Numerical simulations for impact damage detection in composites using vibrothermography
International Nuclear Information System (INIS)
Pieczonka, L J; Uhl, T; Szwedo, M; Staszewski, W J; Aymerich, F
2010-01-01
Composite materials are widely used in many engineering applications due to their high strength-to-weight ratios. However, it is well known that composites are susceptible to impact damage. Detection of impact damage is an important issue in maintenance of composite structures. Various non-destructive image-based techniques have been developed for damage detection in composite materials. These include vibrothermography that detects surface temperature changes due to heating associated with frictional energy dissipation by damage. In the present paper numerical simulations are used to investigate heat generation in a composite plate with impact damage in order to support damage detection analysis with vibrothermography. Explicit finite elements are used to model ultrasonic wave propagation in the damaged plate. Simulated delamination and cracks induce frictional heating in the plate. Coupled thermo-mechanical simulations are performed in high frequencies using commercial LS-Dyna finite element code. Very good qualitative agreement between measurements and simulations has been obtained. The area of increased temperature corresponds very well with the damaged area in both experiments and simulations. Numerical model has to be further refined in order to quantitatively match the experiments. The main issues of concern are frictional and thermal properties of composites. The final goal of these research efforts is to predict damage detection sensitivity of vibrothermography in real engineering applications based on numerical models.
Numerical simulation of mechanical behavior of composite materials
Oller, Sergio
2014-01-01
An original mechanical formulation to treat nonlinear orthotropic behavior of composite materials is presented in this book. It also examines different formulations that allow us to evaluate the behavior of composite materials through the composition of its components, obtaining a new composite material. Also two multiple scale homogenization methods are given, one based on the analytical study of the cells (Ad-hoc homogenization), and other one, more general based on the finite element procedure applied on the macro scale (upper-scale) and in the micro scale (sub-scale). A very general formulation to simulate the mechanical behavior for traditional composite structures (plywood, reinforced concrete, masonry, etc.), as well as the new composite materials reinforced with long and short fibers, nanotubes, etc., are also shown in this work. Typical phenomena occurring in composite materials are also described in this work, including fiber-matrix debounding, local buckling of fibers and its coupling with the over...
Numerical Simulation of Effective Properties of 3D Piezoelectric Composites
Directory of Open Access Journals (Sweden)
Ri-Song Qin
2014-01-01
Full Text Available The prediction of the overall effective properties of fibre-reinforced piezocomposites has drawn much interest from investigators recently. In this work, an algorithm used in two-dimensional (2D analysis for calculating transversely isotropic material properties is developed. Since the finite element (FE meshing patterns on the opposite areas are the same, constraint equations can be applied directly to generate appropriate load. The numerical results derived using this model have found a good agreement with those in the literature. The 2D algorithm is then modified and improved in such a way that it is valid for three-dimensional (3D analysis in the case of random distributed shorts and inclusions. Linear interpolation of displacement field is employed to establish constraint equations of nodal displacements between two adjacent elements.
Experimental testing and numerical simulation on natural composite for aerospace applications
Kumar, G. Raj; Vijayanandh, R.; Kumar, M. Senthil; Kumar, S. Sathish
2018-05-01
Nowadays polymers are commonly used in various applications, which make it difficult to avoid its usage even though it causes environmental problems. Natural fibers are best alternate to overcome the polymer based environmental issues. Natural fibers play an important role in developing high performing fully newline biodegradable green composites which will be a key material to solve environmental problems in future. In this paper deals the properties analysis of banana fiber is combined with epoxy resin in order to create a natural composite, which has special characteristics for aerospace applications. The objective of this paper is to investigate the characteristics of failure modes and strength of natural composite using experimental and numerical methods. The test specimen of natural composite has been fabricated as per ASTM standard, which undergoes tensile and compression tests using Tinius Olsen UTM in order to determine mechanical and physical properties. The reference model has been designed by CATIA, and then numerical simulation has been carried out by Ansys Workbench 16.2 for the given boundary conditions.
Numerical simulation of shock initiation of Ni/Al multilayered composites
Energy Technology Data Exchange (ETDEWEB)
Sraj, Ihab; Knio, Omar M., E-mail: omar.knio@duke.edu [Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall, Durham, North Carolina 27708 (United States); Specht, Paul E.; Thadhani, Naresh N. [School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332 (United States); Weihs, Timothy P. [Department of Materials Science and Engineering, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 (United States)
2014-01-14
The initiation of chemical reaction in cold-rolled Ni/Al multilayered composites by shock compression is investigated numerically. A simplified approach is adopted that exploits the disparity between the reaction and shock loading timescales. The impact of shock compression is modeled using CTH simulations that yield pressure, strain, and temperature distributions within the composites due to the shock propagation. The resulting temperature distribution is then used as initial condition to simulate the evolution of the subsequent shock-induced mixing and chemical reaction. To this end, a reduced reaction model is used that expresses the local atomic mixing and heat release rates in terms of an evolution equation for a dimensionless time scale reflecting the age of the mixed layer. The computations are used to assess the effect of bilayer thickness on the reaction, as well as the impact of shock velocity and orientation with respect to the layering. Computed results indicate that initiation and evolution of the reaction are substantially affected by both the shock velocity and the bilayer thickness. In particular, at low impact velocity, Ni/Al multilayered composites with thick bilayers react completely in 100 ms while at high impact velocity and thin bilayers, reaction time was less than 100 μs. Quantitative trends for the dependence of the reaction time on the shock velocity are also determined, for different bilayer thickness and shock orientation.
Numerically stable finite difference simulation for ultrasonic NDE in anisotropic composites
Leckey, Cara A. C.; Quintanilla, Francisco Hernando; Cole, Christina M.
2018-04-01
Simulation tools can enable optimized inspection of advanced materials and complex geometry structures. Recent work at NASA Langley is focused on the development of custom simulation tools for modeling ultrasonic wave behavior in composite materials. Prior work focused on the use of a standard staggered grid finite difference type of mathematical approach, by implementing a three-dimensional (3D) anisotropic Elastodynamic Finite Integration Technique (EFIT) code. However, observations showed that the anisotropic EFIT method displays numerically unstable behavior at the locations of stress-free boundaries for some cases of anisotropic materials. This paper gives examples of the numerical instabilities observed for EFIT and discusses the source of instability. As an alternative to EFIT, the 3D Lebedev Finite Difference (LFD) method has been implemented. The paper briefly describes the LFD approach and shows examples of stable behavior in the presence of stress-free boundaries for a monoclinic anisotropy case. The LFD results are also compared to experimental results and dispersion curves.
Numerical Material Model for Composite Laminates in High-Velocity Impact Simulation
Directory of Open Access Journals (Sweden)
Tao Liu
Full Text Available Abstract A numerical material model for composite laminate, was developed and integrated into the nonlinear dynamic explicit finite element programs as a material user subroutine. This model coupling nonlinear state of equation (EOS, was a macro-mechanics model, which was used to simulate the major mechanical behaviors of composite laminate under high-velocity impact conditions. The basic theoretical framework of the developed material model was introduced. An inverse flyer plate simulation was conducted, which demonstrated the advantage of the developed model in characterizing the nonlinear shock response. The developed model and its implementation were validated through a classic ballistic impact issue, i.e. projectile impacting on Kevlar29/Phenolic laminate. The failure modes and ballistic limit velocity were analyzed, and a good agreement was achieved when comparing with the analytical and experimental results. The computational capacity of this model, for Kevlar/Epoxy laminates with different architectures, i.e. plain-woven and cross-plied laminates, was further evaluated and the residual velocity curves and damage cone were accurately predicted.
International Nuclear Information System (INIS)
Zwanzig, Stephen D.; Lian, Yongsheng; Brehob, Ellen G.
2013-01-01
Highlights: ► A numerical method to study the heat transfer through a PCM composite wallboard is presented. ► PCM wallboard can reduce energy consumption and shift peak electricity load. ► There is an optimal location for the PCM wallboard in the building envelop. ► The PCM wallboard performance depends on weather conditions. - Abstract: Phase change materials (PCMs) have the capability to store/release massive latent heat when undergoing phase change. When impregnated or encapsulated into wallboard or concrete systems, PCMs can greatly enhance their thermal energy storage capacity and effective thermal mass. When used in the building envelope PCM wallboard has the potential to improve building operation by reducing the energy requirement for maintaining thermal comfort, downsizing the AC/heating equipment, and shifting the peak load from the electrical grid. In this work we numerically studied the potential of PCM on energy saving for residential homes. For that purpose we solved the one-dimensional, transient heat equation through the multi-layered building envelope using the Crank–Nicolson discretization scheme. A source term is incorporated to account for the thermal-physical properties of the composite PCM wallboard. Using this code we examined a PCM composite wallboard incorporated into the walls and roof of a typical residential building across various climate zones. The PCM performance was studied under all seasonal conditions using the latest typical meteorological year (TMY3) data for exterior boundary conditions. Our simulations show that PCM performance highly depends on the weather conditions, emphasizing the necessity to choose different PCMs at different climate zones. Comparisons were also made between different PCM wallboard locations. Our work shows that there exists an optimal location for PCM placement within building envelope dependent upon the resistance values between the PCM layer and the exterior boundary conditions. We further
Optimal design of a composite space shield based on numerical simulations
International Nuclear Information System (INIS)
Son, Byung Jin; Yoo, Jeong Hoon; Lee, Min Hyung
2015-01-01
In this study, optimal design of a stuffed Whipple shield is proposed by using numerical simulations and new penetration criterion. The target model was selected based on the shield model used in the Columbus module of the international space station. Because experimental results can be obtained only in the low velocity region below 7 km/s, it is required to derive the Ballistic limit curve (BLC) in the high velocity region above 7 km/s by numerical simulation. AUTODYN-2D, the commercial hydro-code package, was used to simulate the nonlinear transient analysis for the hypervelocity impact. The Smoothed particle hydrodynamics (SPH) method was applied to projectile and bumper modeling to represent the debris cloud generated after the impact. Numerical simulation model and selected material properties were validated through a quantitative comparison between numerical and experimental results. A new criterion to determine whether the penetration occurs or not is proposed from kinetic energy analysis by numerical simulation in the velocity region over 7 km/s. The parameter optimization process was performed to improve the protection ability at a specific condition through the Design of experiment (DOE) method and the Response surface methodology (RSM). The performance of the proposed optimal design was numerically verified.
Numerical simulation of progressive debonding in fiber reinforced composite under transverse loading
DEFF Research Database (Denmark)
Kushch, V.; Shmegera, S.V.; Brøndsted, Povl
2011-01-01
. Then, the effect on debonding progress of local stress redistribution due to interaction between the fibers was studied in the framework of two-inclusion model. Simulation of progressive debonding in fiber reinforced composite using the many-fiber models of composite has been performed. It has been...... shown that the developed model provides detailed analysis of the progressive debonding phenomenon including the interface crack cluster formation, overall stiffness reduction and induced anisotropy of the effective elastic moduli of composite....
Rozel, A. B.; Golabek, G.; Gerya, T.; Jain, C.; Tackley, P. J.
2017-12-01
We study the creation of primordial continental crust (TTG rocks) employing fully self-consistent numerical models of thermo-chemical convection on a global scale at the Archean. We use realistic rheological parameters [1] in 2D spherical annulus geometry using the convection code StagYY [2] for a one billion years period. Starting from a pyrolytic composition and an initially warm core, our simulations first generate mafic crust and depleted mantle in the upper mantle. The basaltic material can be both erupted (cold) and/or intruded (warm) at the base of the crust following a predefined partitioning. At all times, water concentration is considered fully saturated in the top 10 km of the domain, and it simply advected with the deforming material elsewhere. We track the pressure-temperature conditions of the newly formed hydrated basalt and check if it matches the conditions necessary for the formation of proto-continental crust [3]. We systematically test the influence of volcanism (eruption, also called "heat pipe") and plutonism (intrusive magmatism) on the time-dependent geotherm in the lithosphere. We show that the "heat-pipe" model (assuming 100% eruption) suggested to be the main heat loss mechanism during the Archean epoch [4] is not able to produce continental crust since it forms a too cold lithosphere. We also systematically test various friction coefficients and show that an intrusion fraction higher than 60% (in agreement with [5]) combined with a friction coefficient larger than 0.1 produces the expected amount of the three main petrological TTG compositions previously reported [3]. This result seems robust as the amount of TTG rocks formed vary over orders of magnitude. A large eruption over intrusion ratio can result in up to 100 times less TTG felsic crust production than a case where plutonism dominates. This study represents a major step towards the production of self-consistent convection models able to generate the continental crust of the Earth
Numerical tool for SMA material simulation: application to composite structure design
International Nuclear Information System (INIS)
Chemisky, Yves; Tahiri, Vanessa; Duval, Arnaud; Piotrowski, Boris; Ben Zineb, Tarak; Patoor, Etienne
2009-01-01
Composite materials based on shape memory alloys (SMA) have received growing attention over these last few years. In this paper, two particular morphologies of composites are studied. The first one is an SMA/elastomer composite in which a snake-like wire NiTi SMA is embedded into an elastomer ribbon. The second one is a commercial Ni 47 Ti 44 Nb 9 which presents elastic–plastic inclusions in an NiTi SMA matrix. In both cases, the design of such composites required the development of an SMA design tool, based on a macroscopic 3D constitutive law for NiTi alloys. Two different strategies are then applied to compute these composite behaviors. For the SMA/elastomer composite, the macroscopic behavior law is implemented in commercial FEM software, and for the Ni 47 Ti 44 Nb 9 a scale transition approach based on the Mori–Tanaka scheme is developed. In both cases, simulations are compared to experimental data
Directory of Open Access Journals (Sweden)
František KAVIČKA
2010-12-01
Full Text Available The chemical composition of steels has significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The chemical composition of steel affects the thermophysical properties (heat conductivity, specific heat capacity and density in the solid and liquid states often requires more time than the actual numerical calculation of the temperature fields of a continuously cast steel billet. Therefore, an analysis study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation were also determined. The order of significance of the chemical composition on thermophysical properties was determined with respect to the metallurgical length. The analysis was performed by means of a so-called calculation experiment, i.e. by means of the original numerical concasting model developed by the authors of this paper. It is convenient to conduct such an analysis in order to facilitate the simulation of each individual case of concasting, thus enhancing the process of optimization.
Structure-borne noise of railway composite bridge: Numerical simulation and experimental validation
Li, Xiaozhen; Liu, Quanmin; Pei, Shiling; Song, Lizhong; Zhang, Xun
2015-09-01
In order to investigate the characteristics of the noise from steel-concrete composite bridges under high-speed train loading, a model used to predict the bridge-borne noise is established and validated through a field experiment. The numerical model for noise prediction is developed based on the combination of spatial train-track-bridge coupled vibration theory and Statistical Energy Analysis (SEA). Firstly, train-track-bridge coupled vibration is adopted to obtain the velocity time history of the bridge deck vibration. Then, the velocity time history is transferred into frequency domain through FFT to serve as the vibratory energy of SEA deck subsystems. Finally, the transmission of the vibratory energy is obtained by solving the energy balance equations of SEA, and the sound radiation is computed using the vibro-acoustic theory. The numerically computed noise level is verified by a field measurement. It is determined that the dominant frequency of steel-concrete composite bridge-borne noise is 20-1000 Hz. The noise from the bottom flange of steel longitudinal girder is less than other components in the whole frequency bands, while the noise from web of steel longitudinal girder is dominant in high frequency range above 315 Hz. The noise from concrete deck dominates in low-frequency domain ranges from 80 Hz to 160 Hz.
A numerical simulation of the origin and composition of the groundwater below Aespoe
International Nuclear Information System (INIS)
Svensson, Urban
1999-02-01
An attempt is made to calculate the origin (in the time and space) of the waters found below Aespoe. It is assumed that the present water composition is due to the conditions prevailing after the last glaciation (initial conditions) and the hydrological events after this time (resulting in transient boundary conditions). The total time span simulated is from 10,000 years BP to 5 000 years AP. The different water types are tracked by solving an advection/diffusion equation for each of the identified water types. This novel technique is called the 'fluid population method' and is a simple and straightforward computational technique. Results from the simulation include the distribution of different water types in space and time and some detailed results for the conditions at 450 metres below Aespoe (water composition transport time to ground level). The main conclusion from the study is that the simulation model gives plausible results. However, the uncertainties about the basic conceptual model and the boundary conditions do not presently make a direct comparison with field data meaningful
International Nuclear Information System (INIS)
Mouton, S.; Ledoux, Y.; Teissandier, D.; Sebastian, P.
2010-01-01
A key challenge for the future is to reduce drastically the human impact on the environment. In the aeronautic field, this challenge aims at optimizing the design of the aircraft to decrease the global mass. This reduction leads to the optimization of every part constitutive of the plane. This operation is even more delicate when the used material is composite material. In this case, it is necessary to find a compromise between the strength, the mass and the manufacturing cost of the component. Due to these different kinds of design constraints it is necessary to assist engineer with decision support system to determine feasible solutions. In this paper, an approach is proposed based on the coupling of the different key characteristics of the design process and on the consideration of the failure risk of the component. The originality of this work is that the manufacturing deviations due to the RTM process are integrated in the simulation of the assembly process. Two kinds of deviations are identified: volume impregnation (injection phase of RTM process) and geometrical deviations (curing and cooling phases). The quantification of these deviations and the related failure risk calculation is based on finite element simulations (Pam RTM registered and Samcef registered softwares). The use of genetic algorithm allows to estimate the impact of the design choices and their consequences on the failure risk of the component. The main focus of the paper is the optimization of tool design. In the framework of decision support systems, the failure risk calculation is used for making the comparison of possible industrialization alternatives. It is proposed to apply this method on a particular part of the airplane structure: a spar unit made of carbon fiber/epoxy composite.
International Nuclear Information System (INIS)
Sheridan, Robert; VonLockette, Paris R; Roche, Juan; Lofland, Samuel E
2014-01-01
This work seeks to provide a framework for the numerical simulation of magneto-active elastomer (MAE) composite structures for use in origami engineering applications. The emerging field of origami engineering employs folding techniques, an array of crease patterns traditionally on a single flat sheet of paper, to produce structures and devices that perform useful engineering operations. Effective means of numerical simulation offer an efficient way to optimize the crease patterns while coupling to the performance and behavior of the active material. The MAE materials used herein are comprised of nominally 30% v/v, 325 mesh barium hexafarrite particles embedded in Dow HS II silicone elastomer compound. These particulate composites are cured in a magnetic field to produce magneto-elastic solids with anisotropic magnetization, e.g. they have a preferred magnetic axis parallel to the curing axis. The deformed shape and/or blocked force characteristics of these MAEs are examined in three geometries: a monolithic cantilever as well as two- and four-segment composite accordion structures. In the accordion structures, patches of MAE material are bonded to a Gelest OE41 unfilled silicone elastomer substrate. Two methods of simulation, one using the Maxwell stress tensor applied as a traction boundary condition and another employing a minimum energy kinematic (MEK) model, are investigated. Both methods capture actuation due to magnetic torque mechanisms that dominate MAE behavior. Comparison with experimental data show good agreement with only a single adjustable parameter, either an effective constant magnetization of the MAE material in the finite element models (at small and moderate deformations) or an effective modulus in the minimum energy model. The four-segment finite element model was prone to numerical locking at large deformation. The effective magnetization and modulus values required are a fraction of the actual experimentally measured values which suggests a
Luong, Minh Bau; Yu, Gwang Hyeon; Lu, Tianfeng; Chung, Suk-Ho; Yoo, Chun Sang
2015-01-01
The effects of temperature and composition stratifications on the ignition of a lean n-heptane/air mixture at three initial mean temperatures under elevated pressure are investigated using direct numerical simulations (DNSs) with a 58-species
Paik, Seung Hoon; Kim, Ji Yeon; Shin, Sang Joon; Kim, Seung Jo
2004-07-01
Smart structures incorporating active materials have been designed and analyzed to improve aerospace vehicle performance and its vibration/noise characteristics. Helicopter integral blade actuation is one example of those efforts using embedded anisotropic piezoelectric actuators. To design and analyze such integrally-actuated blades, beam approach based on homogenization methodology has been traditionally used. Using this approach, the global behavior of the structures is predicted in an averaged sense. However, this approach has intrinsic limitations in describing the local behaviors in the level of the constituents. For example, the failure analysis of the individual active fibers requires the knowledge of the local behaviors. Microscopic approach for the analysis of integrally-actuated structures is established in this paper. Piezoelectric fibers and matrices are modeled individually and finite element method using three-dimensional solid elements is adopted. Due to huge size of the resulting finite element meshes, high performance computing technology is required in its solution process. The present methodology is quoted as Direct Numerical Simulation (DNS) of the smart structure. As an initial validation effort, present analytical results are correlated with the experiments from a small-scaled integrally-actuated blade, Active Twist Rotor (ATR). Through DNS, local stress distribution around the interface of fiber and matrix can be analyzed.
González, C.; Segurado, J.; LLorca, J.
2004-07-01
The deformation of a composite made up of a random and homogeneous dispersion of elastic spheres in an elasto-plastic matrix was simulated by the finite element analysis of three-dimensional multiparticle cubic cells with periodic boundary conditions. "Exact" results (to a few percent) in tension and shear were determined by averaging 12 stress-strain curves obtained from cells containing 30 spheres, and they were compared with the predictions of secant homogenization models. In addition, the numerical simulations supplied detailed information of the stress microfields, which was used to ascertain the accuracy and the limitations of the homogenization models to include the nonlinear deformation of the matrix. It was found that secant approximations based on the volume-averaged second-order moment of the matrix stress tensor, combined with a highly accurate linear homogenization model, provided excellent predictions of the composite response when the matrix strain hardening rate was high. This was not the case, however, in composites which exhibited marked plastic strain localization in the matrix. The analysis of the evolution of the matrix stresses revealed that better predictions of the composite behavior can be obtained with new homogenization models which capture the essential differences in the stress carried by the elastic and plastic regions in the matrix at the onset of plastic deformation.
Rudraraju, Siva Shankar; Garikipati, Krishna; Waas, Anthony M.; Bednarcyk, Brett A.
2013-01-01
The phenomenon of crack propagation is among the predominant modes of failure in many natural and engineering structures, often leading to severe loss of structural integrity and catastrophic failure. Thus, the ability to understand and a priori simulate the evolution of this failure mode has been one of the cornerstones of applied mechanics and structural engineering and is broadly referred to as "fracture mechanics." The work reported herein focuses on extending this understanding, in the context of through-thickness crack propagation in cohesive materials, through the development of a continuum-level multiscale numerical framework, which represents cracks as displacement discontinuities across a surface of zero measure. This report presents the relevant theory, mathematical framework, numerical modeling, and experimental investigations of through-thickness crack propagation in fiber-reinforced composites using the Variational Multiscale Cohesive Method (VMCM) developed by the authors.
Energy Technology Data Exchange (ETDEWEB)
Karakulov, Valerii V., E-mail: valery@ftf.tsu.ru [National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Smolin, Igor Yu., E-mail: smolin@ispms.ru, E-mail: skrp@ftf.tsu.ru; Skripnyak, Vladimir A., E-mail: smolin@ispms.ru, E-mail: skrp@ftf.tsu.ru [National Research Tomsk State University, Tomsk, 634050, Russia and Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)
2014-11-14
Mechanical behavior of stochastic metal-ceramic composites with the aluminum matrix under high-rate deformation at shock-wave loading is numerically simulated with consideration for structural evolution. Effective values of mechanical parameters of metal-ceramic composites Al
Liu, Hanyang; Tang, Zhanwen; Pan, Lingying; Zhao, Weidong; Sun, Baogang; Jiang, Wenge
2016-05-01
Impact damage has been identified as a critical form of the defects that constantly threatened the reliability of composite structures, such as those used in the aerospace structures and systems. Low energy impacts can introduce barely visible damage and cause the degradation of structural stiffness, furthermore, the flaws caused by low-velocity impact are so dangerous that they can give rise to the further extended delaminations. In order to improve the reliability and load carrying capacity of composite laminates under low-velocity impact, in this paper, the numerical simulatings and experimental studies on the woven fiber-reinforced composite laminates under low-velocity impact with impact energy 16.7J were discussed. The low velocity impact experiment was carried out through drop-weight system as the reason of inertia effect. A numerical progressive damage model was provided, in which the damages of fiber, matrix and interlamina were considered by VUMT subroutine in ABAQUS, to determine the damage modes. The Hashin failure criteria were improved to cover the failure modes of fiber failure in the directions of warp/weft and delaminations. The results of Finite Element Analysis (FEA) were compared with the experimental results of nondestructive examination including the results of ultrasonic C-scan, cross-section stereomicroscope and contact force - time history curves. It is found that the response of laminates under low-velocity impact could be divided into stages with different damage. Before the max-deformation of the laminates occurring, the matrix cracking, fiber breakage and delaminations were simulated during the impactor dropping. During the releasing and rebounding period, matrix cracking and delaminations areas kept increasing in the laminates because of the stress releasing of laminates. Finally, the simulating results showed the good agreements with the results of experiment.
Yao, Lilin; Wang, Fu; Min, Min; Zhang, Ying; Guo, Jianping; Yu, Xiao; Chen, Binglong; Zhao, Yiming; Wang, Lidong
2018-05-01
The atmospheric composition induced extinction effect on return signals of space-based lidar remains incomprehensively understood, especially around 355 nm and 2051 nm channels. Here we simulated the extinction effects of atmospheric gases (e.g., H2O, CO2, and O3) and six types of aerosols (clean continental, clean marine, dust, polluted continental, polluted dust, and smoke) on return signals of space-based lidar system at 355 nm, 532 nm, 1064 nm, and 2051 nm channels, based on a robust lidar return signal simulator in combination with radiative transfer model (LBLRTM). Results show significant Rayleigh (molecular) scattering effects in the return signals at 355 nm and 532 nm channels, which markedly decays with increases in wavelength. The spectral transmittance of CO2 is nearly 0, yet the transmittance of H2O is approximately 100% at 2051 nm, which verifies this 2051 nm channel is suitable for CO2 retrieval. The spectral transmittance also reveals another possible window for CO2 and H2O detection at 2051.6 nm, since their transmittance both near 0.5. Moreover the corresponding Doppler return signals at 2051.6 nm channel can be used to retrieve wind field. Thus we suggest 2051 nm channel may better be centered at 2051.6 nm. Using the threshold for the signal-to-noise ratio (SNR) of return signals, the detection ranges for three representative distribution scenarios for the six types of aerosols at four typical lidar channels are determined. The results clearly show that high SNR values can be seen ubiquitously in the atmosphere ranging from the height of aerosol layer top to 25 km at 355 nm, and can been found at 2051.6 nm in the lower troposphere that highly depends on aerosol distribution scenario in the vertical. This indicates that the Doppler space-based lidar system with a double-channel joint detection mode is able to retrieve atmospheric wind field or profile from 0 to 25 km.
Numerical simulation in astrophysics
International Nuclear Information System (INIS)
Miyama, Shoken
1985-01-01
There have been many numerical simulations of hydrodynamical problems in astrophysics, e.g. processes of star formation, supernova explosion and formation of neutron stars, and general relativistic collapse of star to form black hole. The codes are made to be suitable for computing such problems. In astrophysical hydrodynamical problems, there are the characteristics: problems of self-gravity or external gravity acting, objects of scales very large or very short, objects changing by short period or long time scale, problems of magnetic force and/or centrifugal force acting. In this paper, we present one of methods of numerical simulations which may satisfy these requirements, so-called smoothed particle methods. We then introduce the methods briefly. Then, we show one of the applications of the methods to astrophysical problem (fragmentation and collapse of rotating isothermal cloud). (Mori, K.)
Numerical simulation of plasmas
International Nuclear Information System (INIS)
Dnestrovskii, Y.N.; Kostomarov, D.P.
1986-01-01
This book contains a modern consistent and systematic presentation of numerical computer simulation of plasmas in controlled thermonuclear fusion. The authors focus on the Soviet research in mathematical modelling of Tokamak plasmas, and present kinetic hydrodynamic and transport models with special emphasis on the more recent hybrid models. Compared with the first edition (in Russian) this book has been greatly revised and updated. (orig./WL)
Comments on numerical simulations
International Nuclear Information System (INIS)
Sato, T.
1984-01-01
The author comments on a couple of things about numerical simulation. One is just about the philosophical discussion that is, spontaneous or driven. The other thing is the numerical or technical one. Frankly, the author didn't want to touch on the technical matter because this should be a common sense one for those who are working at numerical simulation. But since many people take numerical simulation results at their face value, he would like to remind you of the reality hidden behind them. First, he would point out that the meaning of ''driven'' in driven reconnection is different from that defined by Schindler or Akasofu. The author's definition is closer to Axford's definition. In the spontaneous case, for some unpredicted reason an excess energy of the system is suddenly released at a certain point. However, one does not answer how such an unstable state far beyond a stable limit is realized in the magnetotail. In the driven case, there is a definite energy buildup phase starting from a stable state; namely, energy in the black box increases from a stable level subject to an external source. When the state has reached a certain position, the energy is released suddenly. The difference between driven and spontaneous is whether the cause (plasma flow) to trigger reconnection is specified or reconnection is triggered unpredictably. Another difference is that in driven reconnection the reconnection rate is dependent on the speed of the external plasma flow, but in spontaneous reconnection the rate is dependent on the internal condition such as the resistivity
Confidence in Numerical Simulations
Energy Technology Data Exchange (ETDEWEB)
Hemez, Francois M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-02-23
This PowerPoint presentation offers a high-level discussion of uncertainty, confidence and credibility in scientific Modeling and Simulation (M&S). It begins by briefly evoking M&S trends in computational physics and engineering. The first thrust of the discussion is to emphasize that the role of M&S in decision-making is either to support reasoning by similarity or to “forecast,” that is, make predictions about the future or extrapolate to settings or environments that cannot be tested experimentally. The second thrust is to explain that M&S-aided decision-making is an exercise in uncertainty management. The three broad classes of uncertainty in computational physics and engineering are variability and randomness, numerical uncertainty and model-form uncertainty. The last part of the discussion addresses how scientists “think.” This thought process parallels the scientific method where by a hypothesis is formulated, often accompanied by simplifying assumptions, then, physical experiments and numerical simulations are performed to confirm or reject the hypothesis. “Confidence” derives, not just from the levels of training and experience of analysts, but also from the rigor with which these assessments are performed, documented and peer-reviewed.
Confidence in Numerical Simulations
International Nuclear Information System (INIS)
Hemez, Francois M.
2015-01-01
This PowerPoint presentation offers a high-level discussion of uncertainty, confidence and credibility in scientific Modeling and Simulation (M&S). It begins by briefly evoking M&S trends in computational physics and engineering. The first thrust of the discussion is to emphasize that the role of M&S in decision-making is either to support reasoning by similarity or to ''forecast,'' that is, make predictions about the future or extrapolate to settings or environments that cannot be tested experimentally. The second thrust is to explain that M&S-aided decision-making is an exercise in uncertainty management. The three broad classes of uncertainty in computational physics and engineering are variability and randomness, numerical uncertainty and model-form uncertainty. The last part of the discussion addresses how scientists ''think.'' This thought process parallels the scientific method where by a hypothesis is formulated, often accompanied by simplifying assumptions, then, physical experiments and numerical simulations are performed to confirm or reject the hypothesis. ''Confidence'' derives, not just from the levels of training and experience of analysts, but also from the rigor with which these assessments are performed, documented and peer-reviewed.
Numerical aerodynamic simulation (NAS)
International Nuclear Information System (INIS)
Peterson, V.L.; Ballhaus, W.F. Jr.; Bailey, F.R.
1984-01-01
The Numerical Aerodynamic Simulation (NAS) Program is designed to provide a leading-edge computational capability to the aerospace community. It was recognized early in the program that, in addition to more advanced computers, the entire computational process ranging from problem formulation to publication of results needed to be improved to realize the full impact of computational aerodynamics. Therefore, the NAS Program has been structured to focus on the development of a complete system that can be upgraded periodically with minimum impact on the user and on the inventory of applications software. The implementation phase of the program is now under way. It is based upon nearly 8 yr of study and should culminate in an initial operational capability before 1986. The objective of this paper is fivefold: 1) to discuss the factors motivating the NAS program, 2) to provide a history of the activity, 3) to describe each of the elements of the processing-system network, 4) to outline the proposed allocation of time to users of the facility, and 5) to describe some of the candidate problems being considered for the first benchmark codes
Leckey, Cara A C; Wheeler, Kevin R; Hafiychuk, Vasyl N; Hafiychuk, Halyna; Timuçin, Doğan A
2018-03-01
Ultrasonic wave methods constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Computational models of ultrasonic wave excitation, propagation, and scattering in CFRP composites can be extremely valuable in designing practicable NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. The development and application of ultrasonic simulation approaches for composite materials is an active area of research in the field of NDE. This paper presents comparisons of guided wave simulations for CFRP composites implemented using four different simulation codes: the commercial finite element modeling (FEM) packages ABAQUS, ANSYS, and COMSOL, and a custom code executing the Elastodynamic Finite Integration Technique (EFIT). Benchmark comparisons are made between the simulation tools and both experimental laser Doppler vibrometry data and theoretical dispersion curves. A pristine and a delamination type case (Teflon insert in the experimental specimen) is studied. A summary is given of the accuracy of simulation results and the respective computational performance of the four different simulation tools. Published by Elsevier B.V.
PELE侵彻复合装甲数值模拟%Numerical Simulation of PELE Penetrating Composite Armor
Institute of Scientific and Technical Information of China (English)
李干; 王志军; 王妍; 李硕
2016-01-01
为了探究横向增强型侵彻体(PELE)侵彻复合装甲后的毁伤效果,采用显式非线性动力分析软件AUTODYN,对装填特氟龙(聚四氟乙烯)的侵彻膨胀弹以900 m/s着靶速度侵彻复合靶板的过程进行了数值模拟,得到PELE弹对复合靶侵彻破坏效应及相关参数.结果表明:聚碳酸酯(玻璃纤维)、聚氨酯(泡沫塑料)与凯夫拉复合装甲的结构均被PELE的横向效应所破坏;复合装甲的夹心材料不同,靶板的破坏程度也不尽相同;复合装甲能对PELE的横向效应起到一定的抑制作用,而凯夫拉材料抑制作用较好.%In order to analyze the damage effect of the penetrator with enhanced lateral efficiency( PELE) penetrating composite armor, an explicit nonlinear dynamic analysis software AUTODYN was used to simulate the process of PELE filled with Teflon( polytetrafluoroethylene) penetrating composite target plate using the speed of 900 m/s, and the destructive effect and relevant parameters of PELE penetrating composite armor were obtained finally. The result shows that the composite armor constructed by polycarbonate( glass fibre) ,polyurethane and Kevlar is damaged seriously by lateral efficiency of PELE. The different composite-armors have different damage. The composite armor has definite inhibitory effect on lateral efficiency of PELE,and the inhibitory effect of Kevlar is better.
Numerical simulation of welding
DEFF Research Database (Denmark)
Hansen, Jan Langkjær; Thorborg, Jesper
Aim of project:To analyse and model the transient thermal field from arc welding (SMAW, V-shaped buttweld in 15mm plate) and to some extend the mechanical response due to the thermal field. - To implement this model in a general purpose finite element program such as ABAQUS.The simulation...... stress is also taken into account.Work carried out:With few means it is possible to define a thermal model which describes the thermal field from the welding process in reasonable agreement with reality. Identical results are found with ABAQUS and Rosenthal’s analytical solution of the governing heat...... transfer equation under same conditions. It is relative easy tointroduce boundary conditions such as convection and radiation where not surprisingly the radiation has the greatest influence especially from the high temperature regions in the weld pool and the heat affected zone.Due to the large temperature...
