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Sample records for 3d numerical dynamos

  1. Effects of a radially varying electrical conductivity on 3D numerical dynamos

    Gomez-Perez, Natalia; Wicht, Johannes; 10.1016/j.pepi.2010.03.006

    2010-01-01

    The transition from liquid metal to silicate rock in the cores of the terrestrial planets is likely to be accompanied by a gradient in the composition of the outer core liquid. The electrical conductivity of a volatile enriched liquid alloy can be substantially lower than a light-element-depleted fluid found close to the inner core boundary. In this paper, we investigate the effect of radially variable electrical conductivity on planetary dynamo action using an electrical conductivity that decreases exponentially as a function of radius. We find that numerical solutions with continuous, radially outward decreasing electrical conductivity profiles result in strongly modified flow and magnetic field dynamics, compared to solutions with homogeneous electrical conductivity. The force balances at the top of the simulated fluid determine the overall character of the flow. The relationship between Coriolis and Lorentz forces near the outer boundary controls the flow and magnetic field intensity and morphology of the...

  2. 3D Babcock-Leighton Solar Dynamo Models

    Miesch, Mark S.; Hazra, Gopal; Karak, Bidya Binay; Teweldebirhan, Kinfe; Upton, Lisa

    2016-05-01

    We present results from the new STABLE (Surface flux Transport and Babcock Leighton) Dynamo Model. STABLE is a 3D Babcock-Leighton/Flux Transport dynamo model in which the source of poloidal field is the explicit emergence, distortion, and dispersal of bipolar magnetic regions (BMRs). In this talk I will discuss initial results with axisymmetric flow fields, focusing on the operation of the model, the general features of the cyclic solutions, and the challenge of achieving supercritical dynamo solutions using only the Babcock-Leighton source term. Then I will present dynamo simulations that include 3D convective flow fields based on the observed velocity power spectrum inferred from photospheric Dopplergrams. I'll use these simulations to assess how the explicit transport and amplification of fields by surface convection influences the operation of the dynamo. I will also discuss the role of surface magnetic fields in regulating the subsurface toroidal flux budget.

  3. A 3D Babcock-Leighton Solar Dynamo Model

    Miesch, Mark S

    2014-01-01

    We present a 3D kinematic solar dynamo model in which poloidal field is generated by the emergence and dispersal of tilted sunspot pairs (more generally Bipolar Magnetic Regions, or BMRs). The axisymmetric component of this model functions similarly to previous 2D Babcock-Leighton (BL) dynamo models that employ a double-ring prescription for poloidal field generation but we generalize this prescription into a 3D flux emergence algorithm that places BMRs on the surface in response to the dynamo-generated toroidal field. In this way, the model can be regarded as a unification of BL dynamo models (2D in radius/latitude) and surface flux transport models (2D in latitude/longitude) into a more self-consistent framework that captures the full 3D structure of the evolving magnetic field. The model reproduces some basic features of the solar cycle including an 11-yr periodicity, equatorward migration of toroidal flux in the deep convection zone, and poleward propagation of poloidal flux at the surface. The poleward-p...

  4. Numerical dynamo action in cylindrical containers

    Nore, Caroline; Castanon Quiroz, Daniel; Guermond, Jean-Luc; Léorat, Jacques; Luddens, Francky

    2015-06-01

    The purpose of this paper is to present results from numerical simulations of dynamo action in relation with two magnetohydrodynamics (MHD) experiments using liquid sodium in cylindrical containers. The first one is the von Kármán sodium (VKS) experiment from Cadarache (France), the second one is a precession-driven dynamo experiment from the DREsden sodium facility for DYNamo and thermohydraulic studies (DRESDYN). Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek

  5. Numerical Simulations of Boundary-Driven Dynamos

    White, K.; Brummell, N.; Glatzmaier, G. A.

    2012-12-01

    An important topic of physics research is how magnetic fields are generated and maintained in the many astrophysical bodies where they are ubiquitously observed. Of particular interest, are reversals of magnetic fields of planets and stars, especially those of the Earth and the Sun. In an attempt to provide intuition on this problem, numerous physical dynamo experiments have been performed in different configurations. Recently, a tremendous breakthrough was made in the Von Karman sodium (VKS) experiments in France when the most realistic laboratory fluid dynamo to date was produced by driving an unconstrained flow in a cylinder of liquid sodium (Monchaux et al, 2007, PRL). One of the curiosities of the VKS experiment however is the effect of the composition of the impellers that drive the flow. Steel blades failed to produce a dynamo, but soft iron impellers, which have much higher magnetic permeability, succeeded. The role of the magnetic properties of the boundaries in boundary-driven dynamos is therefore clearly of interest. Kinematic and laminar numerical dynamo simulations (Giesecke et al, 2010, PRL & Gissinger et al, 2008 EPL) have shed some light but turbulent, nonlinear simulations are necessary. Roberts, Glatzmaier & Clune 2010 created a simplified model of the VKS setup by using three-dimensional numerical simulations in a spherical geometry with differential zonal motions of the boundary replacing the driving impellers of the VKS experiment. We have extended these numerical simulations further towards a more complete understanding of such boundary-forced dynamos. In particular, we have examined the effect of the magnetic boundary conditions - changes in the wall thickness, the magnetic permeability, and the electrical conductivity - on the mechanisms responsible for dynamo generation. Enhanced permeability, conductivity and wall thickness all help dynamo action to different degrees. We are further extending our investigations to asymmetric forcing to

  6. Polarity Reversals from Paleomagnetic Observations and Numerical Dynamo Simulations

    Amit, Hagay; Leonhardt, Roman; Wicht, Johannes

    2010-08-01

    Recent advances in the study of geomagnetic field reversals are reviewed. These include studies of the transitional field during the last geomagnetic reversal and the last geomagnetic excursion based on paleomagnetic observations, and analysis of reversals in self-consistent 3D numerical dynamo simulations. Field models inferred from observations estimate reversal duration in the range of 1-10 kyr (depending on site location). The transitional fields during both the Matuyama/Brunhes reversal and the Laschamp excursion are characterized by low-latitude reversed flux formation and subsequent poleward migration. During both events the dipole as well as the non-dipole field energies decrease. However, while the non-dipole energy dominates the dipole energy for a period of 2 kyr in the reversal, the non-dipole energy merely exceeds the dipole energy for a very brief period during the excursion. Numerical dynamo simulations show that stronger convection, slower rotation, and lower electrical conductivity provide more favorable conditions for reversals. A non-dimensional number that depends on the typical length scale of the flow and represents the relative importance of inertial effects, termed the local Rossby number, seems to determine whether a dynamo will reverse or not. Stable polarity periods in numerical dynamos may last about 1 Myr, whereas reversals may last about 10 kyr. Numerical dynamo reversals often involve prolonged dipole collapse followed by shorter directional instability of the dipole axis, with advective processes governing the field variation. Magnetic upwellings from the equatorial inner-core boundary that produce reversed flux patches at low-latitudes of the core-mantle boundary could be significant in triggering reversals. Inferences from the observational and modeling sides are compared. We summarize with an outlook on some open questions and future prospects.

  7. Numerical simulation of 3D breaking waves

    Fraunie, Philippe; Golay, Frederic

    2015-04-01

    Numerical methods dealing with two phase flows basically can be classified in two ways : the "interface tracking" methods when the two phases are resolved separately including boundary conditions fixed at the interface and the "interface capturing" methods when a single flow is considered with variable density. Physical and numerical properties of the two approaches are discussed, based on some numerical experiments performed concerning 3D breaking waves. Acknowledgements : This research was supported by the Modtercom program of Region PACA.

  8. Numerical simulation of Martian historical dynamo: Impact of the Rayleigh number on the dynamo state

    WANG TianYuan; KUANG WeiJia; MA ShiZhuang

    2009-01-01

    The observed Mars remnant magnetism suggests that there was an active dynamo in the Martian core.We use the MoSST core dynamics model to simulate the Martian historical dynamo,focusing on the variation of the dynamo states with the Rayleigh number Ra (a non-dimensional parameter describing the buoyancy force in the core).Our numerical results show that the mean field length scale does not vary monotonically with the Rayleigh number,and the field morphology at the core mantle boundary changes with Rayleigh number.In particular,it drifts westward with a speed decreasing with Rayleigh number.

  9. Cosmic dynamo analogue and decay of magnetic fields in 3D Ricci flows

    de Andrade, Garcia

    2009-01-01

    Magnetic curvature effects, investigated by Barrow and Tsagas (BT) [Phys Rev D \\textbf{77},(2008)],as a mechanism for magnetic field decay in open Friedmann universes (${\\Lambda}<0$), are applied to dynamo geometric Ricci flows in 3D curved substrate in laboratory. By simple derivation, a covariant three-dimensional magnetic self-induced equation, presence of these curvature effects, indicates that de Sitter cosmological constant (${\\Lambda}\\ge{0}$), leads to enhancement in the fast kinematic dynamo action which adds to stretching of plasma flows. From the magnetic growth rate, the strong shear case, anti-de Sitter case (${\\Lambda}<0$) BT magnetic decaying fields are possible while for weak shear, fast dynamos are possible. The self-induced equation in Ricci flows is similar to the equation derived by BT in $(3+1)$-spacetime continuum. Lyapunov-de Sitter metric is obtained from Ricci flow eigenvalue problem. In de Sitter analogue there is a decay rate of ${\\gamma}\\approx{-{\\Lambda}}\\approx{-10^{-35}s^{-...

  10. Numerical solution of 3D Stokes problems

    Preconditions conjugate gradient algorithms for solving 3D Stokes problems by stable piecewise discontinuous pressure finite elements are presented. The emphasis is on the preconditioning schemes and their numerical implementation for use with Hermitian-based discontinuous pressure elements. For the piecewise constant discontinuous pressure elements, a variant implementation of the preconditioner proposed by Cahouet and Chabard for the continuous pressure elements is employed. For the piecewise linear discontinuous pressure elements, a new preconditioner is presented. Numerical examples are presented for the cubic lid driven cavity problem with two representative elements (i.e., the Q2-P0 and the Q2-P1 brick elements). Numerical results show that the preconditioning schemes are very effective in reducing the number of pressure iterations at very reasonable costs. It is also shown that they are insensitive to the mesh Reynolds number, except for nearly steady flows (Rem → 0), and are almost independent of mesh sizes. It is demonstrated that the schemes performed reasonably well on nonuniform meshes. 15 refs., 6 figs., 1 tab

  11. Determining role of Krein signature for 3D Arnold tongues of oscillatory dynamos

    Kirillov, Oleg N; Stefani, Frank

    2008-01-01

    Using a homotopic family of boundary eigenvalue problems for the mean-field $\\alpha^2$-dynamo with helical turbulence parameter $\\alpha(r)=\\alpha_0+\\gamma\\Delta\\alpha(r)$ and homotopy parameter $\\beta \\in [0,1]$, we show that the underlying network of diabolical points for Dirichlet (idealized, $\\beta=0$) boundary conditions substantially determines the choreography of eigenvalues and thus the character of the dynamo instability for Robin (physically realistic, $\\beta=1$) boundary conditions. In the $(\\alpha_0,\\beta,\\gamma)-$space the Arnold tongues of oscillatory solutions at $\\beta=1$ end up at the diabolical points for $\\beta=0$. In the vicinity of the diabolical points the space orientation of the 3D tongues, which are cones in first-order approximation, is determined by the Krein signature of the modes involved in the diabolical crossings at the apexes of the cones. The Krein space induced geometry of the resonance zones explains the subtleties in finding $\\alpha$-profiles leading to spectral exceptional...

  12. Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers

    Iskakov, A B; Cowley, S C; McWilliams, J C; Proctor, M R E

    2007-01-01

    Direct numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic Reynolds number Rm>>1 and small magnetic Prandtl number Pm6000 compared to Rm_c~60 for Pm>1. Is is not as yet possible to determine numerically whether the growth rate of the magnetic energy is ~Rm^{1/2} in the limit Rm->infinity, as should be the case if the dynamo is driven by the inertial-range motions at the resistive scale.

  13. Numerical Simulations of Dynamos Generated in Spherical Couette Flows

    Guervilly, Céline; 10.1080/03091920903550955

    2010-01-01

    We numerically investigate the efficiency of a spherical Couette flow at generating a self-sustained magnetic field. No dynamo action occurs for axisymmetric flow while we always found a dynamo when non-axisymmetric hydrodynamical instabilities are excited. Without rotation of the outer sphere, typical critical magnetic Reynolds numbers $Rm_c$ are of the order of a few thousands. They increase as the mechanical forcing imposed by the inner core on the flow increases (Reynolds number $Re$). Namely, no dynamo is found if the magnetic Prandtl number $Pm=Rm/Re$ is less than a critical value $Pm_c\\sim 1$. Oscillating quadrupolar dynamos are present in the vicinity of the dynamo onset. Saturated magnetic fields obtained in supercritical regimes (either $Re>2 Re_c$ or $Pm>2Pm_c$) correspond to the equipartition between magnetic and kinetic energies. A global rotation of the system (Ekman numbers $E=10^{-3}, 10^{-4}$) yields to a slight decrease (factor 2) of the critical magnetic Prandtl number, but we find a peculi...

  14. Control volume method for hydromagnetic dynamos in rotating spherical shells: Testing the code against the numerical dynamo benchmark

    Šimkanin, Ján; Hejda, Pavel

    2009-01-01

    Roč. 53, č. 1 (2009), s. 99-110. ISSN 0039-3169 R&D Projects: GA AV ČR IAA300120704 Institutional research plan: CEZ:AV0Z30120515 Keywords : hydromagnetic dynamos * control volume method * numerical dynamo benchmark * efficiency of parallelization Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 1.000, year: 2009

  15. Radiative Transfer in 3D Numerical Simulations

    Stein, R; Stein, Robert; Nordlund, Aake

    2002-01-01

    We simulate convection near the solar surface, where the continuum optical depth is of order unity. Hence, to determine the radiative heating and cooling in the energy conservation equation, we must solve the radiative transfer equation (instead of using the diffusion or optically thin cooling approximations). A method efficient enough to calculate the radiation for thousands of time steps is needed. We assume LTE and a non-gray opacity grouped into 4 bins according to strength. We perform a formal solution of the Feautrier equation along a vertical and four straight, slanted, rays (at four azimuthal angles which are rotated 15 deg. every time step). We present details of our method. We also give some results: comparing simulated and observed line profiles for the Sun, showing the importance of 3D transfer for the structure of the mean atmosphere and the eigenfrequencies of p-modes, illustrating Stokes profiles for micropores, and analyzing the effect of radiation on p-mode asymmetries.

  16. Numerical 3-D Modelling of Overflows

    Larsen, Torben; Nielsen, L.; Jensen, B.; Christensen, E. D.

    2008-01-01

    -dimensional so-called Volume of Fluid Models (VOF-models) based on the full Navier-Stokes 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......The present study uses laboratory experiments to evaluate the reliability of two types of numerical models of sewers systems: - 1-dimensional model based on the extended Saint-Venant equation including the term for curvature of the water surface (the so-called Boussinesq approximation) - 2- and 3...

  17. Numerical experiments on dynamo action in sheared and rotating turbulence

    Yousef, T A; Rincon, F; Schekochihin, A A; Kleeorin, N; Rogachevskii, I; Cowley, S C; McWilliams, J C

    2008-01-01

    Numerical simulations of forced turbulence in elongated shearing boxes are carried out to demonstrate that a nonhelical turbulence in conjunction with a linear shear can give rise to a mean-field dynamo. Exponential growth of magnetic field at scales larger than the outer (forcing) scale of the turbulence is found. Over a range of values of the shearing rate S spanning approximately two orders of magnitude, the growth rate of the magnetic field is proportional to the imposed shear, gamma ~ S, while the characteristic spatial scale of the field is l_b ~ S^(-1/2). The effect is quite general: earlier results for the nonrotating case by Yousef et al. 2008 (PRL 100, 184501) are extended to shearing boxes with Keplerian rotation; it is also shown that the shear dynamo mechanism operates both below and above the threshold for the fluctuation dynamo. The apparently generic nature of the shear dynamo effect makes it an attractive object of study for the purpose of understanding thegeneration of magnetic fields in ast...

  18. Dipole collapse and reversal precursors in a numerical dynamo

    Olson, Peter; Driscoll, Peter; Amit, Hagay

    2009-03-01

    Precursors to extreme geomagnetic field changes are examined in a numerical dynamo with a reversing dipolar magnetic field. A dynamo model with compositional convection in a rotating spherical shell produces a strongly dipolar external magnetic field over 6 Myr of simulated paleomagnetic time, with stable polarity epochs and occasional dipole collapses, some of which result in polarity reversals or dipole axis excursions. We analyze the model behavior during two dipole collapses, one that leads to a polarity reversal and one that does not, focusing on observable precursors. Reversed magnetic field induced in the dynamo interior by intermittent convective variability is the primary cause of dipole collapse. Spots of reversed magnetic flux emerge on the outer boundary at an early stage, then re-emerge with greater intensity at the height of the collapse. The energy in the external field cascades to higher harmonics as these reversed patches appear. Butterfly diagrams showing the reversed and normal flux contributions to the axial dipole reveal poleward migration of the patches during dipole collapse. Axial dipole reduction by precursory reversed flux is several times larger in the reversing case, compared to the non-reversing case. A butterfly diagram of the geomagnetic field since 1840 shows high latitude reversed flux emerging on the core-mantle boundary. Although the reversed geomagnetic flux is presently too weak to be labeled a reversal precursor, it is consistent with early stage dipole collapse in the dynamo model.

  19. 3D numerical design of tunnel hood

    Uystepruyst, David; Monnoyer, François

    2015-01-01

    This paper relates to the parametric study of tunnel hoods in order to reduce the shape, i.e the temporal gradient, of the pressure wave generated by the entry of a High speed train in tunnel. This is achieved by using an in-house three-dimensional numerical solver which solves the Eulerian equations on a Cartesian and unstructured mesh. The efficiency of the numerical methodology is demonstrated through comparisons with both experimental data and empirical formula. For the tunnel hood design, three parameters, that can influence the wave shape, are considered: the shape, the section and the length of the hood. The numerical results show, (i) that a constant section hood is the most efficient shape when compared to progressive (elliptic or conical) section hoods, (ii) an optimal ratio between hood's section and tunnel section where the temporal gradient of the pressure wave can be reduced by half, (iii) a significant efficiency of the hood's length in the range of 2 to 8 times the length of the train nose. Fi...

  20. 3 D Numerical Field Analysis at NAC

    The NAC [1] was established in 1977 as a multi-disciplinary research centre to provide particle beams for basic and applied physics research, for advanced particle radiotherapy and for supplying accelerator-produced radioisotopes for nuclear medicine and research. The finite differences computer programs VEPO 2 and POFEL 3 were developed from the early 1970's over more than one decade for electromagnetic field analysis at NAC[2]. They were successfully used in the design of the sector magnets of our 200 MeV separated-sector cyclotron [3]. In the late 80's NAC implemented the more user-friendly software package Poisson/Super Fish [4], for two-dimensional numerical field analysis

  1. Numerical studies of dynamo action in a turbulent shear flow

    Singh, Nishant K

    2013-01-01

    We perform numerical experiments to study the shear dynamo problem where we look for the growth of large-scale magnetic field due to non-helical stirring at small scales in a background linear shear flow, in previously unexplored parameter regimes. We demonstrate the large-scale dynamo action in the limit when the fluid Reynolds number (Re) is below unity whereas the magnetic Reynolds number (Rem) is above unity; the exponential growth rate scales linearly with shear, which is consistent with earlier numerical works. The limit of low Re is particularly interesting, as seeing the dynamo action in this limit would provide enough motivation for further theoretical investigations, which may focus the attention to this analytically more tractable limit of Re 1. We also perform simulations in the limits when, (i) both (Re, Rem) 1 & Rem < 1, and compute all components of the turbulent transport coefficients (\\alpha_{ij} and \\eta_{ij}) using the test-field method. A reasonably good agreement is seen between ...

  2. Numerical Relativity Towards Simulations of 3D Black Hole Coalescence

    Seidel, E

    1998-01-01

    I review recent developments in numerical relativity, focussing on progress made in 3D black hole evolution. Progress in development of black hole initial data, apparent horizon boundary conditions, adaptive mesh refinement, and characteristic evolution is highlighted, as well as full 3D simulations of colliding and distorted black holes. For true 3D distorted holes, with Cauchy evolution techniques, it is now possible to extract highly accurate, nonaxisymmetric waveforms from fully nonlinear simulations, which are verified by comparison to pertubration theory, and with characteristic techniques extremely long term evolutions of 3D black holes are now possible. I also discuss a new code designed for 3D numerical relativity, called Cactus, that will be made public.

  3. Numerical analysis of 3-D potential flow in centrifugal turbomachines

    Daiguji, H.

    1983-09-01

    A numerical method is developed for analysing a three-dimensional steady incompressible potential flow through an impeller in centrifugal turbomachines. The method is the same as the previous method which was developed for the axial flow turbomachines, except for some treatments in the downstream region. In order to clarify the validity and limitation of the method, a comparison with the existing experimental data and numerical results is made for radial flow compressor impellers. The calculated blade surface pressure distributions almost coincide with the quasi-3-D calculation by Krimerman and Adler (1978), but are different partly from the quasi-3-D calculation using one meridional flow analysis. It is suggested from this comparison that the flow through an impeller with high efficiency near the design point can be predicted by this fully 3-D numerical method.

  4. Solar dynamo models with alpha-effect and turbulent pumping from local 3D convection calculations

    Käpylä, P J; Tuominen, I

    2006-01-01

    (abridged) Results from kinematic solar dynamo models employing alpha-effect and turbulent pumping from local convection calculations are presented. We estimate the magnitude of these effects to be around 2-3 m/s. The rotation profile of the Sun as obtained from helioseismology is applied. We obtain an estimate of the ratio of the two induction effects, C_alpha/C_Omega \\approx 10^-3, which we keep fixed in all models. We also include a one-cell meridional circulation pattern having a magnitude of 10-20 m/s near the surface and 1-2 m/s at the bottom of the convection zone. The model essentially represents a distributed turbulent dynamo, as the alpha-effect is nonzero throughout the convection zone, although it concentrates near the bottom of the convection zone obtaining a maximum around 30 degrees of latitude. Turbulent pumping of the mean fields is predominantly down- and equatorward. We find that, when all these effects are included in the model, it is possible to correctly reproduce many features of the so...

  5. Numerical modeling of wave processes in 3D fractured media

    Golubev V.; Petrov I.

    2014-01-01

    Seismic response from the cluster of vertical oriented cracks is simulated using grid-characteristic method on parallelepiped structured meshes. Synthetic seismograms and wave fields are calculated. The structure of the response including dependency on type of saturator (gas, fluid) is analyzed. Numerical experiments showed the effect of high-frequency daisy-chain wave’s generation from 3D periodic structures.

  6. Finding Apparent Horizons in Dynamic 3D Numerical Spacetimes

    Anninos, P.; Camarda, K.; Libson, J.; Masso, J.; Seidel, E; Suen, W.

    1996-01-01

    We have developed a general method for finding apparent horizons in 3D numerical relativity. Instead of solving for the partial differential equation describing the location of the apparent horizons, we expand the closed 2D surfaces in terms of symmetric trace--free tensors and solve for the expansion coefficients using a minimization procedure. Our method is applied to a number of different spacetimes, including numerically constructed spacetimes containing highly distorted axisymmetric blac...

  7. Direct numerical simulation of 3D transitional fluid flows

    Full text: For the numerical simulation of the 2D-3D transitional homogeneous and stratified incompressible viscous fluid flows, characterizing by the full Navier-Stokes equations, the splitting on physical factors method is used. The explicit hybrid finite difference scheme of the method has the following behaviors: the second order of accuracy in space, minimum scheme viscosity and dispersion, workable in wide range of Reynolds and Froude numbers and monotonicity. The efficiency of the developed numerical method and the advanced performance of the supercomputers allowed simulating 2D-3D transitional uncompressible viscous fluid flows around the bluff bodies in particular around a cylinder. By the numerical simulation of the fluid flows around 3D circular cylinder it was found that the transition to 3D regime arrives at Re>200. At 200< Re<300 the mode A with wavelength 3.5 d<λ<4.0 d (where d is the diameter of the cylinder) for 3D structures along the axis of a cylinder was observed. At 300< Re<400 the mode B with wavelength 0.8 d<λ<0.9 d was observed. At Re=300 the both modes A and B were observed simultaneously. The regime with large dislocations previously discovered experimentally was first obtained numerically at 210< Re<260. This regime is characterized by flow phase dislocation along the axis of the cylinder and as the effect by the amplitude fall of the lift force coefficient and the variations in the drag coefficient. There was simulated numerically the initiation of the attached internal waves behind the circular cylinder and upstream disturbance area at low Froude and moderate Reynolds numbers. (author)

  8. 3-D MHD Numerical Simulations of Cloud-Wind Interactions

    Gregori, G.; Miniati, Francesco; Ryu, Dongsu; Jones, T. W.

    2000-01-01

    We present results from three-dimensional (3-D) numerical simulations investigating the magnetohydrodynamics of cloud-wind interactions. The initial cloud is spherical while the magnetic field is uniform and transverse to the cloud motion. A simplified analytical model that describes the magnetic energy evolution in front of the cloud is developed and compared with simulation results. In addition, it is found the interaction of the cloud with a magnetized interstellar medium (ISM) results in ...

  9. Magnetic field stretching at the top of the shell of numerical dynamos

    Peña, Diego; Amit, Hagay; Pinheiro, Katia J.

    2016-05-01

    The process of magnetic field stretching transfers kinetic energy to magnetic energy and by that maintains dynamos against Ohmic dissipation. Stretching at the top of the outer core may play an important role at specific regions. High-latitude intense magnetic flux patches may be concentrated by flow convergence. Reversed flux patches may emerge due to expulsion of toroidal field advected to the core-mantle boundary by fluid upwelling. Here we analyze snapshots from self-consistent 3D numerical dynamos to unravel the nature of field-flow interactions that induces stretching secular variation at the top of the core. We find that stretching at the top of the shell has a significant influence on the secular variation despite the relatively weak poloidal flow. In addition, locally stretching is often more effective than advection in particular at regions of significant field-aligned flow. Magnetic flux patches are concentrated by fluid downwelling and dispersed by fluid upwelling. Stretching is more efficient than advection in intensifying magnetic flux patches. Both stretching and the poloidal flow mostly depend on the magnetic Prandtl number Pm. Decreasing Pm gives smaller poloidal flow but stronger stretching. Accounting for field-flow interactions in both the advection and stretching terms suggests that the magnetic Reynolds number overestimates the actual ratio of magnetic advection to diffusion by ˜50 %. Morphological resemblance between local stretching in our dynamo models and local observed geomagnetic secular variation may suggest the presence of stretching at the top of the Earth's core. Our results shed light on the kinematic origin of intense geomagnetic flux patches and may have implications to the convective state of the upper outer core.

  10. Using 3-D Numerical Weather Data in Piloted Simulations

    Daniels, Taumi S.

    2016-01-01

    This report describes the process of acquiring and using 3-D numerical model weather data sets in NASA Langley's Research Flight Deck (RFD). A set of software tools implement the process and can be used for other purposes as well. Given time and location information of a weather phenomenon of interest, the user can download associated numerical weather model data. These data are created by the National Oceanic and Atmospheric Administration (NOAA) High Resolution Rapid Refresh (HRRR) model, and are then processed using a set of Mathworks' Matlab(TradeMark) scripts to create the usable 3-D weather data sets. Each data set includes radar re ectivity, water vapor, component winds, temperature, supercooled liquid water, turbulence, pressure, altitude, land elevation, relative humidity, and water phases. An open-source data processing program, wgrib2, is available from NOAA online, and is used along with Matlab scripts. These scripts are described with sucient detail to make future modi cations. These software tools have been used to generate 3-D weather data for various RFD experiments.

  11. Numerical Investigation of 3D Flow Around Two Tandem Cylinders

    Kalvig, Ragnhild Birgitte Hidle

    2015-01-01

    Circular cylinders in tandem arrangement are used in many marine applications like dual pipelines and dual risers. Turbulent flow in 3D around two tandem cylinders is simulated numerically using Large Eddy Simulation (LES) with a Smagorinsky subgrid scale model. The Reynolds number based on the cylinder diameter of 1 meter and free stream velocity of $U=1.31$ m/s is 13100, which is in the subcritical flow regime. The center-to-center spacing between the cylinders is $S/D=5$. The software used...

  12. 3D numerical simulation and analysis of railgun gouging mechanism

    Jin-guo Wu

    2016-04-01

    Full Text Available A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the rail gouging phenomenon. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface, obliquely extruded into the rail when accelerating the armature to a high velocity, can produce gouging. Both controlling the bulge size to a certain range and selecting suitable materials for rail surface coating will suppress the formation of gouging. The numerical simulation had a good agreement with experiments, which validated the computing model and methodology are reliable.

  13. Evolutions in 3D numerical relativity using fixed mesh refinement

    Schnetter, E; Hawke, I; Schnetter, Erik; Hawley, Scott H.; Hawke, Ian

    2004-01-01

    We present results of 3D numerical simulations using a finite difference code featuring fixed mesh refinement (FMR), in which a subset of the computational domain is refined in space and time. We apply this code to a series of test cases including a robust stability test, a nonlinear gauge wave and an excised Schwarzschild black hole in an evolving gauge. We find that the mesh refinement results are comparable in accuracy, stability and convergence to unigrid simulations with the same effective resolution. At the same time, the use of FMR reduces the computational resources needed to obtain a given accuracy. Particular care must be taken at the interfaces between coarse and fine grids to avoid a loss of convergence at high resolutions. This FMR system, "Carpet", is a driver module in the freely available Cactus computational infrastructure, and is able to endow existing Cactus simulation modules ("thorns") with FMR with little or no extra effort.

  14. Towards an experimental von Karman dynamo: numerical studies for an optimized design

    Ravelet, Florent; Chiffaudel, Arnaud; Daviaud, François; Léorat, Jacques

    2004-01-01

    Numerical studies of a kinematic dynamo based on von Karman type flows between two counterrotating disks in a finite cylinder are reported. The flow has been optimized using a water model experiment, varying the driving impellers configuration. A solution leading to dynamo action for the mean flow has been found. This solution may be achieved in VKS2, the new sodium experiment to be performed in Cadarache, France. The optimization process is described and discussed, then the effects of adding...

