flow analyses. Numerical models which are available for this purpose are described and their applications to complex field problems are discussed. The theoretical bases of deterministic modeling are summarized, and advantages and limitations of numerical models are described. The selection of models for specific applications and their calibration procedures are described, and results of a few illustrative case study type applications are provided. (author). 145 refs, 17 figs, 2 tabs

Numerical models of groundwater flow and transport
Energy Technology Data Exchange (ETDEWEB)
Konikow, L F [Geological Survey, Reston, VA (United States)
19961001
This chapter reviews the stateoftheart in deterministic modeling of groundwater flow and transport processes, which can be used for interpretation of isotope data through groundwater flow analyses. Numerical models which are available for this purpose are described and their applications to complex field problems are discussed. The theoretical bases of deterministic modeling are summarized, and advantages and limitations of numerical models are described. The selection of models for specific applications and their calibration procedures are described, and results of a few illustrative case study type applications are provided. (author). 145 refs, 17 figs, 2 tabs.

Evaluation of Offshore Wind Turbine Tower Dynamics with Numerical Analysis
Directory of Open Access Journals (Sweden)
Begum Yurdanur Dagli
20180101
Full Text Available A dynamic behaviour of a cylindirical wind tower with variable cross section is investigated under environmental and earthquake forces. The ground acceleration term is represented by a simple cosine function to investigate both normal and parallel components of the earthquake motions located near ground surface. The function of earthquake force is simplified to apply Rayleigh’s energy method. Wind forces acting on above the water level and wave forces acting on below this level are utilized in computations considering earthquake effect for entire structure. The wind force is divided into two groups: the force acting on the tower and the forces acting on the rotor nacelle assembly (RNA. The drag and the inertial wave forces are calculated with water particle velocities and accelerations due to linear wave theory. The resulting hydrodynamic wave force on the tower in an unsteady viscous flow is determined using the Morison equation. The displacement function of the physical system in which dynamic analysis is performed by Rayleigh’s energy method is obtained by the single degree of freedom (SDOF model. The equation of motion is solved by the fourthorder Runge–Kutta method. The twoway FSI (fluidstructure interaction technique was used to determine the accuracy of the numerical analysis. The results of computational fluid dynamics and structural mechanics are coupled in FSI analysis by using ANSYS software. Timevarying lateral displacements and the first natural frequency values which are obtained from Rayleigh’s energy method and FSI technique are compared. The results are presented by graphs. It is observed from these graphs that the Rayleigh model can be an alternative way at the prelimanary stage of the structural analysis with acceptable accuracy.

Identification of the steel viscosity and dynamic yield stress for the numerical modelling of casting simulations in the semisolid state
Directory of Open Access Journals (Sweden)
Solek K.
20170301
Full Text Available Conditions of some casting processes cause flow of both liquid and semiliquid metal alloys inside the die cavity. Generally, the continuous casting, squeeze casting or thixoforming could be classified as such processes. Design or optimisation of casting technology using numerical simulations requires knowledge of the rheological properties. The main objective of the experimental work, presented in this publication, is an analysis of the viscosity of 1.2080 (X210Cr12 high carbon steel in liquid and semisolid state. The secondary purpose of the experimental work was a development of the viscosity models used in continuous casting and thixoforming simulations. The significant achievement of this particular study was identification of thixotropy phenomenon which occurs not only during thixoforming, but also during magnetohydrodynamic stirring in continuous casting processes.

Numerical 3D Modelling of Overflows
DEFF Research Database (Denmark)
Larsen, Torben; Nielsen, L.; Jensen, B.
20080101
dimensional socalled Volume of Fluid Models (VOFmodels) based on the full NavierStokes equations (named NS3 and developed by DHI Water & Environment) As a general conclusion, the two numerical models show excellent results when compared with measurements. However, considerable errors occur when...