Numerical simulation of flood barriers
Srb, Pavel; Petrů, Michal; Kulhavý, Petr
This paper deals with testing and numerical simulating of flood barriers. The Czech Republic has been hit by several very devastating floods in past years. These floods caused several dozens of causalities and property damage reached billions of Euros. The development of flood measures is very important, especially for the reduction the number of casualties and the amount of property damage. The aim of flood control measures is the detention of water outside populated areas and drainage of water from populated areas as soon as possible. For new flood barrier design it is very important to know its behaviour in case of a real flood. During the development of the barrier several standardized tests have to be carried out. Based on the results from these tests numerical simulation was compiled using Abaqus software and some analyses were carried out. Based on these numerical simulations it will be possible to predict the behaviour of barriers and thus improve their design.
Numerical simulation of laser resonators
International Nuclear Information System (INIS)
Yoo, J. G.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.
2004-01-01
We developed numerical simulation packages for laser resonators on the bases of a pair of integral equations. Two numerical schemes, a matrix formalism and an iterative method, were programmed for finding numeric solutions to the pair of integral equations. The iterative method was tried by Fox and Li, but it was not applicable for high Fresnel numbers since the numerical errors involved propagate and accumulate uncontrollably. In this paper, we implement the matrix method to extend the computational limit further. A great number of case studies are carried out with various configurations of stable and unstable r;esonators to compute diffraction losses, phase shifts, intensity distributions and phases of the radiation fields on mirrors. Our results presented in this paper show not only a good agreement with the results previously obtained by Fox and Li, but also the legitimacy of our numerical procedures for high Fresnel numbers.
International Nuclear Information System (INIS)
Argueello, J.G.
1988-04-01
This report presents the results of a series of structural analyses performed to evaluate the structural interaction of the components of a potential two-component panel entryway seal configuration with each other and with the rock salt formation at the repository horizon of the Waste Isolation Pilot Plant. A two-dimensional axisymmetric geomechanical model is used to numerically simulate the interaction of the components of a 30.48 m (100 ft) long seal, consisting of concrete end caps and a crushed salt core, with each other and with the surrounding formation. Issues addressed in this report pertain to the consolidation of the crushed salt in terms of how much of the seal core reaches effective consolidation in the presence of the stiff concrete end caps since these could conceivably cause bridging (retardation of closure around the core) to occur. In addition, the stress field in the end caps is evaluated to determine if the concrete component maintains its integrity. The stresses induced in the surrounding formation are also evaluated to determine if the presence of the concrete component in the seal system results in a ''tightening'' of the formation around the seal. 20 refs., 43 figs., 2 tabs
Numerical simulation in plasma physics
International Nuclear Information System (INIS)
Samarskii, A.A.
1980-01-01
Plasma physics is not only a field for development of physical theories and mathematical models but also an object of application of the computational experiment comprising analytical and numerical methods adapted for computers. The author considers only MHD plasma physics problems. Examples treated are dissipative structures in plasma; MHD model of solar dynamo; supernova explosion simulation; and plasma compression by a liner. (Auth.)
International Nuclear Information System (INIS)
Taher, Siavash T.; Rizal Zahari; Faizal Mustapha; Ataollahi, Simin
2010-01-01
The present paper is dealing with the implementation of the finite element explicit dynamic analysis code module incorporated ANSYS/ LS-DYNA computer software to the simulation of the crash behavior and energy adsorption characteristics of a novel multi-cell cost-effective crash worthy composite sandwich structure. In a previous paper, the authors developed the concept of the triple-layered foam-filled block and submitted experimental results of the crash behaviour and crash worthiness characteristics of such structure. The obtained numerical results of axial compression model of composite blocks are compared with actual experimental data of crash energy adsorption, load-displacement history and crush zone characteristics, showing very good agreement. Theoretical and experimental results showed good similarities in peak load, average load and energy absorption with and without use of two types of collapse trigger mechanism. (author)
Numerical simulation of Higgs models
International Nuclear Information System (INIS)
Jaster, A.
1995-10-01
The SU(2) Higgs and the Schwinger model on the lattice were analysed. Numerical simulations of the SU(2) Higgs model were performed to study the finite temperature electroweak phase transition. With the help of the multicanonical method the distribution of an order parameter at the phase transition point was measured. This was used to obtain the order of the phase transition and the value of the interface tension with the histogram method. Numerical simulations were also performed at zero temperature to perform renormalization. The measured values for the Wilson loops were used to determine the static potential and from this the renormalized gauge coupling. The Schwinger model was simulated at different gauge couplings to analyse the properties of the Kaplan-Shamir fermions. The prediction that the mass parameter gets only multiplicative renormalization was tested and verified. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Geandier, G.; Weisbecker, P.; Denis, S.; Mocellin, A. [L.S.G.2M., UMR, CNRS/INPL, Ecole des Mines de Nancy, Nancy (France); Hazotte, A. [L.S.G.2M., UMR, CNRS/INPL, Ecole des Mines de Nancy, Nancy (France); LETAM, UMR, CNRS/Metz Univ., ISGMP, Metz (France); Lebrun, J.L. [L.P.M.I., ENSAM Angers, Angers (France); Elkaim, E. [L.U.R.E., Centre Univ. Paris-Sud, Orsay (France)
2002-07-01
Residual stresses in alumina chromium composites have been determined using X ray synchrotron diffraction at LURE. Results show that non-negligible residual stresses exist in the composites. Mean residual stresses calculated by finite element show discrepancies with experimental values that are discussed in relation with experimental difficulties and calculation assumptions. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Caminha, Romulo de Athayde
1999-03-01
This work aims to present an isothermal, one-dimensional, compositional numerical simulator. A two-phase (oil and gas) multicomponent flow is treated implicitly in pressure, saturation and compositions. Flow terms consider gravitational effect, which allows the study of flow in inclined reservoir. The highly non-linear equations, which are necessary to equate the problem, require a numerical solution, which is obtained by the Newton-Raphson method. The one-dimensional treatment given to the problem yields a tridiagonal block Jacobian matrix. It is assumed that the two-phase flow is dominated by convection and that the dispersive effects are neglected. No mobile water is considered in the porous media, and the original gas-oil capillary pressure curve, obtained from the laboratory, is modified to include the variations of interfacial tensions. Instantaneous thermodynamic equilibrium is admitted and it is computed by means of the Peng and Robinson equation of state. The fluids densities are calculated with the equation of state. Gas and oil viscosities are computed using the Lohrenz method. The medium is considered incompressible, homogeneous and isotropic, chemically and physically inert to the fluids. (author)
Combining Narrative and Numerical Simulation
DEFF Research Database (Denmark)
Hansen, Mette Sanne; Ladeby, Klaes Rohde; Rasmussen, Lauge Baungaard
2011-01-01
for decision makers to systematically test several different outputs of possible solutions in order to prepare for future consequences. The CSA can be a way to evaluate risks and address possible unforeseen problems in a more methodical way than either guessing or forecasting. This paper contributes...... to the decision making in operations and production management by providing new insights into modelling and simulation based on the combined narrative and numerical simulation approach as a tool for strategy making. The research question asks, “How can the CSA be applied in a practical context to support strategy...... making?” The paper uses a case study where interviews and observations were carried out in a Danish corporation. The CSA is a new way to address decision making and has both practical value and further expands the use of strategic simulation as a management tool....
Nechaykina, T.; Nikulin, S.; Rozhnov, A.; Molotnikov, A.; Zavodchikov, S.; Estrin, Y.
2018-05-01
Vanadium alloys are promising structural materials for fuel cladding tubes for fast-neutron reactors. However, high solubility of oxygen and nitrogen in vanadium alloys at operating temperatures of 700 °C limits their application. In this work, we present a novel composite structure consisting of vanadium alloy V-4Ti-4Cr (provides high long-term strength of the material) and stainless steel Fe-0.2C-13Cr (as a corrosion resistant protective layer). It is produced by co-extrusion of these materials forming a three-layered tube. Finite element simulations were utilised to explore the influence of the various co-extrusion parameters on manufacturability of multi-layered tubes. Experimental verification of the numerical modelling was performed using co-extrusion with the process parameters suggested by the numerical simulations. Scanning electron microscopy and microhardness measurements revealed a defect-free diffusion layer at the interfaces between both materials indicating a good quality bonding for these co-extrusion conditions.
Numerical Tools for Composite Woven Fabric Preforming
Directory of Open Access Journals (Sweden)
Abel Cherouat
2013-01-01
Full Text Available An important step in the manufacturing processes of thin composite components is the layingup of the reinforcement onto the mould surface. The prediction of the angular distortion of the reinforcement during draping and the changes in fibre orientation are essential for the understanding of the manufacture process and the evaluation of the mechanical properties of the composite structures. This paper presents an optimization-based method for the simulation of the forming processes of woven fabric reinforced composites. Two different approaches are proposed for the simulation of the draping of woven fabric onto complex geometries: geometrical and mechanical approaches. The geometrical approach is based on a fishnet model. It is well adapted to predimensioning fabrics and to give a suitable quantification of the resulting flat patterns. The mechanical approach is based on a mesostructural model. It allows us to take into account the mechanical properties of fibres and resin and the various dominating mode of deformation of woven fabrics during the forming process. Some numerical simulations of the forming process are proposed and compared with the experimental results in order to demonstrate the efficiency of our approaches.
Numerical simulation of fire vortex
Barannikova, D. D.; Borzykh, V. E.; Obukhov, A. G.
2018-05-01
The article considers the numerical simulation of the swirling flow of air around the smoothly heated vertical cylindrical domain in the conditions of gravity and Coriolis forces action. The solutions of the complete system of Navie-Stocks equations are numerically solved at constant viscosity and heat conductivity factors. Along with the proposed initial and boundary conditions, these solutions describe the complex non-stationary 3D flows of viscous compressible heat conducting gas. For various instants of time of the initial flow formation stage using the explicit finite-difference scheme the calculations of all gas dynamics parameters, that is density, temperature, pressure and three velocity components of gas particles, have been run. The current instant lines corresponding to the trajectories of the particles movement in the emerging flow have been constructed. A negative direction of the air flow swirling occurred in the vertical cylindrical domain heating has been defined.
Plasma modelling and numerical simulation
International Nuclear Information System (INIS)
Van Dijk, J; Kroesen, G M W; Bogaerts, A
2009-01-01
Plasma modelling is an exciting subject in which virtually all physical disciplines are represented. Plasma models combine the electromagnetic, statistical and fluid dynamical theories that have their roots in the 19th century with the modern insights concerning the structure of matter that were developed throughout the 20th century. The present cluster issue consists of 20 invited contributions, which are representative of the state of the art in plasma modelling and numerical simulation. These contributions provide an in-depth discussion of the major theories and modelling and simulation strategies, and their applications to contemporary plasma-based technologies. In this editorial review, we introduce and complement those papers by providing a bird's eye perspective on plasma modelling and discussing the historical context in which it has surfaced. (editorial review)
International Nuclear Information System (INIS)
Gasnault, O.
1999-01-01
Gamma-ray and neutron spectrometry sets up a powerful tool of geological and geochemical characterization of planetary surfaces. This method allows to tackle some critical planet science questions: crustal and mantle compositions; ices; volcanism; alteration processes... Most of the neutrons and gamma photons result from the interactions of galactic cosmic rays with matter. The first chapter introduces the physics of these nuclear interactions in planetary soils and in detectors. Our work aims at optimizing the observations by specifying instrumental performances, and by highlighting relations between soil composition and neutron fluxes. Numerical simulations using the GEANT code from CERN support our analysis. The second chapter estimates the performances of the Germanium gamma-ray spectrometer for MARS SURVEYOR 2001. The result of simulations is compared to calibration measurements; then performances are calculated in flight configuration. The background at Mars is estimated to about 160 c/s. The instrument offers a fine sensitivity to: Fe, Mg, K, Si, Th, Cl and O. It will also be possible to measure U, Ti, H, C, S, Ca and Al. The emission lobes at the surface are calculated too. These measurements shall permit a better understanding of the Martian surface. The last chapter deals with fast neutrons [500 keV; 10 MeV] emitted by the Moon. The strong influence of oxygen is underlined. As observed by LUNAR PROSPECTOR, the integrated flux shows a pronounced dependence with regolith content in iron and titanium, allowing the mapping. The influence of the other chemical elements is quantified. A simple mathematical formula is suggested to estimate the integrated neutron flux according to soil composition. At last, a study of hydrogen effects on fast neutron flux is carried out; we examine the possibilities to quantify its abundance in the soil by this method. (author)
High accuracy mantle convection simulation through modern numerical methods
Kronbichler, Martin; Heister, Timo; Bangerth, Wolfgang
2012-01-01
Numerical simulation of the processes in the Earth's mantle is a key piece in understanding its dynamics, composition, history and interaction with the lithosphere and the Earth's core. However, doing so presents many practical difficulties related
Numerical methods used in simulation
International Nuclear Information System (INIS)
Caseau, Paul; Perrin, Michel; Planchard, Jacques
1978-01-01
The fundamental numerical problem posed by simulation problems is the stability of the resolution diagram. The system of the most used equations is defined, since there is a family of models of increasing complexity with 3, 4 or 5 equations although only models with 3 and 4 equations have been used extensively. After defining what is meant by explicit or implicit, the best established stability results is given for one-dimension problems and then for two-dimension problems. It is shown that two types of discretisation may be defined: four and eight point diagrams (in one or two dimensions) and six and ten point diagrams (in one or two dimensions). To end, some results are given on problems that are not usually treated very much, i.e. non-asymptotic stability and the stability of diagrams based on finite elements [fr
Numerical Validation of Chemical Compositional Model for Wettability Alteration Processes
Bekbauov, Bakhbergen; Berdyshev, Abdumauvlen; Baishemirov, Zharasbek; Bau, Domenico
2017-12-01
Chemical compositional simulation of enhanced oil recovery and surfactant enhanced aquifer remediation processes is a complex task that involves solving dozens of equations for all grid blocks representing a reservoir. In the present work, we perform a numerical validation of the newly developed mathematical formulation which satisfies the conservation laws of mass and energy and allows applying a sequential solution approach to solve the governing equations separately and implicitly. Through its application to the numerical experiment using a wettability alteration model and comparisons with existing chemical compositional model's numerical results, the new model has proven to be practical, reliable and stable.
Relativistic positioning systems: Numerical simulations
Puchades Colmenero, Neus
The position of users located on the Earth's surface or near it may be found with the classic positioning systems (CPS). Certain information broadcast by satellites of global navigation systems, as GPS and GALILEO, may be used for positioning. The CPS are based on the Newtonian formalism, although relativistic post-Newtonian corrections are done when they are necessary. This thesis contributes to the development of a different positioning approach, which is fully relativistic from the beginning. In the relativistic positioning systems (RPS), the space-time position of any user (ship, spacecraft, and so on) can be calculated with the help of four satellites, which broadcast their proper times by means of codified electromagnetic signals. In this thesis, we have simulated satellite 4-tuples of the GPS and GALILEO constellations. If a user receives the signals from four satellites simultaneously, the emission proper times read -after decoding- are the user "emission coordinates". In order to find the user "positioning coordinates", in an appropriate almost inertial reference system, there are two possibilities: (a) the explicit relation between positioning and emission coordinates (broadcast by the satellites) is analytically found or (b) numerical codes are designed to calculate the positioning coordinates from the emission ones. Method (a) is only viable in simple ideal cases, whereas (b) allows us to consider realistic situations. In this thesis, we have designed numerical codes with the essential aim of studying two appropriate RPS, which may be generalized. Sometimes, there are two real users placed in different positions, which receive the same proper times from the same satellites; then, we say that there is bifurcation, and additional data are needed to choose the real user position. In this thesis, bifurcation is studied in detail. We have analyzed in depth two RPS models; in both, it is considered that the satellites move in the Schwarzschild's space
Luong, Minhbau
2014-11-01
The effects of the stratifications of temperature, T, and equivalence ratio, φ{symbol}, on the ignition characteristics of a lean homogeneous biodiesel/air mixture at high pressure and intermediate temperature are investigated using direct numerical simulations (DNSs). 2-D DNSs are performed at a constant volume with the variance of temperature and equivalence ratio (T′ and φ{symbol}′) together with a 2-D isotropic velocity spectrum superimposed on the initial scalar fields. In addition, three different T s(-) φ{symbol} correlations are investigated: (1) baseline cases with T′ only or φ{symbol}′ only, (2) uncorrelated T s(-) φ{symbol} distribution, and (3) negatively-correlated T s(-) φ{symbol} distribution. It is found that the overall combustion is more advanced and the mean heat release rate is more distributed over time with increasing T′ and/or φ{symbol}′ for the baseline and uncorrelated T s(-) φ{symbol} cases. However, the temporal advancement and distribution of the overall combustion caused by T′ or φ{symbol}′ only are nearly annihilated by the negatively-correlated T s(-) φ{symbol} fields. The chemical explosive mode and Damköhler number analyses verify that for the baseline and uncorrelated T s(-) φ{symbol} cases, the deflagration mode is predominant at the reaction fronts for large T′ and/or φ{symbol}′. On the contrary, the spontaneous ignition mode prevails for cases with small T′ or φ{symbol}′, especially for cases with negative T s(-) φ{symbol} correlations, and hence, simultaneous auto-ignition occurs throughout the entire domain, resulting in an excessive rate of heat release. It is also found that turbulence with large intensity, u′, and a short time scale can effectively smooth out initial thermal and compositional fluctuations such that the overall combustion is induced primarily by spontaneous ignition. Based on the present DNS results, the generalization of the effects of T′, φ{symbol}′, and u
Directory of Open Access Journals (Sweden)
Ginés A. Abanto
2017-06-01
Different adobes have been studied. Effective thermal conductivity and heat capacity were measured by means of a hot parallel-plate method. Density was estimated using a pycnometer and measuring physical dimensions and mass of each sample, which allowed the calculation of thermal effusivity and diffusivity. Some numerical simulation results displayed good agreement with experimental outcomes. The work presented here has implications for future studies of this traditional building material and might potentially help solving the problem of sustainable housing.
Numerical simulation of muzzle blast
Tyler-Street, M.
2014-01-01
Structural design methods for naval ships include environmental, operational and military load cases. One of the operational loads acting on a typical naval vessel is the muzzle blast from a gun. Simulating the muzzle blast load acting on a ship structure with CFD and ALE methods leads to large
NUMERICAL SIMULATION AND OPTIMIZATION OF ...
African Journals Online (AJOL)
30 juin 2011 ... This article has as an aim the study and the simulation of the photovoltaic cells containing CdTe materials, contributing to the development of renewable energies, and able to feed from the houses, the shelters as well as ... and the output energy of conversion is 18.26%.Optimization is made according to the.
Numerical methods in simulation of resistance welding
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Martins, Paulo A.F.; Zhang, Wenqi
2015-01-01
Finite element simulation of resistance welding requires coupling betweenmechanical, thermal and electrical models. This paper presents the numerical models and theircouplings that are utilized in the computer program SORPAS. A mechanical model based onthe irreducible flow formulation is utilized...... a resistance welding point of view, the most essential coupling between the above mentioned models is the heat generation by electrical current due to Joule heating. The interaction between multiple objects is anothercritical feature of the numerical simulation of resistance welding because it influences...... thecontact area and the distribution of contact pressure. The numerical simulation of resistancewelding is illustrated by a spot welding example that includes subsequent tensile shear testing...
Coincidental match of numerical simulation and physics
Pierre, B.; Gudmundsson, J. S.
2010-08-01
Consequences of rapid pressure transients in pipelines range from increased fatigue to leakages and to complete ruptures of pipeline. Therefore, accurate predictions of rapid pressure transients in pipelines using numerical simulations are critical. State of the art modelling of pressure transient in general, and water hammer in particular include unsteady friction in addition to the steady frictional pressure drop, and numerical simulations rely on the method of characteristics. Comparison of rapid pressure transient calculations by the method of characteristics and a selected high resolution finite volume method highlights issues related to modelling of pressure waves and illustrates that matches between numerical simulations and physics are purely coincidental.
Luong, Minh Bau
2015-12-01
The effects of temperature and composition stratifications on the ignition of a lean n-heptane/air mixture at three initial mean temperatures under elevated pressure are investigated using direct numerical simulations (DNSs) with a 58-species reduced mechanism. Two-dimensional DNSs are performed by varying several key parameters: initial mean temperature, T0, and the variance of temperature and equivalence ratio (T\\' and φ\\') with different T-φcorrelations. It is found that for cases with φ\\' only, the overall combustion occurs more quickly and the mean heat release rate (HRR) increases more slowly with increasing φ\\' regardless of T0. For cases with T\\' only, however, the overall combustion is retarded/advanced in time with increasing T\\' for low/high T0 relative to the negative-temperature coefficient (NTC) regime resulting from a longer/shorter overall ignition delay of the mixture. For cases with uncorrelated T-φfields, the mean HRR is more distributed over time compared to the corresponding cases with T\\' or φ\\' only. For negatively-correlated cases, however, the temporal evolution of the overall combustion exhibits quite non-monotonic behavior with increasing T\\' and φ\\' depending on T0. All of these characteristics are found to be primarily related to the 0-D ignition delays of initial mixtures, the relative timescales between 0-D ignition delay and turbulence, and the dominance of the deflagration mode during the ignition. These results suggest that an appropriate combination of T\\' and φ\\' together with a well-prepared T-φdistribution can alleviate an excessive pressure-rise rate (PRR) and control ignition-timing in homogeneous charge compression-ignition (HCCI) combustion. In addition, critical species and reactions for the ignition of n-heptane/air mixture through the whole ignition process are estimated by comparing the temporal evolution of the mean mass fractions of important species with the overall reaction pathways of n
Numerical simulation of edge plasma in tokamak
International Nuclear Information System (INIS)
Chen Yiping; Qiu Lijian
1996-02-01
The transport process and transport property of plasma in edge layer of Tokamak are simulated by solving numerically two-dimensional and multi-fluid plasma transport equations using suitable simulation code. The simulation results can show plasma parameter distribution characteristics in the area of edge layer, especially the characteristics near the first wall and divertor target plate. The simulation results play an important role in the design of divertor and first wall of Tokamak. (2 figs)
Visualization of numerically simulated aerodynamic flow fields
International Nuclear Information System (INIS)
Hian, Q.L.; Damodaran, M.
1991-01-01
The focus of this paper is to describe the development and the application of an interactive integrated software to visualize numerically simulated aerodynamic flow fields so as to enable the practitioner of computational fluid dynamics to diagnose the numerical simulation and to elucidate essential flow physics from the simulation. The input to the software is the numerical database crunched by a supercomputer and typically consists of flow variables and computational grid geometry. This flow visualization system (FVS), written in C language is targetted at the Personal IRIS Workstations. In order to demonstrate the various visualization modules, the paper also describes the application of this software to visualize two- and three-dimensional flow fields past aerodynamic configurations which have been numerically simulated on the NEC-SXIA Supercomputer. 6 refs
Numerical simulations of disordered superconductors
International Nuclear Information System (INIS)
Bedell, K.S.; Gubernatis, J.E.; Scalettar, R.T.; Zimanyi, G.T.
1997-01-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors carried out Monte Carlo studies of the critical behavior of superfluid 4 He in aerogel. They found the superfluid density exponent increases in the presence of fractal disorder with a value roughly consistent with experimental results. They also addressed the localization of flux lines caused by splayed columnar pins. Using a Sine-Gordon-type of renormalization group study they obtained an analytic form for the critical temperature. They also determined the critical temperature from I-V characteristics obtained from a molecular dynamics simulation. The combined studies enabled one to construct the phase diagram as a function of interaction strength, temperature, and disorder. They also employed the recently developed mapping between boson world-lines and the flux motion to use quantum Monte Carlo simulations to analyze localization in the presence of disorder. From measurements of the transverse flux line wandering, they determined the critical ratio of columnar to point disorder strength needed to localize the bosons
Numerical simulation of HPT processing
International Nuclear Information System (INIS)
Verleysen, P; Van den Abeele, F; Degrieck, J
2014-01-01
The principle of achieving high strength and superior properties in metal alloys through the application of severe plastic deformation has been exploited in the metal processing industry for many decades. In this contribution finite element simulations are presented of the HPT process. As opposed to most studies in literature, in which rigid sample holders are considered, the real elasto-plastic behavior of the holders is modeled. The simulations show that during the compression stage, plastic deformation occurs in the holders: initially, at the outside boundary of the sample cavity and, at a later stage, underneath the centre of the sample. The latter region of plastic deformation is rapidly growing and has a non-negligible effect on the response of the sample. Major conclusion is that the sample holders, and more specific, their deformability is key for the conditions in the specimen. Indeed, it severely affects important parameters for both the microstructural changes in the sample material, such as the amplitude and distribution of the hydrostatic stress, and its final shape
Numerical simulation of hypersonic flight experiment vehicle
Yamamoto, Yukimitsu; Yoshioka, Minako; 山本 行光; 吉岡 美菜子
1994-01-01
Hypersonic aerodynamic characteristics of Hypersonic FLight EXperiment (HYFLEX vehicle were investigated by numerical simulations using Navier-Stokes CFD (Computational Fluid Dynamics) code of NAL. Numerical results were compared with experimental data obtained at Hypersonic Wind Tunnel at NAL. In order to investigate real flight aerodynamic characteristics. numerical calculations corresponding to the flight conditions suffering from maximum aero thermodynamic heating were also made and the d...
Numerical simulation of mechatronic sensors and actuators
Kaltenbacher, Manfred
2007-01-01
Focuses on the physical modeling of mechatronic sensors and actuators and their precise numerical simulation using the Finite Element Method (FEM). This book discusses the physical modeling as well as numerical computation. It also gives a comprehensive introduction to finite elements, including their computer implementation.
Ingebrethsen, Bradley J
2006-12-01
A numerical model of an aerosol containing vaporizable nicotine depositing to the walls of a tube was developed and applied to simulate the vapor deposition of nicotine in a denuder tube and under conditions approximating those in the respiratory tract during mainstream cigarette smoke inhalation. The numerical model was validated by comparison to data for denuder tube collection of nicotine from the smoke of three types of cigarette differing in smoke acidity and nicotine volatility. Simulations predict that the absorption of water by aerosol particles inhibits nicotine vapor deposition to tube walls, and that increased temperature, decreased tube diameter, and increased dilution enhance nicotine vapor deposition rate. The combined effect of changing these four parameters to approximate the transition from conducting to gas exchange regions of the respiratory tract was a significant net increase in predicted nicotine vapor deposition rate. Comparisons of nicotine deposition rates between conditions in the conducting airways and those in the gas exchange region were informative with regard to reported nicotine retention measurements during human smoking. Reports that vaporizable nicotine can penetrate past the conducting airways, that nicotine can be retained at near 100% efficiency from mainstream smoke, and that cigarettes with differing acidity and nicotine volatility have similar nicotine uptake rates are all shown to be consistent with the results of the model simulations.
Numerical simulations of the mantle lithosphere delamination
Morency, C.; Doin, M.-P.
2004-03-01
Sudden uplift, extension, and increased igneous activity are often explained by rapid mechanical thinning of the lithospheric mantle. Two main thinning mechanisms have been proposed, convective removal of a thickened lithospheric root and delamination of the mantle lithosphere along the Moho. In the latter case, the whole mantle lithosphere peels away from the crust by the propagation of a localized shear zone and sinks into the mantle. To study this mechanism, we perform two-dimensional (2-D) numerical simulations of convection using a viscoplastic rheology with an effective viscosity depending strongly on temperature, depth, composition (crust/mantle), and stress. The simulations develop in four steps. (1) We first obtain "classical" sublithospheric convection for a long time period (˜300 Myr), yielding a slightly heterogeneous lithospheric temperature structure. (2) At some time, in some simulations, a strong thinning of the mantle occurs progressively in a small area (˜100 km wide). This process puts the asthenosphere in direct contact with the lower crust. (3) Large pieces of mantle lithosphere then quickly sink into the mantle by the horizontal propagation of a detachment level away from the "asthenospheric conduit" or by progressive erosion on the flanks of the delaminated area. (4) Delamination pauses or stops when the lithospheric mantle part detaches or when small-scale convection on the flanks of the delaminated area is counterbalanced by heat diffusion. We determine the parameters (crustal thicknesses, activation energies, and friction coefficients) leading to delamination initiation (step 2). We find that delamination initiates where the Moho temperature is the highest, as soon as the crust and mantle viscosities are sufficiently low. Delamination should occur on Earth when the Moho temperature exceeds ˜800°C. This condition can be reached by thermal relaxation in a thickened crust in orogenic setting or by corner flow lithospheric erosion in the
Numerical modeling and experimental validation of thermoplastic composites induction welding
Palmieri, Barbara; Nele, Luigi; Galise, Francesco
2018-05-01
In this work, a numerical simulation and experimental test of the induction welding of continuous fibre-reinforced thermoplastic composites (CFRTPCs) was provided. The thermoplastic Polyamide 66 (PA66) with carbon fiber fabric was used. Using a dedicated software (JMag Designer), the influence of the fundamental process parameters such as temperature, current and holding time was investigated. In order to validate the results of the simulations, and therefore the numerical model used, experimental tests were carried out, and the temperature values measured during the tests were compared with the aid of an optical pyrometer, with those provided by the numerical simulation. The mechanical properties of the welded joints were evaluated by single lap shear tests.
Direct Numerical Simulation of Driven Cavity Flows
Verstappen, R.; Wissink, J.G.; Veldman, A.E.P.
Direct numerical simulations of 2D driven cavity flows have been performed. The simulations exhibit that the flow converges to a periodically oscillating state at Re=11,000, and reveal that the dynamics is chaotic at Re=22,000. The dimension of the attractor and the Kolmogorov entropy have been
Numerical Simulation of Cyclic Thermodynamic Processes
DEFF Research Database (Denmark)
Andersen, Stig Kildegård
2006-01-01
This thesis is on numerical simulation of cyclic thermodynamic processes. A modelling approach and a method for finding periodic steady state solutions are described. Examples of applications are given in the form of four research papers. Stirling machines and pulse tube coolers are introduced...... and a brief overview of the current state of the art in methods for simulating such machines is presented. It was found that different simulation approaches, which model the machines with different levels of detail, currently coexist. Methods using many simplifications can be easy to use and can provide...... models flexible and easy to modify, and to make simulations fast. A high level of accuracy was achieved for integrations of a model created using the modelling approach; the accuracy depended on the settings for the numerical solvers in a very predictable way. Selection of fast numerical algorithms...
Numerical Investigation of Masonry Strengthened with Composites
Directory of Open Access Journals (Sweden)
Giancarlo Ramaglia
2018-03-01
Full Text Available In this work, two main fiber strengthening systems typically applied in masonry structures have been investigated: composites made of basalt and hemp fibers, coupled with inorganic matrix. Starting from the experimental results on composites, the out-of-plane behavior of the strengthened masonry was assessed according to several numerical analyses. In a first step, the ultimate behavior was assessed in terms of P (axial load-M (bending moment domain (i.e., failure surface, changing several mechanical parameters. In order to assess the ductility capacity of the strengthened masonry elements, the P-M domain was estimated starting from the bending moment-curvature diagrams. Key information about the impact of several mechanical parameters on both the capacity and the ductility was considered. Furthermore, the numerical analyses allow the assessment of the efficiency of the strengthening system, changing the main mechanical properties. Basalt fibers had lower efficiency when applied to weak masonry. In this case, the elastic properties of the masonry did not influence the structural behavior under a no tension assumption for the masonry. Conversely, their impact became non-negligible, especially for higher values of the compressive strength of the masonry. The stress-strain curve used to model the composite impacted the flexural strength. Natural fibers provided similar outcomes, but a first difference regards the higher mechanical compatibility of the strengthening system with the substrate. In this case, the ultimate condition is due to the failure mode of the composite. The stress-strain curves used to model the strengthening system are crucial in the ductility estimation of the strengthened masonry. However, the behavior of the composite strongly influences the curvature ductility in the case of higher compressive strength for masonry. The numerical results discussed in this paper provide the base to develop normalized capacity models able to
Practical integrated simulation systems for coupled numerical simulations in parallel
Energy Technology Data Exchange (ETDEWEB)
Osamu, Hazama; Zhihong, Guo [Japan Atomic Energy Research Inst., Centre for Promotion of Computational Science and Engineering, Tokyo (Japan)
2003-07-01
In order for the numerical simulations to reflect 'real-world' phenomena and occurrences, incorporation of multidisciplinary and multi-physics simulations considering various physical models and factors are becoming essential. However, there still exist many obstacles which inhibit such numerical simulations. For example, it is still difficult in many instances to develop satisfactory software packages which allow for such coupled simulations and such simulations will require more computational resources. A precise multi-physics simulation today will require parallel processing which again makes it a complicated process. Under the international cooperative efforts between CCSE/JAERI and Fraunhofer SCAI, a German institute, a library called the MpCCI, or Mesh-based Parallel Code Coupling Interface, has been implemented together with a library called STAMPI to couple two existing codes to develop an 'integrated numerical simulation system' intended for meta-computing environments. (authors)
Numerical simulation of sand jet in water
Energy Technology Data Exchange (ETDEWEB)
Azimi, A.H.; Zhu, D.; Rajaratnam, N. [Alberta Univ., Edmonton, AB (Canada). Dept. of Civil and Environmental Engineering
2008-07-01
A numerical simulation of sand jet in water was presented. The study involved a two-phase flow using two-phase turbulent jets. A literature review was also presented, including an experiment on particle laden air jet using laser doppler velocimetry (LDV); experiments on the effect of particle size and concentration on solid-gas jets; an experimental study of solid-liquid jets using particle image velocimetry (PIV) technique where mean velocity and fluctuations were measured; and an experimental study on solid-liquid jets using the laser doppler anemometry (LDA) technique measuring both water axial and radial velocities. Other literature review results included a photographic study of sand jets in water; a comparison of many two-phase turbulent flow; and direct numerical simulation and large-eddy simulation to study the effect of particle in gas jet flow. The mathematical model and experimental setup were also included in the presentation along with simulation results for sand jets, concentration, and kinetic energy. The presentation concluded with some proposed future studies including numerical simulation of slurry jets in water and numerical simulation of slurry jets in MFT. tabs., figs.
Numerical simulation of "an American haboob"
Vukovic, A.; Vujadinovic, M.; Pejanovic, G.; Andric, J.; Kumjian, M. R.; Djurdjevic, V.; Dacic, M.; Prasad, A. K.; El-Askary, H. M.; Paris, B. C.; Petkovic, S.; Nickovic, S.; Sprigg, W. A.
2014-01-01
A dust storm of fearful proportions hit Phoenix in the early evening hours of 5 July 2011. This storm, an American haboob, was predicted hours in advance because numerical, land–atmosphere modeling, computing power and remote sensing of dust events have improved greatly over the past decade. High-resolution numerical models are required for accurate simulation of the small scales of the haboob process, with high velocity surface winds produced by strong convection and severe...
Numerical simulation of radial compressor stage
Syka, T.; Luňáček, O.
2013-04-01
Article describes numerical simulations of air flow in radial compressor stage in NUMECA CFD software. In simulations geometry variants with and without seals are used. During tasks evaluating was observed seals influence on flow field and performance parameters of compressor stage. Also is described CFDresults comparison with results from design software based on experimental measurements and monitoring of influence of seals construction on compressor stage efficiency.
Numerical simulation of radial compressor stage
Luňáček O.; Syka T.
2013-01-01
Article describes numerical simulations of air flow in radial compressor stage in NUMECA CFD software. In simulations geometry variants with and without seals are used. During tasks evaluating was observed seals influence on flow field and performance parameters of compressor stage. Also is described CFDresults comparison with results from design software based on experimental measurements and monitoring of influence of seals construction on compressor stage efficiency.
Numerical simulation of radial compressor stage
Directory of Open Access Journals (Sweden)
Luňáček O.
2013-04-01
Full Text Available Article describes numerical simulations of air flow in radial compressor stage in NUMECA CFD software. In simulations geometry variants with and without seals are used. During tasks evaluating was observed seals influence on flow field and performance parameters of compressor stage. Also is described CFDresults comparison with results from design software based on experimental measurements and monitoring of influence of seals construction on compressor stage efficiency.