  15. Numerical simulations of current generation and dynamo excitation in a mechanically-forced, turbulent flow

    Bayliss, R A; Nornberg, M D; Terry, P W

    2006-01-01

    The role of turbulence in current generation and self-excitation of magnetic fields has been studied in the geometry of a mechanically driven, spherical dynamo experiment, using a three dimensional numerical computation. A simple impeller model drives a flow which can generate a growing magnetic field, depending upon the magnetic Reynolds number, Rm, and the fluid Reynolds number. When the flow is laminar, the dynamo transition is governed by a simple threshold in Rm, above which a growing magnetic eigenmode is observed. The eigenmode is primarily a dipole field tranverse to axis of symmetry of the flow. In saturation the Lorentz force slows the flow such that the magnetic eigenmode becomes marginally stable. For turbulent flow, the dynamo eigenmode is suppressed. The mechanism of suppression is due to a combination of a time varying large-scale field and the presence of fluctuation driven currents which effectively enhance the magnetic diffusivity. For higher Rm a dynamo reappears, however the structure of t...

  16. 3-D NUMERICAL SIMULATIONS OF FLOW LOSS IN HELICAL CHANNEL

    ZHAO Ling-zhi; PENG Yan; LU Fang; LI Jian; LI Ran; LIU Bao-lin

    2012-01-01

    The flow loss of a helical channel Magnetohydrodynamic (MHD) thruster without MHD effect was numerically studied with 3-D simulations,and a flow loss coefficient ξ was defined to quantify the flow loss and its influencing factors were studied.The results show that ξ decreases in a first-order exponential manner with the pitch of a helical wall and the Reynolds number,and it declines slowly when t / T > 0.2 and Re > 105,a flow guide makes the flow more smooth and uniform,especially in the flow guide and helical wall sub-regions and thus reduces the flow loss greatly,by about 30% with the averaged value of ξ from 0.0385to 0.027,a rectifier weakens the helical flow and strengthens the axial one in the rectifier and outlet sub-regions,thus reduces the rotational kinetic pressure with the averaged value of ξ declining about 4% from 0.0385 to 0.037,and ξ decreases with a rectifier's axial length when Re > 105.

  17. Evolutions in 3D numerical relativity using fixed mesh refinement

    We present results of 3D numerical simulations using a finite difference code featuring fixed mesh refinement (FMR), in which a subset of the computational domain is refined in space and time. We apply this code to a series of test cases including a robust stability test, a nonlinear gauge wave and an excised Schwarzschild black hole in an evolving gauge. We find that the mesh refinement results are comparable in accuracy, stability and convergence to unigrid simulations with the same effective resolution. At the same time, the use of FMR reduces the computational resources needed to obtain a given accuracy. Particular care must be taken at the interfaces between coarse and fine grids to avoid a loss of convergence at higher resolutions, and we introduce the use of 'buffer zones' as one resolution of this issue. We also introduce a new method for initial data generation, which enables higher order interpolation in time even from the initial time slice. This FMR system, 'Carpet', is a driver module in the freely available Cactus computational infrastructure, and is able to endow generic existing Cactus simulation modules ('thorns') with FMR with little or no extra effort

  18. 3-D MHD Numerical Simulations of Cloud-Wind Interactions

    Gregori, G; Ryu, D; Jones, T W; Miniati, Francesco; Ryu, Dongsu

    2000-01-01

    We present results from three-dimensional (3-D) numerical simulations investigating the magnetohydrodynamics of cloud-wind interactions. The initial cloud is spherical while the magnetic field is uniform and transverse to the cloud motion. A simplified analytical model that describes the magnetic energy evolution in front of the cloud is developed and compared with simulation results. In addition, it is found the interaction of the cloud with a magnetized interstellar medium (ISM) results in the formation of a highly structured magnetotail. The magnetic flux in the wake of the cloud organizes into flux ropes and a reconnection, current sheet is developed, as field lines of opposite polarity are brought close together near the symmetry axis. At the same time, magnetic pressure is strongly enhanced at the leading edge of the cloud from the stretching of the field lines that occurs there. This has an important dynamical effect on the subsequent evolution of the cloud, since some unstable modes tend to be strongl...

  19. 3D numerical modeling of India-Asia-like collision

    -Erika Püsök, Adina; Kaus, Boris; Popov, Anton

    2013-04-01

    above a strong mantle lithosphere - the jelly sandwich model (Burov and Watts, 2006). 3D models are thus needed to investigate these hypotheses. However, fully 3D models of the dynamics of continent collision zones have only been developed very recently, and presently most research groups have relied on certain explicit assumptions for their codes. Here, we employ the parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model), with a finite difference staggered grid solver, which is capable of simulating lithospheric deformation while simultaneously taking mantle flow and a free surface into account. We here report on first lithospheric and upper-mantle scale simulations in which the Indian lithosphere is indented into Asia. Acknowledgements. Funding was provided by the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830. Numerical computations have been performed on JUQUEEN of the Jülich high-performance computing center. • Beaumont, C., Jamieson, R.A., Nguyen, M.H., Medvedev, S.E., 2004. Crustal channel flows: 1. Numerical models with applications to the tectonics of the Himalayan-Tibetan orogeny. J. Geophys. Res. 109, B06406. • Burov, E. & Watts, W.S., 2006. The long-term strength of continental lithosphere: "jelly sandwich" or "crème brûlée"?. GSA Today, 16, doi: 10.1130/1052-5173(2006)10161132.1130.CO;1132. • England P., Houseman, G., 1986. Finite strain calculations of continental deformation. 2. Comparison with the India-Asia collision zone. J. Geophys. Res.- Solid Earth and Planets 91 (B3), 3664-3676. • Jackson, J., 2002. Strength of the continental lithosphere: time to abandon the jelly sandwich?. GSA Today, September, 4-10. • Lechmann, S.M., May, D.A., Kaus, B.J.P., Schmalholz, S.M., 2011. Comparing thin-sheet models with 3D multilayer models for continental collision. Geophy. Int. J. doi: 10.1111/j.1365-246X.2011.05164.x • Royden, L.H., Burchfiel, B.C., King, R

  20. 3-D numerical modelling of flow around a groin

    Miller, R.; Roulund, A.; Sumer, B. Mutlu;

    2003-01-01

    A 3-D flow code, EllipSys3D, has been implemented to simulate the 3-D flow around a groin in steady current. The k  turbulence model has been used for closure. Two kinds of groins are considered: (1) A vertical-wall groin, and (2) A groin with a side slope. Steady-flow simulations were conducted....... The paper reports early results of the investigation. The simulations capture main features of the flow around the groin. The horseshoe vortex in front of the vertical-wall groin is resolved. The vortex shedding at the head is not resolved because no transient flow simulations have been conducted at...

  1. Numerical modelling of 3D woven preform deformations

    Green, S D; Long, A.C.; El Said, B. S. F.; Hallett, S. R.

    2014-01-01

    In order to accurately predict the performance of 3D woven composites, it is necessary that realistic textile geometry is considered, since failure typically initiates at regions of high deformation or resin pockets. This paper presents the development of a finite element model based on the multi-chain digital element technique, as applied to simulate weaving and compaction of an orthogonal 3D woven composite. The model was reduced to the scale of the unit cell facilitating high fidelity resu...

  2. 3D Printing device adaptable to Computer Numerical Control (CNC)

    Gardan, Julien; DANESI, Frédéric; Roucoules, Lionel; Schneider, A

    2014-01-01

    This article presents the development of a 3D printing device for the additive manufacturing adapted to a CNC machining. The application involves the integration of a specific printing head. Additive manufacturing technology is most commonly used for modeling, prototyping, tooling through an exclusive machine or 3D printer. A global review and analysis of technologies show the additive manufacturing presents little independent solutions [6][9]. The problem studied especially the additive manu...

  3. Numerical Results of 3-D Modeling of Moon Accumulation

    Khachay, Yurie; Anfilogov, Vsevolod; Antipin, Alexandr

    2014-05-01

    For the last time for the model of the Moon usually had been used the model of mega impact in which the forming of the Earth and its sputnik had been the consequence of the Earth's collision with the body of Mercurial mass. But all dynamical models of the Earth's accumulation and the estimations after the Pb-Pb system, lead to the conclusion that the duration of the planet accumulation was about 1 milliard years. But isotopic results after the W-Hf system testify about a very early (5-10) million years, dividing of the geochemical reservoirs of the core and mantle. In [1,2] it is shown, that the account of energy dissipating by the decay of short living radioactive elements and first of all Al26,it is sufficient for heating even small bodies with dimensions about (50-100) km up to the iron melting temperature and can be realized a principal new differentiation mechanism. The inner parts of the melted preplanets can join and they are mainly of iron content, but the cold silicate fragments return to the supply zone and additionally change the content of Moon forming to silicates. Only after the increasing of the gravitational radius of the Earth, the growing area of the future Earth's core can save also the silicate envelope fragments [3]. For understanding the further system Earth-Moon evolution it is significant to trace the origin and evolution of heterogeneities, which occur on its accumulation stage.In that paper we are modeling the changing of temperature,pressure,velocity of matter flowing in a block of 3d spherical body with a growing radius. The boundary problem is solved by the finite-difference method for the system of equations, which include equations which describe the process of accumulation, the Safronov equation, the equation of impulse balance, equation Navier-Stocks, equation for above litho static pressure and heat conductivity in velocity-pressure variables using the Businesque approach.The numerical algorithm of the problem solution in velocity

  4. Towards a von Karman dynamo: numerical studies based on experimental flows

    Ravelet, F; Daviaud, F; Leorat, J; Chiffaudel, Arnaud; Daviaud, Francois; Leorat, Jacques; Ravelet, Florent; ccsd-00003337, ccsd

    2004-01-01

    Numerical studies of a kinematic dynamo based on von K{\\'a}rm{\\'a}n type flows between two counterrotating disks in a finite cylinder are reported. The flow has been optimized using a water model experiment, varying the driving impellers configuration. A solution leading to dynamo action for the mean flow has been found. This solution may be achieved in VKS2, the new sodium experiment to be performed in Cadarache, France. The optimization process is briefly described and discussed, then the effects of adding a stationary conducting layer around the flow on the threshold, on the shape of the neutral mode and on the magnetic energy balance are studied. Finally, the possible processes involved into kinematic dynamo action in a von Karman flow are reviewed and discussed. Among the possible processes we highlight the joint effect of the boundary-layer radial velocity shear and of the Ohmic dissipation localized at the flow/outer-shell boundary.

  5. Numerical Results of Earth's Core Accumulation 3-D Modelling

    Khachay, Yurie; Anfilogov, Vsevolod

    2013-04-01

    For a long time as a most convenient had been the model of mega impact in which the early forming of the Earth's core and mantle had been the consequence of formed protoplanet collision with the body of Mercurial mass. But all dynamical models of the Earth's accumulation and the estimations after the Pb-Pb system, lead to the conclusion that the duration of the planet accumulation was about 1 milliard years. But isotopic results after the W-Hf system testify about a very early (5-10) million years, dividing of the geochemical reservoirs of the core and mantle. In [1,3] it is shown, that the account of energy dissipating by the decay of short living radioactive elements and first of all Al,it is sufficient for heating even small bodies with dimensions about (50-100) km up to the iron melting temperature and can be realized a principal new differentiation mechanism. The inner parts of the melted preplanets can join and they are mainly of iron content, but the cold silicate fragments return to the supply zone. Only after the increasing of the gravitational radius, the growing area of the future core can save also the silicate envelope fragments. All existing dynamical accumulation models are constructed by using a spherical-symmetrical model. Hence for understanding the further planet evolution it is significant to trace the origin and evolution of heterogeneities, which occur on the planet accumulation stage. In that paper we are modeling distributions of temperature, pressure, velocity of matter flowing in a block of 3D- spherical body with a growing radius. The boundary problem is solved by the finite-difference method for the system of equations, which include equations which describe the process of accumulation, the Safronov equation, the equation of impulse balance, equation Navier-Stocks, equation for above litho static pressure and heat conductivity in velocity-pressure variables using the Businesque approach. The numerical algorithm of the problem solution in

  6. 3-D numerical modeling of methane hydrate deposits

    Pinero, Elena; W. Rottke; Fuchs, T.; Hensen, Christian; Haeckel, Matthias; Wallmann, Klaus

    2011-01-01

    Within the German gas hydrate initiative SUGAR, we have developed a new tool for predicting the formation of sub-seafloor gas hydrate deposits. For this purpose, a new 2D/3D module simulating the biogenic generation of methane from organic material and the formation of gas hydrates has been added to the petroleum systems modeling software package PetroMod®. T ypically, PetroMod® simulates the thermogenic generation of multiple hydrocarbon components including oil and gas, their migration t...

  7. Simulation of Fully Nonlinear 3-D Numerical Wave Tank

    张晓兔; 滕斌; 宁德志

    2004-01-01

    A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order boundary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.

  8. Numerical study of 3-D constraint effects in ferritic steels

    The presentation reviews the results of a numerical investigation, in which single-edge cracked bars in three point bend SE(B) specimens, with different relative crack lengths and thickness, were systematically studied via detailed three-dimensional finite element analyses

  9. 3D numerical modeling of YSO accretion shocks

    Matsakos T.

    2014-01-01

    Full Text Available The dynamics of YSO accretion shocks is determined by radiative processes as well as the strength and structure of the magnetic field. A quasi-periodic emission signature is theoretically expected to be observed, but observations do not confirm any such pattern. In this work, we assume a uniform background field, in the regime of optically thin energy losses, and we study the multi-dimensional shock evolution in the presence of perturbations, i.e. clumps in the stream and an acoustic energy flux flowing at the base of the chromosphere. We perform 3D MHD simulations using the PLUTO code, modelling locally the impact of the infalling gas onto the chromosphere. We find that the structure and dynamics of the post-shock region is strongly dependent on the plasma-beta (thermal over magnetic pressure, different values of which may give distinguishable emission signatures, relevant for observations. In particular, a strong magnetic field effectively confines the plasma inside its flux tubes and leads to the formation of quasi-independent fibrils. The fibrils may oscillate out of phase and hence the sum of their contributions in the emission results in a smooth overall profile. On the contrary, a weak magnetic field is not found to have any significant effect on the shocked plasma and the turbulent hot slab that forms is found to retain its periodic signature.

  10. 3-D Numerical Simulations of Twisted Stacked Tape Cables

    Krüger, Philipp A. C.; Zermeño, Victor M. R.; Takayasu, Makoto; Grilli, Francesco

    2014-01-01

    Different magnet applications require compact high current cables. Among the proposed solutions, the Twisted Stacked Tape Cable (TSTC) is easy to manufacture and has very high tape length usage efficiency. In this kind of cables the tapes are closely packed, so that their electromagnetic interaction is very strong and determines the overall performance of the cable. Numerical models are necessary tools to precisely evaluate this interaction and to predict the cable's behavior, e.g. in terms o...

  11. Gravitational collapse of gravitational waves in 3D numerical relativity.

    Alcubierre, M.; Allen, G; Brügmann, B.; Lanfermann, G.; Seidel, E; Suen, W; Tobias, M

    2000-01-01

    We demonstrate that evolutions of three-dimensional, strongly non-linear gravitational waves can be followed in numerical relativity, hence allowing many interesting studies of both fundamental and observational consequences. We study the evolution of time-symmetric, axisymmetric and non-axisymmetric Brill waves, including waves so strong that they collapse to form black holes under their own self-gravity. An estimate for the critical amplitude for black hole formation in a particular interpo...

  12. Numerical simulation of 3D flows in atmospheric boundary layer

    Šimonek, Jiří; Kozel, K.; Jaňour, Zbyněk

    Praha : Ústav termomechaniky AV ČR, v. v. i, 2012 - (Šimurda, D.; Kozel, K.), s. 93-96 ISBN 978-80-87012-40-6. [Topical Problems of Fluid Mechanics 2012 . Praha (CZ), 15.02. 2012 -17.02. 2012 ] R&D Projects: GA ČR GAP101/12/1271 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical solution * atmospheric boundary layer * Navier-Stokes equation s Subject RIV: DG - Athmosphere Sciences, Meteorology

  13. NUMERICAL STUDY OF 3D EXPLOSION BUBBLES ADJACENT TO STRUCTURES

    2002-01-01

    The bejavior of a bubble near a rigid structure was considered by using the local surface fitting method and the "jet prediction" method. The convergence difficulty caused by the abnormality of the elements was overcome. The flow was numerically simulated by using the boundary-integral method on the assumption that the water was inviscid and incompressible, and the bubble gas obeyed the isoentropic rule. The evolution of the bubble was investigated by means of the mixed Euler-Lagrange method, and the Runge-Kutta method. The important behavior of the bubble, such as migration and jetting, was analyzed in several examples. And the solution of one period of the explosion bubble was obtained.

  14. 3D numerical simulations of vesicle and inextensible capsule dynamics

    Farutin, Alexander; Biben, Thierry; Misbah, Chaouqi

    2014-10-01

    Vesicles are locally-inextensible fluid membranes, capsules are endowed with in-plane shear elasticity mimicking the cytoskeleton of red blood cells (RBCs), but are extensible, while RBCs are inextensible. We use boundary integral (BI) methods based on the Green function techniques to model and solve numerically their dynamics. We regularize the single layer integral by subtraction of exact identities for the terms involving the normal and the tangential components of the force. The stability and precision of BI calculation is enhanced by taking advantage of additional quadrature nodes located in vertices of an auxiliary mesh, constructed by a standard refinement procedure from the main mesh. We extend the partition of unity technique to boundary integral calculation on triangular meshes. The proposed algorithm offers the same treatment of near-singular integration regardless whether the source and the target points belong to the same surface or not. Bending forces are calculated by using expressions derived from differential geometry. Membrane incompressibility is handled by using two penalization parameters per suspended entity: one for deviation of the global area from prescribed value and another for the sum of squares of local strains defined on each vertex. Extensible or inextensible capsules, a model of RBC, are studied by storing the position in the reference configuration for each vertex. The elastic force is then calculated by direct variation of the elastic energy. Various nonequilibrium physical examples on vesicles and capsules will be presented and the convergence and precision tests highlighted. Overall, a good convergence is observed with numerical error inversely proportional to the number of vertices used for surface discretization, the highest order of convergence allowed by piece-wise linear interpolation of the surface.

  15. Numerical modelling of gravel unconstrained flow experiments with the DAN3D and RASH3D codes

    Sauthier, Claire; Pirulli, Marina; Pisani, Gabriele; Scavia, Claudio; Labiouse, Vincent

    2015-12-01

    Landslide continuum dynamic models have improved considerably in the last years, but a consensus on the best method of calibrating the input resistance parameter values for predictive analyses has not yet emerged. In the present paper, numerical simulations of a series of laboratory experiments performed at the Laboratory for Rock Mechanics of the EPF Lausanne were undertaken with the RASH3D and DAN3D numerical codes. They aimed at analysing the possibility to use calibrated ranges of parameters (1) in a code different from that they were obtained from and (2) to simulate potential-events made of a material with the same characteristics as back-analysed past-events, but involving a different volume and propagation path. For this purpose, one of the four benchmark laboratory tests was used as past-event to calibrate the dynamic basal friction angle assuming a Coulomb-type behaviour of the sliding mass, and this back-analysed value was then used to simulate the three other experiments, assumed as potential-events. The computational findings show good correspondence with experimental results in terms of characteristics of the final deposits (i.e., runout, length and width). Furthermore, the obtained best fit values of the dynamic basal friction angle for the two codes turn out to be close to each other and within the range of values measured with pseudo-dynamic tilting tests.

  16. A fully covariant mean-field dynamo closure for numerical 3+1 resistive GRMHD

    Bucciantini, N

    2012-01-01

    The powerful high-energy phenomena typically encountered in astrophysics invariably involve physical engines, like neutron stars and black hole accretion disks, characterized by a combination of highly magnetized plasmas, strong gravitational fields, and relativistic motions. In recent years numerical schemes for General Relativistic MHD (GRMHD) have been developed to model the multidimensional dynamics of such systems, including the possibility of an evolving spacetime. Such schemes have been also extended beyond the ideal limit including the effects of resistivity, in an attempt to model dissipative physical processes acting on small scales (sub-grid effects) over the global dynamics. Along the same lines, magnetic fields could be amplified by the presence of turbulent dynamo processes, as often invoked to explain the high values of magnetization required in accretion disks and neutron stars. Here we present, for the first time, a further extension to include the possibility of a mean-field dynamo action wi...

  17. Single-sided sheet-to-tube spot welding investigated by 3D numerical simulations

    Nielsen, Chris Valentin; Chergui, Azeddine; Zhang, Wenqi

    The single-sided resistance spot welding process is analyzed by a 3D numerical study of sheet-to-tube joining. Finite element simulations are carried out in SORPAS® 3D. Two levels of electrode force and five levels of welding current are simulated. The overall effects of changing current and forc...

  18. Numerical simulation of laminar plasma dynamos in a cylindrical von K\\'arm\\'an flow

    Khalzov, I V; Ebrahimi, F; Schnack, D D; Forest, C B; 10.1063/1.3559472

    2011-01-01

    The results of a numerical study of the magnetic dynamo effect in cylindrical von K\\'arm\\'an plasma flow are presented with parameters relevant to the Madison Plasma Couette Experiment. This experiment is designed to investigate a broad class of phenomena in flowing plasmas. In a plasma, the magnetic Prandtl number Pm can be of order unity (i.e., the fluid Reynolds number Re is comparable to the magnetic Reynolds number Rm). This is in contrast to liquid metal experiments, where Pm is small (so, Re>>Rm) and the flows are always turbulent. We explore dynamo action through simulations using the extended magnetohydrodynamic NIMROD code for an isothermal and compressible plasma model.We also study two-fluid effects in simulations by including the Hall term in Ohm's law. We find that the counter-rotating von K\\'arm\\'an flow results in sustained dynamo action and the self-generation of magnetic field when the magnetic Reynolds number exceeds a critical value. For the plasma parameters of the experiment, this field ...

  19. Interplay between experimental and numerical approaches in the fluid dynamo problem

    Léorat, Jacques; Nore, Caroline

    2008-09-01

    After years of purely analytical and numerical investigations, the dynamo fluid problem has advanced to a phase of experimental study. We present an outline of the numerical steps that have accompanied the Von Kármán Sodium (VKS) experiment at Cadarache for the past ten years. We show how various numerical studies contributed progressively to the optimization of the experimental facility. The recent success of the VKS2 experiment of September 2006 in achieving dynamo action has prompted an extension of the numerical code. Modeling of the electromotive force induced in the volume of the impellers shows that an axial dipole is excited, as observed in the experiment. We infer from these results that the observed value of the critical magnetic Reynolds number may be linked to the soft iron of the impellers and not to turbulence which occurs for any choice of materials. We conclude with proposals for further lines of numerical development. To cite this article: J. Léorat, C. Nore, C. R. Physique 9 (2008).

  20. Interpreting geomagnetic reversal frequency using numerical dynamos (Invited)

    Olson, P.; Amit, H.

    2013-12-01

    We derive scaling relationships for the frequency of polarity reversals in numerical geodynamo models powered by thermochemical convection for comparison with the geomagnetic polarity record. We find that the average number of reversals per unit of time scales with the local Rossby number of the convection. For uniform core-mantle boundary conditions, polarity reversals are absent below a critical value of the local Rossby number near 0.05, beyond which reversal frequency increases approximately linearly with that parameter. The relative standard deviation of the dipole intensity fluctuations increases with reversal frequency and the local Rossby number. For tomographic boundary conditions that model the observed large-scale seismic heterogeneity in the Earth's lower mantle, reversal frequency also exhibits linear dependence on the local Rossby number, and in addition, increases approximately as the square root of the amplitude of the boundary heterogeneity. Applied to the history of the geodynamo, our results indicate that outer core convection was relatively weak and homogeneous with small local Rossby number during geomagnetic superchrons and relatively vigorous with larger local Rossby number at times when geomagnetic reversals were frequent. Translated into core energetics, we find that the difference between the present-day geomagnetic reversal frequency and superchron conditions requires a 25% change in the total heat flux across the core-mantle boundary, or alternatively, a 75% change in the amplitude of the boundary heterogeneity. Our results also indicate that polarity reversals were likely throughout Earth history and may also have been commonplace in the early history of other terrestrial planets.

  1. Numerical simulation of 3D backward facing step flows at various Reynolds numbers

    Louda Petr

    2015-01-01

    Full Text Available The work deals with the numerical simulation of 3D turbulent flow over backward facing step in a narrow channel. The mathematical model is based on the RANS equations with an explicit algebraic Reynolds stress model (EARSM. The numerical method uses implicit finite volume upwind discretization. While the eddy viscosity models fail in predicting complex 3D flows, the EARSM model is shown to provide results which agree well with experimental PIV data. The reference experimental data provide the 3D flow field. The simulations are compared with experiment for 3 values of Reynolds number.

  2. Study of 3-D Numerical Simulation for Gas Transfer in the Goaf of the Coal Mining

    WU Zheng-yan; JIANG Shu-guang; HE Xin-jian; WANG Lan-yun; LIN Bai-quan

    2007-01-01

    In order to simulate field distribution rules, mathematical models for 3-D air flows and gas transfer in the goaf of the coal mining are established, based on theories of permeability and dynamic dispersion through porous media. A gas dispersion equation in a 3-D field is calculated by use of numerical method on a weighted upstream multi-element balance. Based on data of an example with a U type ventilation mode, surface charts of air pressure distribution and gas concentration are drawn by Graphtool software. Finally, a comparison between actually measured results in the model test and the numerical simulation results is made to proves the numerical implementation feasible.

  3. Numerical stability of coupling schemes in the 3d/0d modelling ofairflows and blood flows

    Fouchet-Incaux, Justine; Grandmont, Céline; Martin, Sebastien

    2014-01-01

    We consider models which are classically used in the simulation of airflows and blood flows andinvestigate the numerical stability of some discretization strategies. The geometrical complexity of the networksin which air/blood flows leads to a classical decomposition of two areas: a truncated 3D geometry correspondingto the largest contribution of the domain and a 0D part connected to the 3D part, modelling air/blood flowsin smaller airways/vessels. The resulting Navier-Stokes system in the 3...

  4. A simple stochastic model for dipole moment fluctuations in numerical dynamo simulations

    Domenico G. eMeduri

    2016-04-01

    Full Text Available Earth's axial dipole field changes in a complex fashion on many differenttime scales ranging from less than a year to tens of million years.Documenting, analysing, and replicating this intricate signalis a challenge for data acquisition, theoretical interpretation,and dynamo modelling alike. Here we explore whether axial dipole variationscan be described by the superposition of a slow deterministic driftand fast stochastic fluctuations, i.e. by a Langevin-type system.The drift term describes the time averaged behaviour of the axial dipole variations,whereas the stochastic part mimics complex flow interactions over convective time scales.The statistical behaviour of the system is described by a Fokker-Planck equation whichallows useful predictions, including the average rates of dipole reversals and excursions.We analyse several numerical dynamo simulations, most of which havebeen integrated particularly long in time, and also the palaeomagneticmodel PADM2M which covers the past 2 Myr.The results show that the Langevin description provides a viable statistical modelof the axial dipole variations on time scales longer than about 1 kyr.For example, the axial dipole probability distribution and the average reversalrate are successfully predicted.The exception is PADM2M where the stochastic model reversal rate seems too low.The dependence of the drift on the axial dipolemoment reveals the nonlinear interactions that establish thedynamo balance. A separate analysis of inductive and diffusive magnetic effectsin three dynamo simulations suggests that the classical quadraticquenching of induction predicted by mean-field theory seems at work.

  5. Application of 3-D numerical simulation software SRIFCAST to produce ductile iron castings

    2005-01-01

    Based on a method using numerical simulation equations and their solution schemes for liquid metal flows and heat transfer during mold filling and the solidification process of casting, 3-D numerical simulation software SRIFCAST was created. This includes enmeshment of casting; velocity and temperature fields calculation; displaying iso-temperature lines;velocity vectors and 3-D temperature fields on a Windows 9x operating system. SRIFCAST was applied to produce sound castings of automobile and diesel engines, and also to connect with microstructure simulation for ductile iron castings.

  6. GENETIC ALGORITHM IN REDUCTION OF NUMERICAL DISPERSION OF 3-D ADI-FDTD METHOD

    Zhang Yan; Lǖ Shanwei; Gao Wenjun

    2007-01-01

    A new method to reduce the numerical dispersion of the three-dimensional Alternating Direction Implicit Finite-Difference Time-Domain(3-D ADI-FDTD)method is proposed.Firstly,the numerical formulations of the 3-D ADI-FDTD method are modified with the artificial anisotropy,and the new numerical dispersion relation is derived.Secondly,the relative permittivity tensor of the artificial anisotropy can be obtained by the Adaptive Genetic Algorithm(AGA).In order to demonstrate the accuracy and efficiency of this new method,a monopole antenna is simulated as an example.And the numerical results and the computational requirements of the proposed method are cornpared with those of the conventional ADI-FDTD method and the measured data.In addition the reduction of the numerical dispersion is investigated as the objective function of the AGA.It is found that this new method is accurate and efficient by choosing proper objective function.

  7. Numerical dynamos with outer boundary heat flux inferred from probabilistic tomography—consequences for latitudinal distribution of magnetic flux

    Amit, Hagay; Deschamps, Frédéric; Choblet, Gaël

    2015-11-01

    Mantle control on the geodynamo is often simulated using numerical dynamos with imposed outer boundary heat flux inferred from lower mantle tomography, assuming that seismic and thermal anomalies in the lowermost mantle are highly correlated. However, non-thermal effects might perturb this idealized linear seismic-thermal mapping. Here we use a probabilistic tomography model to isolate the thermal part of the seismic anomaly in order to impose a more realistic core-mantle boundary heat flux pattern on the outer boundary of numerical dynamo simulations. We demonstrate that on time average these dynamo models have more low-latitude convective and magnetic activity than corresponding models with conventional tomographic heat flux. In addition, the low-latitude magnetic flux and kinetic energy contributions are more time-dependent in the dynamo models with a probabilistic tomography heat flux, and thus may recover the observed latitudinal distribution of geomagnetic flux on the core-mantle boundary, which we propose as a morphological criterion for Earth-like dynamo models.