A qualitative numerical study of high dimensional dynamical systems
Science.gov (United States)
Albers, David James
Since Poincare, the father of modern mathematical dynamical systems, much effort has been exerted to achieve a qualitative understanding of the physical world via a qualitative understanding of the functions we use to model the physical world. In this thesis, we construct a numerical framework suitable for a qualitative, statistical study of dynamical systems using the space of artificial neural networks. We analyze the dynamics along intervals in parameter space, separating the set of neural networks into roughly four regions: the fixed point to the first bifurcation; the route to chaos; the chaotic region; and a transition region between chaos and finitestate neural networks. The study is primarily with respect to highdimensional dynamical systems. We make the following general conclusions as the dimension of the dynamical system is increased: the probability of the first bifurcation being of type NeimarkSacker is greater than ninetypercent; the most probable route to chaos is via a cascade of bifurcations of highperiod periodic orbits, quasiperiodic orbits, and 2tori; there exists an interval of parameter space such that hyperbolicity is violated on a countable, Lebesgue measure 0, "increasingly dense" subset; chaos is much more likely to persist with respect to parameter perturbation in the chaotic region of parameter space as the dimension is increased; moreover, as the number of positive Lyapunov exponents is increased, the likelihood that any significant portion of these positive exponents can be perturbed away decreases with increasing dimension. The maximum KaplanYorke dimension and the maximum number of positive Lyapunov exponents increases linearly with dimension. The probability of a dynamical system being chaotic increases exponentially with dimension. The results with respect to the first bifurcation and the route to chaos comment on previous results of Newhouse, Ruelle, Takens, Broer, Chenciner, and Iooss. Moreover, results regarding the high

Tensor viscosity method for convection in numerical fluid dynamics
International Nuclear Information System (INIS)
Dukowicz, J.K.; Ramshaw, J.D.
19790101
A new method, called the tensor viscosity method, is described for differencing the convective terms in multidimensional numerical fluid dynamics. The method is the proper generalization to two or three dimensions of interpolated donor cell differencing in one dimension, and is designed to achieve numerical stability with minimal numerical damping. It is a singlestep method that is distinguished by simplicity and case of implementation, even in the case of an arbitrary nonrectangular mesh. It should therefore be useful in finiteelement as well as finitedifference formulations

Anthropogenic and volcanic emission impacts on SO2 dynamics and acid rain profiles. Numerical study using WRFChem in a highresolution modeling
Science.gov (United States)
Vela, A. V.; González, C. M.; Ynoue, R.; Rojas, N. Y.; Aristizábal, B. H.; Wahl, M.
20171201
Eulerian 3D chemistry transport models (CTM) have been widely used for the study of air quality in urban environments, becoming an essential tool for studying the impacts and dynamics of gases and aerosols on air quality. However, their use in Colombia is scarce, especially in mediumsized cities, which are experimenting a fast urban growth, increasing the risk associated with possible air pollution episodes. In the densely populated mediumsized Andean city of Manizales, Colombia  a city located on the western slopes of the central range of the Andes (urban population 368000; 2150 m.a.s.l), there is an influence of the active Nevado del Ruiz volcano, located 28 km to the southwest. This natural source emits daily gas and particle fluxes, which could influence the atmospheric chemistry of the city and neighboring towns. Hence, the zone presents a unique combination of anthropogenic and volcanic sulfur gas emissions, which affects SO2 dynamics in the urban area, influencing also in the formation of acid rain phenomenon in the city. Therefore, studies analyzing the relative contribution of anthropogenic and volcanic emission could contribute with a deep understanding about causes and dynamics of both acid rain phenomenon and ambient SO2 levels in Manizales. This work aimed to analyze the influence of anthropogenic (onroad vehicular and industrial pointsources) and volcanic sulfur emissions in SO2 atmospheric chemistry dynamics, evaluating its possible effects on acid rain profiles. Ambient SO2 levels and daynight rain samples were measured and used to analyze results obtained from the application of the fullycoupled online WRFChem model. Two highresolution simulations were performed during two dry and wet oneweek periods in 2015. Analysis of SO2 dispersion patterns and comparison with SO2 observations in the urban area were performed for three different scenarios in which natural and anthropogenic emissions were simulated separately. Results suggest that