Numerical Simulation of Steady Supercavitating Flows
Ali Jafarian; Ahmad-Reza Pishevar
2016-01-01
In this research, the Supercavitation phenomenon in compressible liquid flows is simulated. The one-fluid method based on a new exact two-phase Riemann solver is used for modeling. The cavitation is considered as an isothermal process and a consistent equation of state with the physical behavior of the water is used. High speed flow of water over a cylinder and a projectile are simulated and the results are compared with the previous numerical and experimental results. The cavitation bubble p...
Numerical Simulation Of Silicon-Ribbon Growth
Woda, Ben K.; Kuo, Chin-Po; Utku, Senol; Ray, Sujit Kumar
1987-01-01
Mathematical model includes nonlinear effects. In development simulates growth of silicon ribbon from melt. Takes account of entire temperature and stress history of ribbon. Numerical simulations performed with new model helps in search for temperature distribution, pulling speed, and other conditions favoring growth of wide, flat, relatively defect-free silicon ribbons for solar photovoltaic cells at economically attractive, high production rates. Also applicable to materials other than silicon.
Spectral Methods in Numerical Plasma Simulation
DEFF Research Database (Denmark)
Coutsias, E.A.; Hansen, F.R.; Huld, T.
1989-01-01
An introduction is given to the use of spectral methods in numerical plasma simulation. As examples of the use of spectral methods, solutions to the two-dimensional Euler equations in both a simple, doubly periodic region, and on an annulus will be shown. In the first case, the solution is expanded...
Simple Numerical Simulation of Strain Measurement
Tai, H.
2002-01-01
By adopting the basic principle of the reflection (and transmission) of a plane polarized electromagnetic wave incident normal to a stack of films of alternating refractive index, a simple numerical code was written to simulate the maximum reflectivity (transmittivity) of a fiber optic Bragg grating corresponding to various non-uniform strain conditions including photo-elastic effect in certain cases.
Numerical simulation of large deformation polycrystalline plasticity
International Nuclear Information System (INIS)
Inal, K.; Neale, K.W.; Wu, P.D.; MacEwen, S.R.
2000-01-01
A finite element model based on crystal plasticity has been developed to simulate the stress-strain response of sheet metal specimens in uniaxial tension. Each material point in the sheet is considered to be a polycrystalline aggregate of FCC grains. The Taylor theory of crystal plasticity is assumed. The numerical analysis incorporates parallel computing features enabling simulations of realistic models with large number of grains. Simulations have been carried out for the AA3004-H19 aluminium alloy and the results are compared with experimental data. (author)
Fluid dynamics theory, computation, and numerical simulation
Pozrikidis, C
2001-01-01
Fluid Dynamics Theory, Computation, and Numerical Simulation is the only available book that extends the classical field of fluid dynamics into the realm of scientific computing in a way that is both comprehensive and accessible to the beginner The theory of fluid dynamics, and the implementation of solution procedures into numerical algorithms, are discussed hand-in-hand and with reference to computer programming This book is an accessible introduction to theoretical and computational fluid dynamics (CFD), written from a modern perspective that unifies theory and numerical practice There are several additions and subject expansions in the Second Edition of Fluid Dynamics, including new Matlab and FORTRAN codes Two distinguishing features of the discourse are solution procedures and algorithms are developed immediately after problem formulations are presented, and numerical methods are introduced on a need-to-know basis and in increasing order of difficulty Matlab codes are presented and discussed for a broad...
Fluid Dynamics Theory, Computation, and Numerical Simulation
Pozrikidis, Constantine
2009-01-01
Fluid Dynamics: Theory, Computation, and Numerical Simulation is the only available book that extends the classical field of fluid dynamics into the realm of scientific computing in a way that is both comprehensive and accessible to the beginner. The theory of fluid dynamics, and the implementation of solution procedures into numerical algorithms, are discussed hand-in-hand and with reference to computer programming. This book is an accessible introduction to theoretical and computational fluid dynamics (CFD), written from a modern perspective that unifies theory and numerical practice. There are several additions and subject expansions in the Second Edition of Fluid Dynamics, including new Matlab and FORTRAN codes. Two distinguishing features of the discourse are: solution procedures and algorithms are developed immediately after problem formulations are presented, and numerical methods are introduced on a need-to-know basis and in increasing order of difficulty. Matlab codes are presented and discussed for ...
Experiments and Numerical Simulations of Electrodynamic Tether
Iki, Kentaro; Kawamoto, Satomi; Takahashi, Ayaka; Ishimoto, Tomori; Yanagida, Atsushi; Toda, Susumu
As an effective means of suppressing space debris growth, the Aerospace Research and Development Directorate of the Japan Aerospace Exploration Agency (JAXA) has been investigating an active space debris removal system that employs highly efficient electrodynamic tether (EDT) technology for orbital transfer. This study investigates tether deployment dynamics by means of on-ground experiments and numerical simulations of an electrodynamic tether system. Some key parameters used in the numerical simulations, such as the elastic modulus and damping ratio of the tether, the spring constant of the coiling of the tether, and deployment friction, must be estimated, and various experiments are conducted to determine these values. As a result, the following values were obtained: The elastic modulus of the tether was 40 GPa, and the damping ratio of the tether was 0.02. The spring constant and the damping ratio of the tether coiling were 10-4 N/m and 0.025 respectively. The deployment friction was 0.038ν + 0.005 N. In numerical simulations using a multiple mass tether model, tethers with lengths of several kilometers are deployed and the attitude dynamics of satellites attached to the end of the tether and tether libration are calculated. As a result, the simulations confirmed successful deployment of the tether with a length of 500 m using the electrodynamic tether system.
Numerical Simulation of a Tornado Generating Supercell
Proctor, Fred H.; Ahmad, Nashat N.; LimonDuparcmeur, Fanny M.
2012-01-01
The development of tornadoes from a tornado generating supercell is investigated with a large eddy simulation weather model. Numerical simulations are initialized with a sounding representing the environment of a tornado producing supercell that affected North Carolina and Virginia during the Spring of 2011. The structure of the simulated storm was very similar to that of a classic supercell, and compared favorably to the storm that affected the vicinity of Raleigh, North Carolina. The presence of mid-level moisture was found to be important in determining whether a supercell would generate tornadoes. The simulations generated multiple tornadoes, including cyclonic-anticyclonic pairs. The structure and the evolution of these tornadoes are examined during their lifecycle.
Reactor numerical simulation and hydraulic test research
International Nuclear Information System (INIS)
Yang, L. S.
2009-01-01
In recent years, the computer hardware was improved on the numerical simulation on flow field in the reactor. In our laboratory, we usually use the Pro/e or UG commercial software. After completed topology geometry, ICEM-CFD is used to get mesh for computation. Exact geometrical similarity is maintained between the main flow paths of the model and the prototype, with the exception of the core simulation design of the fuel assemblies. The drive line system is composed of drive mechanism, guide bush assembly, fuel assembly and control rod assembly, and fitted with the rod level indicator and drive mechanism power device
Contributions to reinforced concrete structures numerical simulations
International Nuclear Information System (INIS)
Badel, P.B.
2001-07-01
In order to be able to carry out simulations of reinforced concrete structures, it is necessary to know two aspects: the behaviour laws have to reflect the complex behaviour of concrete and a numerical environment has to be developed in order to avoid to the user difficulties due to the softening nature of the behaviour. This work deals with these two subjects. After an accurate estimation of two behaviour models (micro-plan and mesoscopic models), two damage models (the first one using a scalar variable, the other one a tensorial damage of the 2 order) are proposed. These two models belong to the framework of generalized standard materials, which renders their numerical integration easy and efficient. A method of load control is developed in order to make easier the convergence of the calculations. At last, simulations of industrial structures illustrate the efficiency of the method. (O.M.)
Numerical simulation of electrostatic waves in plasmas
International Nuclear Information System (INIS)
Erz, U.
1981-08-01
In this paper the propagation of electrostatic waves in plasmas and the non-linear interactions, which occur in the case of large wave amplitudes, are studied using a new numerical method for plasma simulation. This mathematical description is based on the Vlasov-model. Changes in the distribution-function are taken into account and thus plasma kinetic effects can be treated. (orig./HT) [de
Numerical simulations on ion acoustic double layers
International Nuclear Information System (INIS)
Sato, T.; Okuda, H.
1980-07-01
A comprehensive numerical study of ion acoustic double layers has been performed for both periodic as well as for nonperiodic systems by means of one-dimensional particle simulations. For a nonperiodic system, an external battery and a resistance are used to model the magnetospheric convection potential and the ionospheric Pedersen resistance. It is found that the number of double layers and the associated potential buildup across the system increases with the system length
Numerical Simulations of Hyperfine Transitions of Antihydrogen
Kolbinger, B.; Diermaier, M.; Lehner, S.; Malbrunot, C.; Massiczek, O.; Sauerzopf, C.; Simon, M.C.; Widmann, E.
2015-02-04
One of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration's goals is the measurement of the ground state hyperfine transition frequency in antihydrogen, the antimatter counterpart of one of the best known systems in physics. This high precision experiment yields a sensitive test of the fundamental symmetry of CPT. Numerical simulations of hyperfine transitions of antihydrogen atoms have been performed providing information on the required antihydrogen events and the achievable precision.
Numerical simulations of hyperfine transitions of antihydrogen
Energy Technology Data Exchange (ETDEWEB)
Kolbinger, B., E-mail: bernadette.kolbinger@oeaw.ac.at; Capon, A.; Diermaier, M.; Lehner, S. [Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences (Austria); Malbrunot, C. [CERN (Switzerland); Massiczek, O.; Sauerzopf, C.; Simon, M. C.; Widmann, E. [Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences (Austria)
2015-08-15
One of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration’s goals is the measurement of the ground state hyperfine transition frequency in antihydrogen, the antimatter counterpart of one of the best known systems in physics. This high precision experiment yields a sensitive test of the fundamental symmetry of CPT. Numerical simulations of hyperfine transitions of antihydrogen atoms have been performed providing information on the required antihydrogen events and the achievable precision.
Energy Technology Data Exchange (ETDEWEB)
Zalewski, L.
1996-11-27
The objective of this work is the analysis of a passive solar component: the composite solar wall, a building component, which includes an insulating panel located behind the massive wall. This panel has two vents located at the top and at the bottom, which allow the air to circulate from the room to the layer in contact with the back of the massive wall, where it is heated, and then back to the room. The solar energy is transferred to the building by conduction through the massive wall, and then by convection using a thermosyphon phenomenon. The monitoring of 2 solar houses in Verdun-Thierville (Meuse, France) has clearly shown, control issues of the air layer. The wall must be operated as autonomously as possible, to not be a constraint for the occupants and to get an optimization of the energy gains. To solve these problems, a composite solar wall prototype was erected in a test cell at Cadarache and tested in real operating conditions. This allows to use a more complete instrumentation, to have access more easily to the sensors and to study various configurations. The first experiments revealed an inverse thermosyphon phenomenon. To avoid this effect, two systems were designed, tested at Cadarache and then implemented in the walls at Verdun. (author) 77 refs.
NUMERICAL MODEL APPLICATION IN ROWING SIMULATOR DESIGN
Directory of Open Access Journals (Sweden)
Petr Chmátal
2016-04-01
Full Text Available The aim of the research was to carry out a hydraulic design of rowing/sculling and paddling simulator. Nowadays there are two main approaches in the simulator design. The first one includes a static water with no artificial movement and counts on specially cut oars to provide the same resistance in the water. The second approach, on the other hand uses pumps or similar devices to force the water to circulate but both of the designs share many problems. Such problems are affecting already built facilities and can be summarized as unrealistic feeling, unwanted turbulent flow and bad velocity profile. Therefore, the goal was to design a new rowing simulator that would provide nature-like conditions for the racers and provide an unmatched experience. In order to accomplish this challenge, it was decided to use in-depth numerical modeling to solve the hydraulic problems. The general measures for the design were taken in accordance with space availability of the simulator ́s housing. The entire research was coordinated with other stages of the construction using BIM. The detailed geometry was designed using a numerical model in Ansys Fluent and parametric auto-optimization tools which led to minimum negative hydraulic phenomena and decreased investment and operational costs due to the decreased hydraulic losses in the system.
Mathematical models and numerical simulation in electromagnetism
Bermúdez, Alfredo; Salgado, Pilar
2014-01-01
The book represents a basic support for a master course in electromagnetism oriented to numerical simulation. The main goal of the book is that the reader knows the boundary-value problems of partial differential equations that should be solved in order to perform computer simulation of electromagnetic processes. Moreover it includes a part devoted to electric circuit theory based on ordinary differential equations. The book is mainly oriented to electric engineering applications, going from the general to the specific, namely, from the full Maxwell’s equations to the particular cases of electrostatics, direct current, magnetostatics and eddy currents models. Apart from standard exercises related to analytical calculus, the book includes some others oriented to real-life applications solved with MaxFEM free simulation software.
Numerical Simulation of a Seaway with Breaking
Dommermuth, Douglas; O'Shea, Thomas; Brucker, Kyle; Wyatt, Donald
2012-11-01
The focus of this presentation is to describe the recent efforts to simulate a fully non-linear seaway with breaking by using a high-order spectral (HOS) solution of the free-surface boundary value problem to drive a three-dimensional Volume of Fluid (VOF) solution. Historically, the two main types of simulations to simulate free-surface flows are the boundary integral equations method (BIEM) and high-order spectral (HOS) methods. BIEM calculations fail at the point at which the surface impacts upon itself, if not sooner, and HOS methods can only simulate a single valued free-surface. Both also employ a single-phase approximation in which the effects of the air on the water are neglected. Due to these limitations they are unable to simulate breaking waves and air entrainment. The Volume of Fluid (VOF) method on the other hand is suitable for modeling breaking waves and air entrainment. However it is computationally intractable to generate a realistic non-linear sea-state. Here, we use the HOS solution to quickly drive, or nudge, the VOF solution into a non-linear state. The computational strategies, mathematical formulation, and numerical implementation will be discussed. The results of the VOF simulation of a seaway with breaking will also be presented, and compared to the single phase, single valued HOS results.
Numerical simulation of real-world flows
Energy Technology Data Exchange (ETDEWEB)
Hayase, Toshiyuki, E-mail: hayase@ifs.tohoku.ac.jp [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 (Japan)
2015-10-15
Obtaining real flow information is important in various fields, but is a difficult issue because measurement data are usually limited in time and space, and computational results usually do not represent the exact state of real flows. Problems inherent in the realization of numerical simulation of real-world flows include the difficulty in representing exact initial and boundary conditions and the difficulty in representing unstable flow characteristics. This article reviews studies dealing with these problems. First, an overview of basic flow measurement methodologies and measurement data interpolation/approximation techniques is presented. Then, studies on methods of integrating numerical simulation and measurement, namely, four-dimensional variational data assimilation (4D-Var), Kalman filters (KFs), state observers, etc are discussed. The first problem is properly solved by these integration methodologies. The second problem can be partially solved with 4D-Var in which only initial and boundary conditions are control parameters. If an appropriate control parameter capable of modifying the dynamical structure of the model is included in the formulation of 4D-Var, unstable modes are properly suppressed and the second problem is solved. The state observer and KFs also solve the second problem by modifying mathematical models to stabilize the unstable modes of the original dynamical system by applying feedback signals. These integration methodologies are now applied in simulation of real-world flows in a wide variety of research fields. Examples are presented for basic fluid dynamics and applications in meteorology, aerospace, medicine, etc. (topical review)
Numerical model simulation of atmospheric coolant plumes
International Nuclear Information System (INIS)
Gaillard, P.
1980-01-01
The effect of humid atmospheric coolants on the atmosphere is simulated by means of a three-dimensional numerical model. The atmosphere is defined by its natural vertical profiles of horizontal velocity, temperature, pressure and relative humidity. Effluent discharge is characterised by its vertical velocity and the temperature of air satured with water vapour. The subject of investigation is the area in the vicinity of the point of discharge, with due allowance for the wake effect of the tower and buildings and, where application, wind veer with altitude. The model equations express the conservation relationships for mometum, energy, total mass and water mass, for an incompressible fluid behaving in accordance with the Boussinesq assumptions. Condensation is represented by a simple thermodynamic model, and turbulent fluxes are simulated by introduction of turbulent viscosity and diffusivity data based on in-situ and experimental water model measurements. The three-dimensional problem expressed in terms of the primitive variables (u, v, w, p) is governed by an elliptic equation system which is solved numerically by application of an explicit time-marching algorithm in order to predict the steady-flow velocity distribution, temperature, water vapour concentration and the liquid-water concentration defining the visible plume. Windstill conditions are simulated by a program processing the elliptic equations in an axisymmetrical revolution coordinate system. The calculated visible plumes are compared with plumes observed on site with a view to validate the models [fr
Lagrangian numerical methods for ocean biogeochemical simulations
Paparella, Francesco; Popolizio, Marina
2018-05-01
We propose two closely-related Lagrangian numerical methods for the simulation of physical processes involving advection, reaction and diffusion. The methods are intended to be used in settings where the flow is nearly incompressible and the Péclet numbers are so high that resolving all the scales of motion is unfeasible. This is commonplace in ocean flows. Our methods consist in augmenting the method of characteristics, which is suitable for advection-reaction problems, with couplings among nearby particles, producing fluxes that mimic diffusion, or unresolved small-scale transport. The methods conserve mass, obey the maximum principle, and allow to tune the strength of the diffusive terms down to zero, while avoiding unwanted numerical dissipation effects.
Efficient Numerical Simulation of Aerothermoelastic Hypersonic Vehicles
Klock, Ryan J.
Hypersonic vehicles operate in a high-energy flight environment characterized by high dynamic pressures, high thermal loads, and non-equilibrium flow dynamics. This environment induces strong fluid, thermal, and structural dynamics interactions that are unique to this flight regime. If these vehicles are to be effectively designed and controlled, then a robust and intuitive understanding of each of these disciplines must be developed not only in isolation, but also when coupled. Limitations on scaling and the availability of adequate test facilities mean that physical investigation is infeasible. Ever growing computational power offers the ability to perform elaborate numerical simulations, but also has its own limitations. The state of the art in numerical simulation is either to create ever more high-fidelity physics models that do not couple well and require too much processing power to consider more than a few seconds of flight, or to use low-fidelity analytical models that can be tightly coupled and processed quickly, but do not represent realistic systems due to their simplifying assumptions. Reduced-order models offer a middle ground by distilling the dominant trends of high-fidelity training solutions into a form that can be quickly processed and more tightly coupled. This thesis presents a variably coupled, variable-fidelity, aerothermoelastic framework for the simulation and analysis of high-speed vehicle systems using analytical, reduced-order, and surrogate modeling techniques. Full launch-to-landing flights of complete vehicles are considered and used to define flight envelopes with aeroelastic, aerothermal, and thermoelastic limits, tune in-the-loop flight controllers, and inform future design considerations. A partitioned approach to vehicle simulation is considered in which regions dominated by particular combinations of processes are made separate from the overall solution and simulated by a specialized set of models to improve overall processing
Consolidation modelling for thermoplastic composites forming simulation
Xiong, H.; Rusanov, A.; Hamila, N.; Boisse, P.
2016-10-01
Pre-impregnated thermoplastic composites are widely used in the aerospace industry for their excellent mechanical properties, Thermoforming thermoplastic prepregs is a fast manufacturing process, the automotive industry has shown increasing interest in this manufacturing processes, in which the reconsolidation is an essential stage. The model of intimate contact is investigated as the consolidation model, compression experiments have been launched to identify the material parameters, several numerical tests show the influents of the temperature and pressure applied during processing. Finally, a new solid-shell prismatic element has been presented for the simulation of consolidation step in the thermoplastic composites forming process.
Spectral methods in numerical plasma simulation
International Nuclear Information System (INIS)
Coutsias, E.A.; Hansen, F.R.; Huld, T.; Knorr, G.; Lynov, J.P.
1989-01-01
An introduction is given to the use of spectral methods in numerical plasma simulation. As examples of the use of spectral methods, solutions to the two-dimensional Euler equations in both a simple, doubly periodic region, and on an annulus will be shown. In the first case, the solution is expanded in a two-dimensional Fourier series, while a Chebyshev-Fourier expansion is employed in the second case. A new, efficient algorithm for the solution of Poisson's equation on an annulus is introduced. Problems connected to aliasing and to short wavelength noise generated by gradient steepening are discussed. (orig.)
Numerical simulation of the cavitation's hydrodynamic excitement
International Nuclear Information System (INIS)
Hassis, H.; Dueymes, E.; Lauro, J.F.
1993-01-01
First, we study the motion, the velocity, the phases plane and the acoustic sources associated to a spherical bubble in a compressible or incompressible medium. The bubble can be excited by periodic or random excitements. We study the parameters which influence their behaviour: periodicity or not of motion, implosion and explosion or oscillation of bubble. We take into account this behaviour in a model of cavitation: it is a numerical simulation using population of bubbles which are with positions (in the cavitation volume) and sizes are random. These bubbles are excited by a random excitement: a model of turbulent flow or implosion and explosion of bubble. (author)
Numerical Simulations Of Flagellated Micro-Swimmers
Rorai, Cecilia; Markesteijn, Anton; Zaitstev, Mihail; Karabasov, Sergey
2017-11-01
We study flagellated microswimmers locomotion by representing the entire swimmer body. We discuss and contrast the accuracy and computational cost of different numerical approaches including the Resistive Force Theory, the Regularized Stokeslet Method and the Finite Element Method. We focus on how the accuracy of the methods in reproducing the swimming trajectories, velocities and flow field, compares to the sensitivity of these quantities to certain physical parameters, such as the body shape and the location of the center of mass. We discuss the opportunity and physical relevance of retaining inertia in our models. Finally, we present some preliminary results toward collective motion simulations. Marie Skodowska-Curie Individual Fellowship.
The numerical simulation of accelerator components
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.; Hanerfeld, H.
1987-05-01
The techniques of the numerical simulation of plasmas can be readily applied to problems in accelerator physics. Because the problems usually involve a single component ''plasma,'' and times that are at most, a few plasma oscillation periods, it is frequently possible to make very good simulations with relatively modest computation resources. We will discuss the methods and illustrate them with several examples. One of the more powerful techniques of understanding the motion of charged particles is to view computer-generated motion pictures. We will show several little movie strips to illustrate the discussions. The examples will be drawn from the application areas of Heavy Ion Fusion, electron-positron linear colliders and injectors for free-electron lasers. 13 refs., 10 figs., 2 tabs
Numerical simulation of human biped locomotion
International Nuclear Information System (INIS)
Ishiguro, Misako; Fujisaki, Masahide
1988-04-01
This report describes the numerical simulation of the motion of human-like robot which is one of the research theme of human acts simulation program (HASP) begun at the Computing Center of JAERI in 1987. The purpose of the theme is to model the human motion using robotics kinematic/kinetic equations and to get the joint angles as the solution. As the first trial, we treat the biped locomotion (walking) which is the most fundamental human motion. We implemented a computer program on FACOM M-780 computer, where the program is originated from the book of M. Vukobratovic in Yugoslavia, and made a graphic program to draw a walking shot sequence. Mainly described here are the mathematical model of the biped locomotion, implementation method of the computer program, input data for basic walking pattern, computed results and its validation, and graphic representation of human walking image. Literature survey on robotics equation and biped locomotion is also included. (author)
Direct numerical simulation of annular flows
Batchvarov, Assen; Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Craster, Richard V.; Matar, Omar K.
2017-11-01
Vertical counter-current two-phase flows are investigated using direct numerical simulations. The computations are carried out using Blue, a front-tracking-based CFD solver. Preliminary results show good qualitative agreement with experimental observations in terms of interfacial phenomena; these include three-dimensional, large-amplitude wave formation, the development of long ligaments, and droplet entrainment. The flooding phenomena in these counter current systems are closely investigated. The onset of flooding in our simulations is compared to existing empirical correlations such as Kutateladze-type and Wallis-type. The effect of varying tube diameter and fluid properties on the flooding phenomena is also investigated in this work. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM).
Numerical Simulation of Duplex Steel Multipass Welding
Directory of Open Access Journals (Sweden)
Giętka T.
2016-12-01
Full Text Available Analyses based on FEM calculations have significantly changed the possibilities of determining welding strains and stresses at early stages of product design and welding technology development. Such an approach to design enables obtaining significant savings in production preparation and post-weld deformation corrections and is also important for utility properties of welded joints obtained. As a result, it is possible to make changes to a simulated process before introducing them into real production as well as to test various variants of a given solution. Numerical simulations require the combination of problems of thermal, mechanical and metallurgical analysis. The study presented involved the SYSWELD software-based analysis of GMA welded multipass butt joints made of duplex steel sheets. The analysis of the distribution of stresses and displacements were carried out for typical welding procedure as during real welding tests.
Numerical simulation of a sour gas flare
Energy Technology Data Exchange (ETDEWEB)
Chambers, A. [Alberta Research Council, Devon, AB (Canada)
2008-07-01
Due to the limited amount of information in the literature on sour gas flares and the cost of conducting wind tunnel and field experiments on sour flares, this presentation presented a modelling project that predicted the effect of operating conditions on flare performance and emissions. The objectives of the project were to adapt an existing numerical model suitable for flare simulation, incorporate sulfur chemistry, and run simulations for a range of conditions typical of sour flares in Alberta. The study involved the use of modelling expertise at the University of Utah, and employed large eddy simulation (LES) methods to model open flames. The existing model included the prediction of turbulent flow field; hydrocarbon reaction chemistry; soot formation; and radiation heat transfer. The presentation addressed the unique features of the model and discussed whether LES could predict the flow field. Other topics that were presented included the results from a University of Utah comparison; challenges of the LES model; an example of a run time issue; predicting the impact of operating conditions; and the results of simulations. Last, several next steps were identified and preliminary results were provided. Future work will focus on reducing computation time and increasing information reporting. figs.
Visualization techniques in plasma numerical simulations
International Nuclear Information System (INIS)
Kulhanek, P.; Smetana, M.
2004-01-01
Numerical simulations of plasma processes usually yield a huge amount of raw numerical data. Information about electric and magnetic fields and particle positions and velocities can be typically obtained. There are two major ways of elaborating these data. First of them is called plasma diagnostics. We can calculate average values, variances, correlations of variables, etc. These results may be directly comparable with experiments and serve as the typical quantitative output of plasma simulations. The second possibility is the plasma visualization. The results are qualitative only, but serve as vivid display of phenomena in the plasma followed-up. An experience with visualizing electric and magnetic fields via Line Integral Convolution method is described in the first part of the paper. The LIC method serves for visualization of vector fields in two dimensional section of the three dimensional plasma. The field values can be known only in grid points of three-dimensional grid. The second part of the paper is devoted to the visualization techniques of the charged particle motion. The colour tint can be used for particle temperature representation. The motion can be visualized by a trace fading away with the distance from the particle. In this manner the impressive animations of the particle motion can be achieved. (author)
Structural Health Monitoring: Numerical Damage Predictor for Composite Structures
National Research Council Canada - National Science Library
Lannamann, Daniel
2001-01-01
.... Wide use of composites is found in aircraft, armored vehicles, ships and civil structures This present research demonstrates the ability to numerically detect damage in a composite sandwich structure...
Direct numerical simulation of turbulent reacting flows
Energy Technology Data Exchange (ETDEWEB)
Chen, J.H. [Sandia National Laboratories, Livermore, CA (United States)
1993-12-01
The development of turbulent combustion models that reflect some of the most important characteristics of turbulent reacting flows requires knowledge about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between the turbulence and the chemistry is so strong in certain regimes that is is very difficult to isolate the role played by one individual phenomenon. Direct numerical simulation (DNS) is an extremely useful tool to study in detail the turbulence-chemistry interactions in certain well defined regimes. Globally, non-premixed flames are controlled by two limiting cases: the fast chemistry limit, where the turbulent fluctuations. In between these two limits, finite-rate chemical effects are important and the turbulence interacts strongly with the chemical processes. This regime is important because industrial burners operate in regimes in which, locally the flame undergoes extinction, or is at least in some nonequilibrium condition. Furthermore, these nonequilibrium conditions strongly influence the production of pollutants. To quantify the finite-rate chemistry effect, direct numerical simulations are performed to study the interaction between an initially laminar non-premixed flame and a three-dimensional field of homogeneous isotropic decaying turbulence. Emphasis is placed on the dynamics of extinction and on transient effects on the fine scale mixing process. Differential molecular diffusion among species is also examined with this approach, both for nonreacting and reacting situations. To address the problem of large-scale mixing and to examine the effects of mean shear, efforts are underway to perform large eddy simulations of round three-dimensional jets.
Ginés A. Abanto; Mustapha Karkri; Gilles Lefebvre; Manfred Horn; Jose L. Solis; Mónica M. Gómez
2017-01-01
The adobe is a widely used traditional material in popular constructions in rural areas of Peru and more generally in Andean countries. In order to increase comfort and energy efficiency of constructions, it is necessary to better know the thermal characteristics of the adobe, seen as a bio-composite material. Different adobes have been studied. Effective thermal conductivity and heat capacity were measured by means of a hot parallel-plate method. Density was estimated using a pycnometer a...
Numerical simulation of premixed turbulent methane combustion
International Nuclear Information System (INIS)
Bell, John B.; Day, Marcus S.; Grcar, Joseph F.
2001-01-01
In this paper we study the behavior of a premixed turbulent methane flame in three dimensions using numerical simulation. The simulations are performed using an adaptive time-dependent low Mach number combustion algorithm based on a second-order projection formulation that conserves both species mass and total enthalpy. The species and enthalpy equations are treated using an operator-split approach that incorporates stiff integration techniques for modeling detailed chemical kinetics. The methodology also incorporates a mixture model for differential diffusion. For the simulations presented here, methane chemistry and transport are modeled using the DRM-19 (19-species, 84-reaction) mechanism derived from the GRIMech-1.2 mechanism along with its associated thermodynamics and transport databases. We consider a lean flame with equivalence ratio 0.8 for two different levels of turbulent intensity. For each case we examine the basic structure of the flame including turbulent flame speed and flame surface area. The results indicate that flame wrinkling is the dominant factor leading to the increased turbulent flame speed. Joint probability distributions are computed to establish a correlation between heat release and curvature. We also investigate the effect of turbulent flame interaction on the flame chemistry. We identify specific flame intermediates that are sensitive to turbulence and explore various correlations between these species and local flame curvature. We identify different mechanisms by which turbulence modulates the chemistry of the flame
Numerical simulation of heterogeneous phase transformations
International Nuclear Information System (INIS)
Combeau, H.; Lacaze, J.
1993-01-01
A numerical model is presented for the simulation of diffusion controlled phase transformations in multicomponent alloys. A closed system is considered, with simple geometric shape, either planar, cylindrical or spherical. The temperature inside this microscopic volume is homogeneous, but can vary according to any specified monoteneous law. Particular care has been given to the description of the solute profiles where the concentration gradients are the steepest, i.e. near the interface between the parent and the resultant phases. Solute redistribution at the interface is described by means of an original method which ensures that the overall solute balance is satisfied. A non linear system is obtained which includes the diffusion equations in both phases and the boundary conditions. The solution of this system makes use of a special algorithm which has been devised for a quick convergence. An example is presented which deals with microsegregation build-up during solidification of a multi-component nickel base alloy. (orig.)
Numerical simulations of coupled problems in engineering
2014-01-01
This book presents and discusses mathematical models, numerical methods and computational techniques used for solving coupled problems in science and engineering. It takes a step forward in the formulation and solution of real-life problems with a multidisciplinary vision, accounting for all of the complex couplings involved in the physical description. Simulation of multifaceted physics problems is a common task in applied research and industry. Often a suitable solver is built by connecting together several single-aspect solvers into a network. In this book, research in various fields was selected for consideration: adaptive methodology for multi-physics solvers, multi-physics phenomena and coupled-field solutions, leading to computationally intensive structural analysis. The strategies which are used to keep these problems computationally affordable are of special interest, and make this an essential book.
Numerical simulation of distorted crystal Darwin width
International Nuclear Information System (INIS)
Wang Li; Xu Zhongmin; Wang Naxiu
2012-01-01
A new numerical simulation method according to distorted crystal optical theory was used to predict the direct-cooling crystal monochromator optical properties(crystal Darwin width) in this study. The finite element analysis software was used to calculate the deformed displacements of DCM crystal and to get the local reciprocal lattice vector of distorted crystal. The broadening of direct-cooling crystal Darwin width in meridional direction was estimated at 4.12 μrad. The result agrees well with the experimental data of 5 μrad, while it was 3.89 μrad by traditional calculation method of root mean square (RMS) of the slope error in the center line of footprint. The new method provides important theoretical support for designing and processing of monochromator crystal for synchrotron radiation beamline. (authors)
Numerical simulation of magnetic heat pumps
International Nuclear Information System (INIS)
Smaili, A.; Masson, C.
2002-01-01
This article presents a numerical method for performance predictions of magnetic heat pump (MHP) devices. Such devices consist primarily of a magnetic regenerator (solid refrigerant media) and circulating fluid. Unlike conventional gas-cycles, MHP devices function according to thermomagnetic cycles which do not require neither compressor nor expander. In this paper, the flow field throughout the regenerator is described by continuity and unsteady incompressible Navier-Stokes equations. The heat transfer between fluid and solid is introduced by considering the corresponding energy equations. The proposed mathematical model has been solved using a control volume finite element method. The fully implicit scheme is used for time discretization. Simulation results including heating capacity and coefficient of performance are presented for a given MHP cycle. Mainly, the effects of cycle frequency, mass flow rate and the magnetic regenerator mass are investigated. (author)
Numerical simulations of convectively excited gravity waves
International Nuclear Information System (INIS)
Glatzmaier, G.A.
1983-01-01
Magneto-convection and gravity waves are numerically simulated with a nonlinear, three-dimensional, time-dependent model of a stratified, rotating, spherical fluid shell heated from below. A Solar-like reference state is specified while global velocity, magnetic field, and thermodynamic perturbations are computed from the anelastic magnetohydrodynamic equations. Convective overshooting from the upper (superadiabatic) part of the shell excites gravity waves in the lower (subadiabatic) part. Due to differential rotation and Coriolis forces, convective cell patterns propagate eastward with a latitudinally dependent phase velocity. The structure of the excited wave motions in the stable region is more time-dependent than that of the convective motions above. The magnetic field tends to be concentrated over giant-cell downdrafts in the convective zone but is affected very little by the wave motion in the stable region
The Beam Break-Up Numerical Simulator
International Nuclear Information System (INIS)
Travish, G.A.
1989-11-01
Beam Break-Up (BBU) is a severe constraint in accelerator design, limiting beam current and quality. The control of BBU has become the focus of much research in the design of the next generation collider, recirculating and linear induction accelerators and advanced accelerators. Determining the effect on BBU of modifications to cavities, the focusing elements or the beam is frequently beyond the ability of current analytic models. A computer code was written to address this problem. The Beam Break-Up Numerical Simulator (BBUNS) was designed to numerically solve for beam break-up (BBU) due to an arbitrary transverse wakefield. BBUNS was developed to be as user friendly as possible on the Cray computer series. The user is able to control all aspects of input and output by using a single command file. In addition, the wakefield is specified by the user and read in as a table. The program can model energy variations along and within the beam, focusing magnetic field profiles can be specified, and the graphical output can be tailored. In this note we discuss BBUNS, its structure and application. Included are detailed instructions, examples and a sample session of BBUNS. This program is available for distribution. 50 refs., 18 figs., 5 tabs
Numerical simulation of installation of skirt foundations
Energy Technology Data Exchange (ETDEWEB)
Vangelsten, Bjoern Vidar
1997-12-31
Skirt foundation has been increasingly used for permanent offshore oil installations and anchors for drilling ships. Suction is commonly used in skirt foundation installing. If a large amount of suction is applied, the soil around the foundation may fail and the foundation become useless. This thesis studies failure due to high seepage gradients, aiming to provide a basis for reducing the risk of such failures. Skirt penetration model testing has shown that to solve the problem one must understand what is going on at the skirt tip during suction installation. A numerical model based on micro mechanics was developed as continuum hypothesis was seen to be unsuitable to describe the processes in the critical phases of the failure. The numerical model combines two-dimensional elliptical particles with the finite difference method for flow to model water flow in a granular material. The key idea is to formulate the permeability as a function of the porosity of the grain assembly and so obtain an interaction between the finite difference method on flow and the particle movement. A computer program, DYNELL, was developed and used to simulate: (1) weight penetration of a skirt wall, (2) combined suction and weight penetration of a skirt wall, and (3) critical gradient tests around a skirt wall to study failure mechanisms. The model calculations agree well with laboratory experiments. 16 refs., 124 figs., 21 tabs.