  8. Numerical dynamos with outer boundary heat flux inferred from probabilistic tomography - Consequences for latitudinal distribution of magnetic flux

    Amit, Hagay; Deschamps, Frédéric; Choblet, Gaël

    2015-04-01

    Mantle control on the geodynamo is often simulated using numerical dynamos with imposed outer boundary heat flux inferred from lower mantle tomography, assuming that seismic and thermal anomalies in the lowermost mantle are highly correlated. However, non-thermal effects might perturb this idealized linear seismic-thermal mapping. Here we use a probabilistic tomography model to isolate the thermal part of the seismic anomaly in order to impose a more realistic core-mantle boundary heat flux pattern on the outer boundary of numerical dynamo simulations. We demonstrate that on time-average these dynamo models have more low-latitudes convective and magnetic activity than corresponding models with conventional tomographic heat flux. In addition, the low-latitudes magnetic flux and kinetic energy contributions are more time-dependent in the dynamo models with a probabilistic tomography heat flux, and thus may recover the observed latitudinal distribution of geomagnetic flux on the core-mantle boundary, which we propose as a morphological criterion for Earth-like dynamo models.

  9. 3D numerical analysis of crack propagation of heterogeneous notched rock under uniaxial tension

    Wang, S. Y.; Sloan, S. W.; Sheng, D. C.; Tang, C. A.

    2016-05-01

    Macroscopic notches play an important role in evaluating the fracture process zone (FPZ) and the strengths of a heterogeneous rock mass. Crack initiation, propagation and coalescence for unnotched, single-notched and double-notched rock specimens are numerically simulated in a 3-D numerical model (RFPA3D). A feature of the code RFPA3D is that it can numerically simulate the evolution of cracks in three-dimensional space, as well as the heterogeneity of the rock mass. For the unnotched case, special attention is given to the complete stress-strain curve and the corresponding AE events for the failure process of rock specimen. By comparing with published experimental results, the simulation results from RFPA3D are found to be satisfactory. For the single-notched case, the effect of the length and the depth of the single notch and the thickness of the specimen on the failure mode and peak stress are evaluated. The 3D FPZ is very different from that in two dimensions. For the double-notched case, the effects of the separation distance and overlap distance of the double notches, as well as influence of the homogeneity index (m) are also investigated. As the overlap distance increases, the direction of the principal tensile stress at each notch-end changes from a perpendicular direction (tensile stress field) to a nearly parallel direction (compressive stress field), which affects the evolution of the cracks from the two notches.

  10. Calculation of residual stresses by means of a 3D numerical weld simulation

    Nicak, Tomas; Huemmer, Matthias [AREVA NP GmbH, Postfach 1109 (Germany)

    2008-07-01

    The numerical weld simulation has developed very fast in recent years. The problem complexity has increased from simple 2D models to full 3D models, which can describe the entire welding process more realistically. As recent research projects indicate, a quantitative assessment of the residual stresses by means of a 3D analysis is possible. The structure integrity can be assessed based on the weld simulation results superimposed with the operating load. Moreover, to support the qualification of welded components parametric studies for optimization of the residual stress distribution in the weld region can be performed. In this paper a full 3D numerical weld simulation for a man-hole drainage nozzle in a steam generator will be presented. The residual stresses are calculated by means of an uncoupled transient thermal and mechanical FE analysis. The paper will present a robust procedure allowing reasonable predictions of the residual stresses for complex structures in industrial practice. (authors)

  11. New results on an equipartition dynamo

    Dorch, S. B. F.; Archontis, V.

    2006-01-01

    linear and non-linear saturation regimes. The means were 3-d non-linear MHD simulations and visualization using the high resolution numerical scheme by Nordlund, Galsgaard and others. We have found that the dynamo has a high growth rate in the linear regime, and that it can saturate at a level...

  12. Improvements to the RELAP5-3D Nearly-Implicit Numerical Scheme

    The RELAP5-3D computer program has been improved with regard to its nearly-implicit numerical scheme for two phase flow and single-phase flow. Changes were made to the nearly-implicit numerical scheme finite difference momentum equations as follows: (1) added the velocity flip-flop mass/energy error mitigation logic, (2) added the modified Henry-Fauske choking model, (3) used the new time void fraction in the horizontal stratification force terms and gravity head, and (4) used an implicit form of the artificial viscosity. The code modifications allow the nearly-implicit numerical scheme to be more implicit and lead to enhanced numerical stability

  13. Improvements to the RELAP5-3D Nearly-Implicit Numerical Scheme

    Richard A. Riemke; Walter L. Weaver; RIchard R. Schultz

    2005-05-01

    The RELAP5-3D computer program has been improved with regard to its nearly-implicit numerical scheme for twophase flow and single-phase flow. Changes were made to the nearly-implicit numerical scheme finite difference momentum equations as follows: (1) added the velocity flip-flop mass/energy error mitigation logic, (2) added the modified Henry-Fauske choking model, (3) used the new time void fraction in the horizontal stratification force terms and gravity head, and (4) used an implicit form of the artificial viscosity. The code modifications allow the nearly-implicit numerical scheme to be more implicit and lead to enhanced numerical stability.

  14. Slab detachment in laterally varying subduction zones: 3-D numerical modeling

    Duretz, T.; Gerya, T.V.; Spakman, W.

    2014-01-01

    Understanding the three-dimensional (3-D) dynamics of subduction-collision systems is a longstanding challenge in geodynamics. We investigate the impact of slab detachment in collision systems that are subjected to along-trench variations. High-resolution thermomechanical numerical models, encompass

  15. Experimental validation of a numerical simulation on a ballscrew system by 3D photoelasticity

    Germaneau A.

    2010-06-01

    Full Text Available The Trimmable Horizontal Stabilizer Actuator (THSA system equips the whole airbus line. One component of this system is a ball-screw system on which spalling problems appear on the balls. This phenomenon is mostly due to local high pressures and reduces the service life of the system. 3D numerical simulations are usually used to tackle this kind of problems but are subjected to assumptions. As the aim of the project is to build a numerical model able to predict pressure distribution, these assumptions need to be experimentally assessed to be perfectly relevant of the real load distribution in the ball screw system. Due to the 3D geometry of the specimen, a 3D measurement technique, Scattered Light Photoelasticity (SLP, has been chosen to perform experimental measurements,. Because of complexity of the geometry, the study is divided in three steps; the present paper is dealing with the second one where a demonstrator ball-screw system is manufactured in casted epoxy to perform the SLP. This technique gives information on 3D stress fields inside the epoxy specimen from the analysis of photoelastic fringes. They are compared to numerical ones and indicate whether numerical boundary conditions are relevant of the experimental ball-screw system behaviour.

  16. Towards the geophysical regime in numerical dynamo models: studies of rapidly-rotating convection driven dynamos with low Pm and constant heat flux boundary conditions

    Sheyko, A.A.; Finlay, Chris; Marti, P.;

    We present a set of numerical dynamo models with the convection strength varied by a factor of 30 and the ratio of magnetic to viscous diffusivities by a factor of 20 at rapid rotation rates (E =nu/(2 Omega d^2 ) = 10-6 and 10-7 ) using a heat flux outer BC. This regime has been little explored...... (aside from a pioneering study by Sakuraba and Roberts 2009) due to the significant computing resources required. Our simulations are carried out using a discretisation of degree and order 256 in spherical harmonics, and 516 finite difference points in radius and parallelized on 516 cores. We report on...

  17. Numerical investigation of the 3D Hubbard model on a Linux cluster

    We investigate numerically the magnetic properties of the 3D Isotropic and Anisotropic Hubbard model at half-filling on a Linux cluster. The behavior of the transition temperature as a function of the anisotropic hopping parameter is qualitatively described. In the Isotropic model we measure the scaling properties of the susceptibility finding agreement with the magnetic critical exponents of the 3D Heisenberg model. We describe several particularities concerning the implementation of our simulation in a cluster of personal computers paying special attention to the issues related with the parallelization of the algorithm

  18. 3-D NUMERICAL SIMULATION OF FLOW THROUGH AN ORIFICE SPILL-WAY TUNNEL

    2002-01-01

    A Large Eddy Simulation (LES) approachbased on the weakly compressible hydrodynamic equation with a single-plase fluid model for the cavitation flow has been de-veloped and employed in simulating 3-D unsteady viscous flowthrough an orifice type spillwy tunnel. The finite volume ap-proach in space and the predictor-corrector method in timehave been used to the numerical discretization, and the "Lawof wall" is applied at the solid boundary. The velocity, pres-sure fields and the cavitation phenomenon are obtained, thecomputational results show that 3-D LES approach can givemore realistic flow field prediction of the orifice type spillwaytunnel.

  19. 3D numerical simulation analysis of passive drag near free surface in swimming

    Zhan, Jie-min; Li, Tian-zeng; Chen, Xue-bin; Li, Yok-sheung; Wai, Wing-hong Onyx

    2015-04-01

    The aim of this work is to build a 3D numerical model to study the characteristics of passive drag on competitive swimmers taking into account the impact of the free surface. This model solves the 3D incompressible Navier-Stokes equations using RNG k- ɛ turbulence closure. The volume of fluid (VOF) method is used to locate the free surface. The 3D virtual model is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. Firstly, a specific posture of swimming is studied. The simulation results are in good agreement with the data from mannequin towing experiments. The effects of a swimmer's arms and legs positions on swimming performance are then studied. Finally, it is demonstrated that the present method is capable of simulating gliding near the free surface.

  20. 3D flow past transonic turbine cascade SE 1050 — Experiment and numerical simulations

    Šimurda, D.; Fürst, J.; Luxa, M.

    2013-08-01

    This paper is concerned with experimental and numerical research on 3D flow past prismatic turbine cascade SE1050 (known in QNET network as open test case SE1050). The primary goal was to assess the influence of the inlet velocity profile on the flow structures in the interblade channel and on the flow field parameters at the cascade exit and to compare these findings to results of numerical simulations. Investigations of 3D flow past the cascade with non-uniform inlet velocity profile were carried out both experimentally and numerically at subsonic ( M 2is = 0.8) and at transonic ( M 2is = 1.2) regime at design angle of incidence. Experimental data was obtained using a traversing device with a five-hole conical probe. Numerically, the 3D flow was simulated by open source code OpenFOAM and in-house code. Analyses of experimental data and CFD simulations have revealed the development of distinctive vortex structures resulting from non-uniform inlet velocity profile. Origin of these structures results in increased loss of kinetic energy and spanwise shift of kinetic energy loss coefficient distribution. Differences found between the subsonic and the transonic case confirm earlier findings available in the literature. Results of CFD and experiments agree reasonably well.

  1. 3-D NUMERICAL STUDY AND COMPARISON OF ECCENTRIC AND CONCENTRIC ANNULAR-FINNED TUBE HEAT EXCHANGERS

    FAROUK TAHROUR; ABDELMOUMENE HAKIM BENMACHICHE; MOUNIR AKSAS; CHERIF BOUGRIOU

    2015-01-01

    The use of 3-D computational fluid dynamics (CFD) is proposed to simulate the conjugate conduction-convection of heat transfer problems in eccentric annularfinned tube heat exchangers. The numerical simulation results allow us to evaluate the heat transfer coefficient over fin surfaces, the fin efficiency and the pressure drop. The aim of the present paper is to determine the optimum tube position in the circular fin that maximizes heat dissipation and minimizes pressure drop. In addition, th...

  2. Numerical Calculation of the Flow Inside Pump Impellers Using 3D Euler Equations

    SARIOĞLU, Kemal; Ayder, Erkan

    1999-01-01

    The flow pattern inside an impeller should be determined for maximum efficiency and performance. The effects of the design parameters on the pump performance can be determined using numerical calculations instead of empirical equations. Incompressible 3D time-dependent Euler equations, written in a conservative form, are used. An artificial pressure term is added to preserve the hyperbolic character of the equations. A finite-volume technique is used for space discretization. A fou...

  3. 2D/1D approximations to the 3D neutron transport equation. II: Numerical comparisons

    In a companion paper [1], (i) several new '2D/1D equations' are introduced as accurate approximations to the 3D Boltzmann transport equation, (ii) the simplest of these approximate equations is systematically discretized, and (iii) a theoretically stable iteration scheme is developed to solve the discrete equations. In this paper, numerical results are presented that confirm the theoretical predictions made in [1]. (authors)

  4. 3D-Workbench : Design and Development of a 3-Dimension Computer Numerical Controlled Machine

    Sandru, Andrei

    2015-01-01

    The purpose of this thesis was to examine and develop a multipurpose Computer Numerical Controlled (CNC) device which would satisfy industrial requirements, but could also be implemented at universities for students to improve and apply their knowledge in different scopes. The topic was specifically chosen because of its close relation to a summer job at a metal factory the author completed and his personal fascination with 3D printers. The project presented in this thesis was commissioned...

  5. 3D Nonlinear Numerical Simulation of Intact and Debonded Reinforced Concrete Beams

    Chen Quan(陈权); Marcus L.

    2004-01-01

    To study the behaviour of reinforced concrete (RC) structures with sections of concrete removed and the reinforcement exposed, 3D nonlinear numerical analysis was performed upon both intact and debonded RC beams by using finite element techniques. The deformational characteristics and the ultimate loads were obtained through numerical models, as well as crack and stress distributions. The failure modes can also be deduced from computational results. Compared with intact beams, the normal assumptions of plane section behaviour is not hold true and the patterns of stress and strain are different in debonded RC beams. The numerical results show good consistency with experimental data. This kind of numerical simulation is a supplement to existing codes.

  6. 3-D Numerical Modeling of Heat Transport Phenomena in Soil under Climatic Conditions of Southern Thailand

    Jompob WAEWSAK

    2014-12-01

    Full Text Available This paper presents a 3-D numerical modeling of heat transport phenomena in soil due to a change of sensible and latent heat, under the ambient conditions of southern Thailand. The vertical soil temperature profile within 3 m was predicted based on energy balance and 3 modes of heat transfer mechanisms, i.e., conduction, convection, and radiation. Mathematical models for estimation of solar radiation intensity, ambient and sky temperatures, relative humidity, and surface wind velocity were used as model inputs. 3-D numerical implicit finite difference schemes, i.e., forward time, and forward, center, and backward spaces were used for discretizing the set of governing, initial, and boundary condition equations. The set of pseudo-linear equations were then solved using the single step Gauss-Seidel iteration method. Computer code was developed by using MATLAB computer software. The soil physical effects; density, thermal conductivity, emissivity, absorptivity, and latent heat on amplitude of soil temperature variation were investigated. Numerical results were validated in comparison to the experimental results. It was found that 3-D numerical modeling could predict the soil temperature to almost the same degree as results that were obtained by experimentation, especially at a depth of 1 m. The root mean square error at ground surface and at depths of 0.5, 1, 1.5, 2, 2.5 and 3 m were 0.169, 0.153, 0.097, 0.116, 0.120, 0.115, and 0.098, respectively. Furthermore, it was found that variation of soil temperature occurred within 0.75 m only.

  7. Twisting Rolls. Heuristic Model and 3D Numerical Simulation of Vortex Patterns

    Bouali, S

    2003-01-01

    We connect an appropriate feedback loop to a model of 2D vertical eddy of airflow which unfolds a wide range of vorticity behavior. Computational fluid dynamics of the twisted roll display a class of long lifespan 3D vortices. On the one hand, the infinitely stable columnar vortex simulated describes waterspouts and tornadoes with extended lifetime. On the other hand, a light modification of the retroaction exhibits strong similarities to tropical cyclones. Moreover, we investigate the outcome of the twisting process vertically shifted. This modelisation leads to the simulation of simultaneous vortices associated to this other class of 3D vortices with short lifespan. Our heuristic dynamical systems lay the foundations of a comprehensive modelisation of vortices since it joins numerical simulations and theory.

  8. An innovative 3-D numerical modelling procedure for simulating repository-scale excavations in rock - SAFETI

    This paper presents current results from work performed within the European Commission project SAFETI. The main objective of SAFETI is to develop and test an innovative 3D numerical modelling procedure that will enable the 3-D simulation of nuclear waste repositories in rock. The modelling code is called AC/DC (Adaptive Continuum/ Dis-Continuum) and is partially based on Itasca Consulting Group's Particle Flow Code (PFC). Results are presented from the laboratory validation study where algorithms and procedures have been developed and tested to allow accurate 'Models for Rock' to be produced. Preliminary results are also presented on the use of AC/DC with parallel processors and adaptive logic. During the final year of the project a detailed model of the Prototype Repository Experiment at SKB's Hard Rock Laboratory will be produced using up to 128 processors on the parallel super computing facility at Liverpool University. (authors)

  9. Numerical solution of 3-D magnetotelluric using vector finite element method

    Prihantoro, Rudy; Sutarno, Doddy; Nurhasan

    2015-09-01

    Magnetotelluric (MT) is a passive electromagnetic (EM) method which measure natural variations of electric and magnetic vector fields at the Earth surface to map subsurface electrical conductivity/resistivity structure. In this study, we obtained numerical solution of three-dimensional (3-D) MT using vector finite element method by solving second order Maxwell differential equation describing diffusion of plane wave through the conductive earth. Rather than the nodes of the element, the edges of the element is used as a vector basis to overcome the occurrence of nonphysical solutions that usually faced by scalar (node based) finite element method. Electric vector fields formulation was used and the resulting system of equation was solved using direct solution method to obtain the electric vector field distribution throughout the earth resistivity model structure. The resulting MT response functions was verified with 1-D layered Earth and 3-D2 COMMEMI outcropping structure. Good agreement is achieved for both structure models.

  10. An innovative 3-D numerical modelling procedure for simulating repository-scale excavations in rock - SAFETI

    Young, R. P.; Collins, D.; Hazzard, J.; Heath, A. [Department of Earth Sciences, Liverpool University, 4 Brownlow street, UK-0 L69 3GP Liverpool (United Kingdom); Pettitt, W.; Baker, C. [Applied Seismology Consultants LTD, 10 Belmont, Shropshire, UK-S41 ITE Shrewsbury (United Kingdom); Billaux, D.; Cundall, P.; Potyondy, D.; Dedecker, F. [Itasca Consultants S.A., Centre Scientifique A. Moiroux, 64, chemin des Mouilles, F69130 Ecully (France); Svemar, C. [Svensk Karnbranslemantering AB, SKB, Aspo Hard Rock Laboratory, PL 300, S-57295 Figeholm (Sweden); Lebon, P. [ANDRA, Parc de la Croix Blanche, 7, rue Jean Monnet, F-92298 Chatenay-Malabry (France)

    2004-07-01

    This paper presents current results from work performed within the European Commission project SAFETI. The main objective of SAFETI is to develop and test an innovative 3D numerical modelling procedure that will enable the 3-D simulation of nuclear waste repositories in rock. The modelling code is called AC/DC (Adaptive Continuum/ Dis-Continuum) and is partially based on Itasca Consulting Group's Particle Flow Code (PFC). Results are presented from the laboratory validation study where algorithms and procedures have been developed and tested to allow accurate 'Models for Rock' to be produced. Preliminary results are also presented on the use of AC/DC with parallel processors and adaptive logic. During the final year of the project a detailed model of the Prototype Repository Experiment at SKB's Hard Rock Laboratory will be produced using up to 128 processors on the parallel super computing facility at Liverpool University. (authors)

  11. Numerical simulations of self-propelled swimming of 3D bionic fish school

    2009-01-01

    Numerical simulations of self-propelled swimming of a three dimensional bionic fish and fish school in a viscous fluid are carried out. This is done with the assistance of a parallel software package produced for 3D moving boundary problems. This computational fluid dynamics package combines the adaptive multi-grid finite volume method, the immersed boundary method and VOF (volume of fluid) method. By using the package results of the self-propelled swimming of a 3D bionic fish and fish school in a vis- cous fluid are obtained. With comparison to the existing experimental measurements of living fishes, the predicted structure of vortical wakes is in good agreement with the measurements.

  12. Numerical simulations of self-propelled swimming of 3D bionic fish school

    WU ChuiJie; WANG Liang

    2009-01-01

    Numerical simulations of self-propelled swimming of a three dimensional bionic fish and fish school in a viscous fluid are carried out. This is done with the assistance of a parallel software package producedfor 3D moving boundary problems. This computational fluid dynamics package combines the adaptive multi-grid finite volume method, the immersed boundary method and VOF (volume of fluid) method. By using the package results of the self-propelled swimming of a 3D bionic fish and fish school in a vis cous fluid are obtained. With comparison to the existing experimental measurements of living fishes, the predicted structure of vortical wakes is in good agreement with the measurements.

  13. Aneesur Rahman Prize for Computational Physics Talk: Numerical Modeling of Accretion Disk Dynamos driven by the MRI

    Stone, James

    2011-04-01

    Numerical methods have proved crucial for the study of the nonlinear regime of the magnetorotational instability (MRI) and resulting dynamo action. After a brief introduction to the methods, a variety of results from new simulations of the MRI in both local (shearing box approximation) and global domains will be presented. Previous work on the saturation level and numerical convergence in both stratified and unstratified domains with no net flux (both with and without explicit dissipation) will be described, and the connection to dynamo theory will be mentioned. Results from several groups in which the size of the computational domain, and the vertical boundary conditions, are varied will be discussed. Finally, new work on the direct comparison between high-resolution global and shearing box simulations will be presented, and new studies of stratified disks with radiative transfer will be introduced.

  14. Numerical methods for 3D tokamak simulations using a flux-surface independent grid

    A numerical approach for 3D tokamak simulations using a flux surface independent grid is presented. The grid consists of few poloidal planes with a Cartesian Isotropic grid within each poloidal plane. Perpendicular operators can be discretised within a poloidal plane using standard second order finite difference methods. The discretisation of parallel operators is achieved with a field line following map and an interpolation. The application of the support operator method to the parallel diffusion operator conserves the self-adjointness of the operator on the discrete level and keeps the numerical decay rate at a low level. The developed numerical methods can be applied to geometries where an X-point is present.

  15. Numerical modelling of pollution dispersion in 3D atmospheric boundary layer

    Benes, L.; Bodnar, T.; Kozel, K. [Czech Technical Univ. of Prague (Czech Republic). Dept. of Technical Mathematics; Fraunie, Ph. [Univ. de Toulon et du Var, La Garde (France). Lab. de Sondages Electromagnetiques et Environnemental Terrestre

    2002-07-01

    The main goal of this work is to present the applicable models and numerical methods for solution of flow and pollution dispersion in 3D atmospheric boundary layer (ABL). Mathematical models are based on the system of Reynolds averaged Navier-Stokes equations and its simplifications. The sets of governing equations are completed by the transport equations for passive impurities and potential temperature. A simple algebraic turbulent closure model is used. The thermal stability phenomenon is taken into account. For each mathematical model a numerical scheme based on finite-difference or finite-volume discretization is proposed and discussed. Some results of numerical tests are presented for pollution dispersion from point sources and flows over simple geometries. (orig.)

  16. 2D and 3D numerical models on compositionally buoyant diapirs in the mantle wedge

    Hasenclever, Jörg; Morgan, Jason Phipps; Hort, Matthias; Rüpke, Lars H.

    2011-11-01

    We present 2D and 3D numerical model calculations that focus on the physics of compositionally buoyant diapirs rising within a mantle wedge corner flow. Compositional buoyancy is assumed to arise from slab dehydration during which water-rich volatiles enter the mantle wedge and form a wet, less dense boundary layer on top of the slab. Slab dehydration is prescribed to occur in the 80-180 km deep slab interval, and the water transport is treated as a diffusion-like process. In this study, the mantle's rheology is modeled as being isoviscous for the benefit of easier-to-interpret feedbacks between water migration and buoyant viscous flow of the mantle. We use a simple subduction geometry that does not change during the numerical calculation. In a large set of 2D calculations we have identified that five different flow regimes can form, in which the position, number, and formation time of the diapirs vary as a function of four parameters: subduction angle, subduction rate, water diffusivity (mobility), and mantle viscosity. Using the same numerical method and numerical resolution we also conducted a suite of 3D calculations for 16 selected parameter combinations. Comparing the 2D and 3D results for the same model parameters reveals that the 2D models can only give limited insights into the inherently 3D problem of mantle wedge diapirism. While often correctly predicting the position and onset time of the first diapir(s), the 2D models fail to capture the dynamics of diapir ascent as well as the formation of secondary diapirs that result from boundary layer perturbations caused by previous diapirs. Of greatest importance for physically correct results is the numerical resolution in the region where diapirs nucleate, which must be high enough to accurately capture the growth of the thin wet boundary layer on top of the slab and, subsequently, the formation, morphology, and ascent of diapirs. Here 2D models can be very useful to quantify the required resolution, which we

  17. Numerical and experimental investigation of the 3D free surface flow in a model Pelton turbine

    This investigation focuses on the numerical and experimental analysis of the 3D free surface flow in a Pelton turbine. In particular, two typical flow conditions occurring in a full scale Pelton turbine - a configuration with a straight inlet as well as a configuration with a 90 degree elbow upstream of the nozzle - are considered. Thereby, the effect of secondary flow due to the 90 degree bending of the upstream pipe on the characteristics of the jet is explored. The hybrid flow field consists of pure liquid flow within the conduit and free surface two component flow of the liquid jet emerging out of the nozzle into air. The numerical results are validated against experimental investigations performed in the laboratory of the Institute of Fluid Mechanics (FLM). For the numerical simulation of the flow the in-house unstructured fully parallelized finite volume solver solver3D is utilized. An advanced interface capturing model based on the classic Volume of Fluid method is applied. In order to ensure sharp interface resolution an additional convection term is added to the transport equation of the volume fraction. A collocated variable arrangement is used and the set of non-linear equations, containing fluid conservation equations and model equations for turbulence and volume fraction, are solved in a segregated manner. For pressure-velocity coupling the SIMPLE and PISO algorithms are implemented. Detailed analysis of the observed flow patterns in the jet and of the jet geometry are presented.

  18. Numerical simulation of a 3-D flow within a storage area hexagonal modular pavement systems

    This numerical study has been performed to predict the flow patterns and characteristics within a storage area Hexagonal Modular Pavement Systems. Throughout the design and planning period for future construction are increasingly integrating computational fluid dynamics (CFD) into the process. A commercially known software, FLOW-3D, is applied to numerically solve the Navier-stokes equations for solution domains which are separated into three regions with overlapping boundaries to efficiently accommodate the grid resolutions, namely the honeycomb shaped modular, gravel and combined honeycomb shaped modular with gravel fill. The filtration of the fluid within the interstices of a permeable pavement is evaluated by integrating the Reynolds Averaged Navier-Stokes equations (RANS) inside the voids rather than making use of the widespread porous media approach. In conclusion, the results from numerical simulation are generally well agreed with the existing data and flow information such as flow patterns at increased flow, discharge rate and pressure is obtained to be used for engineering design purpose. Overall, the potential for FLOW-3D to model various geometries and configurations appears great. It should be noted that CFD should not be considered a complete replacement for physical modelling; however, it can definitely be used as a supplementary tool throughout the pavement design process.

  19. 3-D numerical modelling of stresses around a longwall panel with top coal caving

    Yasitli, N.E.; Unver, B. [University of Hacettepe, Ankara (Turkey). Dept. of Mining Engineering

    2005-06-01

    There is a considerable amount of lignite reserve in the form of thick seams in Turkey. It is rather complicated to predict the characteristics of strata response to mining operation in thick seams. However, a comprehensive evaluation of ground behaviour is a prerequisite for maintaining an efficient production, especially when top coal winning by means of caving behind the face is applied. A comprehensive modelling of deformations and induced stresses is vital for the selection of optimum production strategy. In this study, numerical modelling and analysis of a longwall panel at Omerler underground coalmine have been carried out by using the software called FLAC(3D) developed based on the finite difference technique. Firstly, a 3-D numerical model of the M3 panel has been prepared. Secondly, induced stresses formed around the longwall face have been determined as a function of face advance where the face was located at the bottom of thick coal-seam. Results obtained from modelling studies have revealed that the front abutment vertical stress was maximum at 7 metres in front of the face and magnitude of front abutment stress was found to increase up to a distance of 200 metres away from the face start line. As the face was further advanced after 200 m from the face start line, there was not any significant change in the characteristics of front abutment stresses. Results of numerical analysis of the panel were in good agreement with in situ observations.

  20. Experimental and Numerical Investigation of Forging Process to Reproduce a 3D Aluminium Foam Complex Shape

    Metallic foams represent one of the most exciting materials introduced in the manufacturing scenario in the last years. In the study here addressed, the experimental and numerical investigations on the forging process of a simple foam billet shaped into complex sculptured parts were carried out. In particular, the deformation behavior of metallic foams and the development of density gradients were investigated through a series of experimental forging tests in order to produce a selected portion of a hip prosthesis. The human bone replacement was chosen as case study due to its industrial demand and for its particular 3D complex shape. A finite element code (Deform 3D) was utilized for modeling the foam behavior during the forging process and an accurate material rheology description was used based on a porous material model which includes the measured local density. Once the effectiveness of the utilized Finite Element model was verified through the comparison with the experimental evidences, a numerical study of the influence of the foam density was investigated. The obtained numerical results shown as the initial billet density plays an important role on the prediction of the final shape, the optimization of the flash as well as the estimation of the punch load

  1. Numerical modeling of 3-D Position Reconstruction from 3-Axial Planar Spiral Coil Sensor Sensitivity

    Sanjaya, Edi; Viridi, Sparisoma

    2011-01-01

    A sensitivity profile of a planar spiral coil sensor (PSCS) is proposed and use to generate the relation of 3-D position of object observed using three (PSCS)-s, one in each x, y, and z axis to the sensors response. A numerical procedure using self consistent field-like method to reconstruct the real position of observed object from sensor sensitivity is presented and the results are discussed. Unfortunately, the procedure fails to approach the desired results due to the existence of quadratic terms.

  2. The Numerical Investigation on Vortex Flow Behavior Using FLOW-3D

    Jafar Chapokpour

    2012-01-01

    Full Text Available In this paper a numerical investigation is given for a Rankine type vortex flow inside the cylindrical vortex chamber using FLOW-3D. The FLOW-3D is a general purpose computational fluid dynamics (CFD package. The fluid motion is described with non-linear, transient, second-order differential equations. Additionally the free surface also exists in many simulations carried out with FLOW-3D because flow parameters and materials properties, such as density, velocity and pressure experience a discontinuity at it. After analysis of the vortex by mentioned details, the finding of time-averaged velocity components, turbulent components, turbulence dissipation, in the 2D briefed sections of chamber were depicted. It was found that there are different flow patterns like clockwise/anticlockwise vortices and some sink points combined with each other in different time intervals, decaying and generating along the time. Also the turbulence intensity and dissipations around the boundary conditions of chamber like central flushing discharge are higher than the flow body. It was also found that this CFD package was not able to simulate thoroughly the central air core of chamber after filling of chamber. This analysis is validated by comparison with previous experimental data that was measured in vortex settling basin.

  3. Numerical investigation of band gaps in 3D printed cantilever-in-mass metamaterials

    Qureshi, Awais; Li, Bing; Tan, K. T.

    2016-06-01

    In this research, the negative effective mass behavior of elastic/mechanical metamaterials is exhibited by a cantilever-in-mass structure as a proposed design for creating frequency stopping band gaps, based on local resonance of the internal structure. The mass-in-mass unit cell model is transformed into a cantilever-in-mass model using the Bernoulli-Euler beam theory. An analytical model of the cantilever-in-mass structure is derived and the effects of geometrical dimensions and material parameters to create frequency band gaps are examined. A two-dimensional finite element model is created to validate the analytical results, and excellent agreement is achieved. The analytical model establishes an easily tunable metamaterial design to realize wave attenuation based on locally resonant frequency. To demonstrate feasibility for 3D printing, the analytical model is employed to design and fabricate 3D printable mechanical metamaterial. A three-dimensional numerical experiment is performed using COMSOL Multiphysics to validate the wave attenuation performance. Results show that the cantilever-in-mass metamaterial is capable of mitigating stress waves at the desired resonance frequency. Our study successfully presents the use of one constituent material to create a 3D printed cantilever-in-mass metamaterial with negative effective mass density for stress wave mitigation purposes.

  4. Numerical investigation of band gaps in 3D printed cantilever-in-mass metamaterials

    Qureshi, Awais; Li, Bing; Tan, K. T.

    2016-01-01

    In this research, the negative effective mass behavior of elastic/mechanical metamaterials is exhibited by a cantilever-in-mass structure as a proposed design for creating frequency stopping band gaps, based on local resonance of the internal structure. The mass-in-mass unit cell model is transformed into a cantilever-in-mass model using the Bernoulli-Euler beam theory. An analytical model of the cantilever-in-mass structure is derived and the effects of geometrical dimensions and material parameters to create frequency band gaps are examined. A two-dimensional finite element model is created to validate the analytical results, and excellent agreement is achieved. The analytical model establishes an easily tunable metamaterial design to realize wave attenuation based on locally resonant frequency. To demonstrate feasibility for 3D printing, the analytical model is employed to design and fabricate 3D printable mechanical metamaterial. A three-dimensional numerical experiment is performed using COMSOL Multiphysics to validate the wave attenuation performance. Results show that the cantilever-in-mass metamaterial is capable of mitigating stress waves at the desired resonance frequency. Our study successfully presents the use of one constituent material to create a 3D printed cantilever-in-mass metamaterial with negative effective mass density for stress wave mitigation purposes. PMID:27329828

  5. 3-D-geomechanical-numerical model of the contemporary crustal stress state in the Alberta Basin

    K. Reiter

    2014-08-01

    Full Text Available In the context of examining the potential usage of safe and sustainable geothermal energy in the Alberta Basin whether in deep sediments or crystalline rock, the understanding of the in-situ stress state is crucial. It is a key challenge to estimate the 3-D stress state at an arbitrary chosen point in the crust, based on sparsely distributed in-situ stress data. To address this challenge, we present a large-scale 3-D geomechanical-numerical model (700 km × 1200 km × 80 km from a large portion of the Alberta Basin, to provide a 3-D continuous quantification of the contemporary stress orientations and stress magnitudes. To calibrate the model, we use a large database of in-situ stress orientation (321 SHmax as well as stress magnitude data (981 SV, 1720 SHmin and 2 (+11 SHmax from the Alberta Basin. To find the best-fit model we vary the material properties and primarily the kinematic boundary conditions of the model. This study focusses in detail on the statistical calibration procedure, because of the large amount of available data, the diversity of data types, and the importance of the order of data tests. The best-fit model provides the total 3-D stress tensor for nearly the whole Alberta Basin and allows estimation of stress orientation and stress magnitudes in advance of any well. First order implications for the well design and configuration of enhanced geothermal systems are revealed. Systematic deviations of the modelled stress from in-situ data are found for stress orientations in the Peace River- and the Bow Island Arch as well as for leak-off-test magnitudes.

  6. Numerical Simulation of the Protective Effect of Complex Boundaries Toward Shock Waves in a 3D Explosive Field

    吴开腾; 宁建国

    2003-01-01

    A numerical method is presented that simulates 3D explosive field problems. A code MMIC3D using this method can be used to simulate the propagation and reflected effects of all kinds of rigid boundaries to shock waves produced by an explosive source. These numerical results indicate that the code MMIC3D has the ability in computing cases such as 3D shock waves produced by air explosion, vortex region of the shock wave, the Mach wave, and reflected waves behind rigid boundaries.

  7. A numerical solution of 3D inviscid rotational flow in turbines and ducts

    Oktay, Erdal; Akmandor, Sinan; Üçer, Ahmet

    1998-04-01

    The numerical solutions of inviscid rotational (Euler) flows were obtained using an explicit hexahedral unstructured cell vertex finite volume method. A second-order-accurate, one-step Lax-Wendroff scheme was used to solve the unsteady governing equations discretized in conservative form. The transonic circular bump, in which the location and the strength of the captured shock are well predicted, was used as the first test case. The nozzle guide vanes of the VKI low-speed turbine facility were used to validate the Euler code in highly 3D environment. Despite the high turning and the secondary flows which develop, close agreements have been obtained with experimental and numerical results associated with these test cases.

  8. Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model

    In this paper we present a time-parallel algorithm for the 3D neutrons calculation of a transient model in a nuclear reactor core. The neutrons calculation consists in numerically solving the time dependent diffusion approximation equation, which is a simplified transport equation. The numerical resolution is done with finite elements method based on a tetrahedral meshing of the computational domain, representing the reactor core, and time discretization is achieved using a θ-scheme. The transient model presents moving control rods during the time of the reaction. Therefore, cross-sections (piecewise constants) are taken into account by interpolations with respect to the velocity of the control rods. The parallelism across the time is achieved by an adequate use of the parareal in time algorithm to the handled problem. This parallel method is a predictor corrector scheme that iteratively combines the use of two kinds of numerical propagators, one coarse and one fine. Our method is made efficient by means of a coarse solver defined with large time step and fixed position control rods model, while the fine propagator is assumed to be a high order numerical approximation of the full model. The parallel implementation of our method provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch–Maurer–Werner benchmark

  9. Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model

    Baudron, Anne-Marie, E-mail: anne-marie.baudron@cea.fr [Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); CEA-DRN/DMT/SERMA, CEN-Saclay, 91191 Gif sur Yvette Cedex (France); Lautard, Jean-Jacques, E-mail: jean-jacques.lautard@cea.fr [Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); CEA-DRN/DMT/SERMA, CEN-Saclay, 91191 Gif sur Yvette Cedex (France); Maday, Yvon, E-mail: maday@ann.jussieu.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7598, Laboratoire Jacques-Louis Lions and Institut Universitaire de France, F-75005, Paris (France); Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); Brown Univ, Division of Applied Maths, Providence, RI (United States); Riahi, Mohamed Kamel, E-mail: riahi@cmap.polytechnique.fr [Laboratoire de Recherche Conventionné MANON, CEA/DEN/DANS/DM2S and UPMC-CNRS/LJLL (France); CMAP, Inria-Saclay and X-Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Salomon, Julien, E-mail: salomon@ceremade.dauphine.fr [CEREMADE, Univ Paris-Dauphine, Pl. du Mal. de Lattre de Tassigny, F-75016, Paris (France)

    2014-12-15

    In this paper we present a time-parallel algorithm for the 3D neutrons calculation of a transient model in a nuclear reactor core. The neutrons calculation consists in numerically solving the time dependent diffusion approximation equation, which is a simplified transport equation. The numerical resolution is done with finite elements method based on a tetrahedral meshing of the computational domain, representing the reactor core, and time discretization is achieved using a θ-scheme. The transient model presents moving control rods during the time of the reaction. Therefore, cross-sections (piecewise constants) are taken into account by interpolations with respect to the velocity of the control rods. The parallelism across the time is achieved by an adequate use of the parareal in time algorithm to the handled problem. This parallel method is a predictor corrector scheme that iteratively combines the use of two kinds of numerical propagators, one coarse and one fine. Our method is made efficient by means of a coarse solver defined with large time step and fixed position control rods model, while the fine propagator is assumed to be a high order numerical approximation of the full model. The parallel implementation of our method provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch–Maurer–Werner benchmark.

  10. Effect of Frictions on the Ballistic Performance of a 3D Warp Interlock Fabric: Numerical Analysis

    Ha-Minh, Cuong; Boussu, François; Kanit, Toufik; Crépin, David; Imad, Abdellatif

    2012-06-01

    3D interlock woven fabrics are promising materials to replace the 2D structures in the field of ballistic protection. The structural complexity of this material caused many difficulties in numerical modeling. This paper presents a new tool that permits to generate a geometry model of any woven fabric, then, mesh this model in shell or solid elements, and apply the mechanical properties of yarns to them. The tool shows many advantages over existing software. It is very handy in use with an organization of the functions in menu and using a graphic interface. It can describe correctly the geometry of all textile woven fabrics. With this tool, the orientation of the local axes of finite elements following the yarn direction facilitates defining the yarn mechanical properties in a numerical model. This tool can be largely applied because it is compatible with popular finite element codes such as Abaqus, Ansys, Radioss etc. Thanks to this tool, a finite element model was carried out to describe a ballistic impact on a 3D warp interlock Kevlar KM2® fabric. This work focuses on studying the effect of friction onto the ballistic impact behavior of this textile interlock structure. Results showed that the friction among yarns affects considerably on the impact behavior of this fabric. The effect of the friction between projectile and yarn is less important. The friction plays an important role in keeping the fabric structural stability during the impact event. This phenomenon explained why the projectile is easier to penetrate this 3D warp interlock fabric in the no-friction case. This result also indicates that the ballistic performance of the interlock woven fabrics can be improved by using fibers with great friction coefficients.

  11. 3-D numerical investigation of subsurface flow in anisotropic porous media using multipoint flux approximation method

    Negara, Ardiansyah

    2013-01-01

    Anisotropy of hydraulic properties of subsurface geologic formations is an essential feature that has been established as a consequence of the different geologic processes that they undergo during the longer geologic time scale. With respect to petroleum reservoirs, in many cases, anisotropy plays significant role in dictating the direction of flow that becomes no longer dependent only on the pressure gradient direction but also on the principal directions of anisotropy. Furthermore, in complex systems involving the flow of multiphase fluids in which the gravity and the capillarity play an important role, anisotropy can also have important influences. Therefore, there has been great deal of motivation to consider anisotropy when solving the governing conservation laws numerically. Unfortunately, the two-point flux approximation of finite difference approach is not capable of handling full tensor permeability fields. Lately, however, it has been possible to adapt the multipoint flux approximation that can handle anisotropy to the framework of finite difference schemes. In multipoint flux approximation method, the stencil of approximation is more involved, i.e., it requires the involvement of 9-point stencil for the 2-D model and 27-point stencil for the 3-D model. This is apparently challenging and cumbersome when making the global system of equations. In this work, we apply the equation-type approach, which is the experimenting pressure field approach that enables the solution of the global problem breaks into the solution of multitude of local problems that significantly reduce the complexity without affecting the accuracy of numerical solution. This approach also leads in reducing the computational cost during the simulation. We have applied this technique to a variety of anisotropy scenarios of 3-D subsurface flow problems and the numerical results demonstrate that the experimenting pressure field technique fits very well with the multipoint flux approximation

  12. Laminar Plasma Dynamos

    Wang, Z; Barnes, C W; Barnes, D C; Wang, Zhehui; Pariev, Vladimir I.; Barnes, Cris W.; Barnes, Daniel C.

    2002-01-01

    A new kind of dynamo utilizing flowing laboratory plasmas has been identified. Conversion of plasma kinetic energy to magnetic energy is verified numerically by kinematic dynamo simulations for magnetic Reynolds numbers above 210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed plasma dynamos correspond to laminar flow topology. Modest plasma parameters, 1-20 eV temperatures, 10^{19}-10^{20} m^{-3} densities in 0.3-1.0 m scale-lengths driven by velocities on the order of the Alfven Critical Ionization Velocity (CIV), self-consistently satisfy the conditions needed for the magnetic field amplication. Growth rates for the plasma dynamos are obtained numerically with different geometry and magnetic Reynolds numbers. Magnetic-field-free coaxial plasma guns can be used to sustain the plasma flow and the dynamo.

  13. Implementation of a 3d numerical model of a folded multilayer carbonate aquifer

    Di Salvo, Cristina; Guyennon, Nicolas; Romano, Emanuele; Bruna Petrangeli, Anna; Preziosi, Elisabetta

    2016-04-01

    The main objective of this research is to present a case study of the numerical model implementation of a complex carbonate, structurally folded aquifer, with a finite difference, porous equivalent model. The case study aquifer (which extends over 235 km2 in the Apennine chain, Central Italy) provides a long term average of 3.5 m3/s of good quality groundwater to the surface river network, sustaining the minimum vital flow, and it is planned to be exploited in the next years for public water supply. In the downstream part of the river in the study area, a "Site of Community Importance" include the Nera River for its valuable aquatic fauna. However, the possible negative effects of the foreseen exploitation on groundwater dependent ecosystems are a great concern and model grounded scenarios are needed. This multilayer aquifer was conceptualized as five hydrostratigraphic units: three main aquifers (the uppermost unconfined, the central and the deepest partly confined), are separated by two locally discontinuous aquitards. The Nera river cuts through the two upper aquifers and acts as the main natural sink for groundwater. An equivalent porous medium approach was chosen. The complex tectonic structure of the aquifer requires several steps in defining the conceptual model; the presence of strongly dipping layers with very heterogeneous hydraulic conductivity, results in different thicknesses of saturated portions. Aquifers can have both unconfined or confined zones; drying and rewetting must be allowed when considering recharge/discharge cycles. All these characteristics can be included in the conceptual and numerical model; however, being the number of flow and head target scarce, the over-parametrization of the model must be avoided. Following the principle of parsimony, three steady state numerical models were developed, starting from a simple model, and then adding complexity: 2D (single layer), QUASI -3D (with leackage term simulating flow through aquitards) and

  14. Coolability of a 3D homogeneous debris bed, experimental and numerical investigations

    Within the framework of nuclear safety analysis, we present here experimental and numerical results in the field of debris bed coolability. Experimental data are provided by the SILFIDE 3D experimental facility in which the debris bed is heated by induction, at Electricite de France (EDF). Numerical computations are obtained with MC3D-REPO which is a 3-phase and 3D code developed by the Commissariat a l'Energie Atomique (CEA). The uniform debris bed consists of 2 and 3,17 mm diameter steel beads contained in a 50 cm x 60 cm x 10 cm vessel. Water is used as a coolant and can be introduced either by the top or the bottom of the bed at a determined temperature. Due to heterogeneous power distribution within the bed, two definitions for the critical heat flux are proposed: the classical mean value and the local flux (much higher). Even in the first case, the measured dryout heat flux is higher than the Lipinsky 1-D flux. Temperature curve analyses show that the dryout phenomenon is very local, therefore one should be careful about the right flux definition to use. As the injected power is being increased stepwise, steady temperature stages above saturation temperature before dryout can be observed. A discussion is proposed. For some very high values of the induction power, some spheres melted together, leading to a bigger non-porous region. Even if the local temperature went over 1300 C, the bed was still coolable and the critical heat flux value was not impacted. Some parametric studies led to the following conclusions: bottom coolant injection leads to a twice time higher critical flux than by top injection, the influence of the height of the water pool above debris bed is negligible, a sub-cooled liquid injection has no influence on the coolability. Fluidization of surface particles is also discussed. The MC3D-REPO model assumes a thermal equilibrium between the three phases, which gives results in agreement with experiments until dryout occurs. (author)

  15. Terascale direct numerical simulations of turbulent combustion using S3D

    Chen, J. H.; Choudhary, A.; de Supinski, B.; DeVries, M.; Hawkes, E. R.; Klasky, S.; Liao, W. K.; Ma, K. L.; Mellor-Crummey, J.; Podhorszki, N.; Sankaran, R.; Shende, S.; Yoo, C. S.

    2009-01-01

    Computational science is paramount to the understanding of underlying processes in internal combustion engines of the future that will utilize non-petroleum-based alternative fuels, including carbon-neutral biofuels, and burn in new combustion regimes that will attain high efficiency while minimizing emissions of particulates and nitrogen oxides. Next-generation engines will likely operate at higher pressures, with greater amounts of dilution and utilize alternative fuels that exhibit a wide range of chemical and physical properties. Therefore, there is a significant role for high-fidelity simulations, direct numerical simulations (DNS), specifically designed to capture key turbulence-chemistry interactions in these relatively uncharted combustion regimes, and in particular, that can discriminate the effects of differences in fuel properties. In DNS, all of the relevant turbulence and flame scales are resolved numerically using high-order accurate numerical algorithms. As a consequence terascale DNS are computationally intensive, require massive amounts of computing power and generate tens of terabytes of data. Recent results from terascale DNS of turbulent flames are presented here, illustrating its role in elucidating flame stabilization mechanisms in a lifted turbulent hydrogen/air jet flame in a hot air coflow, and the flame structure of a fuel-lean turbulent premixed jet flame. Computing at this scale requires close collaborations between computer and combustion scientists to provide optimized scaleable algorithms and software for terascale simulations, efficient collective parallel I/O, tools for volume visualization of multiscale, multivariate data and automating the combustion workflow. The enabling computer science, applied to combustion science, is also required in many other terascale physics and engineering simulations. In particular, performance monitoring is used to identify the performance of key kernels in the DNS code, S3D and especially memory

  16. Terascale direct numerical simulations of turbulent combustion using S3D

    Computational science is paramount to the understanding of underlying processes in internal combustion engines of the future that will utilize non-petroleum-based alternative fuels, including carbon-neutral biofuels, and burn in new combustion regimes that will attain high efficiency while minimizing emissions of particulates and nitrogen oxides. Next-generation engines will likely operate at higher pressures, with greater amounts of dilution and utilize alternative fuels that exhibit a wide range of chemical and physical properties. Therefore, there is a significant role for high-fidelity simulations, direct numerical simulations (DNS), specifically designed to capture key turbulence-chemistry interactions in these relatively uncharted combustion regimes, and in particular, that can discriminate the effects of differences in fuel properties. In DNS, all of the relevant turbulence and flame scales are resolved numerically using high-order accurate numerical algorithms. As a consequence terascale DNS are computationally intensive, require massive amounts of computing power and generate tens of terabytes of data. Recent results from terascale DNS of turbulent flames are presented here, illustrating its role in elucidating flame stabilization mechanisms in a lifted turbulent hydrogen/air jet flame in a hot air coflow, and the flame structure of a fuel-lean turbulent premixed jet flame. Computing at this scale requires close collaborations between computer and combustion scientists to provide optimized scaleable algorithms and software for terascale simulations, efficient collective parallel I/O, tools for volume visualization of multiscale, multivariate data and automating the combustion workflow. The enabling computer science, applied to combustion science, is also required in many other terascale physics and engineering simulations. In particular, performance monitoring is used to identify the performance of key kernels in the DNS code, S3D and especially memory

  17. Generating Irregular Models for 3D Spherical-Particle-Based Numerical Methods

    Gang-Hai Huang

    2013-01-01

    Full Text Available The realistic representation of an irregular geological body is essential to the construction of a particle simulation model. A three-dimensional (3D sphere generator for an irregular model (SGIM, which is based on the platform of Microsoft Foundation Classes (MFC in VC++, is developed to accurately simulate the inherent discontinuities in geological bodies. OpenGL is employed to visualize the modeling in the SGIM. Three key functions, namely, the basic-model-setup function, the excavating function, and the cutting function, are implemented. An open-pit slope is simulated using the proposed model. The results demonstrate that an extremely irregular 3D model of a geological body can be generated using the SGIM and that various types of discontinuities can be inserted to cut the model. The data structure of the model that is generated by the SGIM is versatile and can be easily modified to match various numerical calculation tools. This can be helpful in the application of particle simulation methods to large-scale geoengineering projects.

  18. 3D numerical investigation of turbulent flow through lateral intake in open channel

    The flow at a channel bifurcation is turbulent, highly three-dimensional (3D) and has many complex features. There is transverse motion accompanying the main flow and an extensive separation zone that develops in the branch channel. This zone causes hydraulic and sedimentation problems that must be known before designing the system. This necessitates a deeper insight into the flow patterns and shear stress distributions near the solid boundaries. This paper reports a 3D numerical investigation of flow pattern and shear stress distribution at a lateral intake in an open channel. Simulations are done on rectangular channel geometry, with smooth bed and sidewalls. The CFD model uses the standard k-ε and k-ω model of Wilcox turbulence closure schemes as implemented in the FLUENT code. The simulation results were compared with available experimental data. It was found that both turbulence models used accurately predicted velocity profiles in the main channel but in the branch channel, the k-ω model is performed better than the k-ε turbulence model. (author)

  19. 3D printing device for numerical control machine and wood deposition

    Julien Gardan

    2014-12-01

    Full Text Available The paper presents the development of a new sustainable approach in additive manufacturing adapted on a Numerical Control (NC machining. Wood has several advantages that are transferable to various derivatives allowing the introduction of sustainable material into the product lifecycle. The application involves the integration of wood pulp into rapid prototyping solutions. Wood is the main material studied for its ecological aspect. The primary goal was to create reconstituted wood objects through a rapid manufacturing. Additive manufacturing technology is most commonly used for modeling, prototyping, tooling through an exclusive machine or 3D printer. An overall review and an analysis of technologies show that the additive manufacturing presents some little independent solutions [9] [12]. The problem studied especially the additive manufacturing limits to produce an ecological product with materials from biomass. The study developed a 3d printing head as solution for shaping wood pulp or powder materials. Some technological problematic require enslavement to the NC controller, the programming building of model, and the realization of wood pulp. This work also presents a wood pulping process characterized by adding wood flour and starch. A machine implementation and some application examples used for its development are presented.

  20. 3D numerical simulation of the transport of chemical signature compounds from buried landmines

    Irrazabal, Maik; Borrero, Ernesto; Briano, Julio G.; Castro, Miguel; Hernandez, Samuel P.

    2005-06-01

    The transport of the chemical signature compounds from buried landmines in a three-dimensional (3D) array has been numerically modeled using the finite-volume technique. Compounds such as trinitrotoluene, dinitrotoluene, and their degradation products, are semi volatile and somewhat soluble in water. Furthermore, they can strongly adsorb to the soil and undergo chemical and biological degradation. Consequently, the spatial and temporal concentration distributions of such chemicals depend on the mobility of the water and gaseous phases, their molecular and mechanical diffusion, adsorption characteristics, soil water content, compaction, and environmental factors. A 3D framework is required since two-dimensional (2D) symmetry may easily fade due to terrain topography: non-flat surfaces, soil heterogeneity, or underground fractures. The spatial and temporal distribution of the chemical-signature-compounds, in an inclined grid has been obtained. The fact that the chemicals may migrate horizontally, giving higher surface concentrations at positions not directly on top of the objects, emphasizes the need for understanding the transport mechanism when a chemical detector is used. Deformation in the concentration contours after rainfall is observed in the inclined surface and is attributed to both: the advective flux, and to the water flux at the surface caused by the slope. The analysis of the displacements in the position of the maximum concentrations at the surface, respect to the actual location of the mine, in an inclined system, is presented.

  1. Direct numerical simulation of the axial dipolar dynamo in the Von Kármán Sodium experiment

    Nore, C.; Castanon Quiroz, D.; Cappanera, L.; Guermond, J.-L.

    2016-06-01

    For the first time, a direct numerical simulation of the incompressible, fully nonlinear, magnetohydrodynamic (MHD) equations for the Von Kármán Sodium (VKS) experiment is presented with the two counter-rotating impellers realistically represented. Dynamo thresholds are obtained for various magnetic permeabilities of the impellers and it is observed that the threshold decreases as the magnetic permeability increases. Hydrodynamic results compare well with experimental data in the same range of kinetic Reynolds numbers: at small impeller rotation frequency, the flow is steady; at larger frequency, the fluctuating flow is characterized by small scales and helical vortices localized between the blades. MHD computations show that two distinct magnetic families compete at small kinetic Reynolds number and these two families merge at larger kinetic Reynolds number. In both cases, using ferromagnetic material for the impellers decreases the dynamo threshold and enhances the axisymmetric component of the magnetic field: the resulting dynamo is a mostly axisymmetric axial dipole with an azimuthal component concentrated in the impellers as observed in the VKS experiment.

  2. Numerical modeling of time domain 3-D problems in accelerator physics

    Time domain analysis is relevant in particle accelerators to study the electromagnetic field interaction of a moving source particle on a lagging test particle as the particles pass an accelerating cavity or some other structure. These fields are called wake fields. The travelling beam inside a beam pipe may undergo more complicated interactions with its environment due to the presence of other irregularities like wires, thin slots, joints and other types of obstacles. Analytical solutions of such problems is impossible and one has to resort to a numerical method. In this paper we present results of our first attempt to model these problems in 3-D using our finite difference time domain (FDTD) code. 10 refs., 9 figs

  3. Slab detachment in laterally varying subduction zones: 3-D numerical modeling

    Duretz, T.; Gerya, T. V.; Spakman, W.

    2014-03-01

    Understanding the three-dimensional (3-D) dynamics of subduction-collision systems is a longstanding challenge in geodynamics. We investigate the impact of slab detachment in collision systems that are subjected to along-trench variations. High-resolution thermomechanical numerical models, encompassing experimentally derived flow laws and a pseudo free surface, are employed to unravel lithospheric and topographic evolutions. First, we consider coeval subduction of adjacent continental and oceanic lithospheres (SCO). This configuration yields to two-stage slab detachment during collision, topographic buildup and extrusion, variable along-trench convergence rates, and associated trench deformation. The second setting considers a convergent margin, which is laterally limited by a transform boundary (STB). Such collisional system is affected by a single slab detachment, little trench deformation, and moderately confined upper plate topography. The effect of initial thermal slab age on SCO and STB models are explored. Similarities with natural analogs along the Arabia-Eurasia collision are discussed.

  4. Numerical determination of OPE coefficients in the 3D Ising model from off-critical correlators

    Caselle, M; Magnoli, N

    2015-01-01

    We propose a general method for the numerical evaluation of OPE coefficients in three dimensional Conformal Field Theories based on the study of the conformal perturbation of two point functions in the vicinity of the critical point. We test our proposal in the three dimensional Ising Model, looking at the magnetic perturbation of the $$, $$ and $$ correlators from which we extract the values of $C^{\\sigma}_{\\sigma\\epsilon}=1.07(3)$ and $C^{\\epsilon}_{\\epsilon\\epsilon}=1.45(30)$. Our estimate for $C^{\\sigma}_{\\sigma\\epsilon}$ agrees with those recently obtained using conformal bootstrap methods, while $C^{\\epsilon}_{\\epsilon\\epsilon}$, as far as we know, is new and could be used to further constrain conformal bootstrap analyses of the 3d Ising universality class.

  5. Full 3-D numerical modeling of borehole electric image logging and the evaluation model of fracture

    2008-01-01

    A full 3-D finite element method numerical modeling program is written based on the principle and technical specification of borehole electric image well logging tool. The response of well logging is computed in the formation media model with a single fracture. The effect of changing fracture aperture and resistivity ratio to the logging response is discussed. The identification ability for two parallel fractures is also present. A quantitative evaluation formula of fracture aperture from borehole electric image logging data is set up. A case study of the model well is done to verify the accuracy of the for-mula. The result indicates that the formula is more accurate than the foreign one.

  6. Volatile transport on inhomogeneous surfaces: II. Numerical calculations (VT3D)

    Young, Leslie A

    2015-01-01

    Several distant icy worlds have atmospheres that are in vapor-pressure equilibrium with their surface volatiles, including Pluto, Triton, and, probably, several large KBOs near perihelion. Studies of the volatile and thermal evolution of these have been limited by computational speed, especially for models that treat surfaces that vary with both latitude and longitude. In order to expedite such work, I present a new numerical model for the seasonal behavior of Pluto and Triton which (i) uses initial conditions that improve convergence, (ii) uses an expedient method for handling the transition between global and non-global atmospheres, (iii) includes local conservation of energy and global conservation of mass to partition energy between heating, conduction, and sublimation or condensation, (iv) uses time-stepping algorithms that ensure stability while allowing larger timesteps, and (v) can include longitudinal variability. This model, called VT3D, has been used in Young (2012), Young (2013), Olkin et al. (201...

  7. 3D numerical investigation on landslide generated tsunamis around a conical island

    Montagna, Francesca; Bellotti, Giorgio

    2010-05-01

    This paper presents numerical computations of tsunamis generated by subaerial and submerged landslides falling along the flank of a conical island. The study is inspired by the tsunamis that on 30th December 2002 attacked the coast of the volcanic island of Stromboli (South Tyrrhenian sea, Italy). In particular this paper analyzes the important feature of the lateral spreading of landside generated tsunamis and the associated flooding hazard. The numerical model used in this study is the full three dimensional commercial code FLOW-3D. The model has already been successfully used (Choi et al., 2007; 2008; Chopakatla et al, 2008) to study the interaction of waves and structures. In the simulations carried out in this work a particular feature of the code has been employed: the GMO (General Moving Object) algorithm. It allows to reproduce the interaction between moving objects, as a landslide, and the water. FLOW-3D has been firstly validated using available 3D experiments reproducing tsunamis generated by landslides at the flank of a conical island. The experiments have been carried out in the LIC laboratory of the Polytechnic of Bari, Italy (Di Risio et al., 2009). Numerical and experimental time series of run-up and sea level recorded at gauges located at the flanks of the island and offshore have been successfully compared. This analysis shows that the model can accurately represent the generation, the propagation and the inundation of landslide generated tsunamis and suggests the use of the numerical model as a tool for preparing inundation maps. At the conference we will present the validation of the model and parametric analyses aimed to investigate how wave properties depend on the landslide kinematic and on further parameters such as the landslide volume and shape, as well as the radius of the island. The expected final results of the research are precomputed inundation maps that depend on the characteristics of the landslide and of the island. Finally we

  8. 3-D NUMERICAL SIMULATION OF CONVOY-GENERATED WAVES IN A RESTRICTED WATERWAY

    JI Sheng Cheng; OUAHSINE Abdellatif; SMAOUI Hassan; SERGENT Philippe

    2012-01-01

    We consider waves generated by the passing of convoys in a restricted waterway.The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy,such as the speed and the hull geometry.The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown.Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k-ε model for turbulent processes.The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rh(o)ne (CNR).