Coupled numerical simulation of fire in tunnel
Pesavento, F.; Pachera, M.; Schrefler, B. A.; Gawin, D.; Witek, A.
2018-01-01
In this work, a coupling strategy for the analysis of a tunnel under fire is presented. This strategy consists in a "one-way" coupling between a tool considering the computational fluid dynamics and radiation with a model treating concrete as a multiphase porous material exposed to high temperature. This global approach allows for taking into account in a realistic manner the behavior of the "system tunnel", composed of the fluid and the solid domain (i.e. the concrete structures), from the fire onset, its development and propagation to the response of the structure. The thermal loads as well as the moisture exchange between the structure surface and the environment are calculated by means of computational fluid dynamics. These set of data are passed in an automatic way to the numerical tool implementing a model based on Multiphase Porous Media Mechanics. Thanks to this strategy the structural verification is no longer based on the standard fire curves commonly used in the engineering practice, but it is directly related to a realistic fire scenario. To show the capability of this strategy some numerical simulations of a fire in the Brenner Base Tunnel, under construction between Italy and Austria, is presented. The numerical simulations show the effects of a more realistic distribution of the thermal loads with respect to the ones obtained by using the standard fire curves. Moreover, it is possible to highlight how the localized thermal load generates a non-uniform pressure rise in the material, which results in an increase of the structure stress state and of the spalling risk. Spalling is likely the most dangerous collapse mechanism for a concrete structure. This coupling approach still represents a "one way" strategy, i.e. realized without considering explicitly the mass and energy exchange from the structure to the fluid through the interface. This results in an approximation, but from physical point of view the current form of the solid-fluid coupling is
Numerical simulations of capillary barrier field tests
International Nuclear Information System (INIS)
Morris, C.E.; Stormont, J.C.
1997-01-01
Numerical simulations of two capillary barrier systems tested in the field were conducted to determine if an unsaturated flow model could accurately represent the observed results. The field data was collected from two 7-m long, 1.2-m thick capillary barriers built on a 10% grade that were being tested to investigate their ability to laterally divert water downslope. One system had a homogeneous fine layer, while the fine soil of the second barrier was layered to increase its ability to laterally divert infiltrating moisture. The barriers were subjected first to constant infiltration while minimizing evaporative losses and then were exposed to ambient conditions. The continuous infiltration period of the field tests for the two barrier systems was modelled to determine the ability of an existing code to accurately represent capillary barrier behavior embodied in these two designs. Differences between the field test and the model data were found, but in general the simulations appeared to adequately reproduce the response of the test systems. Accounting for moisture retention hysteresis in the layered system will potentially lead to more accurate modelling results and is likely to be important when developing reasonable predictions of capillary barrier behavior
Numerical simulation for nuclear pumped laser
Energy Technology Data Exchange (ETDEWEB)
Sakasai, Kaoru [Japan Atomic Energy Research Inst., Tokyo (Japan)
1998-07-01
To apply nuclear pumped laser of {sup 3}He-Ne-Ar gas to detect neutron, the optimum gas mixture was investigated by numerical simulation. When {sup 3}He-Ne-Ar mixture gas are irradiated by neutron, proton and triton with high velocity are produced by {sup 3}He(np)T and two charge particles ionized {sup 3}He, Ne and Ar which reacted each other and attained to 3p`(1/2){sub 0}-3S`(1/2). The calculation method is constructed by defining the rate equations of each ion and exited atom and the electron energy balance equation and by time integrating the simultaneous differential equations of the above two equations and the law of conservation of charge. Penning ionization and energy transport by elastic collision of neutral atom were considered in the transport process of electron energy direct ionization by secondary charge particle. Calculation time was 1 msec. The optimum component was shown 3 atm He, 24 Torr He and 8 Torr Ar by simulation. Laser oscilation was generated under the conditions 3.3 x 10{sup 14} (N/cm{sup 2}/5) thermal neutron flux at 50 cm laser cell length and 99% coefficient of reflection of mirror. After laser oscilation, laser output was proportional to neutron flux. These results showed nuclear pumped laser of {sup 3}He-Ne-Ar was able to detect optically neutron. (S.Y)
Collisionless microinstabilities in stellarators. II. Numerical simulations
International Nuclear Information System (INIS)
Proll, J. H. E.; Xanthopoulos, P.; Helander, P.
2013-01-01
Microinstabilities exhibit a rich variety of behavior in stellarators due to the many degrees of freedom in the magnetic geometry. It has recently been found that certain stellarators (quasi-isodynamic ones with maximum-J geometry) are partly resilient to trapped-particle instabilities, because fast-bouncing particles tend to extract energy from these modes near marginal stability. In reality, stellarators are never perfectly quasi-isodynamic, and the question thus arises whether they still benefit from enhanced stability. Here, the stability properties of Wendelstein 7-X and a more quasi-isodynamic configuration, QIPC, are investigated numerically and compared with the National Compact Stellarator Experiment and the DIII-D tokamak. In gyrokinetic simulations, performed with the gyrokinetic code GENE in the electrostatic and collisionless approximation, ion-temperature-gradient modes, trapped-electron modes, and mixed-type instabilities are studied. Wendelstein 7-X and QIPC exhibit significantly reduced growth rates for all simulations that include kinetic electrons, and the latter are indeed found to be stabilizing in the energy budget. These results suggest that imperfectly optimized stellarators can retain most of the stabilizing properties predicted for perfect maximum-J configurations
Numerical simulation of the Polywell device
International Nuclear Information System (INIS)
Simmons, K.H.; Santarius, J.F.
1995-01-01
Recent ideas concerning inertial-electrostatic confinement (IEC) of fusion plasmas coupled with recent experimental results have motivated looking at the problem of confinement of these plasmas in both the gridded (pure electrostatic) and magnetically assisted (via confinement of high beta plasmas in a magnetic cusp) configuration. Questions exist as to the nature of the potential well structure and the confinement properties of high beta plasmas in magnetic cusp configurations. This work focuses on the magnetically assisted concept known as the Polywell trademark. Results are reported on the numerical simulation of IEC plasmas aimed at answering some of these questions. In particular the authors focus on two aspects of the Polywell, namely the structure of the magnetic cusp field in the Polywell configuration and the nature of the confinement of a high beta plasma in a magnetic cusp field. The existence of line cusps in the Polywell is still in dispute. A computer code for modeling the magnetic field structure and mod-B surface has been written and results are presented for the Polywell. Another source of controversy is the nature of the confinement of a high beta plasma in a magnetic cusp, and in particular in the polywell. Results from 2-D Particle In Cell (PIC) simulations aimed at answering some of these questions are presented
Direct numerical simulation of human phonation
Bodony, Daniel; Saurabh, Shakti
2017-11-01
The generation and propagation of the human voice in three-dimensions is studied using direct numerical simulation. A full body domain is employed for the purpose of directly computing the sound in the region past the speaker's mouth. The air in the vocal tract is modeled as a compressible and viscous fluid interacting with the elastic vocal folds. The vocal fold tissue material properties are multi-layered, with varying stiffness, and a linear elastic transversely isotropic model is utilized and implemented in a quadratic finite element code. The fluid-solid domains are coupled through a boundary-fitted interface and utilize a Poisson equation-based mesh deformation method. A kinematic constraint based on a specified minimum gap between the vocal folds is applied to prevent collision during glottal closure. Both near VF flow dynamics and far-field acoustics have been studied. A comparison is drawn to current two-dimensional simulations as well as to data from the literature. Near field vocal fold dynamics and glottal flow results are studied and in good agreement with previous three-dimensional phonation studies. Far-field acoustic characteristics, when compared to their two-dimensional counterpart, are shown to be sensitive to the dimensionality. Supported by the National Science Foundation (CAREER Award Number 1150439).
Hybrid Simulation of Composite Structures
DEFF Research Database (Denmark)
Høgh, Jacob Herold
experiment. The technique has primarily been used within earthquake engineering but many other fields of engineering have utilized the method with benefit. However, these previous efforts have focused on structures with a simple boundary between the numerical and physical substructure i.e. few degrees...... the transfer system and the control and monitoring techniques in the shared boundary is therefore a key issue in this type of hybrid simulation. During the research, hybrid simulation platforms have been programmed capable of running on different time scales with advanced control and monitoring techniques...
Numerical Simulations of Hypersonic Boundary Layer Transition
Bartkowicz, Matthew David
Numerical schemes for supersonic flows tend to use large amounts of artificial viscosity for stability. This tends to damp out the small scale structures in the flow. Recently some low-dissipation methods have been proposed which selectively eliminate the artificial viscosity in regions which do not require it. This work builds upon the low-dissipation method of Subbareddy and Candler which uses the flux vector splitting method of Steger and Warming but identifies the dissipation portion to eliminate it. Computing accurate fluxes typically relies on large grid stencils or coupled linear systems that become computationally expensive to solve. Unstructured grids allow for CFD solutions to be obtained on complex geometries, unfortunately, it then becomes difficult to create a large stencil or the coupled linear system. Accurate solutions require grids that quickly become too large to be feasible. In this thesis a method is proposed to obtain more accurate solutions using relatively local data, making it suitable for unstructured grids composed of hexahedral elements. Fluxes are reconstructed using local gradients to extend the range of data used. The method is then validated on several test problems. Simulations of boundary layer transition are then performed. An elliptic cone at Mach 8 is simulated based on an experiment at the Princeton Gasdynamics Laboratory. A simulated acoustic noise boundary condition is imposed to model the noisy conditions of the wind tunnel and the transitioning boundary layer observed. A computation of an isolated roughness element is done based on an experiment in Purdue's Mach 6 quiet wind tunnel. The mechanism for transition is identified as an instability in the upstream separation region and a comparison is made to experimental data. In the CFD a fully turbulent boundary layer is observed downstream.
Process simulations for manufacturing of thick composites
Kempner, Evan A.
The availability of manufacturing simulations for composites can significantly reduce the costs associated with process development. Simulations provide a tool for evaluating the effect of processing conditions on the quality of parts produced without requiring numerous experiments. This is especially significant in parts that have troublesome features such as large thickness. The development of simulations for thick walled composites has been approached by examining the mechanics of resin flow and fiber deformation during processing, applying these evaluations to develop simulations, and evaluating the simulation with experimental results. A unified analysis is developed to describe the three-dimensional resin flow and fiber preform deformation during processing regardless of the manufacturing process used. It is shown how the generic governing evaluations in the unified analysis can be applied to autoclave molding, compression molding, pultrusion, filament winding, and resin transfer molding. A comparison is provided with earlier models derived individually for these processes. The evaluations described for autoclave curing were used to produce a one-dimensional cure simulation for autoclave curing of thick composites. The simulation consists of an analysis for heat transfer and resin flow in the composite as well as bleeder plies used to absorb resin removed from the part. Experiments were performed in a hot press to approximate curing in an autoclave. Graphite/epoxy laminates of 3 cm and 5 cm thickness were cured while monitoring temperatures at several points inside the laminate and thickness. The simulation predicted temperatures fairly closely, but difficulties were encountered in correlation of thickness results. This simulation was also used to study the effects of prepreg aging on processing of thick composites. An investigation was also performed on filament winding with prepreg tow. Cylinders were wound of approximately 12 mm thickness with pressure
Numerical simulation of a semi-indirect evaporative cooler
Energy Technology Data Exchange (ETDEWEB)
Martin, R. Herrero [Departamento de Ingenieria Termica y de Fluidos, Universidad Politecnica de Cartagena, C/Dr. Fleming, s/n (Campus Muralla), 30202 Cartagena, Murcia (Spain)
2009-11-15
This paper presents the experimental study and numerical simulation of a semi-indirect evaporative cooler (SIEC), which acts as an energy recovery device in air conditioning systems. The numerical simulation was conducted by applying the CFD software FLUENT implementing a UDF to model evaporation/condensation. The numerical model was validated by comparing the simulation results with experimental data. Experimental data and numerical results agree for the lower relative humidity series but not for higher relative humidity values. (author)
Numerical simulation of "an American haboob"
Vukovic, A.; Vujadinovic, M.; Pejanovic, G.; Andric, J.; Kumjian, M. R.; Djurdjevic, V.; Dacic, M.; Prasad, A. K.; El-Askary, H. M.; Paris, B. C.; Petkovic, S.; Nickovic, S.; Sprigg, W. A.
2014-04-01
A dust storm of fearful proportions hit Phoenix in the early evening hours of 5 July 2011. This storm, an American haboob, was predicted hours in advance because numerical, land-atmosphere modeling, computing power and remote sensing of dust events have improved greatly over the past decade. High-resolution numerical models are required for accurate simulation of the small scales of the haboob process, with high velocity surface winds produced by strong convection and severe downbursts. Dust productive areas in this region consist mainly of agricultural fields, with soil surfaces disturbed by plowing and tracks of land in the high Sonoran Desert laid barren by ongoing draught. Model simulation of the 5 July 2011 dust storm uses the coupled atmospheric-dust model NMME-DREAM (Non-hydrostatic Mesoscale Model on E grid, Janjic et al., 2001; Dust REgional Atmospheric Model, Nickovic et al., 2001; Pérez et al., 2006) with 4 km horizontal resolution. A mask of the potentially dust productive regions is obtained from the land cover and the normalized difference vegetation index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS). The scope of this paper is validation of the dust model performance, and not use of the model as a tool to investigate mechanisms related to the storm. Results demonstrate the potential technical capacity and availability of the relevant data to build an operational system for dust storm forecasting as a part of a warning system. Model results are compared with radar and other satellite-based images and surface meteorological and PM10 observations. The atmospheric model successfully hindcasted the position of the front in space and time, with about 1 h late arrival in Phoenix. The dust model predicted the rapid uptake of dust and high values of dust concentration in the ensuing storm. South of Phoenix, over the closest source regions (~25 km), the model PM10 surface dust concentration reached ~2500 μg m-3, but
Hot forming of composite prepreg: Numerical analyses
Guzman-Maldonado, Eduardo; Hamila, Nahiène; Boisse, Philippe; El Azzouzi, Khalid; Tardif, Xavier; Moro, Tanguy; Chatel, Sylvain; Fideu, Paulin
2017-10-01
The work presented here is part of the "FORBANS" project about the Hot Drape Forming (HDF) process consisting of unidirectional prepregs laminates. To ensure a fine comprehension of this process a combination strategy between experiment and numerical analysis is adopted. This paper is focused on the numerical analysis using the finite element method (FEM) with a hyperelastic constitutive law. Each prepreg layer is modelled by shell elements. These elements consider the tension, in-plane shear and bending behaviour of the ply at different temperatures. The contact/friction during the forming process is taken into account using forward increment Lagrange multipliers.
Transonic aeroelastic numerical simulation in aeronautical engineering
International Nuclear Information System (INIS)
Yang, G.
2005-01-01
An LU-SGS (lower-upper symmetric Gauss-Seidel) subiteration scheme is constructed for time-marching of the fluid equations. The HLLEW (Harten-Lax-van Leer-Einfeldt-Wada) scheme is used for the spatial discretization. The same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Through subiteration between the fluid and structural equations, a fully implicit aeroelastic solver is obtained for the numerical simulation of fluid/structure interaction. To improve the ability for application to complex configurations, a multiblock grid is used for the flow field calculation and Transfinite Interpolation (TFI) is employed for the adaptive moving grid deformation. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between the fluid and structure. The developed code was first validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. Then the flutter character of a tail wing with control surface was analyzed. Finally, flutter boundaries of a complex aircraft configuration were predicted. (author)
Proton decay: Numerical simulations confront grand unification
International Nuclear Information System (INIS)
Brower, R.C.; Maturana, G.; Giles, R.C.; Moriarty, K.J.M.; Samuel, S.
1985-01-01
The Grand Unified Theories of the electromagnetic, weak and strong interactions constitute a far reaching attempt to synthesize our knowledge of theoretical particle physics into a consistent and compelling whole. Unfortunately, many quantitative predictions of such unified theories are sensitive to the analytically intractible effects of the strong subnuclear theory (Quantum Chromodynamics or QCD). The consequence is that even ambitious experimental programs exploring weak and super-weak interaction effects often fail to give definitive theoretical tests. This paper describes large-scale calculations on a supercomputer which can help to overcome this gap between theoretical predictions and experimental results. Our focus here is on proton decay, though the methods described are useful for many weak processes. The basic algorithms for the numerical simulation of QCD are well known. We will discuss the advantages and challenges of applying these methods to weak transitions. The algorithms require a very large data base with regular data flow and are natural candidates for vectorization. Also, 32-bit floating point arithmetic is adequate. Thus they are most naturally approached using a supercomputer alone or in combination with a dedicated special purpose processor. (orig.)
High accuracy mantle convection simulation through modern numerical methods
Kronbichler, Martin
2012-08-21
Numerical simulation of the processes in the Earth\\'s mantle is a key piece in understanding its dynamics, composition, history and interaction with the lithosphere and the Earth\\'s core. However, doing so presents many practical difficulties related to the numerical methods that can accurately represent these processes at relevant scales. This paper presents an overview of the state of the art in algorithms for high-Rayleigh number flows such as those in the Earth\\'s mantle, and discusses their implementation in the Open Source code Aspect (Advanced Solver for Problems in Earth\\'s ConvecTion). Specifically, we show how an interconnected set of methods for adaptive mesh refinement (AMR), higher order spatial and temporal discretizations, advection stabilization and efficient linear solvers can provide high accuracy at a numerical cost unachievable with traditional methods, and how these methods can be designed in a way so that they scale to large numbers of processors on compute clusters. Aspect relies on the numerical software packages deal.II and Trilinos, enabling us to focus on high level code and keeping our implementation compact. We present results from validation tests using widely used benchmarks for our code, as well as scaling results from parallel runs. © 2012 The Authors Geophysical Journal International © 2012 RAS.
Directory of Open Access Journals (Sweden)
Mespoulet Jérôme
2015-01-01
Full Text Available Response of pressurized composite-Al vessels to hypervelocity impact of aluminum spheres have been numerically investigated to evaluate the influence of initial pressure on the vulnerability of these vessels. Investigated tanks are carbon-fiber overwrapped prestressed Al vessels. Explored internal air pressure ranges from 1 bar to 300 bar and impact velocity are around 4400 m/s. Data obtained from experiments (Xray radiographies, particle velocity measurement and post-mortem vessels have been compared to numerical results given from LS-DYNA ALE-Lagrange-SPH full coupling models. Simulations exhibit an under estimation in term of debris cloud evolution and shock wave propagation in pressurized air but main modes of damage/rupture on the vessels given by simulations are coherent with post-mortem recovered vessels from experiments. First results of this numerical work are promising and further simulation investigations with additional experimental data will be done to increase the reliability of the simulation model. The final aim of this crossed work is to numerically explore a wide range of impact conditions (impact angle, projectile weight, impact velocity, initial pressure that cannot be explore experimentally. Those whole results will define a rule of thumbs for the definition of a vulnerability analytical model for a given pressurized vessel.
A Numerical Simulation for a Deterministic Compartmental ...
African Journals Online (AJOL)
In this work, an earlier deterministic mathematical model of HIV/AIDS is revisited and numerical solutions obtained using Eulers numerical method. Using hypothetical values for the parameters, a program was written in VISUAL BASIC programming language to generate series for the system of difference equations from the ...
Numerical simulation of pulse-tube refrigerators
Lyulina, I.A.; Mattheij, R.M.M.; Tijsseling, A.S.; Waele, de A.T.A.M.
2004-01-01
A new numerical model has been introduced to study steady oscillatory heat and mass transfer in the tube section of a pulse-tube refrigerator. Conservation equations describing compressible gas flow in the tube are solved numerically, using high resolution schemes. The equation of conservation of
Numerical modeling of isothermal compositional grading by convex splitting methods
Li, Yiteng
2017-04-09
In this paper, an isothermal compositional grading process is simulated based on convex splitting methods with the Peng-Robinson equation of state. We first present a new form of gravity/chemical equilibrium condition by minimizing the total energy which consists of Helmholtz free energy and gravitational potential energy, and incorporating Lagrange multipliers for mass conservation. The time-independent equilibrium equations are transformed into a system of transient equations as our solution strategy. It is proved our time-marching scheme is unconditionally energy stable by the semi-implicit convex splitting method in which the convex part of Helmholtz free energy and its derivative are treated implicitly and the concave parts are treated explicitly. With relaxation factor controlling Newton iteration, our method is able to converge to a solution with satisfactory accuracy if a good initial estimate of mole compositions is provided. More importantly, it helps us automatically split the unstable single phase into two phases, determine the existence of gas-oil contact (GOC) and locate its position if GOC does exist. A number of numerical examples are presented to show the performance of our method.
Experimental and Numerical Analysis of Notched Composites Under Tension Loading
Aidi, Bilel; Case, Scott W.
2015-12-01
Experimental quasi-static tests were performed on center notched carbon fiber reinforced polymer (CFRP) composites having different stacking sequences made of G40-600/5245C prepreg. The three-dimensional Digital Image Correlation (DIC) technique was used during quasi-static tests conducted on quasi-isotropic notched samples to obtain the distribution of strains as a function of applied stress. A finite element model was built within Abaqus to predict the notched strength and the strain profiles for comparison with measured results. A user-material subroutine using the multi-continuum theory (MCT) as a failure initiation criterion and an energy-based damage evolution law as implemented by Autodesk Simulation Composite Analysis (ASCA) was used to conduct a quantitative comparison of strain components predicted by the analysis and obtained in the experiments. Good agreement between experimental data and numerical analyses results are observed. Modal analysis was carried out to investigate the effect of static damage on the dominant frequencies of the notched structure using the resulted degraded material elements. The first in-plane mode was found to be a good candidate for tracking the level of damage.
Large-scale numerical simulations of plasmas
International Nuclear Information System (INIS)
Hamaguchi, Satoshi
2004-01-01
The recent trend of large scales simulations of fusion plasma and processing plasmas is briefly summarized. Many advanced simulation techniques have been developed for fusion plasmas and some of these techniques are now applied to analyses of processing plasmas. (author)
Development of Pelton turbine using numerical simulation
Energy Technology Data Exchange (ETDEWEB)
Patel, K; Patel, B; Yadav, M [Hydraulic Engineer, ALSTOM Hydro R and D India Ltd., GIDC Maneja, Vadodara - 390 013, Gujarat (India); Foggia, T, E-mail: patel@power.alstom.co [Hydraulic Engineer, Alstom Hydro France, Etablissement de Grenoble, 82, avenue Leon Blum BP 75, 38041 Grenoble Cedex (France)
2010-08-15
This paper describes recent research and development activities in the field of Pelton turbine design. Flow inside Pelton turbine is most complex due to multiphase (mixture of air and water) and free surface in nature. Numerical calculation is useful to understand flow physics as well as effect of geometry on flow. The optimized design is obtained using in-house special optimization loop. Either single phase or two phase unsteady numerical calculation could be performed. Numerical results are used to visualize the flow pattern in the water passage and to predict performance of Pelton turbine at full load as well as at part load. Model tests are conducted to determine performance of turbine and it shows good agreement with numerically predicted performance.
Development of Pelton turbine using numerical simulation
Patel, K.; Patel, B.; Yadav, M.; Foggia, T.
2010-08-01
This paper describes recent research and development activities in the field of Pelton turbine design. Flow inside Pelton turbine is most complex due to multiphase (mixture of air and water) and free surface in nature. Numerical calculation is useful to understand flow physics as well as effect of geometry on flow. The optimized design is obtained using in-house special optimization loop. Either single phase or two phase unsteady numerical calculation could be performed. Numerical results are used to visualize the flow pattern in the water passage and to predict performance of Pelton turbine at full load as well as at part load. Model tests are conducted to determine performance of turbine and it shows good agreement with numerically predicted performance.
Coherent Structures in Numerically Simulated Plasma Turbulence
DEFF Research Database (Denmark)
Kofoed-Hansen, O.; Pécseli, H.L.; Trulsen, J.
1989-01-01
Low level electrostatic ion acoustic turbulence generated by the ion-ion beam instability was investigated numerically. The fluctuations in potential were investigated by a conditional statistical analysis revealing propagating coherent structures having the form of negative potential wells which...
Development of Pelton turbine using numerical simulation
International Nuclear Information System (INIS)
Patel, K; Patel, B; Yadav, M; Foggia, T
2010-01-01
This paper describes recent research and development activities in the field of Pelton turbine design. Flow inside Pelton turbine is most complex due to multiphase (mixture of air and water) and free surface in nature. Numerical calculation is useful to understand flow physics as well as effect of geometry on flow. The optimized design is obtained using in-house special optimization loop. Either single phase or two phase unsteady numerical calculation could be performed. Numerical results are used to visualize the flow pattern in the water passage and to predict performance of Pelton turbine at full load as well as at part load. Model tests are conducted to determine performance of turbine and it shows good agreement with numerically predicted performance.
Numerical simulation of single bubble boiling behavior
Directory of Open Access Journals (Sweden)
Junjie Liu
2017-06-01
Full Text Available The phenomena of a single bubble boiling process are studied with numerical modeling. The mass, momentum, energy and level set equations are solved using COMSOL multi-physics software. The bubble boiling dynamics, the transient pressure field, velocity field and temperature field in time are analyzed, and reasonable results are obtained. The numeral model is validated by the empirical equation of Fritz and could be used for various applications.
Modular numerical tool for gas turbine simulation
Sampedro Casis, Rodrigo
2015-01-01
In this work a free tool for the simulation of turboprops was implemented, capable of simulating the various components of a jet engine, separately or in conjunction, with different degrees of thermodynamic modelling or complexity, in order to simulate an entire jet engine. The main characteristics of this software includes its compatibility, open code and GNU license, non-existing in today's market. Furthermore, the tool was designed with a greater flexibility and a more adapted work environ...
Numerical simulation of turbulent combustion: Scientific challenges
Ren, ZhuYin; Lu, Zhen; Hou, LingYun; Lu, LiuYan
2014-08-01
Predictive simulation of engine combustion is key to understanding the underlying complicated physicochemical processes, improving engine performance, and reducing pollutant emissions. Critical issues as turbulence modeling, turbulence-chemistry interaction, and accommodation of detailed chemical kinetics in complex flows remain challenging and essential for high-fidelity combustion simulation. This paper reviews the current status of the state-of-the-art large eddy simulation (LES)/prob-ability density function (PDF)/detailed chemistry approach that can address the three challenging modelling issues. PDF as a subgrid model for LES is formulated and the hybrid mesh-particle method for LES/PDF simulations is described. Then the development need in micro-mixing models for the PDF simulations of turbulent premixed combustion is identified. Finally the different acceleration methods for detailed chemistry are reviewed and a combined strategy is proposed for further development.
Detailed numerical simulations of laser cooling processes
Ramirez-Serrano, J.; Kohel, J.; Thompson, R.; Yu, N.
2001-01-01
We developed a detailed semiclassical numerical code of the forces applied on atoms in optical and magnetic fields to increase the understanding of the different roles that light, atomic collisions, background pressure, and number of particles play in experiments with laser cooled and trapped atoms.
NUMERICAL SIMULATION AND MODELING OF UNSTEADY FLOW ...
African Journals Online (AJOL)
2014-06-30
Jun 30, 2014 ... objective of this study is to control the simulation of unsteady flows around structures. ... Aerospace, our results were in good agreement with experimental .... Two-Equation Eddy-Viscosity Turbulence Models for Engineering.
Numerical simulation of ion-surface interactions
International Nuclear Information System (INIS)
Hou, M.
1994-01-01
This paper, based on examples from the author's contribution, aims to illustrate the role of ballistic simulations of the interaction between an ion beam and a surface in the characterization of surface properties. Several aspects of the ion-surface interaction have been modelled to various levels of sophistication by computer simulation. Particular emphasis is given to the ion scattering in the impact mode, in the multiple scattering regime and at grazing incidence, as well as to the Auger emission resulting from electronic excitation. Some examples are then given in order to illustrate the use of the combination between simulation and experiment to study the ion-surface interaction and surface properties. Ion-induced Auger emission, the determination of potentials and of overlay structures are discusse. The possibility to tackle dynamical surface properties by menas of a combination between molecular dynamics, ballistic simulations and ion scattering measurements in then briefly discussed. (orig.)
A numerical simulation of a contrail
Energy Technology Data Exchange (ETDEWEB)
Levkov, L.; Boin, M.; Meinert, D. [GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht (Germany)
1997-12-31
The formation of a contrail from an aircraft flying near the tropopause is simulated using a three-dimensional mesoscale atmospheric model including a very complex scheme of parameterized cloud microphysical processes. The model predicted ice concentrations are in very good agreement with data measured during the International Cirrus Experiment (ICE), 1989. Sensitivity simulations were run to determine humidity forcing on the life time of contrails. (author) 4 refs.
A numerical simulation of a contrail
Energy Technology Data Exchange (ETDEWEB)
Levkov, L; Boin, M; Meinert, D [GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht (Germany)
1998-12-31
The formation of a contrail from an aircraft flying near the tropopause is simulated using a three-dimensional mesoscale atmospheric model including a very complex scheme of parameterized cloud microphysical processes. The model predicted ice concentrations are in very good agreement with data measured during the International Cirrus Experiment (ICE), 1989. Sensitivity simulations were run to determine humidity forcing on the life time of contrails. (author) 4 refs.
Numerical Simulation of the Kinetic Critical Nucleus
Sanada, Masaaki; Nishioka, Kazumi; Okada, Masahumi; Maksimov, Igor, L.
1997-01-01
Our main interest is to see whether the number density indicates a peak at the kinetically stable critical nucleus due to its kinetical stability. We have numerically calculated the time evolution of the number densities of clusters in the case of water vapor nucleation. We employ the condition in which the difference between the size of the thermodynamic crtitical nucleus and that of the kinetic one is appreciable. The results show that the peak does not appear in the number densities of clu...
Numerical simulation of hemorrhage in human injury
Chong, Kwitae; Jiang, Chenfanfu; Santhanam, Anand; Benharash, Peyman; Teran, Joseph; Eldredge, Jeff
2015-11-01
Smoothed Particle Hydrodynamics (SPH) is adapted to simulate hemorrhage in the injured human body. As a Lagrangian fluid simulation, SPH uses fluid particles as computational elements and thus mass conservation is trivially satisfied. In order to ensure anatomical fidelity, a three-dimensional reconstruction of a portion of the human body -here, demonstrated on the lower leg- is sampled as skin, bone and internal tissue particles from the CT scan image of an actual patient. The injured geometry is then generated by simulation of ballistic projectiles passing through the anatomical model with the Material Point Method (MPM) and injured vessel segments are identified. From each such injured segment, SPH is used to simulate bleeding, with inflow boundary condition obtained from a coupled 1-d vascular tree model. Blood particles interact with impermeable bone and skin particles through the Navier-Stokes equations and with permeable internal tissue particles through the Brinkman equations. The SPH results are rendered in post-processing for improved visual fidelity. The overall simulation strategy is demonstrated on several injury scenarios in the lower leg.
Numerical characteristics of quantum computer simulation
Chernyavskiy, A.; Khamitov, K.; Teplov, A.; Voevodin, V.; Voevodin, Vl.
2016-12-01
The simulation of quantum circuits is significantly important for the implementation of quantum information technologies. The main difficulty of such modeling is the exponential growth of dimensionality, thus the usage of modern high-performance parallel computations is relevant. As it is well known, arbitrary quantum computation in circuit model can be done by only single- and two-qubit gates, and we analyze the computational structure and properties of the simulation of such gates. We investigate the fact that the unique properties of quantum nature lead to the computational properties of the considered algorithms: the quantum parallelism make the simulation of quantum gates highly parallel, and on the other hand, quantum entanglement leads to the problem of computational locality during simulation. We use the methodology of the AlgoWiki project (algowiki-project.org) to analyze the algorithm. This methodology consists of theoretical (sequential and parallel complexity, macro structure, and visual informational graph) and experimental (locality and memory access, scalability and more specific dynamic characteristics) parts. Experimental part was made by using the petascale Lomonosov supercomputer (Moscow State University, Russia). We show that the simulation of quantum gates is a good base for the research and testing of the development methods for data intense parallel software, and considered methodology of the analysis can be successfully used for the improvement of the algorithms in quantum information science.
Numerical simulation of baseflow modification due to effects of ...
African Journals Online (AJOL)
Numerical simulation of baseflow modification due to effects of sediment yield. ... Physically-based mathematical modelling affords the opportunity to look at this kind of interaction, which should be simulated by deterministic responses of both water and fluvial processes. In addition to simulating the streamflow and ...
Numerical simulation for quenching meshes with TONUS platform
International Nuclear Information System (INIS)
Bin, Chen; Hongxing, Yu
2009-01-01
For mitigation of hydrogen risks during severe accidents to protect the integrity of containment, PAR and ignitors are used in current advanced nuclear power plants. But multiple combustions induced by ignitors and consequent DDT phenomena are not practically eliminated. An innovative design call 'quenching meshes' is considered to confine hydrogen flame within one compartment by metallic meshes, so that hazardous flame propagation can be prevented. The numerical simulation results based on discretization of the full Navier-Stokes equations with global one-step reaction represented by Arrhenius laminar combustion model have shown the possibility of flame quenching 'numerically'. This is achieved via multiplication of the combustion rate expression by a Heaviside function having an ignition temperature as a parameter. Qualitative behavior of the computed flow shows that the flame velocity diminishes while passing through a quenching mesh, while qualitative analysis based on the energy balance reveals the mechanism of flame quenching. All the above analysis has been performed for a stoichiometric mixture and normal initial pressure and temperature for initial conditions. For further research we would like to suggest the investigation of the influence of the mixture composition, initial pressure and/or temperature on the quenching criteria
Numerical simulations of progressive hardening by using ABAQUS FEA software
Directory of Open Access Journals (Sweden)
Domański Tomasz
2018-01-01
Full Text Available The paper concerns numerical simulations of progressive hardening include phase transformations in solid state of steel. Abaqus FEA software is used for numerical analysis of temperature field and phase transformations. Numerical subroutines, written in fortran programming language are used in computer simulations where models of the distribution of movable heat source, kinetics of phase transformations in solid state as well as thermal and structural strain are implemented. Model for evaluation of fractions of phases and their kinetics is based on continuous heating diagram and continuous cooling diagram. The numerical analysis of thermal fields, phase fractions and strain associated progressive hardening of elements made of steel were done.
Numerical simulations of nanostructured gold films
DEFF Research Database (Denmark)
Repän, Taavi; Frydendahl, Christian; Novikov, Sergey M.
2017-01-01
We present an approach to analyse near-field effects on nanostructured gold films by finite element simulations. The studied samples are formed by fabricating gold films near the percolation threshold and then applying laser damage. Resulting samples have complicated structures, which...
Numerical simulation of cross field amplifiers
International Nuclear Information System (INIS)
Eppley, K.