  9. A NUMERICAL SIMULATION OF 3-D INNER FLOW IN UP-STREAM PUMPING MECHANICAL SEAL

    ZHANG Jin-feng; YUAN Shou-qi; FU Yong-hong; FANG Yu-jian

    2006-01-01

    Numerical simulation of 3-D inner flow between Up-stream Pumping Mechanical Face Seals (UPMFS) faces was initially done by CFD software, which made the flow visualization come true.Simulation results directly discover the action of hydrodynamic lubrication, and by comparison with that of Conventional Mechanic Face Seals (CMFS), the advantage over bigger bearing capability, less friction and much less leakage are explained clearly.Otherwise there are also some different ideas and results from precedent analysis and computational research results: dynamic and static pressure profiles can be obtained respectively instead of the analytic total pressure distribution only, pressure distribution is nonlinear, while always be solved as linear, lower pressure is observed at the area of inner diameter caused by the grooves, but its possible cavitations effects to the performance of UPMFS still need further study.

  10. Comparison between the 3D numerical simulation and experiment of the bubble near different boundaries

    ZHANG AMan; YAO XiongLiang; LI Jia; GUO Jun

    2008-01-01

    Based on the potential flow theory,the vortex ring is introduced to simulate the toroidal bubble,and the boundary element method is applied to simulate the evo-lution of the bubble.Elastic-plasticity of structure being taken into account,the interaction between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite element method (FEM),and a corresponding 3D computing program is developed.This program is used to simulate the three-dimensional bubble dynamics in free field,near wall and near the elastic-plastic structure,and the numerical results are compared with the existing experimental results.The error is within 10%.The effects of different boundaries upon the bubble dynamics are presented by studying the bubble dy-namics near different boundaries.

  11. Comparison between the 3D numerical simulation and experiment of the bubble near different boundaries

    2008-01-01

    Based on the potential flow theory, the vortex ring is introduced to simulate the toroidal bubble, and the boundary element method is applied to simulate the evo- lution of the bubble. Elastic-plasticity of structure being taken into account, the interaction between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite element method (FEM), and a corresponding 3D computing program is developed. This program is used to simulate the three-dimensional bubble dynamics in free field, near wall and near the elastic-plastic structure, and the numerical results are compared with the existing experimental results. The error is within 10%. The effects of different boundaries upon the bubble dynamics are presented by studying the bubble dy- namics near different boundaries.

  12. Temperature distributions in the laser-heated diamond anvil cell from 3-D numerical modeling

    We present TempDAC, a 3-D numerical model for calculating the steady-state temperature distribution for continuous wave laser-heated experiments in the diamond anvil cell. TempDAC solves the steady heat conduction equation in three dimensions over the sample chamber, gasket, and diamond anvils and includes material-, temperature-, and direction-dependent thermal conductivity, while allowing for flexible sample geometries, laser beam intensity profile, and laser absorption properties. The model has been validated against an axisymmetric analytic solution for the temperature distribution within a laser-heated sample. Example calculations illustrate the importance of considering heat flow in three dimensions for the laser-heated diamond anvil cell. In particular, we show that a “flat top” input laser beam profile does not lead to a more uniform temperature distribution or flatter temperature gradients than a wide Gaussian laser beam

  13. Numerical Investigation of Nozzle Geometry Effect on Turbulent 3-D Water Offset Jet Flows

    Negar Mohammad Aliha

    2016-01-01

    Full Text Available Using the Yang-Shih low Reynolds k-ε turbulence model, the mean flow field of a turbulent offset jet issuing from a long circular pipe was numerically investigated. The experimental results were used to verify the numerical results such as decay rate of streamwise velocity, locus of maximum streamwise velocity, jet half width in the wall normal and lateral directions, and jet velocity profiles. The present study focused attention on the influence of nozzle geometry on the evolution of a 3D incompressible turbulent offset jet. Circular, square-shaped, and rectangular nozzles were considered here. A comparison between the mean flow characteristics of offset jets issuing from circular and square-shaped nozzles, which had equal area and mean exit velocity, were made numerically. Moreover, the effect of aspect ratio of rectangular nozzles on the main features of the flow was investigated. It was shown that the spread rate, flow entrainment, and mixing rate of an offset jet issuing from circular nozzle are lower than square-shaped one. In addition, it was demonstrated that the aspect ratio of the rectangular nozzles only affects the mean flow field of the offset jet in the near field (up to 15 times greater than equivalent diameter of the nozzles. Furthermore, other parameters including the wall shear stress, flow entrainment and the length of potential core were also investigated.

  14. Landslide/reservoir interaction: 3D numerical modelling of the Vajont rockslide and generated water wave

    Crosta, G.; Imposimato, S.; Roddeman, D.; Frattini, P.

    2012-04-01

    Fast moving landslides can be originated along slopes in mountainous terrains with natural and artificial lakes, or fjords at the slope foot. This landslides can reach extremely high speed and the impact with the immobile reservoir water can be influenced by the local topography and the landslide mass profile. The impact can generate large impulse waves and landslide tsunami. Initiation, propagation and runup are the three phases that need to be considered. The landslide evolution and the consequent wave can be controlled by the initial mass position (subaerial, partially or completely submerged), the landslide speed, the type of material, the subaerial and subaqueous slope geometry, the landslide depth and length at the impact, and the water depth. Extreme events have been caused by subaerial landslides: the 1963 Vajont rockslide (Italy), the 1958 Lituya Bay event (Alaska), the Tafjord and the Loen multiple events event (Norway), also from volcanic collapses (Hawaii and Canary islands). Various researchers completed a systematic experimental work on 2D and 3D wave generation and propagation (Kamphuis and Bowering, 1970; Huber, 1980; Müller, 1995; Huber and Hager, 1997; Fritz, 2002; Zweifel, 2004; Panizzo et al., 2005; Heller, 2007; Heller and Kinnear, 2010; Sælevik et al., 2009), using both rigid blocks and deformable granular" masses. Model data and results have been used to calibrate and validate numerical modelling tools (Harbitz, 1992; Jiang and LeBlond, 1993; Grilli et al., 2002; Grilli and Watts, 2005; Lynett and Liu, 2005; Tinti et al., 2006; Abadie et al., 2010) generally considering simplified rheologies (e.g. viscous rheologies) for subaerial subaqueous spreading. We use a FEM code (Roddeman, 2011; Crosta et al., 2006, 2009, 2010, 2011) adopting an Eulerian-Lagrangian approach to give accurate results for large deformations. We model both 2D and fully 3D events considering different settings. The material is considered as a fully deformable elasto

  15. Laminar Plasma Dynamos

    Wang, Zhehui; Pariev, Vladimir I.; Barnes, Cris W.; Barnes, Daniel C.

    2002-01-01

    A new kind of dynamo utilizing flowing laboratory plasmas has been identified. Conversion of plasma kinetic energy to magnetic energy is verified numerically by kinematic dynamo simulations for magnetic Reynolds numbers above 210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed plasma dynamos correspond to laminar flow topology. Modest plasma parameters, 1-20 eV temperatures, 10^{19}-10^{20} m^{-3} densities in 0.3-1.0 m scale-lengths driven by velocities on the orde...

  16. 3D geomechanical-numerical modelling of the absolute stress state for geothermal reservoir exploration

    Reiter, Karsten; Heidbach, Oliver; Moeck, Inga

    2013-04-01

    For the assessment and exploration of a potential geothermal reservoir, the contemporary in-situ stress is of key importance in terms of well stability and orientation of possible fluid pathways. However, available data, e.g. Heidbach et al. (2009) or Zang et al. (2012), deliver only point wise information of parts of the six independent components of the stress tensor. Moreover most measurements of the stress orientation and magnitude are done for hydrocarbon industry obvious in shallow depth. Interpolation across long distances or extrapolation into depth is unfavourable, because this would ignore structural features, inhomogeneity's in the crust or other local effects like topography. For this reasons geomechanical numerical modelling is the favourable method to quantify orientations and magnitudes of the 3D stress field for a geothermal reservoir. A geomechanical-numerical modelling, estimating the 3D absolute stress state, requires the initial stress state as model constraints. But in-situ stress measurements within or close by a potential reservoir are rare. For that reason a larger regional geomechanical-numerical model is necessary, which derive boundary conditions for the wanted local reservoir model. Such a large scale model has to be tested against in-situ stress measurements, orientations and magnitudes. Other suitable and available data, like GPS measurements or fault slip rates are useful to constrain kinematic boundary conditions. This stepwise approach from regional to local scale takes all stress field factors into account, from first over second up to third order. As an example we present a large scale crustal and upper mantle 3D-geomechanical-numerical model of the Alberta Basin and the surroundings, which is constructed to describe continuously the full stress tensor. In-situ stress measurements are the most likely data, because they deliver the most direct information's of the stress field and they provide insights into different depths, a

  17. 3D numerical model of the Omega Nebula (M17): simulated thermal X-ray emission

    Reyes-Iturbide, J; Rosado, M; Rodríguez-Gónzalez, A; González, R F; Esquivel, A

    2009-01-01

    We present 3D hydrodynamical simulations of the superbubble M17, also known as the Omega nebula, carried out with the adaptive grid code yguazu'-a, which includes radiative cooling. The superbubble is modelled considering the winds of 11 individual stars from the open cluster inside the nebula (NGC 6618), for which there are estimates of the mass loss rates and terminal velocities based on their spectral types. These stars are located inside a dense interstellar medium, and they are bounded by two dense molecular clouds. We carried out three numerical models of this scenario, considering different line of sight positions of the stars (the position in the plane of the sky is known, thus fixed). Synthetic thermal X-ray emission maps are calculated from the numerical models and compared with ROSAT observations of this astrophysical object. Our models reproduce successfully both the observed X-ray morphology and the total X-ray luminosity, without taking into account thermal conduction effects.

  18. The Making of FR Is I. Numerical Hydrodynamic 3D Simulations of Low Power Jets

    Massaglia, S; Rossi, P; Capetti, S; Mignone, A

    2016-01-01

    Extragalactic radiosources have been classified in two classes, Fanaroff-Riley I and II, which differ in morphology and radio power. Strongly emitting sources belong to the edge brightened FR II class while the weak ones to the edge darkened FR I class. The origin of this dichotomy is not yet fully understood. Numerical simulations are successful in generating FR~II morphologies but they fail to reproduce the diffuse structure of FR Is. By means of hydro-dynamical 3D simulations of supersonic jets, we investigate how the displayed morphologies depend on the jet parameters. Bow shocks and Mach disks at the jet's head, likely responsible for the presence of hot spots in the FR II sources, disappear for a jet kinetic power less than 10^43 erg/s. This threshold compares favorably with the luminosity at which the FR~I/FR~II transition is observed. The problem is addressed by numerical means carrying out three-dimensional HD simulations of supersonic jets that propagate in a non homogeneous medium with the ambient ...

  19. A parametric study of mucociliary transport by numerical simulations of 3D non-homogeneous mucus.

    Chatelin, Robin; Poncet, Philippe

    2016-06-14

    Mucociliary clearance is the natural flow of the mucus which covers and protects the lung from the outer world. Pathologies, like cystic fibrosis, highly change the biological parameters of the mucus flow leading to stagnation situations and pathogens proliferation. As the lung exhibits a complex dyadic structure, in-vivo experimental study of mucociliary clearance is almost impossible and numerical simulations can bring important knowledge about this biological flow. This paper brings a detailed study of the biological parameters influence on the mucociliary clearance, in particular for pathological situations such as cystic fibrosis. Using recent suitable numerical methods, a non-homogeneous mucus flow (including non-linearities) can be simulated efficiently in 3D, allowing the identification of the meaningful parameters involved in this biological flow. Among these parameters, it is shown that the mucus viscosity, the stiffness transition between pericilliary fluid and mucus, the pericilliary fluid height as well as both cilia length and beating frequency have a great influence on the mucociliary transport. PMID:27126985

  20. 3D numerical simulations of negative hydrogen ion extraction using realistic plasma parameters, geometry of the extraction aperture and full 3D magnetic field map

    Mochalskyy, S.; Wünderlich, D.; Ruf, B.; Franzen, P.; Fantz, U.; Minea, T.

    2014-02-01

    Decreasing the co-extracted electron current while simultaneously keeping negative ion (NI) current sufficiently high is a crucial issue on the development plasma source system for ITER Neutral Beam Injector. To support finding the best extraction conditions the 3D Particle-in-Cell Monte Carlo Collision electrostatic code ONIX (Orsay Negative Ion eXtraction) has been developed. Close collaboration with experiments and other numerical models allows performing realistic simulations with relevant input parameters: plasma properties, geometry of the extraction aperture, full 3D magnetic field map, etc. For the first time ONIX has been benchmarked with commercial positive ions tracing code KOBRA3D. A very good agreement in terms of the meniscus position and depth has been found. Simulation of NI extraction with different e/NI ratio in bulk plasma shows high relevance of the direct negative ion extraction from the surface produced NI in order to obtain extracted NI current as in the experimental results from BATMAN testbed.

  1. Optimising GPR modelling: A practical, multi-threaded approach to 3D FDTD numerical modelling

    Millington, T. M.; Cassidy, N. J.

    2010-09-01

    The demand for advanced interpretational tools has lead to the development of highly sophisticated, computationally demanding, 3D GPR processing and modelling techniques. Many of these methods solve very large problems with stepwise methods that utilise numerically similar functions within iterative computational loops. Problems of this nature are readily parallelised by splitting the computational domain into smaller, independent chunks for direct use on cluster-style, multi-processor supercomputers. Unfortunately, the implications of running such facilities, as well as time investment needed to develop the parallel codes, means that for most researchers, the use of these advanced methods is too impractical. In this paper, we propose an alternative method of parallelisation which exploits the capabilities of the modern multi-core processors (upon which today's desktop PCs are built) by multi-threading the calculation of a problem's individual sub-solutions. To illustrate the approach, we have applied it to an advanced, 3D, finite-difference time-domain (FDTD) GPR modelling tool in which the calculation of the individual vector field components is multi-threaded. To be of practical use, the FDTD scheme must be able to deliver accurate results with short execution times and we, therefore, show that the performance benefits of our approach can deliver runtimes less than half those of the more conventional, serial programming techniques. We evaluate implementations of the technique using different programming languages (e.g., Matlab, Java, C++), which will facilitate the construction of a flexible modelling tool for use in future GPR research. The implementations are compared on a variety of typical hardware platforms, having between one and eight processing cores available, and also a modern Graphical Processing Unit (GPU)-based computer. Our results show that a multi-threaded xyz modelling approach is easy to implement and delivers excellent results when implemented

  2. 3D NUMERICAL INVESTIGATION ON SETTLING BASIN LAYOUT : A case study on Mai Khola Hydropower Project, Nepal

    Shrestha, Bishwo Vijaya

    2012-01-01

    This study is about 3D Numerical Investigation of Settling basin layout by using numerical modeling program SSIIM. This study is carried out by using SSIIM windows version 1 (SSIIM 1.0). SSIIM is numerical modeling software, developed at NTNU by Professor Nils Reidar B. Olsen. This program has been used for investigation numerical modeling of hydraulic and sediment transport for different layouts geometry of settling basin.In this study a case study has carried out on settling basin layout of...

  3. 3D NUMERICAL INVESTIGATION ON SETTLING BASIN LAYOUT: A case study on Mai Khola Hydropower Project, Nepal

    Shrestha, Bishwo Vijaya

    2012-01-01

    This study is about 3D Numerical Investigation of Settling basin layout by using numerical modeling program SSIIM. This study is carried out by using SSIIM windows version 1 (SSIIM 1.0). SSIIM is numerical modeling software, developed at NTNU by Professor Nils Reidar B. Olsen. This program has been used for investigation numerical modeling of hydraulic and sediment transport for different layouts geometry of settling basin.In this study a case study has carried out on settling basin layout of...

  4. Comparison of 3-D finite element model of ashlar masonry with 2-D numerical models of ashlar masonry

    Beran, Pavel

    2016-06-01

    3-D state of stress in heterogeneous ashlar masonry can be also computed by several suitable chosen 2-D numerical models of ashlar masonry. The results obtained from 2-D numerical models well correspond to the results obtained from 3-D numerical model. The character of thermal stress is the same. While using 2-D models the computational time is reduced more than hundredfold and therefore this method could be used for computation of thermal stresses during long time periods with 10 000 of steps.

  5. Numerical 3D models support two distinct hydrothermal circulation systems at fast spreading ridges

    Hasenclever, Jörg; Theissen-Krah, Sonja; Rüpke, Lars

    2013-04-01

    We present 3D numerical calculations of hydrothermal fluid flow at fast spreading ridges. The setup of the 3D models is based our previous 2D studies, in which we have coupled numerical models for crustal accretion and hydrothermal fluid flow. One result of these calculations is a crustal permeability field that leads to a thermal structure in the crust that matches seismic tomography data of the East Pacific Rise (EPR). The 1000°C isotherm obtained from the 2D results is now used as the lower boundary of the 3D model domain, while the upper boundary is a smoothed bathymetry of the EPR. The same permeability field as in the 2D models is used, with the highest permeability at the ridge axis and a decrease with both depth and distance to the ridge. Permeability is also reduced linearly between 600 and 1000°C. Using a newly developed parallel finite element code written in Matlab that solves for thermal evolution, fluid pressure and Darcy flow, we simulate the flow patterns of hydrothermal circulation in a segment of 5000m along-axis, 10000m across-axis and up to 5000m depth. We observe two distinct hydrothermal circulation systems: An on-axis system forming a series of vents with a spacing ranging from 100 to 500m that is recharged by nearby (100-200m) downflows on both sides of the ridge axis. Simultaneously a second system with much broader extensions both laterally and vertically exists off-axis. It is recharged by fluids intruding between 1500m to 5000m off-axis and sampling both upper and lower crust. These fluids are channeled in the deepest and hottest regions with high permeability and migrate up-slope following the 600°C isotherm until reaching the edge of the melt lens. Depending on the width of the melt lens these off-axis fluids either merge with the on-axis hydrothermal system or form separate vents. We observe separate off-axis vent fields if the magma lens half-width exceeds 1000m and confluence of both systems for half-widths smaller than 500m. For

  6. A novel code for numerical 3-D MHD studies of CME expansion

    J. Kleimann

    2009-03-01

    Full Text Available A recent third-order, essentially non-oscillatory central scheme to advance the equations of single-fluid magnetohydrodynamics (MHD in time has been implemented into a new numerical code. This code operates on a 3-D Cartesian, non-staggered grid, and is able to handle shock-like gradients without producing spurious oscillations.

    To demonstrate the suitability of our code for the simulation of coronal mass ejections (CMEs and similar heliospheric transients, we present selected results from test cases and perform studies of the solar wind expansion during phases of minimum solar activity. We can demonstrate convergence of the system into a stable Parker-like steady state for both hydrodynamic and MHD winds. The model is subsequently applied to expansion studies of CME-like plasma bubbles, and their evolution is monitored until a stationary state similar to the initial one is achieved. In spite of the model's (current simplicity, we can confirm the CME's nearly self-similar evolution close to the Sun, thus highlighting the importance of detailed modelling especially at small heliospheric radii.

    Additionally, alternative methods to implement boundary conditions at the coronal base, as well as strategies to ensure a solenoidal magnetic field, are discussed and evaluated.

  7. Numerical simulation of the 3D behavior of thermal buoyant airflows in pentahedral spaces

    Ridouane, El Hassan [Department of Mechanical Engineering, University of Vermont, 33 Colchester Avenue, 201 Votey Building, Burlington, VT 05405 (United States)], E-mail: eridouan@uvm.edu; Campo, Antonio [Department of Mechanical Engineering, University of Vermont, 33 Colchester Avenue, 201 Votey Building, Burlington, VT 05405 (United States)

    2008-10-15

    A numerical study of three-dimensional natural convection in an attic space with heated horizontal base and cooled upper walls is presented. Every previous study pertinent to this subject as of today has assumed that the flow in attics is two-dimensional and restricted to triangular cavities. This problem is examined for fixed aspect ratios holding width to height of 2 and depth to height of 3.33 and Rayleigh numbers ranging from 10{sup 4} to 8 x 10{sup 5}. The coupled system of conservation equations, subject to the proper boundary conditions, along with the equation of state assuming the air behaves as a perfect gas are solved with the finite volume method. In the conservation equations, the second-order-accurate QUICK scheme was used for the discretization of the convective terms and the SIMPLE scheme for the pressure-velocity coupling. It is categorically found that the flow in the attic is 3D. From the physics of the problem, two steady-state solutions are possible. The symmetrical solution prevails for relatively low Rayleigh numbers. However, as the Ra is gradually increased, a transition occurs at a critical value Ra{sub C}. Above this value of Ra{sub C}, an asymmetrical solution exhibiting a pitchfork bifurcation arises and eventually becomes steady. Results are presented detailing the occurrence of the pitchfork bifurcation and the resulting flow patterns are described.

  8. Numerical study of elastic turbulence in a 3D curvilinear micro-channel

    Zhang, Hongna; Kunugi, Tomoaki; Li, Fengchen

    2012-11-01

    Elastic turbulence is an intriguing phenomenon of viscoelastic fluid flow, and dominated by the strong nonlinear elasticity due to the existence of flexible microstructures. It implies the possibility to generate a turbulent state (so-called an elastic turbulence) in the micro-scale devices by introducing the viscoelastic fluids, which could significantly enhance the mixing efficiency therein. Several experiments have been carried out to study its characteristics and underlying physics. However, the difficulty in measuring the flow information and behaviors of the microstructures, especially in the cross section normal to the mean flow direction, limits our current understanding and controlling. In the present study, the nondimensionalization method in which the characteristic velocity is defined as the ratio of the solution viscosity to the width of the channel was adopted to simulate the elastic turbulence in the micro-scale devices. And the elastic turbulent flow was obtained numerically in the 3D curvilinear micro-channel. Therein, the characteristics of the velocity field and polymer's behavior are discussed. Moreover, the energy transfer between the kinetic energy and the polymer's elastic energy is also investigated to understand its physical mechanism. Supported by the Japan Society for the Promotion of Science research fellowship and the Ministry of Education, Culture, Sports, Science and Technology via `Energy Science in the Age of Global Warming' of Global Center of Excellence (G-COE) program (J-051).

  9. Analytic and numerical demonstration of quantum self-correction in the 3D Cubic Code

    Bravyi, Sergey

    2011-01-01

    A big open question in the quantum information theory concerns feasibility of a self-correcting quantum memory. A quantum state recorded in such memory can be stored reliably for a macroscopic time without need for active error correction if the memory is put in contact with a cold enough thermal bath. In this paper we derive a rigorous lower bound on the memory time $T_{mem}$ of the 3D Cubic Code model which was recently conjectured to have a self-correcting behavior. Assuming that dynamics of the memory system can be described by a Markovian master equation of Davies form, we prove that $T_{mem}\\ge L^{c\\beta}$ for some constant $c>0$, where $L$ is the lattice size and $\\beta$ is the inverse temperature of the bath. However, this bound applies only if the lattice size does not exceed certain critical value $L^*\\sim e^{\\beta/3}$. We also report a numerical Monte Carlo simulation of the studied memory indicating that our analytic bounds on $T_{mem}$ are tight up to constant coefficients. In order to model the ...

  10. Method of internal 3D flow field numerical simulation for hydrodynamic torque converter

    Tao SHANG; Dingxuan ZHAO; Yuankun ZHANG; Xiangen GUO; Xiangzhong SHI

    2008-01-01

    To enhance the performance of a hydrody-namic torque converter and thoroughly understand the trait of inside flow, a numerical simulation method of internal 3D flow for the three-element centrifugal hydrodynamic torque converter was systematically researched and expatiated in this paper. First, the internal flow field of each impeller was calculated. The curves that illustrate the relationships between the pressure differences of the inlet and outlet versus flux were drawn. Second, the concurrent working point of each impeller was approximately estimated. Finally, a calculation was performed considering the influence on each impeller. The flow field of a working point was solved by multiple calculations and the actual working condition was gradually determined. The pressure and velocity distributions of the flow field were proposed. The performance parameters of the hydrodynamic torque converter were predicted. The calculation method, and the proposed pressure and velocity distribution of the flow field, have practical significance for the design and improvement of a hydrodynamic torque converter.

  11. Micro-mechanics based damage mechanics for 3D Orthogonal Woven Composites: Experiment and Numerical Modelling

    Saleh, Mohamed Nasr

    2016-01-08

    Damage initiation and evolution of three-dimensional (3D) orthogonal woven carbon fibre composite (3DOWC) is investigated experimentally and numerically. Meso-scale homogenisation of the representative volume element (RVE) is utilised to predict the elastic properties, simulate damage initiation and evolution when loaded in tension. The effect of intra-yarns transverse cracking and shear diffused damage on the in-plane transverse modulus and shear modulus is investigated while one failure criterion is introduced to simulate the matrix damage. The proposed model is based on two major assumptions. First, the effect of the binder yarns, on the in-plane properties, is neglected, so the 3DOWC unit cell can be approximated as a (0o/90o) cross-ply laminate. Second, a micro-mechanics based damage approach is used at the meso-scale, so damage indicators can be correlated, explicitly, to the density of cracks within the material. Results from the simulated RVE are validated against experimental results along the warp (0o direction) and weft (90o direction). This approach paves the road for more predictive models as damage evolution laws are obtained from micro mechanical considerations and rely on few well-defined material parameters. This largely differs from classical damage mechanics approaches in which the evolution law is obtained by retrofitting experimental observations.

  12. Numerical Calculations of 3-D High-Lift Flows and Comparison with Experiment

    Compton, William B, III

    2015-01-01

    Solutions were obtained with the Navier-Stokes CFD code TLNS3D to predict the flow about the NASA Trapezoidal Wing, a high-lift wing composed of three elements: the main-wing element, a deployed leading-edge slat, and a deployed trailing-edge flap. Turbulence was modeled by the Spalart-Allmaras one-equation turbulence model. One case with massive separation was repeated using Menter's two-equation SST (Menter's Shear Stress Transport) k-omega turbulence model in an attempt to improve the agreement with experiment. The investigation was conducted at a free stream Mach number of 0.2, and at angles of attack ranging from 10.004 degrees to 34.858 degrees. The Reynolds number based on the mean aerodynamic chord of the wing was 4.3 x 10 (sup 6). Compared to experiment, the numerical procedure predicted the surface pressures very well at angles of attack in the linear range of the lift. However, computed maximum lift was 5% low. Drag was mainly under predicted. The procedure correctly predicted several well-known trends and features of high-lift flows, such as off-body separation. The two turbulence models yielded significantly different solutions for the repeated case.

  13. Numerical investigation of wave attenuation by vegetation using a 3D RANS model

    Marsooli, Reza; Wu, Weiming

    2014-12-01

    Vegetation has been recognized as an important natural shoreline protection against storm surges and waves. Understanding of wave-vegetation interaction is essential for assessing the ability of vegetation patches, such as wetlands, to mitigate storm damages. In this study the wave attenuation by vegetation is investigated numerically using a 3-D model which solves the Reynolds-Averaged Navier-Stokes equations (RANS) by means of a finite-volume method based on collocated hexahedron mesh. A mixing length model is used for turbulence closure of the RANS equations. The water surface boundary is tracked using the Volume-of-Fluid (VOF) method with the Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM) to solve the VOF advection equation. The presence of vegetation is taken into account by adding the vegetation drag and inertia forces to the momentum equations. The model is validated by several laboratory experiments of short wave propagation through vegetation over flat and sloping beds. The comparisons show good agreement between the measured data and calculated results, but the swaying motion of flexible vegetation which is neglected in this study can influence the accuracy of the wave height predictions. The model is then applied to one of the validation tests with different vegetation properties, revealing that the wave height attenuation by vegetation depends not only on the wave conditions, but also the vegetation characteristics such as vegetation height and density.

  14. High resolution 3D hydraulic numerical modelling for WEP environmental approval and engineering

    Fissel, D.B.; Jiang, J. [ASL Environmental Sciences Inc., Sidney, BC (Canada)

    2009-07-01

    This paper discussed biophysical analyses conducted to determine the impacts of a new powerhouse at the Waneta Dam on the Pen d'Oreille River. A hydraulic 3-D numerical model with a high resolution was calibrated and validated using data from field studies of river velocities, water levels, temperatures. Pre-and post-project river velocities and temperatures were compared in order to determine their impacts on the deepwater habitat of the Waneta. The aim of the study was to determine the effects of the Waneta Expansion Project (WEP) on the sub-population of white sturgeon in the confluence waters. The model assessed the impacts of various factors on sturgeon egg deposition areas in late summer water temperatures. It was concluded that the analyses will serve as a useful guide for the WEP diversion channel design and excavation, and will help determine measures for preventing bottom sediment contaminants from being re-suspended during the construction of the channel. 19 refs., 1 tab., 10 figs.

  15. Influence of aggregate shapes on drying and carbonation phenomena in 3D concrete numerical samples

    This study aims at generating numerical 3D samples of concrete so as to study the effects of the granular inclusions shape on the macroscopic kinetics of reactive transport phenomena. Two types of meso-structure configurations are considered: the first one is composed of a matrix of mortar in which are randomly distributed inclusions corresponding to the concrete coarse aggregates, and the second one also includes a steel rebar. The choice of a mesoscopic modeling for the mortar matrix is based on the need to obtain numerical structures of reasonable size. In particular, the Interfacial Transition Zones (ITZs) are assumed to be incorporated into the homogenized mortar properties. This study is applied to the case of drying and atmospheric carbonation by using simplified models solved by the finite element code Cast3M. The purpose is to quantify the influence of the aggregate shape on the kinetics of macroscopic transfer and the iso-value lines for some physical variables representative of the reactive transport problems: saturation degree for drying, and porosity, calcite and portlandite concentrations for carbonation. Basic aggregates shapes are studied (spheres, cubes), as well as more complex ones (Voronoi particles) which are supposed to be more representative of real aggregates. The effects of 'non-isotropic' shapes (oblate and prolate ones) are also investigated. It is shown that the influence of the aggregate shapes appears negligibly small on macroscopic indicators, except for oblate shapes with aspect ratios of 3. This latter case also exhibits substantial local delayed effects and a more important variability, which may have some importance for a precise description and estimation of degradation processes related to steel rebar corrosion. (authors)

  16. Simulations of astrophysical dynamos

    Brandenburg, Axel

    2010-01-01

    Numerical aspects of dynamos in periodic domains are discussed. Modifications of the solutions by numerically motivated alterations of the equations are being reviewed using the examples of magnetic hyperdiffusion and artificial diffusion when advancing the magnetic field in its Euler potential representation. The importance of using integral kernel formulations in mean-field dynamo theory is emphasized in cases where the dynamo growth rate becomes comparable with the inverse turnover time. Finally, the significance of microscopic magnetic Prandtl number in controlling the conversion from kinetic to magnetic energy is highlighted.

  17. Geodynamic background of the 2008 Wenchuan earthquake based on 3D visco-elastic numerical modelling

    Liu, Chang; Zhu, Bojing; Yang, Xiaolin; Shi, Yaolin

    2016-03-01

    The 2008 Wenchuan earthquake (Mw7.9) occurred in the Longmen Shan fault zone. The stress change and crustal deformation during the accumulation period is computed using 3D finite element modelling assuming visco-elastic rheology. Our results support that the eastward movement of the Tibetan Plateau resulting from the India-Eurasia collision is obstructed at the Longmen Shan fault zone by the strong Yangtze craton. In response, the Tibetan ductile crust thickens and accumulates at the contact between the Tibetan Plateau and the Sichuan Basin. This process implies a strong uplift with the rate of about 1.8 mm/a of the upper crust and induces a stress concentration nearly at the bottom of the Longmen Shan fault zone. We believe that the stress concentration in the Longmen Shan fault zone provides a very important geodynamic background of the 2008 Wenchuan earthquake. Using numerical experiments we find that the key factor controlling this stress concentration process is the large viscosity contrast in the middle and lower crusts between the Tibetan Plateau and the Sichuan Basin. The results show that large viscosity contrast in the middle and lower crusts accelerates the stress concentration in the Longmen Shan fault zone. Fast moving lower crustal flow accelerates this stress accumulation process. During the inter-seismic period, spatially the maximum stress accumulation rate of the eastern margin of the Tibetan Plateau is located nearly at the bottom of the brittle upper crust of the Longmen Shan fault zone. The spatial distribution of the stress accumulation along the strike of the Longmen Shan fault zone is as follows: the normal stress decreases while the shear stress increases from southwest to northeast along the Longmen Shan fault zone. This stress distribution explains the thrust motion in the SW and strike-slip motion in the NE during the 2008 Wenchuan earthquake.

  18. Imaging 3D geological structure of the Mygdonian basin (Northern Greece) with geological numerical modeling and geophysical methods.

    Cédric, Guyonnet-Benaize; Fabrice, Hollender; Maria, Manakou; Alexandros, Savvaidis; Elena, Zargli; Cécile, Cornou; Nikolaos, Veranis; Dimitrios, Raptakis; Artemios, Atzemoglou; Pierre-Yves, Bard; Nikolaos, Theodulidis; Kyriazis, Pitilakis; Emmanuelle, Chaljub

    2013-04-01

    The Mygdonian basin, located 30 km E-NE close to Thessaloniki, is a typical active tectonic basin, trending E-NW, filled by sediments 200 to 400 m thick. This basin has been chosen as a European experimental site since 1993 (European Commission research projects - EUROSEISTEST). It has been investigated for experimental and theoretical studies on site effects. The Mygdonian basin is currently covered by a permanent seismological network and has been mainly characterized in 2D and 3D with geophysical and geotechnical studies (Bastani et al, 2011; Cadet and Savvaidis, 2011; Gurk et al, 2007; Manakou et al, 2007; Manakou et al, 2010; Pitilakis et al, 1999; Raptakis et al, 2000; Raptakis et al, 2005). All these studies allowed understanding the influence of geological structures and local site conditions on seismic site response. For these reasons, this site has been chosen for a verification exercise for numerical simulations in the framework of an ongoing international collaborative research project (Euroseistest Verification and Validation Project - E2VP). The verification phase has been made using a first 3D geophysical and geotechnical model (Manakou, 2007) about 5 km wide and 15 km long, centered on the Euroseistest site. After this verification phase, it has been decided to update, optimize and extend this model in order to obtain a more detailed model of the 3D geometry of the entire basin, especially the bedrock 3D geometry which can affect drastically the results of numerical simulations for site effect studies. In our study, we build a 3D geological model of the present-day structure of the entire Mygdonian basin. This "precise" model is 12 km wide, 65 km long and is 400 m deep in average. It has been built using geophysical, geotechnical and geological data. The database is heterogeneous and composed of hydrogeological boreholes, seismic refraction surveys, array microtremor measurements, electrical and geotechnical surveys. We propose an integrated

  19. Numerical simulation of standing wave with 3D predictor-corrector finite difference method for potential flow equations

    罗志强; 陈志敏

    2013-01-01

    A three-dimensional (3D) predictor-corrector finite difference method for standing wave is developed. It is applied to solve the 3D nonlinear potential flow equa-tions with a free surface. The 3D irregular tank is mapped onto a fixed cubic tank through the proper coordinate transform schemes. The cubic tank is distributed by the staggered meshgrid, and the staggered meshgrid is used to denote the variables of the flow field. The predictor-corrector finite difference method is given to develop the difference equa-tions of the dynamic boundary equation and kinematic boundary equation. Experimental results show that, using the finite difference method of the predictor-corrector scheme, the numerical solutions agree well with the published results. The wave profiles of the standing wave with different amplitudes and wave lengths are studied. The numerical solutions are also analyzed and presented graphically.

  20. Analytical and Numerical Study of the Aharonov--Bohm Effect in 3D and 4D Abelian Higgs Model

    Chernodub, M. N.; Gubarev, F. V.; Polikarpov, M.I.

    1996-01-01

    We discuss the Aharonov--Bohm effect in three and four dimensional non--compact lattice Abelian Higgs model. We show analytically that this effect leads to the long--range Coulomb interaction of the charged particles, which is confining in three dimensions. The Aharonov--Bohm effect is found in numerical calculations in 3D Abelian Higgs model.

  1. Numerical 3D Investigation of Non-Metallic (Glass, Carbon) Fiber Pull-out Micromechanics (in Concrete Matrix)

    Krasņikovs, A; Khabaz, A; Teļnova, I; Machanovsky, A; Klavinsh, J

    2010-01-01

    In the paper short glass and carbon fiber micro-mechanics in concrete matrix is under consideration. In present work was performed pull-out 3D numerical modeling. Numerical results were compared with realized experiments for single and few (fibre bundle) AR glass and carbon fibers pulling out of concrete matrix. Investigated were one fiber pull-out dynamics as well micro-stresses in the material. During performed single fiber pull out experiments were established such process mains steps: a) ...

  2. Experimental and numerical investigation of 3D aerofoil characteristics on a MW wind turbine

    Troldborg, Niels; Bak, Christian; Sørensen, Niels N.; Aagaard Madsen, Helge; Réthoré, Pierre-Elouan; Zahle, Frederik; Guntur, Srinivas

    2013-01-01

    3D aerofoil characteristics on a MW wind turbine is investigated through a combination of field measurements, wind tunnel tests and computational fluid dynamics (CFD). Surface pressuremeasurements as well as the integrated force coefficients for selected aerofoil sections on a blade of the turbine...... resolved 3D computations on the wind turbine as well as 2D aerofoil simulations....... is compared to wind tunnel measurements on the same aerofoil sections in order to reveal the difference in performance of aerofoils on full scale rotors in atmospheric conditions and aerofoils in wind tunnels. The findings of the measurements are backed up by analogous CFD analysis involving fully...

  3. 3D wake dynamics of the VAWT: experimental and numerical investigation

    Ferreira, C.; Hofemann, C.; Dixon, K.; Kuik, G. A. M.; Van Bussel, G.J.W.

    2010-01-01

    The Vertical Axis Wind Turbine, in its 2D form, is characterized by a complex unsteady aerodynamic flow, including dynamic stall and blade vortex interaction. Adding to this complexity, the 3D flow causes spanwise effects and the presence of trailing vorticity and tip vortices. The objective of the current paper is to bring insight into the 3D development of the near wake of a H-VAWT, understanding: • The spanwise blade load distribution in the upwind and the downwind blade passages. • The tr...

  4. Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

    This paper presents a computer-numerical-controlled ultraviolet light-emitting diode (CNC UV-LED) lithography scheme for three-dimensional (3D) microfabrication. The CNC lithography scheme utilizes sequential multi-angled UV light exposures along with a synchronized switchable UV light source to create arbitrary 3D light traces, which are transferred into the photosensitive resist. The system comprises a switchable, movable UV-LED array as a light source, a motorized tilt-rotational sample holder, and a computer-control unit. System operation is such that the tilt-rotational sample holder moves in a pre-programmed routine, and the UV-LED is illuminated only at desired positions of the sample holder during the desired time period, enabling the formation of complex 3D microstructures. This facilitates easy fabrication of complex 3D structures, which otherwise would have required multiple manual exposure steps as in the previous multidirectional 3D UV lithography approach. Since it is batch processed, processing time is far less than that of the 3D printing approach at the expense of some reduction in the degree of achievable 3D structure complexity. In order to produce uniform light intensity from the arrayed LED light source, the UV-LED array stage has been kept rotating during exposure. UV-LED 3D fabrication capability was demonstrated through a plurality of complex structures such as V-shaped micropillars, micropanels, a micro-‘hi’ structure, a micro-‘cat’s claw,’ a micro-‘horn,’ a micro-‘calla lily,’ a micro-‘cowboy’s hat,’ and a micro-‘table napkin’ array. (paper)

  5. Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

    Kim, Jungkwun; Yoon, Yong-Kyu; Allen, Mark G.

    2016-03-01

    This paper presents a computer-numerical-controlled ultraviolet light-emitting diode (CNC UV-LED) lithography scheme for three-dimensional (3D) microfabrication. The CNC lithography scheme utilizes sequential multi-angled UV light exposures along with a synchronized switchable UV light source to create arbitrary 3D light traces, which are transferred into the photosensitive resist. The system comprises a switchable, movable UV-LED array as a light source, a motorized tilt-rotational sample holder, and a computer-control unit. System operation is such that the tilt-rotational sample holder moves in a pre-programmed routine, and the UV-LED is illuminated only at desired positions of the sample holder during the desired time period, enabling the formation of complex 3D microstructures. This facilitates easy fabrication of complex 3D structures, which otherwise would have required multiple manual exposure steps as in the previous multidirectional 3D UV lithography approach. Since it is batch processed, processing time is far less than that of the 3D printing approach at the expense of some reduction in the degree of achievable 3D structure complexity. In order to produce uniform light intensity from the arrayed LED light source, the UV-LED array stage has been kept rotating during exposure. UV-LED 3D fabrication capability was demonstrated through a plurality of complex structures such as V-shaped micropillars, micropanels, a micro-‘hi’ structure, a micro-‘cat’s claw,’ a micro-‘horn,’ a micro-‘calla lily,’ a micro-‘cowboy’s hat,’ and a micro-‘table napkin’ array.

  6. Some Methods of Applied Numerical Analysis to 3d Facial Reconstruction Software

    Roşu, Şerban; Ianeş, Emilia; Roşu, Doina

    2010-09-01

    This paper deals with the collective work performed by medical doctors from the University Of Medicine and Pharmacy Timisoara and engineers from the Politechnical Institute Timisoara in the effort to create the first Romanian 3d reconstruction software based on CT or MRI scans and to test the created software in clinical practice.

  7. Mechanical Modelling of Pultrusion Process: 2D and 3D Numerical Approaches

    Baran, Ismet; Hattel, Jesper Henri; Akkerman, Remko;

    2015-01-01

    mechanical analysis should be performed. In the present work, the two dimensional (2D) quasi-static plane strain mechanical model for the pultrusion of a thick square profile developed by the authors is further improved using generalized plane strain elements. In addition to that, a more advanced 3D thermo...

  8. Numerical Simulation of Injection Molding Cooling Process Based on 3D Surface Model

    CUIShu-biao; ZHOUHua-min; LIDe-qun

    2004-01-01

    The design of the coohng system of injection molds directly affects both productivity and the quality of the final part. Using the cooling process CAE system to instruct the mold design, the efficiency and quality of design can be improved greatly. At the same time, it is helpful to confirm the cooling system structure and optimize the process conditions. In this paper, the 3D surface model of mold cavity is used to replace the middle-plane model in the simulation by Boundary Element Method, which break the bottleneck of the application of the injection molding simulation softwares base on the middle-plane model. With the improvements of this paper, a practical and commercial simulation software of injection molding cooling process named as HsCAE3D6.0 is developed.

  9. Numerical simulation of the filling stage in injection molding based on a 3D model

    GENG Tie; LI De-qun; ZHOU Hua-min

    2005-01-01

    Most injection molded parts are three-dimensional, with complex geometrical configurations and thick/thin wall sections. The change of the thickness of parts has significant influence on flow during injection molding. This paper presents a 3D finite element model to deal with the three-dimensional flow, which can more accurately predict the filling process than a 2. 5D model. In this model, equal-order velocity-pressure interpolation method is successfully employed and the relation between velocity and pressure is obtained from the discretized momentum equation in order to derive the pressure equation. A 3D control volume scheme is employed to track the flow front. The validity of the model has been tested through the analysis of the flow in a cavity.

  10. Cross-Wire Calibration for Freehand 3D Ultrasonography: Measurement and Numerical Issues

    J. Jan

    2005-06-01

    Full Text Available 3D freehand ultrasound is an imaging technique, which is graduallyfinding clinical applications. A position sensor is attached to aconventional ultrasound probe, so that B-scans are acquired along withtheir relative locations. This allows the B-scans to be inserted into a3D regular voxel array, which can then be visualized usingarbitrary-plane slicing, and volume or surface rendering. A keyrequirement for correct reconstruction is the calibration: determiningthe position and orientation of the B-scans with respect to theposition sensor's receiver. Following calibration, interpolation in theset of irregularly spaced B-scans is required to reconstruct aregular-voxel array. This text describes a freehand measurement of 2Dultrasonic data, an approach to the calibration problem and severalnumerical issues concerned with the calibration and reconstruction.

  11. Twisting Rolls. An Heuristic Model and 3D Numerical Simulations of Vortex Patterns

    Bouali, Safieddine

    2003-01-01

    We connect an appropriate feedback loop to a model of 2D vertical eddy of airflow which unfolds a wide range of vorticity behavior. Computational fluid dynamics of the twisted roll display a class of long lifespan 3D vortices. On the one hand, the infinitely stable columnar vortex simulated describes waterspouts and tornadoes with extended lifetime. On the other hand, a light modification of the retroaction exhibits strong similarities to tropical cyclones. Moreover, we investigate the outcom...

  12. Soil-structure interaction during tunnelling in urban area: observations and 3D numerical modelling

    Fargnoli, Valentina

    2015-01-01

    This work illustrates a soil-tunnel-structure interaction study performed by an integrated,geotechnical and structural,approach based on 3D finite element analyses and validated against experimental observations.The study aims at analysing the response of reinforced concrete framed buildings on discrete foundations in interaction with metro lines.It refers to the case of the twin tunnels of the Milan (Italy) metro line 5,recently built in coarse grained materials using EPB machines,for which ...

  13. Comment on "Numerical Study on Aging Dynamics in the 3D Ising Spin Glass Model"

    Marinari, Enzo; Parisi, Giorgio; Ruiz-Lorenzo, Juan J.

    1999-01-01

    We show that the dynamical behavior of the 3D Ising spin glass with Gaussian couplings is not compatible with a droplet dynamics. We show that this is implied from the data of reference cond-mat/9904143, that, when analyzed in an accurate way, give multiple evidences of this fact. Our study is based on the analysis of the overlap-overlap correlation function, at different values of the separation r and of the time t.

  14. Numerical Simulation of the Effect of 3D Needle Movement on Cavitation and Spray Formation in a Diesel Injector

    Mandumpala Devassy, B.; Edelbauer, W.; Greif, D.

    2015-12-01

    Cavitation and its effect on spray formation and its dispersion play a crucial role in proper engine combustion and controlled emission. This study focuses on these effects in a typical common rail 6-hole diesel injector accounting for 3D needle movement and flow compressibility effects. Coupled numerical simulations using 1D and 3D CFD codes are used for this investigation. Previous studies in this direction have already presented a detailed structure of the adopted methodology. Compared to the previous analysis, the present study investigates the effect of 3D needle movement and cavitation on the spray formation for pilot and main injection events for a typical diesel engine operating point. The present setup performs a 3D compressible multiphase simulation coupled with a standalone 1D high pressure flow simulation. The simulation proceeds by the mutual communication between 1D and 3D solvers. In this work a typical common rail injector with a mini-sac nozzle is studied. The lateral and radial movement of the needle and its effect on the cavitation generation and the subsequent spray penetration are analyzed. The result indicates the effect of compressibility of the liquid on damping the needle forces, and also the difference in the spray penetration levels due to the asymmetrical flow field. Therefore, this work intends to provide an efficient and user-friendly engineering tool for simulating a complete fuel injector including spray propagation.

  15. 3D Numerical Simulation on the Sloshing Waves Excited by the Seismic Shacking

    Zhang, Lin; Wu, Tso-Ren

    2016-04-01

    In the event of 2015 Nepal earthquake, a video clip broadcasted worldwide showed a violent water spilling in a hotel swimming pool. This sloshing phenomenon indicates a potential water loss in the sensitive facilities, e.g. the spent fuel pools in nuclear power plant, has to be taken into account carefully under the consideration of seismic-induced ground acceleration. In the previous studies, the simulation of sloshing mainly focused on the pressure force on the structure by using a simplified Spring-Mass Method developed in the field of solid mechanics. However, restricted by the assumptions of plane water surface and limited wave height, significant error will be made in evaluating the amount of water loss in the tank. In this paper, the computational fluid dynamical model, Splash3D, was adopted for studying the sloshing problem accurately. Splash3D solved 3D Navier-Stokes Equation directly with Large-Eddy Simulation (LES) turbulent closure. The Volume-of-fluid (VOF) method with piecewise linear interface calculation (PLIC) was used to track the complex breaking water surface. The time series acceleration of a design seismic was loaded to excite the water. With few restrictions from the assumptions, the accuracy of the simulation results were improved dramatically. A series model validations were conducted by compared to a 2D theoretical solution, and a 3D experimental data. Good comparisons can be seen. After the validation, we performed the simulation for considering a sloshing case in a rectangular water tank with a dimension of 12 m long, 8 m wide, 8 m deep, which contained water with 7 m in depth. The seismic movement was imported by considering time-series acceleration in three dimensions, which were about 0.5 g to 1.2 g in the horizontal directions, and 0.3 g to 1 g in the vertical direction. We focused the discussions on the kinematics of the water surface, wave breaking, velocity field, pressure field, water force on the side walls, and, most

  16. A hybrid experimental-numerical technique for determining 3D velocity fields from planar 2D PIV data

    Eden, A.; Sigurdson, M.; Mezić, I.; Meinhart, C. D.

    2016-09-01

    Knowledge of 3D, three component velocity fields is central to the understanding and development of effective microfluidic devices for lab-on-chip mixing applications. In this paper we present a hybrid experimental-numerical method for the generation of 3D flow information from 2D particle image velocimetry (PIV) experimental data and finite element simulations of an alternating current electrothermal (ACET) micromixer. A numerical least-squares optimization algorithm is applied to a theory-based 3D multiphysics simulation in conjunction with 2D PIV data to generate an improved estimation of the steady state velocity field. This 3D velocity field can be used to assess mixing phenomena more accurately than would be possible through simulation alone. Our technique can also be used to estimate uncertain quantities in experimental situations by fitting the gathered field data to a simulated physical model. The optimization algorithm reduced the root-mean-squared difference between the experimental and simulated velocity fields in the target region by more than a factor of 4, resulting in an average error less than 12% of the average velocity magnitude.

  17. Numerical Simulation and Experimental Investigation of 3-D Separated Flow Field around a Blunt Body

    1999-01-01

    @@Motivated by re-designing a fuselage in engineering application, the numerical and experimental investigation of the separated flow field around a special blunt body is described in this thesis. The aerodynamic response of the blunt body is successively studied. The thesis consists of four parts: the numerical simulation of the flow field around a two-dimensional blunt body; the numerical simulation of the flow field around a three-dimensional blunt body; the flow

  18. Numerical simulation of complex 3D compressible viscous flows through rotating blade passage

    Despotović M.; Babić Milun; Milovanović D.; Šušteršič Vanja

    2003-01-01

    This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech­nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design ...

  19. Numerical Simulations of High-Frequency Respiratory Flows in 2D and 3D Lung Bifurcation Models

    Chen, Zixi; Parameswaran, Shamini; Hu, Yingying; He, Zhaoming; Raj, Rishi; Parameswaran, Siva

    2014-07-01

    To better understand the human pulmonary system and optimize the high-frequency oscillatory ventilation (HFOV) design, numerical simulations were conducted under normal breathing frequency and HFOV condition using a CFD code Ansys Fluent and its user-defined C programs. 2D and 3D double bifurcating lung models were created, and the geometry corresponds to fifth to seventh generations of airways with the dimensions based on the Weibel's pulmonary model. Computations were carried out for different Reynolds numbers (Re = 400 and 1000) and Womersley numbers (α = 4 and 16) to study the air flow fields, gas transportation, and wall shear stresses in the lung airways. Flow structure was compared with experimental results. Both 2D and 3D numerical models successfully reproduced many results observed in the experiment. The oxygen concentration distribution in the lung model was investigated to analyze the influence of flow oscillation on gas transport inside the lung model.

  20. Estimation of thawing cryolithic area with numerical modeling in 3D geometry while exploiting underground small nuclear power plant

    Melnikov N. N.

    2016-03-01

    Full Text Available The paper presents results on 3D numerical calculation of a thermal task related to assessing a thawing area when placing modules with reactor and steam-turbine facility of a small nuclear power plant in thickness of permafrost rocks. The paper discusses influence of the coefficient of thermal conductivity for large-scaled underground excavations lining and cryolithic area porosity on thawing depth and front movement velocity under different spatial directions

  1. NUMERICAL SIMULATION OF 3-D FLOW FIELD IN ARCIFORM PLUNGE POOL

    2002-01-01

    The 3-D complex turbulent flow fields in aplunge pool with arciform bottom are simulated by using thek-ε model in body-fitted coordinates. The calculated results re-veal the flow characteristics in the arciform plunge pool underthe different flood discharge conditions, which can not be easi-ly obtained in the physical model test because the measure-ment of the complex velocity is very difficult. The calculatedflow fields are helpful to understand in depth the hydrauliccharacteristics of plunge pool. The calculated and the meas-ured pressure distributions on the pool bottom are comparedand in good agreement.

  2. Numerical computation of critical properties and atomic basins from 3D grid electron densities

    Katan, C; Lecomte, C; Guezo, M; Oison, V; Souhassou, M

    2003-01-01

    InteGriTy is a software package that performs topological analysis following AIM approach on electron densities given on 3D grids. Use of tricubic interpolation is made to get the density, its gradient and hessian matrix at any required position. Critical points and integrated atomic properties have been derived from theoretical densities calculated for the compounds NaCl and TTF-2,5Cl2BQ, thus covering the different kinds of chemical bonds: ionic, covalent, hydrogen bonds and other intermolecular contacts.

  3. Plasma dynamo

    Rincon, F; Schekochihin, A A; Valentini, F

    2015-01-01

    Magnetic fields pervade the entire Universe and, through their dynamical interactions with matter, affect the formation and evolution of astrophysical systems from cosmological to planetary scales. How primordial cosmological seed fields arose and were further amplified to $\\mu$Gauss levels reported in nearby galaxy clusters, near equipartition with kinetic energy of plasma motions and on scales of at least tens of kiloparsecs, is a major theoretical puzzle still largely unconstrained by observations. Extragalactic plasmas are weakly collisional (as opposed to collisional magnetohydrodynamic fluids), and whether magnetic-field growth and its sustainment through an efficient dynamo instability driven by chaotic motions is possible in such plasmas is not known. Fully kinetic numerical simulations of the Vlasov equation in a six-dimensional phase space necessary to answer this question have until recently remained beyond computational capabilities. Here, we show by means of such simulations that magnetic-field a...

  4. 3-D parallel program for numerical calculation of gas dynamics problems with heat conductivity on distributed memory computational systems (CS)

    Sofronov, I.D.; Voronin, B.L.; Butnev, O.I. [VNIIEF (Russian Federation)] [and others

    1997-12-31

    The aim of the work performed is to develop a 3D parallel program for numerical calculation of gas dynamics problem with heat conductivity on distributed memory computational systems (CS), satisfying the condition of numerical result independence from the number of processors involved. Two basically different approaches to the structure of massive parallel computations have been developed. The first approach uses the 3D data matrix decomposition reconstructed at temporal cycle and is a development of parallelization algorithms for multiprocessor CS with shareable memory. The second approach is based on using a 3D data matrix decomposition not reconstructed during a temporal cycle. The program was developed on 8-processor CS MP-3 made in VNIIEF and was adapted to a massive parallel CS Meiko-2 in LLNL by joint efforts of VNIIEF and LLNL staffs. A large number of numerical experiments has been carried out with different number of processors up to 256 and the efficiency of parallelization has been evaluated in dependence on processor number and their parameters.

  5. Numerical and Experimental Verification of a 3D Quasi-Optical System

    Zejian Lu

    2015-01-01

    Full Text Available A modular and efficient Gaussian beam (GB analysis method, incorporating frame-based Gabor transformation, GB reflection, and a 3D GB diffraction technique, was developed to analyze both the reflectors and frequency selective surface (FSS in quasi-optical (QO system. To validate this analysis method, a 3D dual-channel QO system operating at 183 and 325 GHz was designed and tested. The proposed QO system employs two-layer structure with a FSS of perforated hexagonal array transmitting the 325 GHz signal on the top layer while diverting the 183 GHz signal to the bottom layer. Measured results of the system demonstrate that the agreement can be achieved down to −30 dB signal level for both channels in the far field pattern. The discrepancy between the calculation and measurement is within 2 dB in the main beam region (2.5 times −3 dB beamwidth, verifying the effectiveness and accuracy of the proposed method.

  6. Analytical and numerical aspects in solving the controlled 3D Gross-Pitaevskii equation

    The results of recently developed investigations, that have been carried out within the framework of the controlling potential method (CPM), are reviewed. This method allows one to decompose a three dimensional (3D) Gross-Pitaevskii equation (GPE) into the pair of coupled Schroedinger-type equations. Under suitable mathematical conditions, the solutions of the 3D controlled GPE can be constructed from the solutions of a 2D linear Schroedinger equation (the transverse component of the GPE) coupled with a 1D nonlinear Schroedinger equation (the longitudinal component of the GPE). Such decomposition allows one to cast the solutions in the form of the product of the solutions of the transverse and the longitudinal components of the GPE. The coupling between these two equations is the functional of both the transverse and the longitudinal profiles. It is shown that the CPM can be used to obtain a new class of three-dimensional solitary waves solutions of the GPE, which governs the dynamics of Bose-Einstein condensates. By imposing an external controlling potential, the desired time-dependent shape of the localized BECs is obtained. The stability of the exact solutions was checked with direct simulations of the time -dependent, three-dimensional GPE. Our simulations show that the localized condensates are stable with respect to perturbed initial conditions.

  7. Ash3d: A finite-volume, conservative numerical model for ash transport and tephra deposition

    Schwaiger, Hans F.; Denlinger, Roger P.; Mastin, Larry G.

    2012-01-01

    We develop a transient, 3-D Eulerian model (Ash3d) to predict airborne volcanic ash concentration and tephra deposition during volcanic eruptions. This model simulates downwind advection, turbulent diffusion, and settling of ash injected into the atmosphere by a volcanic eruption column. Ash advection is calculated using time-varying pre-existing wind data and a robust, high-order, finite-volume method. Our routine is mass-conservative and uses the coordinate system of the wind data, either a Cartesian system local to the volcano or a global spherical system for the Earth. Volcanic ash is specified with an arbitrary number of grain sizes, which affects the fall velocity, distribution and duration of transport. Above the source volcano, the vertical mass distribution with elevation is calculated using a Suzuki distribution for a given plume height, eruptive volume, and eruption duration. Multiple eruptions separated in time may be included in a single simulation. We test the model using analytical solutions for transport. Comparisons of the predicted and observed ash distributions for the 18 August 1992 eruption of Mt. Spurr in Alaska demonstrate to the efficacy and efficiency of the routine.

  8. 3D Numerical Simulation of Overbank Flow in Non-Orthogonal Curvilinear Coordinates

    ZHANG Ming-liang; SHEN Yong-ming; WU Xiu-guang

    2005-01-01

    The velocity field in meandering compound channels with overbank flow is highly three dimensional. To date, its features have been investigated experimentally and little research has been undertaken to investigate the feasibility of reproducing these velocity fields with computer models. If computer modeling were to prove successful in this context, it could become a useful prediction technique and research tool to enhance our understanding of natural river dynamics. A 3-D k-ε turbulence hydrodynamic model in curvilinear coordinates is established to simulate the overbank flow. The body-fitted coordinate is adopted in the horizontal plane, the part grid is adopted in the vertical direction, and the wall-function method is employed to simulate the bed resistance. The model is applied to the simulation of the meandering channel with straight flood plain banks, and the main velocities and secondary velocities for both the longitudinal and cross sections are presented. Comparison and analysis show that the results of simulation are fit to reflect the results of experiment. These results show the application value of the model to 3D overbank flow.

  9. Numerical simulation of complex 3D compressible viscous flows through rotating blade passage

    Despotović M.