1990-01-01
Cross field amplifiers (CFA) have been used in many applications where high power, high frequency microwaves are needed. Although these tubes have been manufactured for decades, theoretical analysis of their properties is not as highly developed as for other microwave devices such as klystrons. One feature distinguishing cross field amplifiers is that the operating current is produced by secondary emission from a cold cathode. This removes the need for a heater and enables the device to act as a switch tube, drawing no power until the rf drive is applied. However, this method of generating the current does complicate the simulation. We are developing a simulation model of cross field amplifiers using the PIC code CONDOR. We simulate an interaction region, one traveling wavelength long, with periodic boundary conditions. An electric field with the appropriate phase velocity is imposed on the upper boundary of the problem. Evaluation of the integral of E·J gives the power interchanged between the wave and the beam. Given the impedance of the structure, we then calculate the change in the traveling wave field. Thus we simulate the growth of the wave through the device. The main advance of our model over previous CFA simulations is the realistic tracking of absorption and secondary emission. The code uses experimental curves to calculate secondary production as a function of absorbed energy, with a theoretical expression for the angular dependence. We have used this code to model the 100 MW X-band CFA under construction at SLAC, as designed by Joseph Feinstein and Terry Lee. We are examining several questions of practical interest, such as the power and spectrum of absorbed electrons, the minimum traveling wave field needed to initiate spoke formation, and the variation of output power with dc voltage, anode-cathode gap, and magnetic field. 5 refs., 8 figs
Numerical simulation of avascular tumor growth
Energy Technology Data Exchange (ETDEWEB)
Slezak, D Fernandez; Suarez, C; Soba, A; Risk, M; Marshall, G [Laboratorio de Sistemas Complejos, Departamento de Computacion, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (C1428EGA) Buenos Aires (Argentina)
2007-11-15
A mathematical and numerical model for the description of different aspects of microtumor development is presented. The model is based in the solution of a system of partial differential equations describing an avascular tumor growth. A detailed second-order numeric algorithm for solving this system is described. Parameters are swiped to cover a range of feasible physiological values. While previous published works used a single set of parameters values, here we present a wide range of feasible solutions for tumor growth, covering a more realistic scenario. The model is validated by experimental data obtained with a multicellular spheroid model, a specific type of in vitro biological model which is at present considered to be optimum for the study of complex aspects of avascular microtumor physiology. Moreover, a dynamical analysis and local behaviour of the system is presented, showing chaotic situations for particular sets of parameter values at some fixed points. Further biological experiments related to those specific points may give potentially interesting results.
Numerical Simulation of 3-D Wave Crests
Institute of Scientific and Technical Information of China (English)
YU Dingyong; ZHANG Hanyuan
2003-01-01
A clear definition of 3-D wave crest and a description of the procedures to detect the boundary of wave crest are presented in the paper. By using random wave theory and directional wave spectrum, a MATLAB-platformed program is designed to simulate random wave crests for various directional spectral conditions in deep water. Statistics of wave crests with different directional spreading parameters and different directional functions are obtained and discussed.
Numerical simulation of distributed parameter processes
Colosi, Tiberiu; Unguresan, Mihaela-Ligia; Muresan, Vlad
2013-01-01
The present monograph defines, interprets and uses the matrix of partial derivatives of the state vector with applications for the study of some common categories of engineering. The book covers broad categories of processes that are formed by systems of partial derivative equations (PDEs), including systems of ordinary differential equations (ODEs). The work includes numerous applications specific to Systems Theory based on Mpdx, such as parallel, serial as well as feed-back connections for the processes defined by PDEs. For similar, more complex processes based on Mpdx with PDEs and ODEs as components, we have developed control schemes with PID effects for the propagation phenomena, in continuous media (spaces) or discontinuous ones (chemistry, power system, thermo-energetic) or in electro-mechanics (railway – traction) and so on. The monograph has a purely engineering focus and is intended for a target audience working in extremely diverse fields of application (propagation phenomena, diffusion, hydrodyn...
Fluid dynamics theory, computation, and numerical simulation
Pozrikidis, C
2017-01-01
This book provides an accessible introduction to the basic theory of fluid mechanics and computational fluid dynamics (CFD) from a modern perspective that unifies theory and numerical computation. Methods of scientific computing are introduced alongside with theoretical analysis and MATLAB® codes are presented and discussed for a broad range of topics: from interfacial shapes in hydrostatics, to vortex dynamics, to viscous flow, to turbulent flow, to panel methods for flow past airfoils. The third edition includes new topics, additional examples, solved and unsolved problems, and revised images. It adds more computational algorithms and MATLAB programs. It also incorporates discussion of the latest version of the fluid dynamics software library FDLIB, which is freely available online. FDLIB offers an extensive range of computer codes that demonstrate the implementation of elementary and advanced algorithms and provide an invaluable resource for research, teaching, classroom instruction, and self-study. This ...
Partial Differential Equations Modeling and Numerical Simulation
Glowinski, Roland
2008-01-01
This book is dedicated to Olivier Pironneau. For more than 250 years partial differential equations have been clearly the most important tool available to mankind in order to understand a large variety of phenomena, natural at first and then those originating from human activity and technological development. Mechanics, physics and their engineering applications were the first to benefit from the impact of partial differential equations on modeling and design, but a little less than a century ago the Schrödinger equation was the key opening the door to the application of partial differential equations to quantum chemistry, for small atomic and molecular systems at first, but then for systems of fast growing complexity. Mathematical modeling methods based on partial differential equations form an important part of contemporary science and are widely used in engineering and scientific applications. In this book several experts in this field present their latest results and discuss trends in the numerical analy...
Direct Numerical Simulations of Statistically Stationary Turbulent Premixed Flames
Im, Hong G.; Arias, Paul G.; Chaudhuri, Swetaprovo; Uranakara, Harshavardhana A.
2016-01-01
Direct numerical simulations (DNS) of turbulent combustion have evolved tremendously in the past decades, thanks to the rapid advances in high performance computing technology. Today’s DNS is capable of incorporating detailed reaction mechanisms
Numerical simulations of a large scale oxy-coal burner
Energy Technology Data Exchange (ETDEWEB)
Chae, Taeyoung [Korea Institute of Industrial Technology, Cheonan (Korea, Republic of). Energy System R and D Group; Sungkyunkwan Univ., Suwon (Korea, Republic of). School of Mechanical Engineering; Park, Sanghyun; Ryu, Changkook [Sungkyunkwan Univ., Suwon (Korea, Republic of). School of Mechanical Engineering; Yang, Won [Korea Institute of Industrial Technology, Cheonan (Korea, Republic of). Energy System R and D Group
2013-07-01
Oxy-coal combustion is one of promising carbon dioxide capture and storage (CCS) technologies that uses oxygen and recirculated CO{sub 2} as an oxidizer instead of air. Due to difference in physical properties between CO{sub 2} and N{sub 2}, the oxy-coal combustion requires development of burner and boiler based on fundamental understanding of the flame shape, temperature, radiation and heat flux. For design of a new oxy-coal combustion system, computational fluid dynamics (CFD) is an essential tool to evaluate detailed combustion characteristics and supplement experimental results. In this study, CFD analysis was performed to understand the combustion characteristics inside a tangential vane swirl type 30 MW coal burner for air-mode and oxy-mode operations. In oxy-mode operations, various compositions of primary and secondary oxidizers were assessed which depended on the recirculation ratio of flue gas. For the simulations, devolatilization of coal and char burnout by O{sub 2}, CO{sub 2} and H{sub 2}O were predicted with a Lagrangian particle tracking method considering size distribution of pulverized coal and turbulent dispersion. The radiative heat transfer was solved by employing the discrete ordinate method with the weighted sum of gray gases model (WSGGM) optimized for oxy-coal combustion. In the simulation results for oxy-model operation, the reduced swirl strength of secondary oxidizer increased the flame length due to lower specific volume of CO{sub 2} than N{sub 2}. The flame length was also sensitive to the flow rate of primary oxidizer. The oxidizer without N{sub 2} that reduces thermal NO{sub x} formation makes the NO{sub x} lower in oxy-mode than air-mode. The predicted results showed similar trends with measured temperature profiles for various oxidizer compositions. Further numerical investigations are required to improve the burner design combined with more detailed experimental results.
NUMERICAL METHODS FOR THE SIMULATION OF HIGH INTENSITY HADRON SYNCHROTRONS.
Energy Technology Data Exchange (ETDEWEB)
LUCCIO, A.; D' IMPERIO, N.; MALITSKY, N.
2005-09-12
Numerical algorithms for PIC simulation of beam dynamics in a high intensity synchrotron on a parallel computer are presented. We introduce numerical solvers of the Laplace-Poisson equation in the presence of walls, and algorithms to compute tunes and twiss functions in the presence of space charge forces. The working code for the simulation here presented is SIMBAD, that can be run as stand alone or as part of the UAL (Unified Accelerator Libraries) package.
Numerical simulation and physical aspects of supersonic vortex breakdown
Liu, C. H.; Kandil, O. A.; Kandil, H. A.
1993-01-01
Existing numerical simulations and physical aspects of subsonic and supersonic vortex-breakdown modes are reviewed. The solution to the problem of supersonic vortex breakdown is emphasized in this paper and carried out with the full Navier-Stokes equations for compressible flows. Numerical simulations of vortex-breakdown modes are presented in bounded and unbounded domains. The effects of different types of downstream-exit boundary conditions are studied and discussed.
Numerical simulation of exploding pusher targets
Atzeni, S.; Rosenberg, M. J.; Gatu Johnson, M.; Petrasso, R. D.
2017-10-01
Exploding pusher targets, i.e. gas-filled large aspect-ratio glass or plastic shells, driven by a strong laser-generated shock, are widely used as pulsed sources of neutrons and fast charged particles. Recent experiments on exploding pushers provided evidence for the transition from a purely fluid behavior to a kinetic one. Indeed, fluid models largely overpredict yield and temperature as the Knudsen number Kn (ratio of ion mean-free path to compressed gas radius) is comparable or larger than one. At Kn = 0.3 - 1, fluid codes reasonably estimate integral quantities as yield and neutron-averaged temperatures, but do not reproduce burn radii, burn profiles and DD/DHe3 yield ratio. This motivated a detailed simulation study of intermediate-Kn exploding pushers. We will show how simulation results depend on models for laser-interaction, electron conductivity (flux-limited local vs nonlocal), viscosity (physical vs artificial), and ion mixing. Work partially supported by Sapienza Project C26A15YTMA, Sapienza 2016 (n. 257584), and Eurofusion Project AWP17-ENR-IFE-CEA-01.
Experimental and Numerical Study of FRP Encased Composite Concrete Columns
Directory of Open Access Journals (Sweden)
Mohsen Ishaghian
2017-02-01
Full Text Available A new type of composite column is presented and assessed through experimental testing and numerical modeling. The objective of this research is to investigate design options for a composite column without the use of ferrous materials. This is to avoid the current problem of deterioration of concrete due to expansion of rusting reinforcement members. Such a target can be achieved by replacing the steel reinforcement of concrete columns with pultruded I-shape glass FRP structural sections. The composite column utilizes a glass FRP tube that surrounds a pultruded I-section glass FRP, which is subsequently filled with concrete. The GFRP tube acts as a stay-in-place form in addition to providing confinement to the concrete. A total of four composite columns were tested under monotonic axial loading. The experimental ultimate capacity of each of the tested composite column was compared to the predicted numerical capacity using ANSYS program. The comparison showed that the predicted numerical values were in good agreement with the experimental ones.
Direct Numerical Simulations of turbulent flow in a driven cavity
Verstappen, R.; Wissink, J.G.; Cazemier, W.; Veldman, A.E.P.
Direct numerical simulations (DNS) of 2 and 3D turbulent flows in a lid-driven cavity have been performed. DNS are numerical solutions of the unsteady (here: incompressible) Navier-Stokes equations that compute the evolution of all dynamically significant scales of motion. In view of the large
Numerical simulation of a precessing vortex breakdown
International Nuclear Information System (INIS)
Jochmann, P.; Sinigersky, A.; Hehle, M.; Schaefer, O.; Koch, R.; Bauer, H.-J.
2006-01-01
The objective of this work is to present the results of time-dependent numerical predictions of a turbulent symmetry breaking vortex breakdown in a realistic gas turbine combustor. The unsteady Reynolds-averaged Navier-Stokes (URANS) equations are solved by using the k-ε two-equation model as well as by a full second-order closure using the Reynolds stress model of Speziale, Sarkar and Gatski (SSG). The results for a Reynolds number of 5.2 x 10 4 , a swirl number of 0.52 and an expansion ratio of 5 show that the flow is emerging from the swirler as a spiral gyrating around a zone of strong recirculation which is also asymmetric and precessing. These flow structures which are typical for the spiral type (S-type) vortex breakdown have been confirmed by PIV and local LDA measurements in a corresponding experimental setup. Provided that high resolution meshes are employed the calculations with both turbulence models are capable to reproduce the spatial and temporal dynamics of the flow
Numerical simulation of superconducting accelerator magnets
Kurz, Stefan
2002-01-01
Modeling and simulation are key elements in assuring the fast and successful design of superconducting magnets. After a general introduction the paper focuses on electromagnetic field computations, which are an indipensable tool in the design process. A technique which is especially well suited for the accurate computation of magnetic fields in superconducting magnets is presented. This method couples Boundary Elements (BEM) which discretize the surface of the iron yoke and Finite Elements (FEM) for the modeling of the non linear interior of the yoke. The formulation is based on a total magnetic scalar potential throughout the whole problem domain. The results for a short dipole model are presented and compared to previous results, which have been obtained from a similar BEM-FEM coupled vector potential formulation. 10 Refs. --- 25 --- AN
Numerical simulation of aeolian sand ripples
International Nuclear Information System (INIS)
Kang Liqiang; Guo Liejin
2004-01-01
With a new horizontal saltation displacement vector, a model is implemented to simulate the initiation and evolution of aeolian sand ripples. In the model, saltation distance considers the effects of surface height and slope. A linear stability analysis is also carried out for formation of sand ripples. The results show that, the model can be able to successfully reproduce sand ripples which can increase in scale by merging of small ripples. The linear stability analysis indicates that sand ripples appear when the relaxation rate parameter is below a threshold value and wind strength parameter is larger than a critical value. The results also verified that the formation of sand ripples is a self-organization process
A numerical relativity scheme for cosmological simulations
Daverio, David; Dirian, Yves; Mitsou, Ermis
2017-12-01
Cosmological simulations involving the fully covariant gravitational dynamics may prove relevant in understanding relativistic/non-linear features and, therefore, in taking better advantage of the upcoming large scale structure survey data. We propose a new 3 + 1 integration scheme for general relativity in the case where the matter sector contains a minimally-coupled perfect fluid field. The original feature is that we completely eliminate the fluid components through the constraint equations, thus remaining with a set of unconstrained evolution equations for the rest of the fields. This procedure does not constrain the lapse function and shift vector, so it holds in arbitrary gauge and also works for arbitrary equation of state. An important advantage of this scheme is that it allows one to define and pass an adaptation of the robustness test to the cosmological context, at least in the case of pressureless perfect fluid matter, which is the relevant one for late-time cosmology.
Batman-cracks. Observations and numerical simulations
Selvadurai, A. P. S.; Busschen, A. Ten; Ernst, L. J.
1991-05-01
To ensure mechanical strength of fiber reinforced plastics (FRP), good adhesion between fibers and the matrix is considered to be an essential requirement. An efficient test of fiber-matrix interface characterization is the fragmentation test which provides information about the interface slip mechanism. This test consists of the longitudinal loading of a single fiber which is embedded in a matrix specimen. At critical loads the fiber experiences fragmentation. This fragmentation will terminate depending upon the shear-slip strength of the fiber-matrix adhesion, which is inversely proportional to average fragment lengths. Depending upon interface strength characteristics either bond or slip matrix fracture can occur at the onset of fiber fracture. Certain particular features of matrix fracture are observed at the locations of fiber fracture in situations where there is sufficient interface bond strength. These refer to the development of fractures with a complex surface topography. The experimental procedure involved in the fragmentation tests is discussed and the boundary element technique to examine the development of multiple matrix fractures at the fiber fracture locations is examined. The mechanics of matrix fracture is examined. When bond integrity is maintained, a fiber fracture results in a matrix fracture. The matrix fracture topography in a fragmentation test is complex; however, simplified conoidal fracture patterns can be used to investigate the crack extension phenomena. Via a mixed-mode fracture criterion, the generation of a conoidal fracture pattern in the matrix is investigated. The numerical results compare favorably with observed experimental data derived from tests conducted on fragmentation test specimens consisting of a single glass fiber which is embedded in a polyester matrix.
Numerical simulation of anisotropic polymeric foams
Directory of Open Access Journals (Sweden)
Volnei Tita
Full Text Available This paper shows in detail the modelling of anisotropic polymeric foam under compression and tension loadings, including discussions on isotropic material models and the entire procedure to calibrate the parameters involved. First, specimens of poly(vinyl chloride (PVC foam were investigated through experimental analyses in order to understand the mechanical behavior of this anisotropic material. Then, isotropic material models available in the commercial software AbaqusTM were investigated in order to verify their ability to model anisotropic foams and how the parameters involved can influence the results. Due to anisotropy, it is possible to obtain different values for the same parameter in the calibration process. The obtained set of parameters are used to calibrate the model according to the application of the structure. The models investigated showed minor and major limitations to simulate the mechanical behavior of anisotropic PVC foams under compression, tension and multi-axial loadings. Results show that the calibration process and the choice of the material model applied to the polymeric foam can provide good quantitative results and save project time. Results also indicate what kind and order of error one will get if certain choices are made throughout the modelling process. Finally, even though the developed calibration procedure is applied to specific PVC foam, it still outlines a very broad drill to analyze other anisotropic cellular materials.
Parallel Numerical Simulations of Water Reservoirs
Torres, Pedro; Mangiavacchi, Norberto
2010-11-01
The study of the water flow and scalar transport in water reservoirs is important for the determination of the water quality during the initial stages of the reservoir filling and during the life of the reservoir. For this scope, a parallel 2D finite element code for solving the incompressible Navier-Stokes equations coupled with scalar transport was implemented using the message-passing programming model, in order to perform simulations of hidropower water reservoirs in a computer cluster environment. The spatial discretization is based on the MINI element that satisfies the Babuska-Brezzi (BB) condition, which provides sufficient conditions for a stable mixed formulation. All the distributed data structures needed in the different stages of the code, such as preprocessing, solving and post processing, were implemented using the PETSc library. The resulting linear systems for the velocity and the pressure fields were solved using the projection method, implemented by an approximate block LU factorization. In order to increase the parallel performance in the solution of the linear systems, we employ the static condensation method for solving the intermediate velocity at vertex and centroid nodes separately. We compare performance results of the static condensation method with the approach of solving the complete system. In our tests the static condensation method shows better performance for large problems, at the cost of an increased memory usage. Performance results for other intensive parts of the code in a computer cluster are also presented.
NUMERICAL SIMULATION OF ICE ACCRETION ON AIRFOIL
Directory of Open Access Journals (Sweden)
Nicusor ALEXANDRESCU
2009-09-01
Full Text Available This work consists in the simulation of the ice accretion in the leading edge of aerodynamic profiles and our proposed model encompasses: geometry generation, calculation of the potential flow around the body, boundary layer thickness computation, water droplet trajectory computation, heat and mass balances and the consequent modification of the geometry by the ice growth. The flow calculation is realized with panel methods, using only segments defined over the body contour. The viscous effects are considered using the Karman-Pohlhausen method for the laminar boundary layer. The local heat transfer coefficient is obtained by applying the Smith-Spalding method for the thermal boundary layer. The ice accretion limits and the collection efficiency are determined by computing water droplet trajectories impinging the surface. The heat transfer process is analyzed with an energy and a mass balance in each segment defining the body. Finally, the geometry is modified by the addition of the computed ice thickness to the respective panel. The process by repeating all the steps. The model validation is done using a selection of problems with experimental solution, CIRA (the CESAR project. Hereinafter, results are obtained for different aerodynamic profiles, angles of attack and meteorological parameters
Direct numerical simulation of non-isothermal flow through dense bidisperse random arrays of spheres
Tavassoli Estahbanati, H.; Peters, E.A.J.F.; Kuipers, J.A.M.
2017-01-01
Extensive direct numerical simulations were performed to obtain the heat transfer coefficients (HTC) of bidisperse random arrays of spheres. We have calculated the HTC for a range of compositions and solids volume fractions for mixtures of spheres with a size ratio of 1:2. The Reynolds numbers are
Tests of numerical simulation algorithms for the Kubo oscillator
International Nuclear Information System (INIS)
Fox, R.F.; Roy, R.; Yu, A.W.
1987-01-01
Numerical simulation algorithms for multiplicative noise (white or colored) are tested for accuracy against closed-form expressions for the Kubo oscillator. Direct white noise simulations lead to spurious decay of the modulus of the oscillator amplitude. A straightforward colored noise algorithm greatly reduces this decay and also provides highly accurate results in the white noise limit
Three-Dimensional Numerical Simulation to Mud Turbine for LWD
Yao, Xiaojiang; Dong, Jingxin; Shang, Jie; Zhang, Guanqi
Hydraulic performance analysis was discussed for a type of turbine on generator used for LWD. The simulation models were built by CFD analysis software FINE/Turbo, and full three-dimensional numerical simulation was carried out for impeller group. The hydraulic parameter such as power, speed and pressure drop, were calculated in two kinds of medium water and mud. Experiment was built in water environment. The error of numerical simulation was less than 6%, verified by experiment. Based on this rationalization proposals would be given to choice appropriate impellers, and the rationalization of methods would be explored.
Mitigation of numerical noise for beam loss simulations
Kesting, Frederik
2017-01-01
Numerical noise emerges in self-consistent simulations of charged particles, and its mitigation is investigated since the first numerical studies in plasma physics. In accelerator physics, recent studies find an artificial diffusion of the particle beam due to numerical noise in particle-in-cell tracking, which is of particular importance for high intensity machines with a long storage time, as the SIS100 at FAIR or in context of the LIU upgrade at CERN. In beam loss simulations for these projects artificial effects must be distinguished from physical beam loss. Therefore, it is important to relate artificial diffusion to artificial beam loss, and to choose simulation parameters such that physical beam loss is well resolved. As a practical tool, we therefore suggest a scaling law to find optimal simulation parameters for a given maximum percentage of acceptable artificial beam loss.
Numerical simulation of random stresses on an annular turbulent flow
International Nuclear Information System (INIS)
Marti-Moreno, Marta
2000-01-01
The flow along a circular cylinder may induce structural vibrations. For the predictive analysis of such vibrations, the turbulent forcing spectrum needs to be characterized. The aim of this work is to study the turbulent fluid forces acting on a single tube in axial flow. More precisely we have performed numerical simulations of an annular flow. These simulations were carried out on a cylindrical staggered mesh by a finite difference method. We consider turbulent flow with Reynolds number up to 10 6 . The Large Eddy Simulation Method has been used. A survey of existent experiments showed that hydraulic diameter acts as an important parameter. We first showed the accuracy of the numerical code by reproducing the experiments of Mulcahy. The agreement between pressure spectra from computations and from experiments is good. Then, we applied this code to simulate new numerical experiments varying the hydraulic diameter and the flow velocity. (author) [fr
Practical considerations in developing numerical simulators for thermal recovery
Energy Technology Data Exchange (ETDEWEB)
Abou-Kassem, J.H. [Chemical and Petroleum Engineering Department, UAE University, Al-Ain (United Arab Emirates)
1996-08-15
Numerical simulation of steam injection and in-situ combustion-based oil recovery processes is of great importance in project design. Development of such numerical simulators is an on-going process, with improvements made as the process description becomes more complete, and also as better methods are devised to resolve certain numerical difficulties. This paper addresses some of the latter, and based on the author`s experience gives useful guidelines for developing more efficient numerical simulators of steam injection and in-situ combustion. The paper takes up a series of questions related to simulating thermal processes. Included are: the elimination of constraint equations at the matrix level, phase change, steam injection rate, alternative treatments of heat loss, relative permeabilities and importance of hysteresis effects, improved solutions to the grid orientation problem and other simulation problems such as potential inversion, grid block size, time-step size control and induced fractures. The points discussed in the paper should be of use to both simulator developers and users alike, and will lead to a better understanding of simulation results
How to determine composite material properties using numerical homogenization
DEFF Research Database (Denmark)
Andreassen, Erik; Andreasen, Casper Schousboe
2014-01-01
Numerical homogenization is an efficient way to determine effective macroscopic properties, such as the elasticity tensor, of a periodic composite material. In this paper an educational description of the method is provided based on a short, self-contained Matlab implementation. It is shown how...... the basic code, which computes the effective elasticity tensor of a two material composite, where one material could be void, is easily extended to include more materials. Furthermore, extensions to homogenization of conductivity, thermal expansion, and fluid permeability are described in detail. The unit...
Numerical investigation of porous materials composites reinforced with natural fibers
Chikhi, M.; Metidji, N.; Mokhtari, F.; Merzouk, N. k.
2018-05-01
The present article tends to predict the effective thermal properties of porous biocomposites materials. The composites matrix consists on porous materials namely gypsum and the reinforcement is a natural fiber as date palm fibers. The numerical study is done using Comsol software resolving the heat transfer equation. The results are fitted with theoretical model and experimental results. The results of this study indicate that the porosity has an effect on the Effective thermal conductivity biocompoites.
Directory of Open Access Journals (Sweden)
Xiaorong eCheng
2015-11-01
Full Text Available A recent hierarchical model of numerical processing, initiated by Fischer and Brugger (2011 and Fisher (2012, suggested that situated factors, such as different body postures and body movements, can influence the magnitude representation and bias numerical processing. Indeed, Loetscher and colleagues (2008 found that participants’ behavior in a random number generation (RNG task was biased by head rotations. More small numbers were reported after leftward than rightward head turns, i.e. a motion–numerical compatibility effect. Here, by carrying out two experiments, we explored whether similar motion–numerical compatibility effects exist for movements of other important body components, e.g. arms, and for composite body movements as well, which are basis for complex human activities in many ecologically meaningful situations. In Experiment 1, a motion-numerical compatibility effect was observed for lateral rotations of two body components, i.e., the head and arms. Relatively large numbers were reported after making rightward compared to leftward movements for both lateral head and arm turns. The motion-numerical compatibility effect was observed again in Experiment 2 when participants were asked to perform composite body movements of congruent movement directions, e.g., simultaneous head left turns and arm left turns. However, it disappeared when the movement directions were incongruent, e.g., simultaneous head left turns and arm right turns. Taken together, our results extended Loetscher et al.'s (2008 finding by demonstrating that their effect is effector-general and exists for arm movements. Moreover, our study reveals for the first time that the impact of spatial information on numerical processing induced by each of the two sensorimotor-based situated factors, e.g., a lateral head turn and a lateral arm turn, can cancel each other out.
Direct Numerical Simulations of Turbulent Autoigniting Hydrogen Jets
Asaithambi, Rajapandiyan
Autoignition is an important phenomenon and a tool in the design of combustion engines. To study autoignition in a canonical form a direct numerical simulation of a turbulent autoigniting hydrogen jet in vitiated coflow conditions at a jet Reynolds number of 10,000 is performed. A detailed chemical mechanism for hydrogen-air combustion and non-unity Lewis numbers for species transport is used. Realistic inlet conditions are prescribed by obtaining the velocity eld from a fully developed turbulent pipe flow simulation. To perform this simulation a scalable modular density based method for direct numerical simulation (DNS) and large eddy simulation (LES) of compressible reacting flows is developed. The algorithm performs explicit time advancement of transport variables on structured grids. An iterative semi-implicit time advancement is developed for the chemical source terms to alleviate the chemical stiffness of detailed mechanisms. The algorithm is also extended from a Cartesian grid to a cylindrical coordinate system which introduces a singularity at the pole r = 0 where terms with a factor 1/r can be ill-defined. There are several approaches to eliminate this pole singularity and finite volume methods can bypass this issue by not storing or computing data at the pole. All methods however face a very restrictive time step when using a explicit time advancement scheme in the azimuthal direction (theta) where the cell sizes are of the order DelrDeltheta. We use a conservative finite volume based approach to remove the severe time step restriction imposed by the CFL condition by merging cells in the azimuthal direction. In addition, fluxes in the radial direction are computed with an implicit scheme to allow cells to be clustered along the jet's shear layer. This method is validated and used to perform the large scale turbulent reacting simulation. The resulting flame structure is found to be similar to a turbulent diusion flame but stabilized by autoignition at the
Polymer Composites Corrosive Degradation: A Computational Simulation
Chamis, Christos C.; Minnetyan, Levon
2007-01-01
A computational simulation of polymer composites corrosive durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured pH factor and is represented by voids, temperature and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.
Comparison of GPU-Based Numerous Particles Simulation and Experiment
International Nuclear Information System (INIS)
Park, Sang Wook; Jun, Chul Woong; Sohn, Jeong Hyun; Lee, Jae Wook
2014-01-01
The dynamic behavior of numerous grains interacting with each other can be easily observed. In this study, this dynamic behavior was analyzed based on the contact between numerous grains. The discrete element method was used for analyzing the dynamic behavior of each particle and the neighboring-cell algorithm was employed for detecting their contact. The Hertzian and tangential sliding friction contact models were used for calculating the contact force acting between the particles. A GPU-based parallel program was developed for conducting the computer simulation and calculating the numerous contacts. The dam break experiment was performed to verify the simulation results. The reliability of the program was verified by comparing the results of the simulation with those of the experiment
Numerical simulation of gasket behaviour during severe accidents (ATHERMIP project)
International Nuclear Information System (INIS)
Castro Lopez, Fernando; Orden Martinez, Alfredo
1998-01-01
This paper summarises the work carried out to numerically simulate the thermo-mechanical behaviour of sealing gasket in large containment penetrations during a severe accident. The gasket material is an elastomeric material and the thermo-mechanical characterization was based on experimentation. The difficulty of numerical simulation lies in the high non-linearity of the analysis, due on one hand, to the high strain levels reached, and on the other, to stiffness changes introduced by contact/takeoff indicators. Also, the stiffness parameters of the gasket material are not constant, but are subject to changes, both regarding the strain level and the environmental conditions (temperature, radiation). The results obtained allow presenting a calculation model capable of simulating and explaining the behaviour of the sealing gasket during a severe accident. Also, the failure hypothesis numerically obtained was environmentally validated. (author)
Numerical Simulation of Anisotropic Preheating Ablative Rayleigh–Taylor Instability
International Nuclear Information System (INIS)
Li-Feng, Wang; Wen-Hua, Ye; Ying-Jun, Li
2010-01-01
The linear growth rate of the anisotropic preheating ablative Rayleigh–Taylor instability (ARTI) is studied by numerical simulations. The preheating model κ(T) = κ SH [1 + f(T)] is applied, where f(T) is the preheating function interpreting the preheating tongue effect in the cold plasma ahead of the ablative front. An arbitrary coefficient D is introduced in the energy equation to study the influence of transverse thermal conductivity on the growth of the ARTI. We find that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. Numerical simulations exhibit a significant stabilization of the ablation front by improving the transverse thermal conduction. Our results are in general agreement with the theory analysis and numerical simulations by Masse [Phys. Rev. Lett. 98 (2007) 245001]. (physics of gases, plasmas, and electric discharges)
Numerical simulation of anisotropic preheating ablative Rayleigh-Taylor instability
International Nuclear Information System (INIS)
Wang Lifeng; Ye Wenhua; Li Yingjun
2010-01-01
The linear growth rate of the anisotropic preheating ablative Rayleigh-Taylor instability (ARTI) is studied by numerical simulations. The preheating model κ(T)=κ SH [1+f(T)] is applied, where f(T) is the preheating function interpreting the preheating tongue effect in the cold plasma ahead of the ablative front. An arbitrary coefficient D is introduced in the energy equation to study the influence of transverse thermal conductivity on the growth of the ARTI. We find that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. Numerical simulations exhibit a significant stabilization of the ablation front by improving the transverse thermal conduction. Our results are in general agreement with the theory analysis and numerical simulations by Masse. (authors)
Vortex locking in direct numerical simulations of quantum turbulence.
Morris, Karla; Koplik, Joel; Rouson, Damian W I
2008-07-04
Direct numerical simulations are used to examine the locking of quantized superfluid vortices and normal fluid vorticity in evolving turbulent flows. The superfluid is driven by the normal fluid, which undergoes either a decaying Taylor-Green flow or a linearly forced homogeneous isotropic turbulent flow, although the back reaction of the superfluid on the normal fluid flow is omitted. Using correlation functions and wavelet transforms, we present numerical and visual evidence for vortex locking on length scales above the intervortex spacing.
Numerical simulation on quantum turbulence created by an oscillating object
Energy Technology Data Exchange (ETDEWEB)
Fujiyama, S; Tsubota, M [Department of Physics, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka City, Osaka (Japan)], E-mail: fujiyama@sci.osaka-cu.ac.jp
2009-02-01
We have conducted a numerical simulation of vortex dynamics in superfluid {sup 4}He in the presence of an oscillating sphere. The experiment on a vibrating wire that measured the transition from laminar to turbulent flow is modelled in our simulations. The simulation exhibits the details of vortex growth by the oscillating sphere. Our result also shows that a more realistic modelling may change the destiny of the vortex rings detached from the sphere. We have evaluated the force driven by the sphere in the simulation and have confirmed the onset of the quantum turbulence.
Recent developments in numerical simulation techniques of thermal recovery processes
Energy Technology Data Exchange (ETDEWEB)
Tamim, M. [Bangladesh University of Engineering and Technology, Bangladesh (Bangladesh); Abou-Kassem, J.H. [Chemical and Petroleum Engineering Department, UAE University, Al-Ain 17555 (United Arab Emirates); Farouq Ali, S.M. [University of Alberta, Alberta (Canada)
2000-05-01
Numerical simulation of thermal processes (steam flooding, steam stimulation, SAGD, in-situ combustion, electrical heating, etc.) is an integral part of a thermal project design. The general tendency in the last 10 years has been to use commercial simulators. During the last decade, only a few new models have been reported in the literature. More work has been done to modify and refine solutions to existing problems to improve the efficiency of simulators. The paper discusses some of the recent developments in simulation techniques of thermal processes such as grid refinement, grid orientation, effect of temperature on relative permeability, mathematical models, and solution methods. The various aspects of simulation discussed here promote better understanding of the problems encountered in the simulation of thermal processes and will be of value to both simulator users and developers.
Direct numerical simulation of noninvasive channel healing in electrical field
Wang, Yi
2017-11-25
Noninvasive channel healing is a new idea to repair the broken pipe wall, using external electric fields to drive iron particles to the destination. The repair can be done in the normal operation of the pipe flow without any shutdown of the pipeline so that this method can be a potentially efficient and safe technology of pipe healing. However, the real application needs full knowledge of healing details. Numerical simulation is an effective method. Thus, in this research, we first established a numerical model for noninvasive channel healing technology to represent fluid–particle interaction. The iron particles can be attached to a cracking area by external electrostatic forces or can also be detached by mechanical forces from the fluid. When enough particles are permanently attached on the cracking area, the pipe wall can be healed. The numerical criterion of the permanent attachment is discussed. A fully three-dimensional finite difference framework of direct numerical simulation is established and applied to different cases to simulate the full process of channel healing. The impact of Reynolds number and particle concentration on the healing process is discussed. This numerical investigation provides valuable reference and tools for further simulation of real pipe healing in engineering.
On the elimination of numerical Cerenkov radiation in PIC simulations
International Nuclear Information System (INIS)
Greenwood, Andrew D.; Cartwright, Keith L.; Luginsland, John W.; Baca, Ernest A.
2004-01-01
Particle-in-cell (PIC) simulations are a useful tool in modeling plasma in physical devices. The Yee finite difference time domain (FDTD) method is commonly used in PIC simulations to model the electromagnetic fields. However, in the Yee FDTD method, poorly resolved waves at frequencies near the cut off frequency of the grid travel slower than the physical speed of light. These slowly traveling, poorly resolved waves are not a problem in many simulations because the physics of interest are at much lower frequencies. However, when high energy particles are present, the particles may travel faster than the numerical speed of their own radiation, leading to non-physical, numerical Cerenkov radiation. Due to non-linear interaction between the particles and the fields, the numerical Cerenkov radiation couples into the frequency band of physical interest and corrupts the PIC simulation. There are two methods of mitigating the effects of the numerical Cerenkov radiation. The computational stencil used to approximate the curl operator can be altered to improve the high frequency physics, or a filtering scheme can be introduced to attenuate the waves that cause the numerical Cerenkov radiation. Altering the computational stencil is more physically accurate but is difficult to implement while maintaining charge conservation in the code. Thus, filtering is more commonly used. Two previously published filters by Godfrey and Friedman are analyzed and compared to ideally desired filter properties
Numerical Simulation of Antennae by Discrete Exterior Calculus
International Nuclear Information System (INIS)
Xie Zheng; Ye Zheng; Ma Yujie
2009-01-01
Numerical simulation of antennae is a topic in computational electromagnetism, which is concerned with the numerical study of Maxwell equations. By discrete exterior calculus and the lattice gauge theory with coefficient R, we obtain the Bianchi identity on prism lattice. By defining an inner product of discrete differential forms, we derive the source equation and continuity equation. Those equations compose the discrete Maxwell equations in vacuum case on discrete manifold, which are implemented on Java development platform to simulate the Gaussian pulse radiation on antennaes. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
On the numerical simulation of tracer flows in porous media
International Nuclear Information System (INIS)
Aquino, J.; Pereira, F.; Amaral Souto, H.P.; Francisco, A.S.
2007-01-01
We discuss in detail a new Lagrangian, locally conservative procedure which has been proposed for the numerical solution of linear transport problems in porous media. The new scheme is computationally efficient, virtually free of numerical diffusion, and can be applied to investigate numerically the time evolution of radionuclide contaminant plumes. Results of two-dimensional simulations of tracer flows will be presented to show the influence on the computed solutions of distinct interpolation functions for evaluating the velocity field at any position of the physical domain, as required by the Lagrangian scheme. (author)
Numerical simulation of explosive magnetic cumulative generator EMG-720
Energy Technology Data Exchange (ETDEWEB)
Deryugin, Yu N; Zelenskij, D K; Kazakova, I F; Kargin, V I; Mironychev, P V; Pikar, A S; Popkov, N F; Ryaslov, E A; Ryzhatskova, E G [All-Russian Research Inst. of Experimental Physics, Sarov (Russian Federation)
1997-12-31
The paper discusses the methods and results of numerical simulations used in the development of a helical-coaxial explosive magnetic cumulative generator (EMG) with the stator up to 720 mm in diameter. In the process of designing, separate units were numerically modeled, as was the generator operation with a constant inductive-ohmic load. The 2-D processes of the armature acceleration by the explosion products were modeled as well as those of the formation of the sliding high-current contact between the armature and stator`s insulated turns. The problem of the armature integrity in the region of the detonation waves collision was numerically analyzed. 8 figs., 2 refs.
NUMERICAL SIMULATION OF SHOCK WAVE REFRACTION ON INCLINED CONTACT DISCONTINUITY
Directory of Open Access Journals (Sweden)
P. V. Bulat
2016-05-01
Full Text Available We consider numerical simulation of shock wave refraction on plane contact discontinuity, separating two gases with different density. Discretization of Euler equations is based on finite volume method and WENO finite difference schemes, implemented on unstructured meshes. Integration over time is performed with the use of the third-order Runge–Kutta stepping procedure. The procedure of identification and classification of gas dynamic discontinuities based on conditions of dynamic consistency and image processing methods is applied to visualize and interpret the results of numerical calculations. The flow structure and its quantitative characteristics are defined. The results of numerical and experimental visualization (shadowgraphs, schlieren images, and interferograms are compared.
Processing biobased polymers using plasticizers: Numerical simulations versus experiments
Desplentere, Frederik; Cardon, Ludwig; Six, Wim; Erkoç, Mustafa
2016-03-01
In polymer processing, the use of biobased products shows lots of possibilities. Considering biobased materials, biodegradability is in most cases the most important issue. Next to this, bio based materials aimed at durable applications, are gaining interest. Within this research, the influence of plasticizers on the processing of the bio based material is investigated. This work is done for an extrusion grade of PLA, Natureworks PLA 2003D. Extrusion through a slit die equipped with pressure sensors is used to compare the experimental pressure values to numerical simulation results. Additional experimental data (temperature and pressure data along the extrusion screw and die are recorded) is generated on a dr. Collin Lab extruder producing a 25mm diameter tube. All these experimental data is used to indicate the appropriate functioning of the numerical simulation tool Virtual Extrusion Laboratory 6.7 for the simulation of both the industrial available extrusion grade PLA and the compound in which 15% of plasticizer is added. Adding the applied plasticizer, resulted in a 40% lower pressure drop over the extrusion die. The combination of different experiments allowed to fit the numerical simulation results closely to the experimental values. Based on this experience, it is shown that numerical simulations also can be used for modified bio based materials if appropriate material and process data are taken into account.
Numerical simulations and mathematical models of flows in complex geometries
DEFF Research Database (Denmark)
Hernandez Garcia, Anier
The research work of the present thesis was mainly aimed at exploiting one of the strengths of the Lattice Boltzmann methods, namely, the ability to handle complicated geometries to accurately simulate flows in complex geometries. In this thesis, we perform a very detailed theoretical analysis...... and through the Chapman-Enskog multi-scale expansion technique the dependence of the kinetic viscosity on each scheme is investigated. Seeking for optimal numerical schemes to eciently simulate a wide range of complex flows a variant of the finite element, off-lattice Boltzmann method [5], which uses...... the characteristic based integration is also implemented. Using the latter scheme, numerical simulations are conducted in flows of different complexities: flow in a (real) porous network and turbulent flows in ducts with wall irregularities. From the simulations of flows in porous media driven by pressure gradients...
Numerical simulation of airfoil trailing edge serration noise
DEFF Research Database (Denmark)
Zhu, Wei Jun; Shen, Wen Zhong
In the present work, numerical simulations are carried out for a low noise airfoil with and without serrated Trailing Edge. The Ffowcs Williams-Hawkings acoustic analogy is implemented into the in-house incompressible flow solver EllipSys3D. The instantaneous hydrodynamic pressure and velocity...... field are obtained using Large Eddy Simulation. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FW-H approach. The extended length of the serration is about 16.7% of the airfoil chord and the geometric angle of the serration...... is 28 degrees. The chord based Reynolds number is around 1.5x106. Simulations are compared with existing wind tunnel experiments at various angles of attack. Even though the airfoil under investigation is already optimized for low noise emission, numerical simulations and wind tunnel experiments show...
Numerical simulations of comets - predictions for Comet Giacobini-Zinner
International Nuclear Information System (INIS)
Fedder, J.A.; Lyon, J.G.; Giuliani, J.L. Jr.
1986-01-01
Simulations of Comet Giacobini-Zinner's interaction with solar wind are described and results are presented. The simulations are carried out via the numerical solution of the ideal MHD equations as an initial value problem in a uniform solar wind. The calculations are performed on a Cartesian mesh centered at the comet. Results reveal that the first significant modifications of the solar wind along the ISEE/ICE trajectory will occur 100,000 km from the solar wind comet axis. 6 references
3D numerical simulation of transient processes in hydraulic turbines
International Nuclear Information System (INIS)
Cherny, S; Chirkov, D; Lapin, V; Eshkunova, I; Bannikov, D; Avdushenko, A; Skorospelov, V
2010-01-01
An approach for numerical simulation of 3D hydraulic turbine flows in transient operating regimes is presented. The method is based on a coupled solution of incompressible RANS equations, runner rotation equation, and water hammer equations. The issue of setting appropriate boundary conditions is considered in detail. As an illustration, the simulation results for runaway process are presented. The evolution of vortex structure and its effect on computed runaway traces are analyzed.
3D numerical simulation of transient processes in hydraulic turbines
Cherny, S.; Chirkov, D.; Bannikov, D.; Lapin, V.; Skorospelov, V.; Eshkunova, I.; Avdushenko, A.
2010-08-01
An approach for numerical simulation of 3D hydraulic turbine flows in transient operating regimes is presented. The method is based on a coupled solution of incompressible RANS equations, runner rotation equation, and water hammer equations. The issue of setting appropriate boundary conditions is considered in detail. As an illustration, the simulation results for runaway process are presented. The evolution of vortex structure and its effect on computed runaway traces are analyzed.
Energy Technology Data Exchange (ETDEWEB)
Muenstermann, Sebastian [RWTH Aachen (Germany). Dept. of Ferrous Metallurgy; Vajragupta, Napat [RWTH Aachen (Germany). Materials Mechanics Group; Weisgerber, Bernadette [ThyssenKrupp Steel Europe AG (Germany). Patent Dept.; Kern, Andreas [ThyssenKrupp Steel Europe AG (Germany). Dept. of Quality Affairs
2013-06-01
The demand for lightweight construction in mechanical and civil engineering has strongly promoted the development of high strength steels with excellent damage tolerance. Nowadays, the requirements from mechanical and civil engineering are even more challenging, as gradients in mechanical properties are demanded increasingly often for components that are utilized close to the limit state of load bearing capacity. A metallurgical solution to this demand is given by composite rolling processes. In this process components with different chemical compositions were jointed, which develop after heat treatment special properties. These are actually evaluated in order to verify that structural steels with the desired gradients in mechanical properties can be processed. A numerical study was performed aiming to numerically predict strenght and toughness properties, as well as the procesing behaviour using Finite Element (FE) simulations with damage mechanics approaches. For determination of mechanical properties, simulations of tensile specimen, SENB sample, and a mobile crane have been carried out for different configurations of composite rolled materias out of high strebght structural steels. As a parameter study, both the geometrical and the metallurgical configurations of the composite rolled steels were modified. Thickness of each steel layer and materials configuration have been varied. Like this, a numerical procedure to define optimum tailored configurations of high strenght steels could be established.
Computer simulations of the atmospheric composition climate of Bulgaria
Energy Technology Data Exchange (ETDEWEB)
Gadzhev, G.; Ganev, K.; Syrkov, D.; Prodanova, M.; Georgieva, I.; Georgiev, G.
2015-07-01
Some extensive numerical simulations of the atmospheric composition fields in Bulgaria have been recently performed. The US EPA Model-3 system was chosen as a modelling tool. As the NCEP Global Analysis Data with 1 degree resolution was used as meteorological background, the MM5 and CMAQ nesting capabilities were applied for downscaling the simulations to a 3 km resolution over Bulgaria. The TNO emission inventory was used as emission input. Special pre-processing procedures are created for introducing temporal profiles and speciation of the emissions. The biogenic emissions of VOC are estimated by the model SMOKE. The simulations were carried out for years 2000-2007. The numerical experiments have been carried out for different emission scenarios, which makes it possible the contribution of emissions from different source categories to be evaluated. The Models-3 “Integrated Process Rate Analysis” option is applied to discriminate the role of different dynamic and chemical processes for the air pollution formation. The obtained ensemble of numerical simulation results is extensive enough to allow statistical treatment – calculating not only the mean concentrations and different source categories contribution mean fields, but also standard deviations, skewness, etc. with their dominant temporal modes (seasonal and/or diurnal variations). Thus some basic facts about the atmospheric composition climate of Bulgaria can be retrieved from the simulation ensemble. (Author)
Computer simulations of the atmospheric composition climate of Bulgaria
Energy Technology Data Exchange (ETDEWEB)
Gadzhev, G.; Ganev, K.; Syrakov, D.; Prodanova, M.; Georgieva, I.; Georgiev, G.
2015-07-01
Some extensive numerical simulations of the atmospheric composition fields in Bulgaria have been recently performed. The US EPA Model-3 system was chosen as a modelling tool. As the NCEP Global Analysis Data with 1 degree resolution was used as meteorological background, the MM5 and CMAQ nesting capabilities were applied for downscaling the simulations to a 3 km resolution over Bulgaria. The TNO emission inventory was used as emission input. Special pre-processing procedures are created for introducing temporal profiles and speciation of the emissions. The biogenic emissions of VOC are estimated by the model SMOKE. The simulations were carried out for years 2000-2007. The numerical experiments have been carried out for different emission scenarios, which makes it possible the contribution of emissions from different source categories to be evaluated. The Models-3 Integrated Process Rate Analysis option is applied to discriminate the role of different dynamic and chemical processes for the air pollution formation. The obtained ensemble of numerical simulation results is extensive enough to allow statistical treatment calculating not only the mean concentrations and different source categories contribution mean fields, but also standard deviations, skewness, etc. with their dominant temporal modes (seasonal and/or diurnal variations). Thus some basic facts about the atmospheric composition climate of Bulgaria can be retrieved from the simulation ensemble. (Author)
Direct Numerical Simulation and Visualization of Subcooled Pool Boiling
Directory of Open Access Journals (Sweden)
Tomoaki Kunugi
2014-01-01
Full Text Available A direct numerical simulation of the boiling phenomena is one of the promising approaches in order to clarify their heat transfer characteristics and discuss the mechanism. During these decades, many DNS procedures have been developed according to the recent high performance computers and computational technologies. In this paper, the state of the art of direct numerical simulation of the pool boiling phenomena during mostly two decades is briefly summarized at first, and then the nonempirical boiling and condensation model proposed by the authors is introduced into the MARS (MultiInterface Advection and Reconstruction Solver developed by the authors. On the other hand, in order to clarify the boiling bubble behaviors under the subcooled conditions, the subcooled pool boiling experiments are also performed by using a high speed and high spatial resolution camera with a highly magnified telescope. Resulting from the numerical simulations of the subcooled pool boiling phenomena, the numerical results obtained by the MARS are validated by being compared to the experimental ones and the existing analytical solutions. The numerical results regarding the time evolution of the boiling bubble departure process under the subcooled conditions show a very good agreement with the experimental results. In conclusion, it can be said that the proposed nonempirical boiling and condensation model combined with the MARS has been validated.
Numerical simulation and experimental validation of coiled adiabatic capillary tubes
Energy Technology Data Exchange (ETDEWEB)
Garcia-Valladares, O. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico (UNAM), Apdo. Postal 34, 62580 Temixco, Morelos (Mexico)
2007-04-15
The objective of this study is to extend and validate the model developed and presented in previous works [O. Garcia-Valladares, C.D. Perez-Segarra, A. Oliva, Numerical simulation of capillary tube expansion devices behaviour with pure and mixed refrigerants considering metastable region. Part I: mathematical formulation and numerical model, Applied Thermal Engineering 22 (2) (2002) 173-182; O. Garcia-Valladares, C.D. Perez-Segarra, A. Oliva, Numerical simulation of capillary tube expansion devices behaviour with pure and mixed refrigerants considering metastable region. Part II: experimental validation and parametric studies, Applied Thermal Engineering 22 (4) (2002) 379-391] to coiled adiabatic capillary tube expansion devices working with pure and mixed refrigerants. The discretized governing equations are coupled using an implicit step by step method. A special treatment has been implemented in order to consider transitions (subcooled liquid region, metastable liquid region, metastable two-phase region and equilibrium two-phase region). All the flow variables (enthalpies, temperatures, pressures, vapor qualities, velocities, heat fluxes, etc.) together with the thermophysical properties are evaluated at each point of the grid in which the domain is discretized. The numerical model allows analysis of aspects such as geometry, type of fluid (pure substances and mixtures), critical or non-critical flow conditions, metastable regions, and transient aspects. Comparison of the numerical simulation with a wide range of experimental data presented in the technical literature will be shown in the present article in order to validate the model developed. (author)
Can numerical simulations accurately predict hydrodynamic instabilities in liquid films?
Denner, Fabian; Charogiannis, Alexandros; Pradas, Marc; van Wachem, Berend G. M.; Markides, Christos N.; Kalliadasis, Serafim
2014-11-01
Understanding the dynamics of hydrodynamic instabilities in liquid film flows is an active field of research in fluid dynamics and non-linear science in general. Numerical simulations offer a powerful tool to study hydrodynamic instabilities in film flows and can provide deep insights into the underlying physical phenomena. However, the direct comparison of numerical results and experimental results is often hampered by several reasons. For instance, in numerical simulations the interface representation is problematic and the governing equations and boundary conditions may be oversimplified, whereas in experiments it is often difficult to extract accurate information on the fluid and its behavior, e.g. determine the fluid properties when the liquid contains particles for PIV measurements. In this contribution we present the latest results of our on-going, extensive study on hydrodynamic instabilities in liquid film flows, which includes direct numerical simulations, low-dimensional modelling as well as experiments. The major focus is on wave regimes, wave height and wave celerity as a function of Reynolds number and forcing frequency of a falling liquid film. Specific attention is paid to the differences in numerical and experimental results and the reasons for these differences. The authors are grateful to the EPSRC for their financial support (Grant EP/K008595/1).
Seasonal cycle of Martian climate : Experimental data and numerical simulation
Rodin, A. V.; Willson, R. J.
2006-01-01
The most adequate theoretical method of investigating the present-day Martian climate is numerical simulation based on a model of general circulation of the atmosphere. First and foremost, such models encounter the greatest difficulties in description of aerosols and clouds, which in turn
Numerical simulation of two phase flows in heat exchangers
International Nuclear Information System (INIS)
Grandotto Biettoli, M.
2006-04-01
The report presents globally the works done by the author in the thermohydraulic applied to nuclear reactors flows. It presents the studies done to the numerical simulation of the two phase flows in the steam generators and a finite element method to compute these flows. (author)
Decoupled numerical simulation of a solid fuel fired retort boiler
International Nuclear Information System (INIS)
Ryfa, Arkadiusz; Buczynski, Rafal; Chabinski, Michal; Szlek, Andrzej; Bialecki, Ryszard A.
2014-01-01
The paper deals with numerical simulation of the retort boiler fired with solid fuel. Such constructions are very popular for heating systems and their development is mostly based on the designer experience. The simulations have been done in ANSYS/Fluent package and involved two numerical models. The former deals with a fixed-bed combustion of the solid fuel and free-board gas combustion. Solid fuel combustion is based on the coal kinetic parameters. This model encompasses chemical reactions, radiative heat transfer and turbulence. Coal properties have been defined with user defined functions. The latter model describes flow of water inside a water jacked that surrounds the combustion chamber and flue gas ducts. The novelty of the proposed approach is separating of the combustion simulation from the water flow. Such approach allows for reducing the number of degrees of freedom and thus lowering the necessary numerical effort. Decoupling combustion from water flow requires defining interface boundary condition. As this boundary condition is unknown it is adjusted iteratively. The results of the numerical simulation have been successfully validated against measurement data. - Highlights: • New decoupled modelling of small scale boiler is proposed. • Fixed-bed combustion model based on kinetic parameters is introduced. • Decoupling reduced the complexity of the model and computational time. • Simple and computationally inexpensive coupling algorithm is proposed. • Model is successfully validated against measurements
A review of numerical simulation of hydrothermal systems.
Mercer, J.W.; Faust, C.R.
1979-01-01
Many advances in simulating single and two-phase fluid flow and heat transport in porous media have recently been made in conjunction with geothermal energy research. These numerical models reproduce system thermal and pressure behaviour and can be used for other heat-transport problems, such as high-level radioactive waste disposal and heat-storage projects. -Authors
Application of HPCN to direct numerical simulation of turbulent flow
Verstappen, RWCP; Veldman, AEP; van Waveren, GM; Hertzberger, B; Sloot, P
1997-01-01
This poster shows how HPCN can be used as a path-finding tool for turbulence research. The parallelization of direct numerical simulation of turbulent flow using the data-parallel model and Fortran 95 constructs is treated, both on a shared memory and a distributed memory computer.
Numerical simulation of thermal fracture in functionally graded
Indian Academy of Sciences (India)
Numerical simulation of thermal fracture in functionally graded materials using element-free ... Initially, the temperature distribution over the domain is obtained by solving the heat transfer problem. ... Department of Mechanical Engineering, National Institute of Technology, Hamirpur 177005, India ... Contact | Site index.
Numerical simulations of the metallicity distribution in dwarf spheroidal galaxies
Ripamonti, E.; Tolstoy, E.; Helmi, A.; Battaglia, G.; Abel, T.
2006-01-01
Abstract: Recent observations show that the number of stars with very low metallicities in the dwarf spheroidal satellites of the Milky Way is low, despite the low average metallicities of stars in these systems. We undertake numerical simulations of star formation and metal enrichment of dwarf
Numerical convergence improvements for porflow unsaturated flow simulations
Energy Technology Data Exchange (ETDEWEB)
Flach, Greg [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2017-08-14
Section 3.6 of SRNL (2016) discusses various PORFLOW code improvements to increase modeling efficiency, in preparation for the next E-Area Performance Assessment (WSRC 2008) revision. This memorandum documents interaction with Analytic & Computational Research, Inc. (http://www.acricfd.com/default.htm) to improve numerical convergence efficiency using PORFLOW version 6.42 for unsaturated flow simulations.
Direct numerical simulation of particulate flow with heat transfer
Tavassoli Estahbanati, H; Kriebitzsch, S.H.L.; Hoef, van der M.A.; Peters, E.A.J.F.; Kuipers, J.A.M.
2013-01-01
The Immersed Boundary (IB) method proposed by Uhlmann for Direct Numerical Simulation (DNS) of fluid flow through dense fluid-particle systems is extended to systems with interphase heat transport. A fixed Eulerian grid is employed to solve the momentum and energy equations by traditional
Experimental and numerical simulation of carbon manganese steel ...
African Journals Online (AJOL)
Experimental and numerical simulation of carbon manganese steel for cyclic plastic behaviour. J Shit, S Dhar, S Acharyya. Abstract. The paper deals with finite element modeling of saturated low cycle fatigue and the cyclic hardening phenomena of the materials Sa333 grade 6 carbon steel and SS316 stainless steel.
Numerical simulation of the drying of inkjet-printed droplets
Siregar, D.P.; Kuerten, J.G.M.; Geld, van der C.W.M.
2013-01-01
In this paper we study the behavior of an inkjet-printed droplet of a solute dissolved in a solvent on a solid horizontal surface by numerical simulation. An extended model for drying of a droplet and the final distribution of the solute on an impermeable substrate is proposed. The model extends the
Direct Numerical Simulation Sediment Transport in Horizontal Channel
International Nuclear Information System (INIS)
Uhlmann, M.
2006-01-01
We numerically simulate turbulent flow in a horizontal plane channel over a bed of mobile particles. All scales of fluid motion are resolved without modeling and the phase interface is accurately represented. Our results indicate a possible scenario for the onset of erosion through collective motion induced by buffer-layer streaks. (Author) 27 refs
Numerical simulations of time-resolved quantum electronics
International Nuclear Information System (INIS)
Gaury, Benoit; Weston, Joseph; Santin, Matthieu; Houzet, Manuel; Groth, Christoph; Waintal, Xavier
2014-01-01
Numerical simulation has become a major tool in quantum electronics both for fundamental and applied purposes. While for a long time those simulations focused on stationary properties (e.g. DC currents), the recent experimental trend toward GHz frequencies and beyond has triggered a new interest for handling time-dependent perturbations. As the experimental frequencies get higher, it becomes possible to conceive experiments which are both time-resolved and fast enough to probe the internal quantum dynamics of the system. This paper discusses the technical aspects–mathematical and numerical–associated with the numerical simulations of such a setup in the time domain (i.e. beyond the single-frequency AC limit). After a short review of the state of the art, we develop a theoretical framework for the calculation of time-resolved observables in a general multiterminal system subject to an arbitrary time-dependent perturbation (oscillating electrostatic gates, voltage pulses, time-varying magnetic fields, etc.) The approach is mathematically equivalent to (i) the time-dependent scattering formalism, (ii) the time-resolved non-equilibrium Green’s function (NEGF) formalism and (iii) the partition-free approach. The central object of our theory is a wave function that obeys a simple Schrödinger equation with an additional source term that accounts for the electrons injected from the electrodes. The time-resolved observables (current, density, etc.) and the (inelastic) scattering matrix are simply expressed in terms of this wave function. We use our approach to develop a numerical technique for simulating time-resolved quantum transport. We find that the use of this wave function is advantageous for numerical simulations resulting in a speed up of many orders of magnitude with respect to the direct integration of NEGF equations. Our technique allows one to simulate realistic situations beyond simple models, a subject that was until now beyond the simulation
Analysis of spring-in in U-shaped composite laminates: Numerical and experimental results
Bellini, Costanzo; Sorrentino, Luca; Polini, Wilma; Parodo, Gianluca
2018-05-01
The phenomena that happen during the cure process of a composite material laminate are responsible for the rise of residual stresses and, consequently, for the deformation at the end of the manufacturing process. The most analyzed deformation is the spring-in, that represent the flange-to-flange angle deviance from the theoretical value. In this work, the influence of some parameters, such as the laminate thickness, the stacking sequence and the mold radius, on the spring-in angle of a U-shaped laminate was studied exploring a full factorial plan through numerical simulations. First of all, a numerical model proper for cure simulation was introduced and its suitability to simulate the deformation behavior was demonstrated. As a result, only the stacking sequence influenced the spring-in value, while the effect of the tool radius and laminate thickness was minimal.
Mathematical modeling and numerical simulation of Czochralski Crystal Growth
Energy Technology Data Exchange (ETDEWEB)
Jaervinen, J.; Nieminen, R. [Center for Scientific Computing, Espoo (Finland)
1996-12-31
A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)
Behavioral modeling of SRIM tables for numerical simulation
Energy Technology Data Exchange (ETDEWEB)
Martinie, S., E-mail: sebastien.martinie@cea.fr; Saad-Saoud, T.; Moindjie, S.; Munteanu, D.; Autran, J.L., E-mail: jean-luc.autran@univ-amu.fr
2014-03-01
Highlights: • Behavioral modeling of SRIM data is performed on the basis of power polynomial fitting functions. • Fast and continuous numerical functions are proposed for the stopping power and projected range. • Functions have been successfully tested for a wide variety of ions and targets. • Typical accuracies below the percent have been obtained in the range 1 keV–1 GeV. - Abstract: This work describes a simple way to implement SRIM stopping power and range tabulated data in the form of fast and continuous numerical functions for intensive simulation. We provide here the methodology of this behavioral modeling as well as the details of the implementation and some numerical examples for ions in silicon target. Developed functions have been successfully tested and used for the simulation of soft errors in microelectronics circuits.
Mathematical modeling and numerical simulation of Czochralski Crystal Growth
Energy Technology Data Exchange (ETDEWEB)
Jaervinen, J; Nieminen, R [Center for Scientific Computing, Espoo (Finland)
1997-12-31
A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)
On the characteristics of a numerical fluid dynamics simulator
International Nuclear Information System (INIS)
Winkler, K.H.A.; Norman, M.L.; Norton, J.L.
1986-01-01
John von Neumann envisioned scientists and mathematicians analyzing and controlling their numerical experiments on nonlinear dynamic systems interactively. The authors describe their concept of a real-time Numerical Fluid Dynamics Simulator NFDS. The authors envision the NFDS to be composed of simulation processors, data storage devices, and image processing devices of extremely high power and capacity, interconnected by very high throughput communication channels. They present individual component performance requirements for both real-time and playback operating modes of the NFDS, using problems of current interest in fluid dynamics as examples. Scaling relations are derived showing the dependence of system requirements on the dimensionality and complexity of the numerical model. The authors conclude by extending their analysis to the system requirements posed in modeling the more involved physics of radiation hydrodynamics
Agglomeration processes in carbonaceous dusty plasmas, experiments and numerical simulations
International Nuclear Information System (INIS)
Dap, S; Hugon, R; De Poucques, L; Bougdira, J; Lacroix, D; Patisson, F
2010-01-01
This paper deals with carbon dust agglomeration in radio frequency acetylene/argon plasma. Two studies, an experimental and a numerical one, were carried out to model dust formation mechanisms. Firstly, in situ transmission spectroscopy of dust clouds in the visible range was performed in order to observe the main features of the agglomeration process of the produced carbonaceous dust. Secondly, numerical simulation tools dedicated to understanding the achieved experiments were developed. A first model was used for the discretization of the continuous population balance equations that characterize the dust agglomeration process. The second model is based on a Monte Carlo ray-tracing code coupled to a Mie theory calculation of dust absorption and scattering parameters. These two simulation tools were used together in order to numerically predict the light transmissivity through a dusty plasma and make comparisons with experiments.
Behavioral modeling of SRIM tables for numerical simulation
International Nuclear Information System (INIS)
Martinie, S.; Saad-Saoud, T.; Moindjie, S.; Munteanu, D.; Autran, J.L.
2014-01-01
Highlights: • Behavioral modeling of SRIM data is performed on the basis of power polynomial fitting functions. • Fast and continuous numerical functions are proposed for the stopping power and projected range. • Functions have been successfully tested for a wide variety of ions and targets. • Typical accuracies below the percent have been obtained in the range 1 keV–1 GeV. - Abstract: This work describes a simple way to implement SRIM stopping power and range tabulated data in the form of fast and continuous numerical functions for intensive simulation. We provide here the methodology of this behavioral modeling as well as the details of the implementation and some numerical examples for ions in silicon target. Developed functions have been successfully tested and used for the simulation of soft errors in microelectronics circuits
Numerical simulation of a possible counterexample to cosmic censorship
International Nuclear Information System (INIS)
Garfinkle, David
2004-01-01
A numerical simulation is presented here of the evolution of initial data of the kind that was conjectured by Hertog, Horowitz, and Maeda to be a violation of cosmic censorship. Those initial data are essentially a thick domain wall connecting two regions of anti-de Sitter space. The initial data have a free parameter that is the initial size of the wall. The simulation shows no violation of cosmic censorship, but rather the formation of a small black hole. The simulation described here is for a moderate wall size and leaves open the possibility that cosmic censorship might be violated for larger walls
3D numerical simulations of multiphase continental rifting
Naliboff, J.; Glerum, A.; Brune, S.
2017-12-01
Observations of rifted margin architecture suggest continental breakup occurs through multiple phases of extension with distinct styles of deformation. The initial rifting stages are often characterized by slow extension rates and distributed normal faulting in the upper crust decoupled from deformation in the lower crust and mantle lithosphere. Further rifting marks a transition to higher extension rates and coupling between the crust and mantle lithosphere, with deformation typically focused along large-scale detachment faults. Significantly, recent detailed reconstructions and high-resolution 2D numerical simulations suggest that rather than remaining focused on a single long-lived detachment fault, deformation in this phase may progress toward lithospheric breakup through a complex process of fault interaction and development. The numerical simulations also suggest that an initial phase of distributed normal faulting can play a key role in the development of these complex fault networks and the resulting finite deformation patterns. Motivated by these findings, we will present 3D numerical simulations of continental rifting that examine the role of temporal increases in extension velocity on rifted margin structure. The numerical simulations are developed with the massively parallel finite-element code ASPECT. While originally designed to model mantle convection using advanced solvers and adaptive mesh refinement techniques, ASPECT has been extended to model visco-plastic deformation that combines a Drucker Prager yield criterion with non-linear dislocation and diffusion creep. To promote deformation localization, the internal friction angle and cohesion weaken as a function of accumulated plastic strain. Rather than prescribing a single zone of weakness to initiate deformation, an initial random perturbation of the plastic strain field combined with rapid strain weakening produces distributed normal faulting at relatively slow rates of extension in both 2D and
Understanding casing flow in Pelton turbines by numerical simulation
Rentschler, M.; Neuhauser, M.; Marongiu, J. C.; Parkinson, E.
2016-11-01
For rehabilitation projects of Pelton turbines, the flow in the casing may have an important influence on the overall performance of the machine. Water sheets returning on the jets or on the runner significantly reduce efficiency, and run-away speed depends on the flow in the casing. CFD simulations can provide a detailed insight into this type of flow, but these simulations are computationally intensive. As in general the volume of water in a Pelton turbine is small compared to the complete volume of the turbine housing, a single phase simulation greatly reduces the complexity of the simulation. In the present work a numerical tool based on the SPH-ALE meshless method is used to simulate the casing flow in a Pelton turbine. Using improved order schemes reduces the numerical viscosity. This is necessary to resolve the flow in the jet and on the casing wall, where the velocity differs by two orders of magnitude. The results are compared to flow visualizations and measurement in a hydraulic laboratory. Several rehabilitation projects proved the added value of understanding the flow in the Pelton casing. The flow simulation helps designing casing insert, not only to see their influence on the flow, but also to calculate the stress in the inserts. In some projects, the casing simulation leads to the understanding of unexpected behavior of the flow. One such example is presented where the backsplash of a deflector hit the runner, creating a reversed rotation of the runner.
Numerical Simulation of Hydrogen Combustion: Global Reaction Model and Validation
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yun [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an (China); Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY (United States); Liu, Yinhe, E-mail: yinheliu@mail.xjtu.edu.cn [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an (China)
2017-11-20
Due to the complexity of modeling the combustion process in nuclear power plants, the global mechanisms are preferred for numerical simulation. To quickly perform the highly resolved simulations with limited processing resources of large-scale hydrogen combustion, a method based on thermal theory was developed to obtain kinetic parameters of global reaction mechanism of hydrogen–air combustion in a wide range. The calculated kinetic parameters at lower hydrogen concentration (C{sub hydrogen} < 20%) were validated against the results obtained from experimental measurements in a container and combustion test facility. In addition, the numerical data by the global mechanism (C{sub hydrogen} > 20%) were compared with the results by detailed mechanism. Good agreement between the model prediction and the experimental data was achieved, and the comparison between simulation results by the detailed mechanism and the global reaction mechanism show that the present calculated global mechanism has excellent predictable capabilities for a wide range of hydrogen–air mixtures.
Numerical simulation of particle settling and cohesion in liquid
Energy Technology Data Exchange (ETDEWEB)
Johno, Y; Nakashima, K; Shigematsu, T; Ono, B [SASEBO National College of Technology, 1-1 Okishin, Sasebo, Nagasaki, 857-1193 (Japan); Satomi, M, E-mail: yjohno@post.cc.sasebo.ac.j [Sony Semiconductor Kyushu Corporation, Kikuchigun, Kumamoto (Japan)
2009-02-01
In this study, the motions of particles and particle clusters in liquid were numerically simulated. The particles of two sizes (Dp=40mum and 20mum) settle while repeating cohesion and dispersion, and finally the sediment of particles are formed at the bottom of a hexahedron container which is filled up with pure water. The flow field was solved with the Navier-Stokes equations and the particle motions were solved with the Lagrangian-type motion equations, where the interaction between fluid and particles due to drag forces were taken into account. The collision among particles was calculated using Distinct Element Method (DEM), and the effects of cohesive forces by van der Waals force acting on particle contact points were taken into account. Numerical simulations were performed under conditions in still flow and in shear flow. It was found that the simulation results enable us to know the state of the particle settling and the particle condensation.
Numerical simulation of manual operation at MID stand control room
International Nuclear Information System (INIS)
Doca, C.; Dobre, A.; Predescu, D.; Mielcioiu, A.