    2003-01-01

    Full Text Available This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech­nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design tool. The mathematical model is based on System of Favre averaged Navier-Stokes equations that are written in relative frame of reference, which rotates with constant angular velocity around axis of rotation. The governing equations are solved using finite vol­ume method applied on structured grids. The numerical procedure is based on the explicit multistage Runge-Kutta scheme that is coupled with modem numerical procedures for convergence acceleration. To demonstrate the accuracy of the described numer­ical method developed software is applied to numerical analysis of flow through impeller of axial turbocompressor, and obtained results are compared with available experimental data.

  10. Strong Field Spherical Dynamos

    Dormy, Emmanuel

    2014-01-01

    Numerical models of the geodynamo are usually classified in two categories: those denominated dipolar modes, observed when the inertial term is small enough, and multipolar fluctuating dynamos, for stronger forcing. I show that a third dynamo branch corresponding to a dominant force balance between the Coriolis force and the Lorentz force can be produced numerically. This force balance is usually referred to as the strong field limit. This solution co-exists with the often described viscous branch. Direct numerical simulations exhibit a transition from a weak-field dynamo branch, in which viscous effects set the dominant length scale, and the strong field branch in which viscous and inertial effects are largely negligible. These results indicate that a distinguished limit needs to be sought to produce numerical models relevant to the geodynamo and that the usual approach of minimizing the magnetic Prandtl number (ratio of the fluid kinematic viscosity to its magnetic diffusivity) at a given Ekman number is mi...

  11. Discrete 3D model as complimentary numerical testing for anisotropic damage

    DELAPLACE, Arnaud; Desmorat, Rodrigue

    2008-01-01

    It is proposed to use a discrete particle model as a complimentary “numerical testing machine” to identify the hydrostatic elasticity-damage coupling and the corresponding sensitivity to hydrostatic stresses parameter. Experimental tri-axial tensile testing is difficult to perform on concrete material, and numerical testing proves then its efficiency. The discrete model used for this purpose is based on a Voronoi assembly that naturally takes into account heterogeneity. Tri-tension tests on a...

  12. NUMERICAL MODELING FOR POSITIVE AND INVERSE PROBLEMS OF 3-D SEEPAGE IN DOUBLE FRACTURED MEDIA

    ZHOU Zhi-fang; GUO Geng-xin

    2005-01-01

    Three-dimensional seepage in double fractured media was modeled in this paper.The determination of hydraulic conductivity tensor of rock mass is a vital problem for the sea water intrusion or sea water encroachment and seepage of fissured medium.According to the geological and hydrogeological conditions for the 2nd-stage construction of the Three Gorges Project (TGP), the physical and mathematical models for the groundwater movement through the 3D double fractured media of rock mass during construction were established in this paper.Based on discontinuity-control inverse theory, some related parameters of double fractured media were inversed with flux being the known quantity and calibration of water table the objective function.Synchronously, the seepage field of the construction region was systematically analyzed and simulated, the results of which exhibit that the double fractured media model of fracture water can comprehensively and correctly describe the geological and hydrogeological conditions in the construction region.

  13. Mechanism of local dynamo action on the Sun

    Kitiashvili, I N; Mansour, N N; Wray, A A

    2013-01-01

    In the quiet Sun, magnetic fields are usually observed as small-scale magnetic elements, `salt and pepper', covering the entire solar surface. By using 3D radiative MHD numerical simulations we demonstrate that these fields are a result of local dynamo action in the top layers of the convection zone, where extremely weak `seed' magnetic fields can locally grow above the mean equipartition field (e.g., from a $10^{-6}$ G `seed' field to more than 1000 G magnetic structures). We find that the local dynamo action takes place only in a shallow, about 500 km deep, subsurface layer, from which the generated field is transported into deeper layers by convection downdrafts. We demonstrate that the observed dominance of vertical magnetic fields at the photosphere and the horizontal fields above the photosphere can be explained by multi-scale magnetic loops produced by the dynamo.

  14. Internal wave attractors examined using laboratory experiments and 3D numerical simulations

    Brouzet, Christophe; Scolan, H; Ermanyuk, E V; Dauxois, Thierry

    2016-01-01

    In the present paper, we combine numerical and experimental approaches to study the dynamics of stable and unstable internal wave attractors. The problem is considered in a classic trapezoidal setup filled with a uniformly stratified fluid. Energy is injected into the system at global scale by the small-amplitude motion of a vertical wall. Wave motion in the test tank is measured with the help of conventional synthetic schlieren and PIV techniques. The numerical setup closely reproduces the experimental one in terms of geometry and the operational range of the Reynolds and Schmidt numbers. The spectral element method is used as a numerical tool to simulate the nonlinear dynamics of a viscous salt-stratified fluid. We show that the results of three-dimensional calculations are in excellent qualitative and quantitative agreement with the experimental data, including the spatial and temporal parameters of the secondary waves produced by triadic resonance instability. Further, we explore experimentally and numeri...

  15. NUMERICAL SIMULATION OF 3-D TURBULENT FLOW IN THE MULTI- INTAKES SUMP OF THE PUMP STATION

    CHEN Hong-xun; GUO Jia-hong

    2007-01-01

    In this article, a numerical model for three-dimensional turbulent flow in the sump of the pump station was presented. A reasonable boundary condition for the flow in the sump with several water intakes at different flow rates was proposed. The finite volume method was employed to solve the governing equations with the body fitted grid generated by the multi-block grid technique. By using the Fluent software, the fluid flow in a model sump of the pump station was calculated. Compared with the experimental result, the numerical result of the example is fairly good.

  16. NUMERICAL SIMULATION OF 3-D REAERATION IN BODY-FITTED COORDINATE SYSTEM

    Fang Xiang-wei; Chen Gang; Shen Chun-ni; Chen Zheng-han; Li Jian-zhong

    2003-01-01

    A three-dimensional numerical model was developed to simulate reaeration using a body-fitted coordinate system. The model was designed to calculate the velocity and oxygen concentration separately, called,"no pairing resolution". The velocity was calculated by SIMPLEC algorithm in the body-fitted coordinate system. The considerably proposed model was checked by a reaeration experiment couducted in an open channel. The computed results agree considerably well with the experimental data. The model was also used to predict the reaeration in an S-shaped channel, and the numerical results are discussed.

  17. Numerical method for calculation of 3D viscous turbomachine flow taking into account stator/rotor unsteady interaction

    Rusanov, A.V.; Yershov, S.V. [Institute of Mechanical Engineering Problems of National Academy of Sciences of Ukraine Kharkov (Ukraine)

    1997-12-31

    The numerical method is suggested for the calculation of the 3D periodically unsteady viscous cascade flow evoked by the aerodynamics interaction of blade rows. Such flow is described by the thin-layer Reynolds-averaged unsteady Navier-Stokes equations. The turbulent effects are simulated with the modified Baldwin-Lomax turbulence model. The problem statement allows to consider an unsteady flow through either a single turbo-machine stage or a multi stage turbomachine. The sliding mesh techniques and the time-space non-oscillatory square interpolation are used in axial spacings to calculate the flow in a computational domain that contains the reciprocally moving elements. The gasdynamical equations are integrated numerically with the implicit quasi-monotonous Godunov`s type ENO scheme of the second or third order of accuracy. The suggested numerical method is incorporated in the FlowER code developed by authors for calculations of the 3D viscous compressible flows through multi stage turbomachines. The numerical results are presented for unsteady turbine stage throughflows. The method suggested is shown to simulate qualitatively properly the main unsteady cascade effects in particular the periodically blade loadings, the propagation of stator wakes through rotor blade passage and the unsteady temperature flowfields for stages with cooled stator blades. (author) 21 refs.

  18. DKE: a fast numerical solver for the 3-D relativistic bounce-averaged electron drift kinetic equation

    Decker, J.; Peysson, Y

    2004-12-01

    A new original code for solving the 3-D relativistic and bounce-averaged electron drift kinetic equation is presented. It designed for the current drive problem in tokamak with an arbitrary magnetic equilibrium. This tool allows self-consistent calculations of the bootstrap current in presence of other external current sources. RF current drive for arbitrary type of waves may be used. Several moments of the electron distribution function are determined, like the exact and effective fractions of trapped electrons, the plasma current, absorbed RF power, runaway and magnetic ripple loss rates and non-thermal Bremsstrahlung. Advanced numerical techniques have been used to make it the first fully implicit (reverse time) 3-D solver, particularly well designed for implementation in a chain of code for realistic current drive calculations in high {beta}{sub p} plasmas. All the details of the physics background and the numerical scheme are presented, as well a some examples to illustrate main code capabilities. Several important numerical points are addressed concerning code stability and potential numerical and physical limitations. (authors)

  19. DKE: a fast numerical solver for the 3-D relativistic bounce-averaged electron drift kinetic equation

    A new original code for solving the 3-D relativistic and bounce-averaged electron drift kinetic equation is presented. It designed for the current drive problem in tokamak with an arbitrary magnetic equilibrium. This tool allows self-consistent calculations of the bootstrap current in presence of other external current sources. RF current drive for arbitrary type of waves may be used. Several moments of the electron distribution function are determined, like the exact and effective fractions of trapped electrons, the plasma current, absorbed RF power, runaway and magnetic ripple loss rates and non-thermal Bremsstrahlung. Advanced numerical techniques have been used to make it the first fully implicit (reverse time) 3-D solver, particularly well designed for implementation in a chain of code for realistic current drive calculations in high βp plasmas. All the details of the physics background and the numerical scheme are presented, as well a some examples to illustrate main code capabilities. Several important numerical points are addressed concerning code stability and potential numerical and physical limitations. (authors)

  20. A Direct Numerical Reconstruction Algorithm for the 3D Calderón Problem

    Delbary, Fabrice; Hansen, Per Christian; Knudsen, Kim

    2011-01-01

    In three dimensions Calderón's problem was addressed and solved in theory in the 1980s in a series of papers, but only recently the numerical implementation of the algorithm was initiated. The main ingredients in the solution of the problem are complex geometrical optics solutions to the conducti...

  1. A numerical study of the 3D random interchange and random loop models

    Barp, Alessandro; Barp, Edoardo Gabriele; Briol, François-Xavier; Ueltschi, Daniel

    2015-08-01

    We have studied numerically the random interchange model and related loop models on the three-dimensional cubic lattice. We have determined the transition time for the occurrence of long loops. The joint distribution of the lengths of long loops is Poisson-Dirichlet with parameter 1 or \\frac{1}{2}.

  2. Numerical scheme for riser motion calculation during 3-D VIV simulation

    Huang, Kevin; Chen, Hamn-Ching; Chen, Chia-Rong

    2011-10-01

    This paper presents a numerical scheme for riser motion calculation and its application to riser VIV simulations. The discretisation of the governing differential equation is studied first. The top tensioned risers are simplified as tensioned beams. A centered space and forward time finite difference scheme is derived from the governing equations of motion. Then an implicit method is adopted for better numerical stability. The method meets von Neumann criteria and is shown to be unconditionally stable. The discretized linear algebraic equations are solved using a LU decomposition method. This approach is then applied to a series of benchmark cases with known solutions. The comparisons show good agreement. Finally the method is applied to practical riser VIV simulations. The studied cases cover a wide range of riser VIV problems, i.e. different riser outer diameter, length, tensioning conditions, and current profiles. Reasonable agreement is obtained between the numerical simulations and experimental data on riser motions and cross-flow VIV a/D . These validations and comparisons confirm that the present numerical scheme for riser motion calculation is valid and effective for long riser VIV simulation.

  3. Research on the Inner Water Flow Field in a Hydrocyclone by the Method of 3D Numerical Simulation

    Hui Li

    2013-01-01

    Full Text Available The inner water flow field in a hydrocyclone was simulated by the software of computational fluid dynamics-FLUENT, using RSM turbulent model. The air core, 3D velocity field distribution and pressure field distribution were simulated and contrasted with experimental results. The results indicated that the air core was through from the inlet to the outlet. The simulated 3D velocity field distribution was consistent with the results obtained by the experiments. The axial symmetry of pressure field distribution was quite good and the pressure gradient was very large. All these results tested the reliability of the method of numerical simulation and provided a reference for the further research of solid-liquid separation and the optimizing design of the hydrocyclone.

  4. 3D micromanipulation at low numerical aperture with a single light beam: the focused-Bessel trap.

    Ayala, Yareni A; Arzola, Alejandro V; Volke-Sepúlveda, Karen

    2016-02-01

    Full-three-dimensional (3D) manipulation of individual glass beads with radii in the range of 2-8 μm is experimentally demonstrated by using a single Bessel light beam focused through a low-numerical-aperture lens (NA=0.40). Although we have a weight-assisted trap with the beam propagating upward, we obtain a stable equilibrium position well away from the walls of the sample cell, and we are able to move the particle across the entire cell in three dimensions. A theoretical analysis for the optical field and trapping forces along the lateral and axial directions is presented for the focused-Bessel trap. This trap offers advantages for 3D manipulation, such as an extended working distance, a large field of view, and reduced aberrations. PMID:26907437

  5. Robustness of numerical TIG welding simulation of 3D structures in stainless steel 316L

    The numerical welding simulation is considered to be one of those mechanical problems that have the great level of nonlinearity and which requires a good knowledge in various scientific fields. The 'Robustness Analysis' is a suitable tool to control the quality and guarantee the reliability of numerical welding results. The robustness of a numerical simulation of welding is related to the sensitivity of the modelling assumptions on the input parameters. A simulation is known as robust if the result that it produces is not very sensitive to uncertainties of the input data. The term 'Robust' was coined in statistics by G.E.P. Box in 1953. Various definitions of greater or lesser mathematical rigor are possible for the term, but in general, referring to a statistical estimator, it means 'insensitive to small deviation from the idealized assumptions for which the estimator is optimized. In order to evaluate the robustness of numerical welding simulation, sensitivity analyses on thermomechanical models and parameters have been conducted. At the first step, we research a reference solution which gives the best agreement with the thermal and mechanical experimental results. The second step consists in determining through numerical simulations which parameters have the largest influence on residual stresses induced by the welding process. The residual stresses were predicted using finite element method performed with Code-Aster of EDF and SYSWELD of ESI-GROUP. An analysis of robustness can prove to be heavy and expensive making it an unjustifiable route. However, only with development such tool of analysis can predictive methods become a useful tool for industry. (author)

  6. Numerical simulation on the evolution of cloud particles in 3-D convective cloud

    LIU XiaoLi; NIU ShengJie

    2009-01-01

    A 3-D convective cloud model with compressible non-hydrostatic dynamics and the spectral bin microphysics of a 2-D slab-symmetric model has been used to simulate an observed supercell storm occurring on 29 June, 2000 near Bird City, Kansas, USA. The main objective of this paper is to study the evolution of particles in this convective storm with bin spectral microphysics scheme. Graupels form and grow through two mechanisms, deposition and riming, with the riming process dominant on top of the inflow and in the upper portion of main updraft. Over the outflow and during the developing and mature stages of the storm, graupel particles mainly grow through deposition with dominant unimodal spectra. Most fall out after growing up. Reducing initial relative humidity disturbance (increasing initial potential temperature disturbance) has negative impact on the formation and growth of graupels over the inflow (outflow). This study shows that large graupel and hail could be suppressed by altering the deposition and coalescence process over the inflow and main updraft. At different locations of the convective cells and with different initial humidity and potential temperature disturbance, the graupel formation and growth mechanisms are different, so as to the feasible hail suppression locations and methods.

  7. 3D Numerical Simulations of AGN Outflows in Clusters and Groups

    Gaspari, M; Brighenti, F; D'Ercole, A

    2009-01-01

    We compute 3D gasdynamical models of jet outflows from the central AGN, that carry mass as well as energy to the hot gas in galaxy clusters and groups. These flows have many attractive attributes for solving the cooling flow problem: why the hot gas temperature and density profiles resemble cooling flows but show no spectral evidence of cooling to low temperatures. Subrelativistic jets, described by a few parameters, are assumed to be activated when gas flows toward or cools near a central SMBH. Using approximate models for a rich cluster (A1795), a poor cluster (2A 0336+096) and a group (NGC 5044), we show that mass-carrying jets with intermediate mechanical efficiencies ($\\sim10^{-3}$) can reduce for many Gyr the global cooling rate to or below the low values implied by X-spectra, while maintaining $T$ and $\\rho$ profiles similar to those observed, at least in clusters. Groups are much more sensitive to AGN heating and present extreme time variability in both profiles. Finally, the intermittency of the feed...

  8. Spent Fuel Ratio Estimates from Numerical Models in ALE3D

    Margraf, J. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dunn, T. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-08-02

    Potential threat of intentional sabotage of spent nuclear fuel storage facilities is of significant importance to national security. Paramount is the study of focused energy attacks on these materials and the potential release of aerosolized hazardous particulates into the environment. Depleted uranium oxide (DUO2) is often chosen as a surrogate material for testing due to the unreasonable cost and safety demands for conducting full-scale tests with real spent nuclear fuel. To account for differences in mechanical response resulting in changes to particle distribution it is necessary to scale the DUO2 results to get a proper measure for spent fuel. This is accomplished with the spent fuel ratio (SFR), the ratio of respirable aerosol mass released due to identical damage conditions between a spent fuel and a surrogate material like depleted uranium oxide (DUO2). A very limited number of full-scale experiments have been carried out to capture this data, and the oft questioned validity of the results typically leads to overly-conservative risk estimates. In the present work, the ALE3D hydrocode is used to simulate DUO2 and spent nuclear fuel pellets impacted by metal jets. The results demonstrate an alternative approach to estimate the respirable release fraction of fragmented nuclear fuel.

  9. RFX first wall thermal power handling: 3D numerical models and experimental validations

    One of the emerging issues for future thermonuclear devices is the non-uniform power deposition on the first wall or divertor surfaces. The localized peaks of power are detrimental both for the lifetime of the plasma facing components and for plasma heating and confinement. The thermal monitoring of the first wall can be done with temperature measurements acquired during the experiments by means of thermocouples and/or infrared camera images. If the measurement system is integrated with analytical or numerical models, it is possible to estimate the applied thermal loads and to obtain a thorough knowledge of the thermal behaviour of the first wall and vacuum vessel system. The numerical model developed for the RFX machine is hereby described and validated by means of comparisons with IR camera and thermocouple temperature measurements

  10. GeoFlow: 3D numerical simulation of supercritical thermal convective states

    Futterer, B; Egbers, C [Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus, Siemens-Halske-Ring 14, 03046 Cottbus (Germany); Hollerbach, R [Department of Applied Mathematics, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT (United Kingdom)], E-mail: futterer@tu-cottbus.de

    2008-11-01

    'GeoFlow' is a thermal convection experiment in rotating spherical shell geometry, which is going to take place in microgravity environment of International Space Station. We present numerical preliminary studies of the spherical Rayleigh-Benard problem under an artificial central force field. Numerical simulation is done with a pseudospectral method. Special focus here is the simulation of flow states at selected parameter points of Rayleigh and Taylor number of a defined plan for experimental runs on ISS. One loop will contain thermal convection without rotation, i.e. rising temperature gradient between inner and outer sphere. Another loop investigates convection superimposed by rotation, i.e. fixing temperature gradient and then rising rotation rate. In such cases different transitions are expected to be observed. Just rising Rayleigh number shows different stable states depending on initial conditions. Fixing Rayleigh number and then rising up Taylor number leads to traverse of different convective states showing rich dynamics of the system.

  11. 2D and 3D numerical modeling of seismic waves from explosion sources

    Over the last decade, nonlinear and linear 2D axisymmetric finite difference codes have been used in conjunction with far-field seismic Green's functions to simulate seismic waves from a variety of sources. In this paper we briefly review some of the results and conclusions that have resulted from numerical simulations and explosion modeling in support of treaty verification research at S-CUBED in the last decade. We then describe in more detail the results from two recent projects. Our goal is to provide a flavor for the kinds of problems that can be examined with numerical methods for modeling excitation of seismic waves from explosions. Two classes of problems have been addressed; nonlinear and linear near-source interactions. In both classes of problems displacements and tractions are saved on a closed surface in the linear region and the representation theorem is used to propagate the seismic waves to the far-field

  12. Wavelet-based adaptive numerical simulation of unsteady 3D flow around a bluff body

    de Stefano, Giuliano; Vasilyev, Oleg

    2012-11-01

    The unsteady three-dimensional flow past a two-dimensional bluff body is numerically simulated using a wavelet-based method. The body is modeled by exploiting the Brinkman volume-penalization method, which results in modifying the governing equations with the addition of an appropriate forcing term inside the spatial region occupied by the obstacle. The volume-penalized incompressible Navier-Stokes equations are numerically solved by means of the adaptive wavelet collocation method, where the non-uniform spatial grid is dynamically adapted to the flow evolution. The combined approach is successfully applied to the simulation of vortex shedding flow behind a stationary prism with square cross-section. The computation is conducted at transitional Reynolds numbers, where fundamental unstable three-dimensional vortical structures exist, by well-predicting the unsteady forces arising from fluid-structure interaction.

  13. 3D FEM Numerical Simulation of Seismic Pile-supported Bridge Structure Reaction in Liquefying Ground

    Ling XianZhang, Tang Liang and Xu Pengju

    2011-04-01

    Full Text Available This study examines the establishment of liquefied ground pile-soil-bridge seismic interaction analysis of three-dimensional finite element analysis method for the simulation of liquefied ground shaking table test of pile-soil seismic interaction analysis, undertake OpenSees finite element based numerical simulation platform, for the shaking table test based on two-phase saturated porous media, Comparative numerical and experimental results, detailed test pile dynamic response of bridge structure and dynamic properties, especially liquefaction pore pressure, liquefaction of pile foundation and the dynamic response of the free field. Finite element method can reasonably predict the site of pore pressure, dynamic response; despite the conventional beam element simulation of pile, pile dynamic response can still accurately simulated.

  14. On the numerical modfeling of 3D-atmospheric boundary layer flow

    Beneš, Luděk; Sládek, Ivo; Jaňour, Zbyněk

    Karlsruhe : Forshungszentrum Karrlsruhe GmbH, 2004 - (Suppan, P.), s. 340-344 ISBN 3-923704-44-5. [Harmonisation within atmospheric Dispersion modeling for regulatory purposes. Garmisch-Partenkirchen (DE), 01.06.2004-04.06.2004] R&D Projects: GA MŠk OC 715.10 Institutional research plan: CEZ:AV0Z2076919 Keywords : atmosphere * pollution * numerical simulation Subject RIV: BA - General Mathematics

  15. Virial theorem analysis of 3D numerical simulations of MHD self-gravitating turbulence

    Shadmehri, Mohsen; Vazquez-Semadeni, Enrique; Ballesteros-Paredes, Javier

    2001-01-01

    We discuss the virial balance of all members of a cloud ensemble in numerical simulations of self-gravitating MHD turbulence. We first discuss the choice of reference frame for evaluating the terms entering the virial theorem (VT), concluding that the balance of each cloud should be measured in its own reference frame. We then report preliminary results suggesting that a) the clouds are far from virial equilibrium, with the ``geometric'' (time derivative) terms dominating the VT. b) The surfa...

  16. I-Simpa, a graphical user interface devoted to host 3D sound propagation numerical codes

    PICAUT, Judicaël; Fortin, Nicolas

    2012-01-01

    Whatever for indoor noise applications (room acoustics, noise in vehicles...) or sound propagation in the environment (open field, urban areas...), many numerical codes have been developed by researchers. Most of them have many common aspects, like the definition of the domain geometry and the materials (boundary conditions, impedance...), the definition of sound sources and of receivers (position, spectrum, directivity...). Moreover, they all have the same objective that is to predict the so...

  17. Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model

    Baudron, Anne-Marie A -M; Maday, Yvon; Riahi, Mohamed Kamel; Salomon, Julien

    2014-01-01

    We present a parareal in time algorithm for the simulation of neutron diffusion transient model. The method is made efficient by means of a coarse solver defined with large time steps and steady control rods model. Using finite element for the space discretization, our implementation provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch-Maurer-Werner (LMW) benchmark [1].

  18. 3D printing device for numerical control machine and wood deposition

    Julien Gardan; Lionel Roucoules

    2014-01-01

    The paper presents the development of a new sustainable approach in additive manufacturing adapted on a Numerical Control (NC) machining. Wood has several advantages that are transferable to various derivatives allowing the introduction of sustainable material into the product lifecycle. The application involves the integration of wood pulp into rapid prototyping solutions. Wood is the main material studied for its ecological aspect. The primary goal was to create reconstituted wo...

  19. Numerical and experimental study of the 3D effect on connecting arm of vertical axis tidal current turbine

    Guo, Wei; Kang, Hai-gui; Chen, Bing; Xie, Yu; Wang, Yin

    2016-03-01

    Vertical axis tidal current turbine is a promising device to extract energy from ocean current. One of the important components of the turbine is the connecting arm, which can bring about a significant effect on the pressure distribution along the span of the turbine blade, herein we call it 3D effect. However, so far the effect is rarely reported in the research, moreover, in numerical simulation. In the present study, a 3D numerical model of the turbine with the connecting arm was developed by using FLUENT software compiling the UDF (User Defined Function) command. The simulation results show that the pressure distribution along the span of blade with the connecting arm model is significantly different from those without the connecting arm. To facilitate the validation of numerical model, the laboratory experiment has been carried out by using three different types of NACA aerofoil connecting arm and circle section connecting arm. And results show that the turbine with NACA0012 connecting arm has the best start-up performance which is 0.346 m/s and the peak point of power conversion coefficient is around 0.33. A further study has been performed and a conclusion is drawn that the aerofoil and thickness of connecting arm are the most important factors on the power conversion coefficient of the vertical axis tidal current turbine.

  20. Efficient 3D Acoustic Numerical modeling in the Logarithmic-grid using the Expanding Domain Method

    Hong, B. R.; Chung, W.; Ko, H.; Bae, H. S.

    2015-12-01

    In the numerical modeling of seismic wave propagation by the use of a discrete computing domain, dispersion analysis is preceded by the determination of the spatial grid spacings in order to ensure accurate modeling results. Grid spacing is a function of wavelength, and the wavelength depends on the minimum velocity and maximum source frequency. Therefore, as the frequency increases, the number of grids increase and this leads to computational overburden. In order to reduce the computing complexity, coordinate transformation techniques such as Riemannian coordinates and logarithmic grid sets are proposed. Riemannian wave-field extrapolation is a way to reformulate the wave-field by expressing it in Riemannian coordinates. In the logarithmic grid, grid spacing changes logarithmically, so this enables us to reduce the number of grids compared to a conventional grid set. Furthermore, this could completely remove boundary reflections by extending the model dimensions. However, numerical modeling in the logarithmic grid is still inefficient because it is performed for whole model at every individual time step. In this study we applied the expanding domain method to the logarithmic modeling in order to improve computational efficiency. This method, based on amplitude comparison, excludes computations for zero wave-fields by considering a non-zero domain boundary. Numerical examples demonstrated that our new modeling method enhances computational efficiency maintaining accuracy compared with conventional modeling methods. In wider and higher-order dimensions, particularly, the efficiency of our modeling method increased. Our new modeling technique could also be applied to the generation of underwater target echo signals requiring high frequency analysis.

  1. Visual numerical steering in 3D AGENT code system for advanced nuclear reactor modeling and design

    Highlights: ► Numerical steering framework developed for deterministic neutron transport code AGENT to speed up the solution. ► Resulting speed up is on the order of 50%. ► Use of the steering framework is demonstrated modeling a TRIGA reactor. ► Numerical steering framework showed to be well suited for the deterministic neutron transport methods. - Abstract: The AGENT simulation system is used for detailed three-dimensional modeling of neutron transport and corresponding properties of nuclear reactors of any design. Numerical solution to the neutron transport equation in the AGENT system is based on the Method of Characteristics (MOCs) and the theory of R-functions. The latter of which is used for accurately describing current and future heterogeneous lattices of reactor core configurations. The AGENT code has been extensively verified to assure a high degree of accuracy for predicting neutron three-dimensional point-wise flux spatial distributions, power peaking factors, reaction rates, and eigenvalues. In this paper, a new AGENT code feature, a computational steering, is presented. This new feature provides a novel way for using deterministic codes for fast evaluation of reactor core parameters, at no loss to accuracy. The computational steering framework as developed at the Technische Universität München is smoothly integrated into the AGENT solver. This framework allows for an arbitrary interruption of AGENT simulation, allowing the solver to restart with updated parameters. One possible use of this is to accelerate the convergence of the final values resulting in significantly reduced simulation times. Using this computational steering in the AGENT system, coarse MOC resolution parameters can initially be selected and later update them – while the simulation is actively running – into fine resolution parameters. The utility of the steering framework is demonstrated using the geometry of a research reactor at the University of Utah: this new

  2. Code and Solution Verification of 3D Numerical Modeling of Flow in the Gust Erosion Chamber

    Yuen, A.; Bombardelli, F. A.

    2014-12-01

    Erosion microcosms are devices commonly used to investigate the erosion and transport characteristics of sediments at the bed of rivers, lakes, or estuaries. In order to understand the results these devices provide, the bed shear stress and flow field need to be accurately described. In this research, the UMCES Gust Erosion Microcosm System (U-GEMS) is numerically modeled using Finite Volume Method. The primary aims are to simulate the bed shear stress distribution at the surface of the sediment core/bottom of the microcosm, and to validate the U-GEMS produces uniform bed shear stress at the bottom of the microcosm. The mathematical model equations are solved by on a Cartesian non-uniform grid. Multiple numerical runs were developed with different input conditions and configurations. Prior to developing the U-GEMS model, the General Moving Objects (GMO) model and different momentum algorithms in the code were verified. Code verification of these solvers was done via simulating the flow inside the top wall driven square cavity on different mesh sizes to obtain order of convergence. The GMO model was used to simulate the top wall in the top wall driven square cavity as well as the rotating disk in the U-GEMS. Components simulated with the GMO model were rigid bodies that could have any type of motion. In addition cross-verification was conducted as results were compared with numerical results by Ghia et al. (1982), and good agreement was found. Next, CFD results were validated by simulating the flow within the conventional microcosm system without suction and injection. Good agreement was found when the experimental results by Khalili et al. (2008) were compared. After the ability of the CFD solver was proved through the above code verification steps. The model was utilized to simulate the U-GEMS. The solution was verified via classic mesh convergence study on four consecutive mesh sizes, in addition to that Grid Convergence Index (GCI) was calculated and based on

  3. Improvement of the 3D numerical model of the spherical particle saltation

    Lukerchenko, Nikolay; Piatsevich, Siarhei; Chára, Zdeněk; Vlasák, Pavel

    Tbilisi : Agricultural University of Wroclaw, Poland, 2006 - (Gochitashvili, T.; Sobota, J.), s. 177-186 ISBN 83-60574-00-6. [International Conference on Transport and Sedimentation of Solid Particles /13./. Tbilisi (GE), 18.09.2006-20.09.2006] R&D Projects: GA ČR GA103/06/1487 Institutional research plan: CEZ:AV0Z20600510 Keywords : particle saltation, * particle-bed collision * Magnus force * contact zone * numerical simulation * deviation angle * relative concentration Subject RIV: BK - Fluid Dynamics

  4. 3-D numerical simulation on the vibration of liquid sodium's free surface in sodium pool of FBR

    This paper succeeds in simulating three-dimensional incompressible flows with free surface, complicated in-flow and out-flow boundary conditions and internal obstacles, and also can treat these fluid flows in arbitrary shape vessel using a partial cell. According to all kinds of the element influencing the free surface's vibration in sodium pool it may give the various wave's form, the highest and lowest position, and the amount of the vibration. This paper introduces the brief principle of VOF numerical method, develops the computational program based on NASA-VOF3D, provides some results about the free surface's vibration in sodium pool of FBR

  5. 3D numerical model for a focal plane view in case of mosaic grating compressor for high energy CPA chain.

    Montant, S; Marre, G; Blanchot, N; Rouyer, C; Videau, L; Sauteret, C

    2006-12-11

    An important issue, mosaic grating compressor, is studied to recompress pulses for multiPetawatt, high energy laser systems. Alignment of the mosaic elements is crucial to control the focal spot and thus the intensity on target. No theoretical approach analyses the influence of compressor misalignment on spatial and temporal profiles in the focal plane. We describe a simple 3D numerical model giving access to the focal plane view after a compressor. This model is computationally inexpensive since it needs only 1D Fourier transforms to access to the temporal profile. We present simulations of monolithic and mosaic grating compressors. PMID:19529688

  6. 3-D numerical simulation of Yb:YAG active slabs with longitudinal doping gradient for thermal load effects assessment.

    Ferrara, P; Ciofini, M; Esposito, L; Hostaša, J; Labate, L; Lapucci, A; Pirri, A; Toci, G; Vannini, M; Gizzi, L A

    2014-03-10

    We present a study of Yb:YAG active media slabs, based on a ceramic layered structure with different doping levels. We developed a procedure allowing 3D numerical analysis of the slab optical properties as a consequence of the thermal load induced by the pump process. The simulations are compared with a set of experimental results in order to validate the procedure. These structured ceramics appear promising in appropriate geometrical configurations, and thus are intended to be applied in the construction of High Energy Diode Pumped Solid State Laser (DPSSL) systems working in high repetition-rate pulsed regimes. PMID:24663877

  7. Numerical simulation of 3D unsteady flow in a rotating pump by dynamic mesh technique

    In this paper, the numerical simulation of unsteady flow for three kinds of typical rotating pumps, roots blower, roto-jet pump and centrifugal pump, were performed using the three-dimensional Dynamic Mesh technique. In the unsteady simulation, all the computational domains, as stationary, were set in one inertial reference frame. The motions of the solid boundaries were defined by the Profile file in FLUENT commercial code, in which the rotational orientation and speed of the rotors were specified. Three methods (Spring-based Smoothing, Dynamic Layering and Local Re-meshing) were used to achieve mesh deformation and re-meshing. The unsteady solutions of flow field and pressure distribution were solved. After a start-up stage, the flow parameters exhibit time-periodic behaviour corresponding to blade passing frequency of rotor. This work shows that Dynamic Mesh technique could achieve numerical simulation of three-dimensional unsteady flow field in various kinds of rotating pumps and have a strong versatility and broad application prospects

  8. 3D numerical simulation and structural optimization of the rod baffle heat exchanger

    YAN Liang-wen; PAN Lei; KAN Shu-lin

    2009-01-01

    Because of the complexities of fluid dynamics equations and the structure of heat exchangers, few theoretical solutions have been acquired to specify the shell side characteristics of the rod baffle heat exchanger (RBHE). Based on the platform of PHEONICS version 3.5.1, a three-dimensionai numerical method for predicting the turbulent fluid flow behavior in the shell side of the rod baffle heat exchangers is developed in this paper. With this method, modeling of the tube bundle is carried out based on the porous media concept using volumetric porosities and applicable flow resistance correlations. Turbulence effects are modeled using a standard κ-ε model. It is shown that the simulation results and experimental results are in good agreement in the shell side. The maximum absolute deviation value of pressure drops is less than 5%, and that of the heat transfer coefficients is less than 8%. Furthermore, the numerical model is used to optimize the structure of the RBHE and improves its performance.

  9. A Numerical Study on the Thermal Conductivity of 3D Woven C/C Composites at High Temperature

    Shigang, Ai; Rujie, He; Yongmao, Pei

    2015-12-01

    Experimental data for Carbon/Carbon (C/C) constituent materials are combined with a three dimensional steady state heat transfer finite element analysis to demonstrate the average in-plane and out-of-plane thermal conductivities (TCs) of C/C composites. The finite element analysis is carried out at two distinct length scales: (a) a micro scale comparable with the diameter of carbon fibres and (b) a meso scale comparable with the carbon fibre yarns. Micro-scale model calculate the TCs at the fibre yarn scale in the three orthogonal directions ( x, y and z). The output results from the micro-scale model are then incorporated in the meso-scale model to obtain the global TCs of the 3D C/C composite. The simulation results are quite consistent with the theoretical and experimental counterparts reported in references. Based on the numerical approach, TCs of the 3D C/C composite are calculated from 300 to 2500 K. Particular attention is given in elucidating the variations of the TCs with temperature. The multi-scale models provide an efficient approach to predict the TCs of 3D textile materials, which is helpful for the thermodynamic property analysis and structure design of the C/C composites.

  10. Geological characterization of Italian reservoirs and numerical 3D modelling of CO2 storage scenarios into saline aquifers

    Beretta, S.; Moia, F.; Guandalini, R.; Cappelletti, F.

    2012-04-01

    The research activities carried out by the Environment and Sustainable Development Department of RSE S.p.A. aim to evaluate the feasibility of CO2 geological sequestration in Italy, with particular reference to the storage into saline aquifers. The identification and geological characterization of the Italian potential storage sites, together with the study of the temporal and spatial evolution of the CO2 plume within the caprock-reservoir system, are performed using different modelling tools available in the Integrated Analysis Modelling System (SIAM) entirely powered in RSE. The numerical modelling approach is the only one that allows to investigate the behaviour of the injected CO2 regarding the fluid dynamic, geochemical and geomechanical aspects and effects due to its spread, in order to verify the safety of the process. The SIAM tools allow: - Selection of potential Italian storage sites through geological and geophysical data collected in the GIS-CO2 web database; - Characterization of caprock and aquifer parameters, seismic risk and environmental link for the selected site; - Creation of the 3D simulation model for the selected domain, using the modeller METHODRdS powered by RSE and the mesh generator GMSH; - Simulation of the injection and the displacement of CO2: multiphase fluid 3D dynamics is based on the modified version of TOUGH2 model; - Evaluation of geochemical reaction effects; - Evaluation of geomechanic effects, using the coupled 3D CANT-SD finite elements code; - Detailed local analysis through the use of open source auxiliary tools, such as SHEMAT and FEHM. - 3D graphic analysis of the results. These numerical tools have been successfully used for simulating the injection and the spread of CO2 into several real Italian reservoirs and have allowed to achieve accurate results in terms of effective storage capacity and safety analysis. The 3D geological models represent the high geological complexity of the Italian subsoil, where reservoirs are

  11. 3D numerical simulations of THz generation by two-color laser filaments

    Tera-hertz (THz) radiation produced by the filamentation of two-color pulses over long distances in argon is numerically investigated using a comprehensive model in full space-time-resolved geometry. We show that the dominant physical mechanism for THz generation in the filamentation regime at clamping intensity is based on quasi-dc plasma currents. The calculated THz spectra for different pump pulse energies and pulse durations are in agreement with previously reported experimental observations. For the same pulse parameters, near-infrared pump pulses at 2 μm are shown to generate a more than 1 order of magnitude greater THz yield than pumps centered at 800 nm. (authors)

  12. 3D Numerical Simulations of f-Mode Propagation Through Magnetic Flux Tubes

    Daiffallah, K; Bendib, A; Cameron, R; Gizon, L

    2010-01-01

    Three-dimensional numerical simulations have been used to study the scattering of a surface-gravity wave packet by vertical magnetic flux tubes, with radii from 200 km to 3 Mm, embedded in stratified polytropic atmosphere. The scattered wave was found to consist primarily of m=0 (axisymmetric) and m=1 modes. It was found that the ratio of the amplitude of these two modes is strongly dependant on the radius of the flux tube: The kink mode is the dominant mode excited in tubes with a small radius while the sausage mode is dominant for large tubes. Simulations of this type provide a simple, efficient and robust way to start understanding the seismic signature of flux tubes, which have recently began to be observed.

  13. NUMERICAL SIMULATION OF 3D KIRLOSKER TV-1 MODEL ENGINE CYLINDER FOR COLD FLOW

    S. SIVA

    2013-12-01

    Full Text Available The definition of an efficient optimization methodology for internal combustion engine design using computational fluid dynamic simulation models is presented. This paper aims at validating the fundamental numerical and computational fluid dynamic aspects which can lead to the definition of following models. The models used for analysis of Standard k-ε model, Realizable k-ε model, V2F k-ε model, AKN k-ε model, and Standard k-ω (Wilcox model. For these reasons, both single-and multi-objective problems will be addressed, where the former are still of relevant interest (i.e. optimization of engine performances, while the later have a much wider range of applications and are often characterized by conflicting objectives.Modeling of the KIRLOSKER OIL ENGINE TV1 will be done using GAMBIT. Flow inside the engine is to be the analysis and validation various turbulence models using STARCD. This is used to find the model which predicts the engine performance better.

  14. A continuous flow microfluidic calorimeter: 3-D numerical modeling with aqueous reactants

    Sen, Mehmet A., E-mail: mehmet.sen@mathworks.com [Northeastern University, Department of Mechanical and Industrial Engineering, 360 Hungtington Avenue, 334 Snell Engineering Center, Boston, MA 02115 (United States); Kowalski, Gregory J., E-mail: gkowal@coe.neu.edu [Northeastern University, Department of Mechanical and Industrial Engineering, 360 Hungtington Avenue, 334 Snell Engineering Center, Boston, MA 02115 (United States); Fiering, Jason, E-mail: jfiering@draper.com [Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA 02139 (United States); Larson, Dale, E-mail: dlarson@draper.com [Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA 02139 (United States)

    2015-03-10

    Highlights: • A co-flow microreactor is modeled in flow, reaction/diffusion, and thermal domains. • Analysis shows how arrayed temperature sensors can provide enthalpy of reaction. • Optical plasmonic temperature sensors could be arrayed suitably for calorimetry. • The reactor studied has a volume of 25 nL. - Abstract: A computational analysis of the reacting flow field, species diffusion and heat transfer processes with thermal boundary layer effects in a microchannel reactor with a coflow configuration was performed. Two parallel adjacent streams of aqueous reactants flow along a wide, shallow, enclosed channel in contact with a substrate, which is affixed to a temperature controlled plate. The Fluent computational fluid dynamics package solved the Navier–Stokes, mass transport and energy equations. The energy model, including the enthalpy of reaction as a nonuniform heat source, was validated by calculating the energy balance at several control volumes in the microchannel. Analysis reveals that the temperature is nearly uniform across the channel thickness, in the direction normal to the substrate surface; hence, measurements made by sensors at or near the surface are representative of the average temperature. Additionally, modeling the channel with a glass substrate and a silicone cover shows that heat transfer is predominantly due to the glass substrate. Finally, using the numerical results, we suggest that a microcalorimeter could be based on this configuration, and that temperature sensors such as optical nanohole array sensors could have sufficient spatial resolution to determine enthalpy of reaction.

  15. Numerical analysis of 3-D unsteady flow in a vaneless counter-rotating turbine

    ZHAO Qingjun; WANG Huishe; ZHAO Xiaolu; XU Jianzhong

    2007-01-01

    To reveal the unsteady flow characteristics of a vaneless counter-rotating turbine (VCRT),a threedimensional,viscous,unsteady computational fluid dynamics (CFD) analysis was performed.The results show that unsteady simulation is superior to steady simulation because more flow characteristics can be obtained.The unsteady effects in upstream airfoil rows are weaker than those in downstream airfoil rows in the VCRT.The static pressure distribution along the span in the pressure surface of a high pressure turbine stator is more uniform than that in the suction surface.The static pressure distributions along the span in the pressure surfaces and the suction surfaces of a high pressure turbine rotor and a low pressure turbine rotor are all uneven.The numerical results also indicate that the load of a high pressure turbine rotor will increase with the increase of the span.The deviation is very big between the direction of air flow at the outlet of a high pressure turbine rotor and the axial direction.A similar result can also be obtained in the outlet of a low pressure turbine rotor.This means that the specific work of a high pressure turbine rotor and a low pressure turbine rotor is big enough to reach the design objectives.

  16. 3-D VARIABLE PARAMETER NUMERICAL MODEL FOR EVALUATION OF THE PLANNED EXPLOITABLE GROUNDWATER RESOURCE IN REGIONAL UNCONSOLIDATED SEDIMENTS

    LUO Zu-jiang; WANG Yan

    2012-01-01

    In order to correctly evaluate the exploitable groundwater resource in regional complex,thick Quaternary unconsolidated sediments,the whole Quaternary unconsolidated sediments are considered as a unified hydrogeological unit and a 3-D unsteady groundwater flow numerical model is adopted.Meanwhile,with the consideration of the dynamic changes of the porosity,the hydraulic conductivity and the specific storage with the groundwater level dropping during the exploitation process,an improved composite element seepage matrix adjustment method is applied to solve the unsteady flow problem of free surface.In order to evaluate the exploitable groundwater resource in Cangzhou,Hebei Province,the hydrogeological conceptual model of Cangzhou is generalized to establish,a 3-D variable parameter numerical model of Cangzhou.Based on the prediction of the present groundwater exploitation,and by adjusting the groundwater exploitation layout,the exploitable groundwater resource is predicted.The model enjoys features like good convergence,good stability and high precision.

  17. 3D NUMERICAL STUDY ON LAMINAR FORCED CONVECTION IN V-BAFFLED SQUARE CHANNEL

    Amnart Boonloi

    2013-01-01

    Full Text Available The article presents a mathematical study of fully developed periodic laminar flow visualization and heat transfer characteristics in an isothermal wall square-channel fitted with V-shaped baffles on one wall. The computations based on the finite volume method together with the SIMPLE algorithm have been performed. The investigation covers a range of Re based on the hydraulic diameter of the channel, Re = 100-1200. To create a pair of main streamwise vortex flows through the tested section, the V-baffles with the attack angle of 30° with the main flow direction are mounted in tandem and pointing downstream on the lower channel wall only. Effects of different baffle heights and pitches on heat transfer and pressure drop in the channel are examined and the results obtained are compared with smooth channel with no baffle. The numerical result shows that the presence of the V-baffle yields a significant heat transfer enhancement compared with the smooth channel. It is visible that the main vortex flows, a pair of streamwise twisted vortex (P-vortex can induce impingement flows on the walls leading to a drastic increase in heat transfer rate over the channel. In addition, the increase in the baffle height leads to the rise in the heat transfer and pressure loss while that in the baffle pitch provides the opposite trend. The predicted results expose that the maximum thermal enhancement factors for the V-baffles with BR = 0.3, 0.3 and 0.4; and PR = 1, 1.5 and 2 are, respectively, about 2.44, 2.29 and 2.37 at higher Re.

  18. A numerical study of the transition to oscillatory flow in 3D lid-driven cubic cavity flows

    Chiu, Shang-Huan; He, Jiwen; Guo, Aixia; Glowinski, Roland

    2016-01-01

    In this article, three dimensional (3D) lid-driven cubic cavity flows have been studied numerically for various values of Reynolds number ($Re$). The numerical solution of the Navier-Stokes equations modeling incompressible viscous fluid flow in a cubic cavity is obtained via a methodology combining a first order accurate operator-splitting, $L^2$-projection Stokes solver, a wave-like equation treatment of the advection and finite element methods. The numerical results obtained for Re$=$400, 1000, and 3200 show a good agreement with available numerical and experimental results in literature. Simulation results predict that the critical Re$_{cr}$ for the transition from steady flow to oscillatory (a Hopf bifurcation) is somewhere in [1870, 1875] for the mesh size $h=1/96$. Via studying the flow field distortion of fluid flow at Re before and after Re$_{cr}$, the occurrence of the first pair of Taylor-G\\"ortler-like vortices is connected to the flow field distortion at the transition from steady flow to oscilla...

  19. MODELING STATISTICAL PROPERTIES OF SOLAR ACTIVE REGIONS THROUGH DIRECT NUMERICAL SIMULATIONS OF 3D-MHD TURBULENCE

    Malapaka, Shiva Kumar; Mueller, Wolf-Christian [Max-Planck Institute for Plasma Physics, Boltzmannstrasse 2, D-85748 Garching bei Muenchen (Germany)

    2013-09-01

    Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the active regions (ARs), have been studied using the line-of-sight data from magnetograms taken by the Solar and Heliospheric Observatory and several other instruments. This includes structure functions and their exponents, flatness curves, and correlation functions. In these works, the dependence of structure function exponents ({zeta}{sub p}) of the order of the structure functions (p) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper, we compare some of the observations from Abramenko et al. with the log-Poisson model used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustained by forcing, freely decaying, and a flow initially driven and later allowed to decay (case 3). The respective DNS replicate the properties seen in the plots of {zeta}{sub p} against p of ARs. We also reproduce the trends and changes observed in intermittency in flatness and correlation functions of ARs. It is suggested from this analysis that an AR in the onset phase of a flare can be treated as a forced 3D-MHD turbulent system in its simplest form and that the flaring stage is representative of decaying 3D-MHD turbulence. It is also inferred that significant changes in intermittency from the initial onset phase of a flare to its final peak flaring phase are related to the time taken by the system to reach the initial onset phase.

  20. MODELING STATISTICAL PROPERTIES OF SOLAR ACTIVE REGIONS THROUGH DIRECT NUMERICAL SIMULATIONS OF 3D-MHD TURBULENCE

    Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the active regions (ARs), have been studied using the line-of-sight data from magnetograms taken by the Solar and Heliospheric Observatory and several other instruments. This includes structure functions and their exponents, flatness curves, and correlation functions. In these works, the dependence of structure function exponents (ζp) of the order of the structure functions (p) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper, we compare some of the observations from Abramenko et al. with the log-Poisson model used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustained by forcing, freely decaying, and a flow initially driven and later allowed to decay (case 3). The respective DNS replicate the properties seen in the plots of ζp against p of ARs. We also reproduce the trends and changes observed in intermittency in flatness and correlation functions of ARs. It is suggested from this analysis that an AR in the onset phase of a flare can be treated as a forced 3D-MHD turbulent system in its simplest form and that the flaring stage is representative of decaying 3D-MHD turbulence. It is also inferred that significant changes in intermittency from the initial onset phase of a flare to its final peak flaring phase are related to the time taken by the system to reach the initial onset phase

  1. 3D numerical simulation on fluid-structure interaction of structure subjected to underwater explosion with cavitation

    A-man ZHANG; Shao-fei REN; Qing LI; Jia LI

    2012-01-01

    In the underwater-shock environment,cavitation occurs near the structural surface.The dynamic response of fluid-structure interactions is influenced seriously by the cavitation effects.It is also the difficulty in the field of underwater explosion.With the traditional boundary element method and the finite element method (FEM),it is difficult to solve the nonlinear problem with cavitation effects subjected to the underwater explosion.To solve this problem,under the consideration of the cavitation effects and fluid compressibility,with fluid viscidity being neglected,a 3D numerical model of transient nonlinear fluid-structure interaction subjected to the underwater explosion is built.The fluid spectral element method (SEM) and the FEM are adopted to solve this model.After comparison with the FEM,it is shown that the SEM is more precise than the FEM,and the SEM results are in good coincidence with benchmark results and experiment results.Based on this,combined with ABAQUS,the transient fluid-structure interaction mechanism of the 3D submerged spherical shell and ship stiffened plates subjected to the underwater explosion is discussed,and the cavitation region and its influence on the structural dynamic responses are presented.The paper aims at providing references for relevant research on transient fluid-structure interaction of ship structures subjected to the underwater explosion.

  2. The Global Solar Dynamo

    Cameron, R H; Brandenburg, A

    2016-01-01

    A brief summary of the various observations and constraints that underlie solar dynamo research are presented. The arguments that indicate that the solar dynamo is an alpha-omega dynamo of the Babcock-Leighton type are then shortly reviewed. The main open questions that remain are concerned with the subsurface dynamics, including why sunspots emerge at preferred latitudes as seen in the familiar butterfly wings, why the cycle is about 11 years long, and why the sunspot groups emerge tilted with respect to the equator (Joy's law). Next, we turn to magnetic helicity, whose conservation property has been identified with the decline of large-scale magnetic fields found in direct numerical simulations at large magnetic Reynolds numbers. However, magnetic helicity fluxes through the solar surface can alleviate this problem and connect theory with observations, as will be discussed.

  3. The Global Solar Dynamo

    Cameron, R. H.; Dikpati, M.; Brandenburg, A.

    2016-02-01

    A brief summary of the various observations and constraints that underlie solar dynamo research are presented. The arguments that indicate that the solar dynamo is an alpha-omega dynamo of the Babcock-Leighton type are then shortly reviewed. The main open questions that remain are concerned with the subsurface dynamics, including why sunspots emerge at preferred latitudes as seen in the familiar butterfly wings, why the cycle is about 11 years long, and why the sunspot groups emerge tilted with respect to the equator (Joy's law). Next, we turn to magnetic helicity, whose conservation property has been identified with the decline of large-scale magnetic fields found in direct numerical simulations at large magnetic Reynolds numbers. However, magnetic helicity fluxes through the solar surface can alleviate this problem and connect theory with observations, as will be discussed.

  4. Numerical 3D Model of Viscous Turbulent Flow in One Stage Gas Turbine and Its Experimental Validation

    Yu.V. STARODUBTSEV; I.G. GOGOLEV; V.G. SOLODOV

    2005-01-01

    @@ The paper describes 3D numerical Reynolds Averaged Navier-Stokes (RANS) model and approximate sector approach for viscous turbulent flow through flow path of one stage axial supercharge gas turbine of marine diesel engine. Computational data are tested by comparison with experimental data. The back step flow path opening and tip clearance jet are taken into account.This approach could be applied for variety of turbine theory and design tasks: for offer optimal design in order to minimize kinetic energy stage losses; for solution of partial supply problem; for analysis of flow pattern in near extraction stages; for estimation of rotational frequency variable forces on blades; for sector vane adjustment (with thin leading edges mainly), for direct flow modeling in the turbine etc. The development of this work could be seen in the direction of unsteady stage model application.

  5. Magnetic fields end-face effect investigation of HTS bulk over PMG with 3D-modeling numerical method

    Qin, Yujie; Lu, Yiyun

    2015-09-01

    In this paper, the magnetic fields end-face effect of high temperature superconducting (HTS) bulk over a permanent magnetic guideway (PMG) is researched with 3D-modeling numerical method. The electromagnetic behavior of the bulk is simulated using finite element method (FEM). The framework is formulated by the magnetic field vector method (H-method). A superconducting levitation system composed of one rectangular HTS bulk and one infinite long PMG is successfully investigated using the proposed method. The simulation results show that for finite geometrical HTS bulk, even the applied magnetic field is only distributed in x-y plane, the magnetic field component Hz which is along the z-axis can be observed interior the HTS bulk.

  6. A Sensory 3D Map of the Odor Description Space Derived from a Comparison of Numeric Odor Profile Databases.

    Zarzo, Manuel

    2015-06-01

    Many authors have proposed different schemes of odor classification, which are useful to aid the complex task of describing smells. However, reaching a consensus on a particular classification seems difficult because our psychophysical space of odor description is a continuum and is not clustered into well-defined categories. An alternative approach is to describe the perceptual space of odors as a low-dimensional coordinate system. This idea was first proposed by Crocker and Henderson in 1927, who suggested using numeric profiles based on 4 dimensions: "fragrant," "acid," "burnt," and "caprylic." In the present work, the odor profiles of 144 aroma chemicals were compared by means of statistical regression with comparable numeric odor profiles obtained from 2 databases, enabling a plausible interpretation of the 4 dimensions. Based on the results and taking into account comparable 2D sensory maps of odor descriptors from the literature, a 3D sensory map (odor cube) has been drawn up to improve understanding of the similarities and dissimilarities of the odor descriptors most frequently used in fragrance chemistry. PMID:25847969

  7. Evaluation of the Heading Confinement Pressure Effect on Ground Settlement for EPBTBM Using Full 3D Numerical Analysis

    Amir Hossein Haghi

    2013-06-01

    Full Text Available Ground settlement is often the most serious concern when tunneling under an old city with numerous historic monuments. A successful engineering design under these conditions would require getting the most out of the ground strength parameters and avoiding any weakening maneuver throughout the operation. Knowing that surface settlement is highly affected by tunneling parameters in EPB shield tunneling lead us to estimate the optimum values for the machine heading pressure with the lower amount of the ground settlement in fragile structure of the old city for the Esfahan Subway Project. Tunnels were dug underneath some of the most prominent historical sites along the path of the project. To improve precision and efficiency in tunneling operation, at the first step, tunnel heading confinement pressure is calculated by using an advanced 3D mathematical approach based on the limit equilibrium theory. Then, a promoted 3D finite element model is developed, taking into account the tunneling procedures and the designed heading confinement pressure from the first step. Settlements were pre-calculated and the surface displacement was checked at all sensitive locations. At the third step, settlement is estimated by exerting executed face supporting pressure to the tunnel face and the concluded amounts for displacement are compared with the outputs of extensometers. This comparison leads us to check the reliability of calculated settlements and the accuracy of the designed tunnel heading confinement pressure. Furthermore, evaluating the relation between extensometer outputs and executed tunnel face pressure at the points of extensometers stations validates the assumption that the safe face supporting pressure causes least surface displacement. Although the minimum pressure occurred in short term fluctuations, this approach confirms the sensibility of settlement with the least executed face supporting pressure.. It is also found that higher executed face

  8. Effective grouting area of jointed slope and stress deformation responses by numerical analysis with FLAC3D

    ZHU Zi-qiang; LIU Qun-yi; ZENG Fan-he; QING Du-gan

    2009-01-01

    To study the grouting reinforcement mechanism in jointed rock slope, first, the theoretical deduction was done to calculate the critical length of slipping if the slope angle is larger than that of joint inclination; Second, the numerical calculation model was founded by FLAG3D, so as to find the stress and deformation responses of rock mass in the state before and after grouting, the analysis results show that the range between the boundary of critical slipping block and the joint plane that passes the slope toe is the effective grouting area (EGA). After excavation, large deformation occurs along the joint plane. After grouting, the displacements of rock particles become uniform and continuous, and large deformations along the joint plane are controlled; the dynamic displacement can reflect the deformation response of slope during excavation in the state before and after grouting, as well as the shear location of potential slip plane. After grouting, the dynamic displacement of each monitoring point reaches the peak value with very few time steps,which indicate that the parameters of the joint plane, such as strength and stiffness, are improved; the stress field becomes uniform. Tensile area reduces gradually; whole stability of the slope and its ability to resist tensile and shear stress are improved greatly.

  9. 3D experimental and numerical study of fatigue of a slanted crack path in a thin sheet

    Propagation of fatigue cracks in 7075-T6 aluminum and S355 steel were experimentally characterized in air and in a corrosive solution in a CCP specimen. A technique of crack front marking, coupled with a 3D topographic reconstruction of the crack, allowed to characterize the three-dimensional crack path and the crack growth rate at any point of the crack front. Transverse and longitudinal profiles at different propagation stages were used to calculate the twist and tilt angle. In an elastic XFEM framework, stress intensity factors I, II and III, were calculated. While the correlation of experimental crack growth rate with ΔKI is unsatisfactory, the correlation is correct with ΔKeq emphasizing the major contribution of shear modes to the crack driving force. A finite element analysis in elasto plasticity coupled with the application of a local fatigue criterion, which depend on the equivalent plastic strain ahead of the crack front, was qualitatively able to predict the shear lips growth. A modification of the XFEM method is proposed to improve computations with cyclic plasticity. This part is based on an analytical study which suggests to replace the discontinuous 'Heaviside' enrichment by a new continuous enrichment in the elements cut by the crack. The sub-division of the elements cut by the crack, inducing a field projection of the internal variables which introduces an error in the numerical computations, is thus avoided. Convergence test cases show the potentiality of this method. (author)

  10. Numerical Simulation of 3D Thermo-Elastic Fatigue Crack Growth Problems Using Coupled FE-EFG Approach

    Pathak, Himanshu; Singh, Akhilendra; Singh, Indra Vir

    2016-06-01

    In this work, finite element method (FEM) and element free Galerkin method (EFGM) are coupled for solving 3D crack domains subjected to cyclic thermal load of constant amplitude. Crack growth contours and fatigue life have been obtained for each of the considered numerical examples. Thermo-elastic problems are decoupled into thermal and elastic problems . Firstly, the unknown temperature field is obtained by solving heat conduction equation, then, it is used as the input load in the elastic problem to calculate the displacement and stress fields. The geometrical discontinuity across crack surface is modelled by extrinsically enriched EFGM and the remaining part of the domain is approximated by standard finite element method. At the crack interface, a ramp function based interpolation scheme has been implemented. This coupled approach combines the advantages of both EFGM and FEM. A linear successive crack increment approach is used to model crack growth. The growing crack surface is traced by level set function. Standard Paris law is used for life estimation of the three-dimensional crack models. Different cases of planar and non-planar crack problems have been solved and their results are compared with the results obtained using extended finite element method to check accuracy, efficiency and robustness of the coupled FE-EFG approach implemented in this study.