2003-01-01
Since 2000 at INR Pitesti a package of software products devoted to numerical simulation of manual operations at fueling machine control room was developed. So far, specified, designed, worked out and implemented was the PUPITRU code. The following issues were solved: graphical aspects of specific computer - human operator interface; functional and graphical simulation of the whole associated equipment of the control desk components; implementation of the main notation as used in the automated schemes of the control desk in view of the fast identification of the switches, lamps, instrumentation, etc.; implementation within PUPITRU code of the entire data base used in the frame of MID tests; implementation of a number of about 1000 numerical simulation equations describing specific operational MID testing situations
Numerical simulation of small scale soft impact tests
International Nuclear Information System (INIS)
Varpasuo, Pentti
2008-01-01
This paper describes the small scale soft missile impact tests. The purpose of the test program is to provide data for the calibration of the numerical simulation models for impact simulation. In the experiments, both dry and fluid filled missiles are used. The tests with fluid filled missiles investigate the release speed and the droplet size of the fluid release. This data is important in quantifying the fire hazard of flammable liquid after the release. The spray release velocity and droplet size are also input data for analytical and numerical simulation of the liquid spread in the impact. The behaviour of the impact target is the second investigative goal of the test program. The response of reinforced and pre-stressed concrete walls is studied with the aid of displacement and strain monitoring. (authors)
Numerical Simulation of Hydrogen Combustion: Global Reaction Model and Validation
International Nuclear Information System (INIS)
Zhang, Yun; Liu, Yinhe
2017-01-01
Due to the complexity of modeling the combustion process in nuclear power plants, the global mechanisms are preferred for numerical simulation. To quickly perform the highly resolved simulations with limited processing resources of large-scale hydrogen combustion, a method based on thermal theory was developed to obtain kinetic parameters of global reaction mechanism of hydrogen–air combustion in a wide range. The calculated kinetic parameters at lower hydrogen concentration (C hydrogen < 20%) were validated against the results obtained from experimental measurements in a container and combustion test facility. In addition, the numerical data by the global mechanism (C hydrogen > 20%) were compared with the results by detailed mechanism. Good agreement between the model prediction and the experimental data was achieved, and the comparison between simulation results by the detailed mechanism and the global reaction mechanism show that the present calculated global mechanism has excellent predictable capabilities for a wide range of hydrogen–air mixtures.
Direct numerical simulations of turbulent lean premixed combustion
International Nuclear Information System (INIS)
Sankaran, Ramanan; Hawkes, Evatt R; Chen, Jacqueline H; Lu Tianfeng; Law, Chung K
2006-01-01
In recent years, due to the advent of high-performance computers and advanced numerical algorithms, direct numerical simulation (DNS) of combustion has emerged as a valuable computational research tool, in concert with experimentation. The role of DNS in delivering new Scientific insight into turbulent combustion is illustrated using results from a recent 3D turbulent premixed flame simulation. To understand the influence of turbulence on the flame structure, a 3D fully-resolved DNS of a spatially-developing lean methane-air turbulent Bunsen flame was performed in the thin reaction zones regime. A reduced chemical model for methane-air chemistry consisting of 13 resolved species, 4 quasi-steady state species and 73 elementary reactions was developed specifically for the current simulation. The data is analyzed to study possible influences of turbulence on the flame thickness. The results show that the average flame thickness increases, in qualitative agreement with several experimental results
Configuration Management File Manager Developed for Numerical Propulsion System Simulation
Follen, Gregory J.
1997-01-01
One of the objectives of the High Performance Computing and Communication Project's (HPCCP) Numerical Propulsion System Simulation (NPSS) is to provide a common and consistent way to manage applications, data, and engine simulations. The NPSS Configuration Management (CM) File Manager integrated with the Common Desktop Environment (CDE) window management system provides a common look and feel for the configuration management of data, applications, and engine simulations for U.S. engine companies. In addition, CM File Manager provides tools to manage a simulation. Features include managing input files, output files, textual notes, and any other material normally associated with simulation. The CM File Manager includes a generic configuration management Application Program Interface (API) that can be adapted for the configuration management repositories of any U.S. engine company.
Numerical simulation investigation on centrifugal compressor performance of turbocharger
International Nuclear Information System (INIS)
Li, Jie; Yin, Yuting; Li, Shuqi; Zhang, Jizhong
2013-01-01
In this paper, the mathematical model of the flow filed in centrifugal compressor of turbocharger was studied. Based on the theory of computational fluid dynamics (CFD), performance curves and parameter distributions of the compressor were obtained from the 3-D numerical simulation by using CFX. Meanwhile, the influences of grid number and distribution on compressor performance were investigated, and numerical calculation method was analyzed and validated, through combining with test data. The results obtained show the increase of the grid number has little influence on compressor performance while the grid number of single-passage is above 300,000. The results also show that the numerical calculation mass flow rate of compressor choke situation has a good consistent with test results, and the maximum difference of the diffuser exit pressure between simulation and experiment decrease to 3.5% with the assumption of 6 kPa additional total pressure loss at compressor inlet. The numerical simulation method in this paper can be used to predict compressor performance, and the difference of total pressure ratio between calculation and test is less than 7%, and the total-to-total efficiency also have a good consistent with test.
Numerical simulation investigation on centrifugal compressor performance of turbocharger
Energy Technology Data Exchange (ETDEWEB)
Li, Jie [China Iron and Steel Research Institute Group, Beijing (China); Yin, Yuting [China North Engine Research Institute, Datong (China); Li, Shuqi; Zhang, Jizhong [Science and Technology Diesel Engine Turbocharging Laboratory, Datong (China)
2013-06-15
In this paper, the mathematical model of the flow filed in centrifugal compressor of turbocharger was studied. Based on the theory of computational fluid dynamics (CFD), performance curves and parameter distributions of the compressor were obtained from the 3-D numerical simulation by using CFX. Meanwhile, the influences of grid number and distribution on compressor performance were investigated, and numerical calculation method was analyzed and validated, through combining with test data. The results obtained show the increase of the grid number has little influence on compressor performance while the grid number of single-passage is above 300,000. The results also show that the numerical calculation mass flow rate of compressor choke situation has a good consistent with test results, and the maximum difference of the diffuser exit pressure between simulation and experiment decrease to 3.5% with the assumption of 6 kPa additional total pressure loss at compressor inlet. The numerical simulation method in this paper can be used to predict compressor performance, and the difference of total pressure ratio between calculation and test is less than 7%, and the total-to-total efficiency also have a good consistent with test.
Numerical simulation in material science: principles and applications
International Nuclear Information System (INIS)
Ruste, Jacky
2006-06-01
The objective is here to describe the main simulation techniques currently used in material science. After a presentation of the concepts of modelling and simulation, of their objectives and uses, of the issue of simulation scale, and of means of numeric simulation, the author addresses simulations performed at a nano-scopic scale: 'ab-initio' methods, molecular dynamics, examples of applications of ab-initio methods to energy issues or to the study of surface properties of nano-materials. The next chapter addresses various Monte Carlo methods (Metropolis, atomic kinetics, objects kinetics, transport with the simulation of particle trajectories, generation of random numbers). The next parts address simulations performed at a mesoscopic scale (simulation and microstructure, phase field methods, dynamics of discrete dislocations, homogeneous chemical kinetics) and at a macroscopic scale (medium discretization with the notion of mesh, simulation of structure mechanics and of fluid behaviour). The issues of code coupling and scale coupling are then discussed. The last part proposes an overview of virtual metallurgy and modelling of industrial processes (welding, vacuum arc re-fusion, rolling, forming)
Numerical simulation of heat transfer in metal foams
Gangapatnam, Priyatham; Kurian, Renju; Venkateshan, S. P.
2018-02-01
This paper reports a numerical study of forced convection heat transfer in high porosity aluminum foams. Numerical modeling is done considering both local thermal equilibrium and non local thermal equilibrium conditions in ANSYS-Fluent. The results of the numerical model were validated with experimental results, where air was forced through aluminum foams in a vertical duct at different heat fluxes and velocities. It is observed that while the LTE model highly under predicts the heat transfer in these foams, LTNE model predicts the Nusselt number accurately. The novelty of this study is that once hydrodynamic experiments are conducted the permeability and porosity values obtained experimentally can be used to numerically simulate heat transfer in metal foams. The simulation of heat transfer in foams is further extended to find the effect of foam thickness on heat transfer in metal foams. The numerical results indicate that though larger foam thicknesses resulted in higher heat transfer coefficient, this effect weakens with thickness and is negligible in thick foams.
Numerical simulation of gas metal arc welding parametrical study
International Nuclear Information System (INIS)
Szanto, M.; Gilad, I.; Shai, I.; Quinn, T.P.
2002-01-01
The Gas Metal Arc Welding (GMAW) is a widely used welding process in the industry. The process variables are usually determined through extensive experiments. Numerical simulation, reduce the cost and extends the understanding of the process. In the present work, a versatile model for numerical simulation of GMAW is presented. The model provides the basis for fundamental understanding of the process. The model solves the magneto-hydrodynamic equations for the flow and temperature fields of the molten electrode and the plasma simultaneously, to form a fully coupled model. A commercial CFD code was extended to include the effects of radiation, Lorentz forces, Joule heating and thermoelectric effects. The geometry of the numerical model assembled to fit an experimental apparatus. To demonstrate the method, an aluminum electrode was modeled in a pure argon arc. Material properties and welding parameters are the input variables in the numerical model. In a typical process, the temperature distribution of the plasma is over 15000 K, resulting high non-linearity of the material properties. Moreover, there is high uncertainty in the available property data, at that range of temperatures. Therefore, correction factors were derived for the material properties to adjust between the numerical and the experimental results. Using the compensated properties, parametric study was performed. The effects of the welding parameters on the process, such the working voltage, electrode feed rate and shielding gas flow, were derived. The principal result of the present work is the ability to predict, by numerical simulation, the mode, size and frequency of the metal transferred from the electrode, which is the main material and energy source for the welding pool in GMAW
Numerical simulation support to the ESA/THOR mission
Valentini, F.; Servidio, S.; Perri, S.; Perrone, D.; De Marco, R.; Marcucci, M. F.; Daniele, B.; Bruno, R.; Camporeale, E.
2016-12-01
THOR is a spacecraft concept currently undergoing study phase as acandidate for the next ESA medium size mission M4. THOR has been designedto solve the longstanding physical problems of particle heating andenergization in turbulent plasmas. It will provide high resolutionmeasurements of electromagnetic fields and particle distribution functionswith unprecedented resolution, with the aim of exploring the so-calledkinetic scales. We present the numerical simulation framework which is supporting the THOR mission during the study phase. The THOR teamincludes many scientists developing and running different simulation codes(Eulerian-Vlasov, Particle-In-Cell, Gyrokinetics, Two-fluid, MHD, etc.),addressing the physics of plasma turbulence, shocks, magnetic reconnectionand so on.These numerical codes are being used during the study phase, mainly withthe aim of addressing the following points:(i) to simulate the response of real particle instruments on board THOR, byemploying an electrostatic analyser simulator which mimics the response ofthe CSW, IMS and TEA instruments to the particle velocity distributions ofprotons, alpha particle and electrons, as obtained from kinetic numericalsimulations of plasma turbulence.(ii) to compare multi-spacecraft with single-spacecraft configurations inmeasuring current density, by making use of both numerical models ofsynthetic turbulence and real data from MMS spacecraft.(iii) to investigate the validity of the Taylor hypothesis indifferent configurations of plasma turbulence
Graphics interfaces and numerical simulations: Mexican Virtual Solar Observatory
Hernández, L.; González, A.; Salas, G.; Santillán, A.
2007-08-01
Preliminary results associated to the computational development and creation of the Mexican Virtual Solar Observatory (MVSO) are presented. Basically, the MVSO prototype consists of two parts: the first, related to observations that have been made during the past ten years at the Solar Observation Station (EOS) and at the Carl Sagan Observatory (OCS) of the Universidad de Sonora in Mexico. The second part is associated to the creation and manipulation of a database produced by numerical simulations related to solar phenomena, we are using the MHD ZEUS-3D code. The development of this prototype was made using mysql, apache, java and VSO 1.2. based GNU and `open source philosophy'. A graphic user interface (GUI) was created in order to make web-based, remote numerical simulations. For this purpose, Mono was used, because it is provides the necessary software to develop and run .NET client and server applications on Linux. Although this project is still under development, we hope to have access, by means of this portal, to other virtual solar observatories and to be able to count on a database created through numerical simulations or, given the case, perform simulations associated to solar phenomena.
Direct numerical simulations of nucleate boiling flows of binary mixtures
International Nuclear Information System (INIS)
Didier Jamet; Celia Fouillet
2005-01-01
Full text of publication follows: Better understand the origin and characteristics of boiling crisis is still a scientific challenge despite many years of valuable studies. One of the reasons why boiling crisis is so difficult to understand is that local and coupled physical phenomena are believed to play a key role in the trigger of instabilities which lead to the dry out of large portions of the heated solid phase. Nucleate boiling of a single bubble is fairly well understood compared to boiling crisis. Therefore, the numerical simulation of a single bubble growth during nucleate boiling is a good candidate to evaluate the capabilities of a numerical method to deal with complex liquid-vapor phenomena with phase-change and eventually to tackle the boiling crisis problem. In this paper, we present results of direct numerical simulations of nucleate boiling. The numerical method used is the second gradient method, which is a diffuse interface method dedicated to liquid vapor flows with phase-change. This study is not intended to provide quantitative results, partly because all the simulations are two-dimensional. However, particular attention is paid to the influence of some parameters on the main features of nucleate boiling, i.e. the radius of departure and the frequency of detachment of bubbles. In particular, we show that, as the contact angle increases, the radius of departure increases whereas the frequency of detachment decreases. Moreover, the influence of the existence of quasi non-condensable gas is studied. Numerical results show an important decrease of the heat exchange coefficient when a small amount of a quasi non-condensable gas is added to the pure liquid-vapor water system. This result is in agreement with experimental observations. Beyond these qualitative results, this numerical study allows to get insight into some important physical phenomena and to confirm that during nucleate boiling, large scale quantities are influenced by small scale
Numerical simulation of the RISOe1-airfoil dynamic stall
Energy Technology Data Exchange (ETDEWEB)
Bertagnolio, F.; Soerensen, N. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)
1997-12-31
In this paper we are concerned with the numerical computation of the dynamic stall that occur in the viscous flowfield over an airfoil. These results are compared to experimental data that were obtained with the new designed RISOe1-airfoil, both for a motionless airfoil and for a pitching motion. Moreover, we present some numerical computations of the plunging and lead-lag motions. We also investigate the possibility of using the pitching motion to simulate the plunging and lead-lag situations. (au)
Modeling and numerical simulations of the influenced Sznajd model
Karan, Farshad Salimi Naneh; Srinivasan, Aravinda Ramakrishnan; Chakraborty, Subhadeep
2017-08-01
This paper investigates the effects of independent nonconformists or influencers on the behavioral dynamic of a population of agents interacting with each other based on the Sznajd model. The system is modeled on a complete graph using the master equation. The acquired equation has been numerically solved. Accuracy of the mathematical model and its corresponding assumptions have been validated by numerical simulations. Regions of initial magnetization have been found from where the system converges to one of two unique steady-state PDFs, depending on the distribution of influencers. The scaling property and entropy of the stationary system in presence of varying level of influence have been presented and discussed.
Numerical simulation of water quality in Yangtze Estuary
Directory of Open Access Journals (Sweden)
Xi Li
2009-12-01
Full Text Available In order to monitor water quality in the Yangtze Estuary, water samples were collected and field observation of current and velocity stratification was carried out using a shipboard acoustic Doppler current profiler (ADCP. Results of two representative variables, the temporal and spatial variation of new point source sewage discharge as manifested by chemical oxygen demand (COD and the initial water quality distribution as manifested by dissolved oxygen (DO, were obtained by application of the Environmental Fluid Dynamics Code (EFDC with solutions for hydrodynamics during tides. The numerical results were compared with field data, and the field data provided verification of numerical application: this numerical model is an effective tool for water quality simulation. For point source discharge, COD concentration was simulated with an initial value in the river of zero. The simulated increments and distribution of COD in the water show acceptable agreement with field data. The concentration of DO is much higher in the North Branch than in the South Branch due to consumption of oxygen in the South Branch resulting from discharge of sewage from Shanghai. The DO concentration is greater in the surface layer than in the bottom layer. The DO concentration is low in areas with a depth of less than 20 m, and high in areas between the 20-m and 30-m isobaths. It is concluded that the numerical model is valuable in simulation of water quality in the case of specific point source pollutant discharge. The EFDC model is also of satisfactory accuracy in water quality simulation of the Yangtze Estuary.
Jylhä, Liisi; Honkamo, Johanna; Jantunen, Heli; Sihvola, Ari
2005-05-01
Effective permittivity was modeled and measured for composites that consist of up to 35vol% of titanium dioxide powder dispersed in a continuous epoxy matrix. The study demonstrates a method that enables fast and accurate numerical modeling of the effective permittivity values of ceramic/polymer composites. The model requires electrostatic Monte Carlo simulations, where randomly oriented homogeneous prism-shaped inclusions occupy random positions in the background phase. The computation cost of solving the electrostatic problem by a finite-element code is decreased by the use of an averaging method where the same simulated sample is solved three times with orthogonal field directions. This helps to minimize the artificial anisotropy that results from the pseudorandomness inherent in the limited computational domains. All the required parameters for numerical simulations are calculated from the lattice structure of titanium dioxide. The results show a very good agreement between the measured and numerically calculated effective permittivities. When the prisms are approximated by oblate spheroids with the corresponding axial ratio, a fairly good prediction for the effective permittivity of the mixture can be achieved with the use of an advanced analytical mixing formula.
Expert System Architecture for Rocket Engine Numerical Simulators: A Vision
Mitra, D.; Babu, U.; Earla, A. K.; Hemminger, Joseph A.
1998-01-01
Simulation of any complex physical system like rocket engines involves modeling the behavior of their different components using mostly numerical equations. Typically a simulation package would contain a set of subroutines for these modeling purposes and some other ones for supporting jobs. A user would create an input file configuring a system (part or whole of a rocket engine to be simulated) in appropriate format understandable by the package and run it to create an executable module corresponding to the simulated system. This module would then be run on a given set of input parameters in another file. Simulation jobs are mostly done for performance measurements of a designed system, but could be utilized for failure analysis or a design job such as inverse problems. In order to use any such package the user needs to understand and learn a lot about the software architecture of the package, apart from being knowledgeable in the target domain. We are currently involved in a project in designing an intelligent executive module for the rocket engine simulation packages, which would free any user from this burden of acquiring knowledge on a particular software system. The extended abstract presented here will describe the vision, methodology and the problems encountered in the project. We are employing object-oriented technology in designing the executive module. The problem is connected to the areas like the reverse engineering of any simulation software, and the intelligent systems for simulation.
Numerical simulation and optimization of nickel-hydrogen batteries
Yu, Li-Jun; Qin, Ming-Jun; Zhu, Peng; Yang, Li
2008-05-01
A three-dimensional, transient numerical model of an individual pressure vessel (IPV) nickel-hydrogen battery has been developed based on energy conservation law, mechanisms of heat and mass transfer, and electrochemical reactions in the battery. The model, containing all components of a battery including the battery shell, was utilized to simulate the transient temperature of the battery, using computational fluid dynamics (CFD) technology. The comparison of the model prediction and experimental data shows a good agreement, which means that the present model can be used for the engineering design and parameter optimization of nickel-hydrogen batteries in aerospace power systems. Two kinds of optimization schemes were provided and evaluated by the simulated temperature field. Based on the model, the temperature simulation during five successive periods in a designed space battery was conducted and the simulation results meet the requirement of safe operation.
Numerical Simulation on Natural Convection Cooling of a FM Target
Energy Technology Data Exchange (ETDEWEB)
Park, Jong Pil; Park, Su Ki [KAERI, Daejeon (Korea, Republic of)
2016-05-15
The irradiated FM(Fission-Molly) target is unloaded from the irradiation hole during normal operation, and then cooled down in the reactor pool for a certain period of time. Therefore, it is necessary to identify the minimum decay time needed to cool down FM target sufficiently by natural convection. In the present work, numerical simulations are performed to predict cooling capability of a FM target cooled by natural convection using commercial computational fluid dynamics (CFD) code, CFX. The present study is carried out using CFD code to investigate cooling capability of a FM target cooled by natural convection. The steady state simulation as well as transient simulation is performed in the present work. Based on the transient simulation (T1), the minimum decay time that the maximum fuel temperature does not reach the design limit temperature (TONB-3 .deg. C) is around 15.60 seconds.
GPU based numerical simulation of core shooting process
Directory of Open Access Journals (Sweden)
Yi-zhong Zhang
2017-11-01
Full Text Available Core shooting process is the most widely used technique to make sand cores and it plays an important role in the quality of sand cores. Although numerical simulation can hopefully optimize the core shooting process, research on numerical simulation of the core shooting process is very limited. Based on a two-fluid model (TFM and a kinetic-friction constitutive correlation, a program for 3D numerical simulation of the core shooting process has been developed and achieved good agreements with in-situ experiments. To match the needs of engineering applications, a graphics processing unit (GPU has also been used to improve the calculation efficiency. The parallel algorithm based on the Compute Unified Device Architecture (CUDA platform can significantly decrease computing time by multi-threaded GPU. In this work, the program accelerated by CUDA parallelization method was developed and the accuracy of the calculations was ensured by comparing with in-situ experimental results photographed by a high-speed camera. The design and optimization of the parallel algorithm were discussed. The simulation result of a sand core test-piece indicated the improvement of the calculation efficiency by GPU. The developed program has also been validated by in-situ experiments with a transparent core-box, a high-speed camera, and a pressure measuring system. The computing time of the parallel program was reduced by nearly 95% while the simulation result was still quite consistent with experimental data. The GPU parallelization method can successfully solve the problem of low computational efficiency of the 3D sand shooting simulation program, and thus the developed GPU program is appropriate for engineering applications.
Ullah, Himayat; Harland, Andy R.; Silberschmidt, Vadim V.
2012-10-01
Textile-reinforced composites such as glass fibre-reinforced polymer (GFRP) used in sports products can be exposed to different in-service conditions such as large bending deformation and multiple impacts. Such loading conditions cause high local stresses and strains, which result in multiple modes of damage and fracture in composite laminates due to their inherent heterogeneity and non-trivial microstructure. In this paper, various damage modes in GFRP laminates are studied using experimental material characterisation, non-destructive micro-structural damage evaluation and numerical simulations. Experimental tests are carried out to characterise the behaviour of these materials under large-deflection bending. To obtain in-plane shear properties of laminates, tensile tests are performed using a full-field strain-measurement digital image correlation technique. X-ray micro computed tomography (Micro CT) is used to investigate internal material damage modes - delamination and cracking. Two-dimensional finite element (FE) models are implemented in the commercial code Abaqus to study the deformation behaviour and damage in GFRP. In these models, multiple layers of bilinear cohesive-zone elements are employed to study the onset and progression of inter-ply delamination and intra-ply fabric fracture of composite laminate, based on the X-ray Micro CT study. The developed numerical models are capable to simulate these features with their mechanisms as well as subsequent mode coupling observed in tests and Micro CT scanning. The obtained results of simulations are in agreement with experimental data.
International Nuclear Information System (INIS)
Wang Zhifeng; Ye Xiongying
2013-01-01
Carbon nanotubes (CNTs) filled polymeric composites can be used as a kind of flexible piezoresistive material in potentially many fields. Due to the diversity of CNTs and polymers, the mechanism and features of their piezoresistive behaviour is still not fully understood. This paper reports our investigations into the mechanism and optimization of piezoresistive CNT/polymer composites. Numerical simulation results showed that the junction resistances between CNTs are a major component of the network conductance of the composite as well as the piezoresistive behaviour. Average junction gap variation (AJGV) was introduced as a quantitative description of the conductance variation of a CNT network caused by strain and the conductance variation of the CNT network was found to be dominated by AJGV. Numerical simulation and analytical results indicated that the key parameters affecting AJGV include the orientation and diameter of CNTs, Poisson’s ratio of the polymer, and the concentration of CNTs in the polymer matrix. An optimizing principle was then given for piezoresistive CNT/polymer composites. (paper)
Adaptive implicit method for thermal compositional reservoir simulation
Energy Technology Data Exchange (ETDEWEB)
Agarwal, A.; Tchelepi, H.A. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Stanford Univ., Palo Alto (United States)
2008-10-15
As the global demand for oil increases, thermal enhanced oil recovery techniques are becoming increasingly important. Numerical reservoir simulation of thermal methods such as steam assisted gravity drainage (SAGD) is complex and requires a solution of nonlinear mass and energy conservation equations on a fine reservoir grid. The most currently used technique for solving these equations is the fully IMplicit (FIM) method which is unconditionally stable, allowing for large timesteps in simulation. However, it is computationally expensive. On the other hand, the method known as IMplicit pressure explicit saturations, temperature and compositions (IMPEST) is computationally inexpensive, but it is only conditionally stable and restricts the timestep size. To improve the balance between the timestep size and computational cost, the thermal adaptive IMplicit (TAIM) method uses stability criteria and a switching algorithm, where some simulation variables such as pressure, saturations, temperature, compositions are treated implicitly while others are treated with explicit schemes. This presentation described ongoing research on TAIM with particular reference to thermal displacement processes such as the stability criteria that dictate the maximum allowed timestep size for simulation based on the von Neumann linear stability analysis method; the switching algorithm that adapts labeling of reservoir variables as implicit or explicit as a function of space and time; and, complex physical behaviors such as heat and fluid convection, thermal conduction and compressibility. Key numerical results obtained by enhancing Stanford's General Purpose Research Simulator (GPRS) were also presented along with a list of research challenges. 14 refs., 2 tabs., 11 figs., 1 appendix.
Direct numerical simulations of gas-liquid multiphase flows
Tryggvason, Grétar; Zaleski, Stéphane
2011-01-01
Accurately predicting the behaviour of multiphase flows is a problem of immense industrial and scientific interest. Modern computers can now study the dynamics in great detail and these simulations yield unprecedented insight. This book provides a comprehensive introduction to direct numerical simulations of multiphase flows for researchers and graduate students. After a brief overview of the context and history the authors review the governing equations. A particular emphasis is placed on the 'one-fluid' formulation where a single set of equations is used to describe the entire flow field and
Numerical simulation of flow behavior in tight lattice rod bundle
International Nuclear Information System (INIS)
Yu Yiqi; Yang Yanhua; Gu Hanyang; Cheng Xu; Song Xiaoming; Wang Xiaojun
2009-01-01
The Numerical investigation is performed on the air turbulent flow in triangular rod bundle array. Based on the experimental data, the eddy viscosity turbulent model and the Reynold stress turbulent model are evaluated to simulate the flow behavior in the tight lattice. The results show that SSG Reynolds Stress Model has shown superior predictive performance than other Reynolds-stress models, which indicates that the simulation of the anisotropy of the turbulence is significant in the tight lattice. The result with different Reynolds number and geometry shows that the magnitude of the secondary flow is almost independent of the Reynolds number, but it increases with the decrease of the P/D. (authors)
Numerical simulation of tornado-borne missile impact
International Nuclear Information System (INIS)
Tu, D.K.; Murray, R.C.
1977-01-01
The feasibility of using a finite element procedure to examine the impact phenomenon of a tornado-borne missile impinging on a reinforced concrete barrier was assessed. The major emphasis of this study was to simulate the impact of a nondeformable missile. Several series of simulations were run, using an 8-in.-dia steel slug as the impacting missile. The numerical results were then compared with experimental field tests and empirical formulas. The work is in support of tornado design practices for fuel reprocessing and fuel fabrication plants
Numerical Simulation of Cast Distortion in Gas Turbine Engine Components
International Nuclear Information System (INIS)
Inozemtsev, A A; Dubrovskaya, A S; Dongauser, K A; Trufanov, N A
2015-01-01
In this paper the process of multiple airfoilvanes manufacturing through investment casting is considered. The mathematical model of the full contact problem is built to determine stress strain state in a cast during the process of solidification. Studies are carried out in viscoelastoplastic statement. Numerical simulation of the explored process is implemented with ProCASTsoftware package. The results of simulation are compared with the real production process. By means of computer analysis the optimization of technical process parameters is done in order to eliminate the defect of cast walls thickness variation. (paper)
Numerical simulation of internal reconnection event in spherical tokamak
International Nuclear Information System (INIS)
Hayashi, Takaya; Mizuguchi, Naoki; Sato, Tetsuya
1999-07-01
Three-dimensional magnetohydrodynamic simulations are executed in a full toroidal geometry to clarify the physical mechanisms of the Internal Reconnection Event (IRE), which is observed in the spherical tokamak experiments. The simulation results reproduce several main properties of IRE. Comparison between the numerical results and experimental observation indicates fairly good agreements regarding nonlinear behavior, such as appearance of localized helical distortion, appearance of characteristic conical shape in the pressure profile during thermal quench, and subsequent appearance of the m=2/n=1 type helical distortion of the torus. (author)
Numerical simulation of void growth under dynamic loading
International Nuclear Information System (INIS)
Iqbal, A.
1996-01-01
Following a brief general review of developments in material behavior under high strain rates, a cylindrical cell surrounding a spherical void in OFHC copper is numerically simulated by Zerri-Armstrong model. This simulation results show that the plastic deformation tends to be concentrated in the vicinity of voids either in the axial or transverse direction depending upon the stress state. This event is associated with the accelerated void through accompanying coalescence causing ductile fracture. A3-node triangular mesh generation code used as input for finite element code is developed by a 'Central Generation' technique. (author)
Numerical simulation of low Mach number reacting flows
International Nuclear Information System (INIS)
Bell, J B; Aspden, A J; Day, M S; Lijewski, M J
2007-01-01
Using examples from active research areas in combustion and astrophysics, we demonstrate a computationally efficient numerical approach for simulating multiscale low Mach number reacting flows. The method enables simulations that incorporate an unprecedented range of temporal and spatial scales, while at the same time, allows an extremely high degree of reaction fidelity. Sample applications demonstrate the efficiency of the approach with respect to a traditional time-explicit integration method, and the utility of the methodology for studying the interaction of turbulence with terrestrial and astrophysical flame structures
Deng, Jian; Zhou, Guangming; Ji, Le; Wang, Xiaopei
2017-12-01
Mechanical properties and failure mechanisms of a newly designed 3D multi-layer braided composites are evaluated by experimental, numerical and theoretical studies. The microstructure of the composites is introduced. The unit cell technique is employed to address the periodic arrangement of the structure. The volume averaging method is used in theoretical solutions while FEM with reasonable periodic boundary conditions and meshing technique in numerical simulations. Experimental studies are also conducted to verify the feasibility of the proposed models. Predicted elastic properties agree well with the experimental data, indicating the feasibility of the proposed models. Numerical evaluation is more accurate than theoretical assessment. Deformations and stress distributions of the unit cell under tension shows displacement and traction continuity, guaranteeing the rationality of the applied periodic boundary conditions. Although compression and tension modulus are close, the compressive strength only reaches 70% of the tension strength. This indicates that the composites can be weakened in compressive loading. Additionally, by analysing the micrograph of fracture faces and strain-stress curves, a brittle failure mechanism is observed both in composites under tension and compression.
Numerical simulation of the accident of Three Mile Island
International Nuclear Information System (INIS)
Perrin, M.H.; Kastelanski, P.
1981-01-01
The chief object of the present study was to assess the ability of our numerical code for the dynamic behavior of power plants, SICLE, to handle the simulation of small accidents in PWRs. In the first part of the paper the authors introduce the main principles, equations and numerical methods of the code. In the second part those of the elements of Three Mile Island Power Plant which were simulated, the different phases of the accident and the results obtained with the code are described. These results are compared to the values recorded in the plant and generally a good agreement is found (for instance the primary pressure). As a conclusion SICLE is the minimum code for representing accidents such as Three Mile Island; its main advantage lies in its ability to take into account all the elements of the plant which are important in the study
Numerical simulation of draft tube flow of a bulb turbine
Energy Technology Data Exchange (ETDEWEB)
Coelho, J.G. [Federal University of Triangulo Mineiro, Institute of Technological and Exact Sciences, Avenida Doutor Randolfo Borges Junior, 1250 – Uberaba – MG (Brazil); Brasil, A.C.P. Jr. [University of Brasilia, Department of Mechanical Engineering, Campus Darcy Ribeiro, Brasilia – DF (Brazil)
2013-07-01
In this work a numerical study of draft tube of a bulb hydraulic turbine is presented, where a new geometry is proposed. This new proposal of draft tube has the unaffected ratio area, a great reduction in his length and approximately the same efficiency of the draft tube conventionally used. The numerical simulations were obtained in commercial software of calculation of flow (CFX-14), using the turbulence model SST, that allows a description of the field fluid dynamic near to the wall. The simulation strategy has an intention of identifying the stall of the boundary layer precisely limits near to the wall and recirculations in the central part, once those are the great causes of the decrease of efficiency of a draft tube. Finally, it is obtained qualitative and quantitative results about the flow in draft tubes.
Numerical simulation of the circulation of the atmosphere of Titan
Hourdin, F.; Levan, P.; Talagrand, O.; Courtin, Regis; Gautier, Daniel; Mckay, Christopher P.
1992-01-01
A three dimensional General Circulation Model (GCM) of Titan's atmosphere is described. Initial results obtained with an economical two dimensional (2D) axisymmetric version of the model presented a strong superrotation in the upper stratosphere. Because of this result, a more general numerical study of superrotation was started with a somewhat different version of the GCM. It appears that for a slowly rotating planet which strongly absorbs solar radiation, circulation is dominated by global equator to pole Hadley circulation and strong superrotation. The theoretical study of this superrotation is discussed. It is also shown that 2D simulations systemically lead to instabilities which make 2D models poorly adapted to numerical simulation of Titan's (or Venus) atmosphere.
Three-dimensional numerical simulation during laser processing of CFRP
Ohkubo, Tomomasa; Sato, Yuji; Matsunaga, Ei-ichi; Tsukamoto, Masahiro
2017-09-01
We performed three-dimensional numerical simulation about laser processing of carbon-fiber-reinforced plastic (CFRP) using OpenFOAM as libraries of finite volume method (FVM). Although a little theoretical or numerical studies about heat affected zone (HAZ) formation were performed, there is no research discussing how HAZ is generated considering time development about removal of each material. It is important to understand difference of removal speed of carbon fiber and resin in order to improve quality of cut surface of CFRP. We demonstrated how the carbon fiber and resin are removed by heat of ablation plume by our simulation. We found that carbon fiber is removed faster than resin at first stage because of the difference of thermal conductivity, and after that, the resin is removed faster because of its low combustion temperature. This result suggests the existence of optimal contacting time of the laser ablation and kerf of the target.
3D numerical simulation and analysis of railgun gouging mechanism
Directory of Open Access Journals (Sweden)
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.
Numerical Relativity Simulations for Black Hole Merger Astrophysics
Baker, John G.
2010-01-01
Massive black hole mergers are perhaps the most energetic astronomical events, establishing their importance as gravitational wave sources for LISA, and also possibly leading to observable influences on their local environments. Advances in numerical relativity over the last five years have fueled the development of a rich physical understanding of general relativity's predictions for these events. Z will overview the understanding of these event emerging from numerical simulation studies. These simulations elucidate the pre-merger dynamics of the black hole binaries, the consequent gravitational waveform signatures ' and the resulting state, including its kick velocity, for the final black hole produced by the merger. Scenarios are now being considered for observing each of these aspects of the merger, involving both gravitational-wave and electromagnetic astronomy.
Ultrasonic NDE Simulation for Composite Manufacturing Defects
Leckey, Cara A. C.; Juarez, Peter D.
2016-01-01
The increased use of composites in aerospace components is expected to continue into the future. The large scale use of composites in aerospace necessitates the development of composite-appropriate nondestructive evaluation (NDE) methods to quantitatively characterize defects in as-manufactured parts and damage incurred during or post manufacturing. Ultrasonic techniques are one of the most common approaches for defect/damage detection in composite materials. One key technical challenge area included in NASA's Advanced Composite's Project is to develop optimized rapid inspection methods for composite materials. Common manufacturing defects in carbon fiber reinforced polymer (CFRP) composites include fiber waviness (in-plane and out-of-plane), porosity, and disbonds; among others. This paper is an overview of ongoing work to develop ultrasonic wavefield based methods for characterizing manufacturing waviness defects. The paper describes the development and implementation of a custom ultrasound simulation tool that is used to model ultrasonic wave interaction with in-plane fiber waviness (also known as marcelling). Wavefield data processing methods are applied to the simulation data to explore possible routes for quantitative defect characterization.
Experimentation and numerical simulation of steel fibre reinforced concrete pipes
International Nuclear Information System (INIS)
Fuente, A. de la; Domingues de Figueiredo, A.; Aguado, A.; Molins, C.; Chama Neto, P. J.
2011-01-01
The results concerning on an experimental and a numerical study related to SFRCP are presented. Eighteen pipes with an internal diameter of 600 mm and fibre dosages of 10, 20 and 40 kg/m3 were manufactured and tested. Some technological aspects were concluded. Likewise, a numerical parameterized model was implemented. With this model, the simulation of the resistant behaviour of SFRCP can be performed. In this sense, the results experimentally obtained were contrasted with those suggested by means MAP reaching very satisfactory correlations. Taking it into account, it could be said that the numerical model is a useful tool for the optimal design of the SFRCP fibre dosages, avoiding the need of the systematic employment of the test as an indirect design method. Consequently, the use of this model would reduce the overall cost of the pipes and would give fibres a boost as a solution for this structural typology. (Author) 27 refs.
Numerical Simulation of Polynomial-Speed Convergence Phenomenon
Li, Yao; Xu, Hui
2017-11-01
We provide a hybrid method that captures the polynomial speed of convergence and polynomial speed of mixing for Markov processes. The hybrid method that we introduce is based on the coupling technique and renewal theory. We propose to replace some estimates in classical results about the ergodicity of Markov processes by numerical simulations when the corresponding analytical proof is difficult. After that, all remaining conclusions can be derived from rigorous analysis. Then we apply our results to seek numerical justification for the ergodicity of two 1D microscopic heat conduction models. The mixing rate of these two models are expected to be polynomial but very difficult to prove. In both examples, our numerical results match the expected polynomial mixing rate well.
Numerical simulation of droplet evaporation between two circular plates
International Nuclear Information System (INIS)
Bam, Hang Jin; Son, Gi Hun
2015-01-01
Numerical simulation is performed for droplet evaporation between two circular plates. The flow and thermal characteristics of the droplet evaporation are numerically investigated by solving the conservation equations of mass, momentum, energy and mass fraction in the liquid and gas phases. The liquid-gas interface is tracked by a sharp-interface level-set method which is modified to include the effects of evaporation at the liquid-gas interface and contact angle hysteresis at the liquid-gas-solid contact line. An analytical model to predict the droplet evaporation is also developed by simplifying the mass and vapor fraction equations in the gas phase. The numerical results demonstrate that the 1-D analytical prediction is not applicable to the high rate evaporation process. The effects of plate gap and receding contact angle on the droplet evaporation are also quantified.
Determination of adsorption parameters in numerical simulation for polymer flooding
Bao, Pengyu; Li, Aifen; Luo, Shuai; Dang, Xu
2018-02-01
A study on the determination of adsorption parameters for polymer flooding simulation was carried out. The study mainly includes polymer static adsorption and dynamic adsorption. The law of adsorption amount changing with polymer concentration and core permeability was presented, and the one-dimensional numerical model of CMG was established under the support of a large number of experimental data. The adsorption laws of adsorption experiments were applied to the one-dimensional numerical model to compare the influence of two adsorption laws on the historical matching results. The results show that the static adsorption and dynamic adsorption abide by different rules, and differ greatly in adsorption. If the static adsorption results were directly applied to the numerical model, the difficulty of the historical matching will increase. Therefore, dynamic adsorption tests in the porous medium are necessary before the process of parameter adjustment in order to achieve the ideal history matching result.
MHD turbulent dynamo in astrophysics: Theory and numerical simulation
Chou, Hongsong
2001-10-01
This thesis treats the physics of dynamo effects through theoretical modeling of magnetohydrodynamic (MHD) systems and direct numerical simulations of MHD turbulence. After a brief introduction to astrophysical dynamo research in Chapter 1, the following issues in developing dynamic models of dynamo theory are addressed: In Chapter 2, nonlinearity that arises from the back reaction of magnetic field on velocity field is considered in a new model for the dynamo α-effect. The dependence of α-coefficient on magnetic Reynolds number, kinetic Reynolds number, magnetic Prandtl number and statistical properties of MHD turbulence is studied. In Chapter 3, the time-dependence of magnetic helicity dynamics and its influence on dynamo effects are studied with a theoretical model and 3D direct numerical simulations. The applicability of and the connection between different dynamo models are also discussed. In Chapter 4, processes of magnetic field amplification by turbulence are numerically simulated with a 3D Fourier spectral method. The initial seed magnetic field can be a large-scale field, a small-scale magnetic impulse, and a combination of these two. Other issues, such as dynamo processes due to helical Alfvénic waves and the implication and validity of the Zeldovich relation, are also addressed in Appendix B and Chapters 4 & 5, respectively. Main conclusions and future work are presented in Chapter 5. Applications of these studies are intended for astrophysical magnetic field generation through turbulent dynamo processes, especially when nonlinearity plays central role. In studying the physics of MHD turbulent dynamo processes, the following tools are developed: (1)A double Fourier transform in both space and time for the linearized MHD equations (Chapter 2 and Appendices A & B). (2)A Fourier spectral numerical method for direct simulation of 3D incompressible MHD equations (Appendix C).
Numerical Simulation of Nanofluid Suspensions in a Geothermal Heat Exchanger
Xiao-Hui Sun; Hongbin Yan; Mehrdad Massoudi; Zhi-Hua Chen; Wei-Tao Wu
2018-01-01
It has been shown that using nanofluids as heat carrier fluids enhances the conductive and convective heat transfer of geothermal heat exchangers. In this paper, we study the stability of nanofluids in a geothermal exchanger by numerically simulating nanoparticle sedimentation during a shut-down process. The nanofluid suspension is modeled as a non-linear complex fluid; the nanoparticle migration is modeled by a particle flux model, which includes the effects of Brownian motion, gravity, turb...
Numerical simulations of the decay of primordial magnetic turbulence
International Nuclear Information System (INIS)
Kahniashvili, Tina; Brandenburg, Axel; Tevzadze, Alexander G.; Ratra, Bharat
2010-01-01
We perform direct numerical simulations of forced and freely decaying 3D magnetohydrodynamic turbulence in order to model magnetic field evolution during cosmological phase transitions in the early Universe. Our approach assumes the existence of a magnetic field generated either by a process during inflation or shortly thereafter, or by bubble collisions during a phase transition. We show that the final configuration of the magnetic field depends on the initial conditions, while the velocity field is nearly independent of initial conditions.
Numerical simulation methods for wave propagation through optical waveguides
International Nuclear Information System (INIS)
Sharma, A.
1993-01-01
The simulation of the field propagation through waveguides requires numerical solutions of the Helmholtz equation. For this purpose a method based on the principle of orthogonal collocation was recently developed. The method is also applicable to nonlinear pulse propagation through optical fibers. Some of the salient features of this method and its application to both linear and nonlinear wave propagation through optical waveguides are discussed in this report. 51 refs, 8 figs, 2 tabs
Numerical Simulation on Zonal Disintegration in Deep Surrounding Rock Mass
Xuguang Chen; Yuan Wang; Yu Mei; Xin Zhang
2014-01-01
Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the generating condition and forming process of zonal disintegration. Via comparing the results with the geomechanical model test, the zonal disintegration p...
Numerical simulation of vertical infiltration for leaching fluid in situ
International Nuclear Information System (INIS)
Li Jinxuan; Shi Weijun; Zhang Weimin
1998-01-01
Based on the analysis of movement law of leaching fluid in breaking and leaching experiment in situ, the movement of leaching fluid can be divided into two main stages in the leaching process in situ: Vertical Infiltration in unsaturation zone and horizontal runoff in saturation zone. The corresponding mathematics models are sep up, and the process of vertical infiltration of leaching fluid is numerically simulated
EXTENDED SCALING LAWS IN NUMERICAL SIMULATIONS OF MAGNETOHYDRODYNAMIC TURBULENCE
International Nuclear Information System (INIS)
Mason, Joanne; Cattaneo, Fausto; Perez, Jean Carlos; Boldyrev, Stanislav
2011-01-01
Magnetized turbulence is ubiquitous in astrophysical systems, where it notoriously spans a broad range of spatial scales. Phenomenological theories of MHD turbulence describe the self-similar dynamics of turbulent fluctuations in the inertial range of scales. Numerical simulations serve to guide and test these theories. However, the computational power that is currently available restricts the simulations to Reynolds numbers that are significantly smaller than those in astrophysical settings. In order to increase computational efficiency and, therefore, probe a larger range of scales, one often takes into account the fundamental anisotropy of field-guided MHD turbulence, with gradients being much slower in the field-parallel direction. The simulations are then optimized by employing the reduced MHD equations and relaxing the field-parallel numerical resolution. In this work we explore a different possibility. We propose that there exist certain quantities that are remarkably stable with respect to the Reynolds number. As an illustration, we study the alignment angle between the magnetic and velocity fluctuations in MHD turbulence, measured as the ratio of two specially constructed structure functions. We find that the scaling of this ratio can be extended surprisingly well into the regime of relatively low Reynolds number. However, the extended scaling easily becomes spoiled when the dissipation range in the simulations is underresolved. Thus, taking the numerical optimization methods too far can lead to spurious numerical effects and erroneous representation of the physics of MHD turbulence, which in turn can affect our ability to identify correctly the physical mechanisms that are operating in astrophysical systems.
Numerical Simulations of Settlement of Jet Grouting Columns
Directory of Open Access Journals (Sweden)
Juzwa Anna
2016-03-01
Full Text Available The paper presents the comparison of results of numerical analyses of interaction between group of jet grouting columns and subsoil. The analyses were conducted for single column and groups of three, seven and nine columns. The simulations are based on experimental research in real scale which were carried out by authors. The final goal for the research is an estimation of an influence of interaction between columns working in a group.
Numerical simulation methods of fires in nuclear power plants
International Nuclear Information System (INIS)
Keski-Rahkonen, O.; Bjoerkman, J.; Heikkilae, L.
1992-01-01
Fire is a significant hazard to the safety of nuclear power plants (NPP). Fire may be serious accident as such, but even small fire at a critical point in a NPP may cause an accident much more serious than fire itself. According to risk assessments a fire may be an initial cause or a contributing factor in a large part of reactor accidents. At the Fire Technology and the the Nuclear Engineering Laboratory of the Technical Research Centre of Finland (VTT) fire safety research for NPPs has been carried out in a large extent since 1985. During years 1988-92 a project Advanced Numerical Modelling in Nuclear Power Plants (PALOME) was carried out. In the project the level of numerical modelling for fire research in Finland was improved by acquiring, preparing for use and developing numerical fire simulation programs. Large scale test data of the German experimental program (PHDR Sicherheitsprogramm in Kernforschungscentral Karlsruhe) has been as reference. The large scale tests were simulated by numerical codes and results were compared to calculations carried out by others. Scientific interaction with outstanding foreign laboratories and scientists has been an important part of the project. This report describes the work of PALOME-project carried out at the Fire Technology Laboratory only. A report on the work at the Nuclear Engineering Laboratory will be published separatively. (au)
Transient productivity index for numerical well test simulations
Energy Technology Data Exchange (ETDEWEB)
Blanc, G.; Ding, D.Y.; Ene, A. [Institut Francais du Petrole, Pau (France)] [and others
1997-08-01
The most difficult aspect of numerical simulation of well tests is the treatment of the Bottom Hole Flowing (BHF) Pressure. In full field simulations, this pressure is derived from the Well-block Pressure (WBP) using a numerical productivity index which accounts for the grid size and permeability, and for the well completion. This productivity index is calculated assuming a pseudo-steady state flow regime in the vicinity of the well and is therefore constant during the well production period. Such a pseudo-steady state assumption is no longer valid for the early time of a well test simulation as long as the pressure perturbation has not reached several grid-blocks around the well. This paper offers two different solutions to this problem: (1) The first one is based on the derivation of a Numerical Transient Productivity Index (NTPI) to be applied to Cartesian grids; (2) The second one is based on the use of a Corrected Transmissibility and Accumulation Term (CTAT) in the flow equation. The representation of the pressure behavior given by both solutions is far more accurate than the conventional one as shown by several validation examples which are presented in the following pages.
Automated numerical simulation of cracked plates, pipes and elbows
International Nuclear Information System (INIS)
Reddy, Babu; Sreehari Kumar, B.; Bhate, S.R.; Kushwaha, H.S.
2008-01-01
In the nuclear industry, piping components are one of the key elements participating in its operation. Integrity of structural tubes and pipes plays a major role in nuclear power plants. The ideal procedure to ensure this aspect would be to conduct experimental studies on pilot/test specimens. However, it may not always be feasible to carry out the experimental investigation, as it requires pre-requisite infrastructure which may not be economically viable. This makes it imperative to conduct numerical simulations of the same particularly in the study of presence of cracks in the critical components. While performing the effect of cracks, the quality of the finite element mesh nearer to the crack tip plays a critical role while estimating J-integral value. The designer is often familiar with design methodology only and he obviously requires a convenient and reliable numerical tool to model and perform the analysis. In this context, an effort has been made in NISA, the general purpose finite element software, to automate the generation of FE meshes for a set of pre-defined components with different crack configurations. To simplify the procedure of FE mesh generation, analysis, and post processing, a graphical user interface (GUI) has been developed accordingly. This paper discusses the automated numerical simulation of plates and pipes with different crack configurations. This simulation software is also designed to help parametric study of cracked pipes. (author)
Efficient numerical simulation of heat storage in subsurface georeservoirs
Boockmeyer, A.; Bauer, S.
2015-12-01
The transition of the German energy market towards renewable energy sources, e.g. wind or solar power, requires energy storage technologies to compensate for their fluctuating production. Large amounts of energy could be stored in georeservoirs such as porous formations in the subsurface. One possibility here is to store heat with high temperatures of up to 90°C through borehole heat exchangers (BHEs) since more than 80 % of the total energy consumption in German households are used for heating and hot water supply. Within the ANGUS+ project potential environmental impacts of such heat storages are assessed and quantified. Numerical simulations are performed to predict storage capacities, storage cycle times, and induced effects. For simulation of these highly dynamic storage sites, detailed high-resolution models are required. We set up a model that accounts for all components of the BHE and verified it using experimental data. The model ensures accurate simulation results but also leads to large numerical meshes and thus high simulation times. In this work, we therefore present a numerical model for each type of BHE (single U, double U and coaxial) that reduces the number of elements and the simulation time significantly for use in larger scale simulations. The numerical model includes all BHE components and represents the temporal and spatial temperature distribution with an accuracy of less than 2% deviation from the fully discretized model. By changing the BHE geometry and using equivalent parameters, the simulation time is reduced by a factor of ~10 for single U-tube BHEs, ~20 for double U-tube BHEs and ~150 for coaxial BHEs. Results of a sensitivity study that quantify the effects of different design and storage formation parameters on temperature distribution and storage efficiency for heat storage using multiple BHEs are then shown. It is found that storage efficiency strongly depends on the number of BHEs composing the storage site, their distance and
Numerical simulator of the CANDU fueling machine driving desk
International Nuclear Information System (INIS)
Doca, Cezar
2008-01-01
As a national and European premiere, in the 2003 - 2005 period, at the Institute for Nuclear Research Pitesti two CANDU fueling machine heads, no.4 and no.5, for the Nuclear Power Plant Cernavoda - Unit 2 were successfully tested. To perform the tests of these machines, a special CANDU fueling machine testing rig was built and was (and is) available for this goal. The design of the CANDU fueling machine test rig from the Institute for Nuclear Research Pitesti is a replica of the similar equipment operating in CANDU 6 type nuclear power plants. High technical level of the CANDU fueling machine tests required the using of an efficient data acquisition and processing Computer Control System. The challenging goal was to build a computer system (hardware and software) designed and engineered to control the test and calibration process of these fuel handling machines. The design takes care both of the functionality required to correctly control the CANDU fueling machine and of the additional functionality required to assist the testing process. Both the fueling machine testing rig and staff had successfully assessed by the AECL representatives during two missions. At same the time, at the Institute for Nuclear Research Pitesti was/is developed a numerical simulator for the CANDU fueling machine operators training. The paper presents the numerical simulator - a special PC program (software) which simulates the graphics and the functions and the operations at the main desk of the computer control system. The simulator permits 'to drive' a CANDU fueling machine in two manners: manual or automatic. The numerical simulator is dedicated to the training of operators who operate the CANDU fueling machine in a nuclear power plant with CANDU reactor. (author)
Numerical Simulation of Liquid Sloshing Problem under Resonant Excitation
Directory of Open Access Journals (Sweden)
Fu-kun Gui
2014-04-01
Full Text Available Numerical simulations were conducted to investigate the fluid resonance in partially filled rectangular tank based on the OpenFOAM package of viscous fluid model. The numerical model was validated by the available theoretical, numerical, and experimental data. The study was mainly focused on the large amplitude sloshing motion and the corresponding impact force around the resonant condition. It was found that, for the 2D situation, the double pressure peaks happened near to the side walls around the still water level. And they were corresponding to the local free surface rising up and set-down, respectively. The impulsive loads on the tank corner with extreme magnitudes were observed as the free surface impacted the ceiling. The 3D numerical results showed that the free surface amplitudes along the side walls varied diversely, depending on the direction and frequency of the external excitation. The characteristics of the pressure around the still water level and tank ceiling were also presented. According to the computational results, it was found that the 2D numerical model can predict the impact loads near the still water level as accurately as 3D model. However, the impulsive pressure near the tank ceiling corner was remarkably underestimated.
NDE and SHM Simulation for CFRP Composites
Leckey, Cara A. C.; Parker, F. Raymond
2014-01-01
Ultrasound-based nondestructive evaluation (NDE) is a common technique for damage detection in composite materials. There is a need for advanced NDE that goes beyond damage detection to damage quantification and characterization in order to enable data driven prognostics. The damage types that exist in carbon fiber-reinforced polymer (CFRP) composites include microcracking and delaminations, and can be initiated and grown via impact forces (due to ground vehicles, tool drops, bird strikes, etc), fatigue, and extreme environmental changes. X-ray microfocus computed tomography data, among other methods, have shown that these damage types often result in voids/discontinuities of a complex volumetric shape. The specific damage geometry and location within ply layers affect damage growth. Realistic threedimensional NDE and structural health monitoring (SHM) simulations can aid in the development and optimization of damage quantification and characterization techniques. This paper is an overview of ongoing work towards realistic NDE and SHM simulation tools for composites, and also discusses NASA's need for such simulation tools in aeronautics and spaceflight. The paper describes the development and implementation of a custom ultrasound simulation tool that is used to model ultrasonic wave interaction with realistic 3-dimensional damage in CFRP composites. The custom code uses elastodynamic finite integration technique and is parallelized to run efficiently on computing cluster or multicore machines.
Numerical simulation of flow-induced vibrations in tube bundles
International Nuclear Information System (INIS)
Elisabeth Longatte; Zaky Bendjeddou; Mhamed Souli
2005-01-01
Full text of publication follows: In many industrial components mechanical structures like rod cluster control assembly, fuel assembly and heat exchanger tube bundles are submitted to complex flows causing possible vibrations and damage. Fluid forces are usually split into two parts: structure motion independent forces and fluid-elastic forces coupled with tube motion and responsible for possible dynamic instability development leading to possible short term failures through high amplitude vibrations. Most classical fluid force identification methods rely on structure response experimental measurements associated with convenient data processes. Owing to recent improvements in Computational Fluid Dynamics (C.F.D.), numerical fluid force identification is now practicable in the presence of industrial configurations. The present paper is devoted to numerical simulation of flow-induced vibrations of tube bundles submitted to single-phase cross flows by using C.F.D. codes. Direct Numerical Simulation (D.N.S.), Arbitrary Lagrange Euler formulation (A.L.E.) and code coupling process are involved to predict fluid forces responsible for tube bundle vibrations in the presence of fluid structure and fluid-elastic coupling effects. In the presence of strong multi-physics coupling, simulation of flow-induced vibrations requires a fluid structure code coupling process. The methodology consists in solving in the same time thermohydraulics and mechanics problems by using an A.L.E. formulation for the fluid computation. The purpose is to take into account coupling between flow and structure motions in order to be able to capture coupling effects. From a numerical point of view, there are three steps in the computation: the fluid problem is solved on the computational domain; fluid forces acting on the moving tube are estimated; finally they are introduced in the structure solver providing the tube displacement that is used to actualize the fluid computational domain. Specific
Direct Numerical Simulations of Rayleigh-Taylor instability
International Nuclear Information System (INIS)
Livescu, D; Wei, T; Petersen, M R
2011-01-01
The development of the Rayleigh-Taylor mixing layer is studied using data from an extensive new set of Direct Numerical Simulations (DNS), performed on the 0.5 Petaflops, 150k compute cores BG/L Dawn supercomputer at Lawrence Livermore National Laboratory. This includes a suite of simulations with grid size of 1024 2 × 4608 and Atwood number ranging from 0.04 to 0.9, in order to examine small departures from the Boussinesq approximation as well as large Atwood number effects, and a high resolution simulation of grid size 4096 2 × 4032 and Atwood number of 0.75. After the layer width had developed substantially, additional branched simulations have been run under reversed and zero gravity conditions. While the bulk of the results will be published elsewhere, here we present preliminary results on: 1) the long-standing open question regarding the discrepancy between the numerically and experimentally measured mixing layer growth rates and 2) mixing characteristics.
Numerical simulation of plasma vertical position stabilization in ITER
International Nuclear Information System (INIS)
Astapkovich, A.M.; Sadakov, S.N.
1992-01-01
The paper deals with numerical simulation of plasma vertical position stabilization in ITER. The calculations are performed using EDDY C-2 code by the method of direct numerical simulation of transient electromagnetic processes taking into account the evolution of plasma position, cross-section shape and full plasma current. When simulating free vertical plasma drift in ITER with twin passive stabilization loops, it was shown that account of the effects of cross-section deformation and plasma current alternations results in almost two fold degradation of passive stabilization parameters as compared to the calculations for 'rigid displacement' model. In terms of methodology, the account of the effects of cross section deformation and plasma current alternations requires clarification of the definitions for reverse increment of vertical instability and for stability margin coefficient. The simulation of plasma pinch return to equilibrium position after the closure of control coils allows to assess the required parameters of active control system and demonstrate the effect of screen current reverse in twin loops. The obtained results were used to develop the ITER conceptual design and affected the choice of the concept of twin passive loops and new positron of control coils as the basis approaches. 11 refs.; 12 figs.; 1 tab
Numerical simulations of rubber bearing tests and shaking table tests
International Nuclear Information System (INIS)
Hirata, K.; Matsuda, A.; Yabana, S.
2002-01-01
Test data concerning rubber bearing tests and shaking table tests of base-isolated model conducted by CRIEPI are provided to the participants of Coordinated Research Program (CRP) on 'Intercomparison of Analysis Methods for predicting the behaviour of Seismically Isolated Nuclear Structure', which is organized by International Atomic Energy Agency (IAEA), for the comparison study of numerical simulation of base-isolated structure. In this paper outlines of the test data provided and the numerical simulations of bearing tests and shaking table tests are described. Using computer code ABAQUS, numerical simulations of rubber bearing tests are conducted for NRBs, LRBs (data provided by CRIEPI) and for HDRs (data provided by ENEA/ENEL and KAERI). Several strain energy functions are specified according to the rubber material test corresponding to each rubber bearing. As for lead plug material in LRB, mechanical characteristics are reevaluated and are made use of. Simulation results for these rubber bearings show satisfactory agreement with the test results. Shaking table test conducted by CRIEPI is of a base isolated rigid mass supported by LRB. Acceleration time histories, displacement time histories of the isolators as well as cyclic loading test data of the LRB used for the shaking table test are provided to the participants of the CRP. Simulations of shaking table tests are conducted for this rigid mass, and also for the steel frame model which is conducted by ENEL/ENEA. In the simulation of the rigid mass model test, where LRBs are used, isolators are modeled either by bilinear model or polylinear model. In both cases of modeling of isolators, simulation results show good agreement with the test results. In the case of the steel frame model, where HDRs are used as isolators, bilinear model and polylinear model are also used for modeling isolators. The response of the model is simulated comparatively well in the low frequency range of the floor response, however, in
Hygrothermal Numerical Simulation Tools Applied to Building Physics
Delgado, João M P Q; Ramos, Nuno M M; Freitas, Vasco Peixoto
2013-01-01
This book presents a critical review on the development and application of hygrothermal analysis methods to simulate the coupled transport processes of Heat, Air, and Moisture (HAM) transfer for one or multidimensional cases. During the past few decades there has been relevant development in this field of study and an increase in the professional use of tools that simulate some of the physical phenomena that are involved in Heat, Air and Moisture conditions in building components or elements. Although there is a significant amount of hygrothermal models referred in the literature, the vast majority of them are not easily available to the public outside the institutions where they were developed, which restricts the analysis of this book to only 14 hygrothermal modelling tools. The special features of this book are (a) a state-of-the-art of numerical simulation tools applied to building physics, (b) the boundary conditions importance, (c) the material properties, namely, experimental methods for the measuremen...
Numerical simulation of plasma processes driven by transverse ion heating
Singh, Nagendra; Chan, C. B.
1993-01-01
The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.
Numerical Simulation of Flow Behavior within a Venturi Scrubber
M. M. Toledo-Melchor; C. del C. Gutiérrez-Torres; J. A. Jiménez-Bernal; J. G. Barbosa-Saldaña; S. A. Martínez-Delgadillo; H. R. Mollinedo-Ponce de León; A. Yoguéz-Seoane; A. Alonzo-García
2014-01-01
The present work details the three-dimensional numerical simulation of single-phase and two-phase flow (air-water) in a venturi scrubber with an inlet and throat diameters of 250 and 122.5 mm, respectively. The dimensions and operating parameters correspond to industrial applications. The mass flow rate conditions were 0.483 kg/s, 0.736 kg/s, 0.861 kg/s, and 0.987 kg/s for the gas only simulation; the mass flow rate for the liquid was 0.013 kg/s and 0.038 kg/s. The gas flow was simulated in f...
Numerical Simulation of Liquid Nitrogen Chilldown of a Vertical Tube
Darr, Samuel; Hu, Hong; Schaeffer, Reid; Chung, Jacob; Hartwig, Jason; Majumdar, Alok
2015-01-01
This paper presents the results of a one-dimensional numerical simulation of the transient chilldown of a vertical stainless steel tube with liquid nitrogen. The direction of flow is downward (with gravity) through the tube. Heat transfer correlations for film, transition, and nucleate boiling, as well as critical heat flux, rewetting temperature, and the temperature at the onset of nucleate boiling were used to model the convection to the tube wall. Chilldown curves from the simulations were compared with data from 55 recent liquid nitrogen chilldown experiments. With these new correlations the simulation is able to predict the time to rewetting temperature and time to onset of nucleate boiling to within 25% for mass fluxes ranging from 61.2 to 1150 kg/(sq m s), inlet pressures from 175 to 817 kPa, and subcooled inlet temperatures from 0 to 14 K below the saturation temperature.
Real-Time Numerical Simulation of the Carnot Cycle
International Nuclear Information System (INIS)
Hurkala, J.; Gall, M.; Kutner, R.; Maciejczyk, M.
2005-01-01
We developed a highly interactive, multi-windows Java applet which made it possible to simulate and visualize within any platform and internet the Carnot cycle (or engine) in a real-time computer experiment. We extended our previous model and algorithm to simulate not only the heat flow but also the macroscopic movement of the piston. since in reality it is impossible to construct a reversible Carnot engine, the question arises whether it is possible to simulate it at least in a numerical experiment? The positive answer to this question which we found is related to our model and algorithm which make it possible to omit the many-body problem arising when many gas particles simultaneously interact with the mobile piston. As usually the considerations of phenomenomenological thermodynamics began with a study of the basic properties of heat engines hence our approach, beside intrinsic physical significance, is also important from the educational, technological and even environmental points of view. (author)
Direct numerical simulation of bubbles with parallelized adaptive mesh refinement
International Nuclear Information System (INIS)
Talpaert, A.
2015-01-01
The study of two-phase Thermal-Hydraulics is a major topic for Nuclear Engineering for both security and efficiency of nuclear facilities. In addition to experiments, numerical modeling helps to knowing precisely where bubbles appear and how they behave, in the core as well as in the steam generators. This work presents the finest scale of representation of two-phase flows, Direct Numerical Simulation of bubbles. We use the 'Di-phasic Low Mach Number' equation model. It is particularly adapted to low-Mach number flows, that is to say flows which velocity is much slower than the speed of sound; this is very typical of nuclear thermal-hydraulics conditions. Because we study bubbles, we capture the front between vapor and liquid phases thanks to a downward flux limiting numerical scheme. The specific discrete analysis technique this work introduces is well-balanced parallel Adaptive Mesh Refinement (AMR). With AMR, we refined the coarse grid on a batch of patches in order to locally increase precision in areas which matter more, and capture fine changes in the front location and its topology. We show that patch-based AMR is very adapted for parallel computing. We use a variety of physical examples: forced advection, heat transfer, phase changes represented by a Stefan model, as well as the combination of all those models. We will present the results of those numerical simulations, as well as the speed up compared to equivalent non-AMR simulation and to serial computation of the same problems. This document is made up of an abstract and the slides of the presentation. (author)
Heavy impurity transport in the TFR tokamak. Comparison of line emission with numerical simulations
International Nuclear Information System (INIS)
1982-10-01
Heavy element ion line emissions have been simulated with a numerical code using two adjustable, independent of radius, parameters in the flux density expression: an anomalous diffusion coefficient Dsub(A) and an inward convective velocity Vsub(A). Previously reported results on the laser blow-off injection of V, Cr, and Ni have thus been interpreted. The quasi-stationary phase of ohmically-heated high-density (nsub(e)(0)approximately1.5x10 14 cm -3 ) discharges has also been simulated, thus allowing the plasma ''chemical'' composition and the radiated power to be calculated
Direct Numerical Simulation of Turbulent Flow Over Complex Bathymetry
Yue, L.; Hsu, T. J.
2017-12-01
Direct numerical simulation (DNS) is regarded as a powerful tool in the investigation of turbulent flow featured with a wide range of time and spatial scales. With the application of coordinate transformation in a pseudo-spectral scheme, a parallelized numerical modeling system was created aiming at simulating flow over complex bathymetry with high numerical accuracy and efficiency. The transformed governing equations were integrated in time using a third-order low-storage Runge-Kutta method. For spatial discretization, the discrete Fourier expansion was adopted in the streamwise and spanwise direction, enforcing the periodic boundary condition in both directions. The Chebyshev expansion on Chebyshev-Gauss-Lobatto points was used in the wall-normal direction, assuming there is no-slip on top and bottom walls. The diffusion terms were discretized with a Crank-Nicolson scheme, while the advection terms dealiased with the 2/3 rule were discretized with an Adams-Bashforth scheme. In the prediction step, the velocity was calculated in physical domain by solving the resulting linear equation directly. However, the extra terms introduced by coordinate transformation impose a strict limitation to time step and an iteration method was applied to overcome this restriction in the correction step for pressure by solving the Helmholtz equation. The numerical solver is written in object-oriented C++ programing language utilizing Armadillo linear algebra library for matrix computation. Several benchmarking cases in laminar and turbulent flow were carried out to verify/validate the numerical model and very good agreements are achieved. Ongoing work focuses on implementing sediment transport capability for multiple sediment classes and parameterizations for flocculation processes.
A numerical analysis of crack growth in brittle microcracking composites
International Nuclear Information System (INIS)
Biner, S.B.
1993-01-01
A set of numerical analyses of crack growth was performed to elucidate the mechanism of microcracking on the observed fracture behavior of brittle solids and composites. The random nucleation, orientation and size effects of discrete microcracks and resulting interactions are fully accounted for in a hybrid finite element model. The results indicate that the energy expenditure due the microcrack nucleation seems not to contribute significantly to the resistance to crack growth. The main controlling parameter appears to be elastic interaction of the microcracks with the main crack in the absence of a reinforcing phase; therefore, the microcrack density plays an important role. In the case of the composites, the interaction of the main crack with the stress fields of the reinforcing phase, rather than interaction of microcracks, is the controlling parameter for the resistance to the crack growth even in the presence of a large population of microcracks. It will be also shown that the crack branching and crack kinking can readily develop as a result of microcracking
Numerical simulation of microstructure of the GeSi alloy
Energy Technology Data Exchange (ETDEWEB)
Rasin, I.
2006-09-08
The goal of this work is to investigate pattern formation processes on the solid-liquid interface during the crystal growth of GeSi. GeSi crystals with cellular structure have great potential for applications in -ray and neutron optics. The interface patterns induce small quasi-periodic distortions of the microstructure called mosaicity. Existence and properties of this mosaicity are important for the application of the crystals. The properties depend on many factors; this dependence, is currently not known even not qualitatively. A better understanding of the physics near the crystal surface is therefore required, in order to optimise the growth process. There are three main physical processes in this system: phase-transition, diffusion and melt flow. Every process is described by its own set of equations. Finite difference methods and lattice kinetic methods are taken for solving these governing equations. We have developed a modification of the kinetic methods for the advectiondiffusion and extended this method for simulations of non-linear reaction diffusion equations. The phase-field method was chosen as a tool for describing the phase-transition. There are numerous works applied for different metallic alloys. An attempt to apply the method directly to simulation GeSi crystal growth showed that this method is unstable. This instability has not been observed in previous works due to the much smaller scale of simulations. We introduced a modified phase-field scheme, which enables to simulate pattern formation with the scale observed in experiment. A flow in the melt was taken in to account in the numerical model. The developed numerical model allows us to investigate pattern formation in GeSi crystals. Modelling shows that the flow near the crystal surface has impact on the patterns. The obtained patterns reproduce qualitatively and in some cases quantitatively the experimental results. (orig.)
Numerical simulation of a mistral wind event occuring
Guenard, V.; Caccia, J. L.; Tedeschi, G.
2003-04-01
The experimental network of the ESCOMPTE field experiment (june-july 2001) is turned into account to investigate the Mistral wind affecting the Marseille area (South of France). Mistral wind is a northerly flow blowing across the Rhône valley and toward the Mediterranean sea resulting from the dynamical low pressure generated in the wake of the Alps ridge. It brings cold, dry air masses and clear sky conditions over the south-eastern part of France. Up to now, few scientific studies have been carried out on the Mistral wind especially the evolution of its 3-D structure so that its mesoscale numerical simulation is still relevant. Non-hydrostatic RAMS model is performed to better investigate this mesoscale phenomena. Simulations at a 12 km horizontal resolution are compared to boundary layer wind profilers and ground measurements. Preliminary results suit quite well with the Mistral statistical studies carried out by the operational service of Météo-France and observed wind profiles are correctly reproduced by the numerical model RAMS which appears to be an efficient tool for its understanding of Mistral. Owing to the absence of diabatic effect in Mistral events which complicates numerical simulations, the present work is the first step for the validation of RAMS model in that area. Further works will consist on the study of the interaction of Mistral wind with land-sea breeze. Also, RAMS simulations will be combined with aerosol production and ocean circulation models to supply chemists and oceanographers with some answers for their studies.
Steel Fibers Reinforced Concrete Pipes - Experimental Tests and Numerical Simulation
Doru, Zdrenghea
2017-10-01
The paper presents in the first part a state of the art review of reinforced concrete pipes used in micro tunnelling realised through pipes jacking method and design methods for steel fibres reinforced concrete. In part two experimental tests are presented on inner pipes with diameters of 1410mm and 2200mm, and specimens (100x100x500mm) of reinforced concrete with metal fibres (35 kg / m3). In part two experimental tests are presented on pipes with inner diameters of 1410mm and 2200mm, and specimens (100x100x500mm) of reinforced concrete with steel fibres (35 kg / m3). The results obtained are analysed and are calculated residual flexural tensile strengths which characterise the post-cracking behaviour of steel fibres reinforced concrete. In the third part are presented numerical simulations of the tests of pipes and specimens. The model adopted for the pipes test was a three-dimensional model and loads considered were those obtained in experimental tests at reaching breaking forces. Tensile stresses determined were compared with mean flexural tensile strength. To validate tensile parameters of steel fibres reinforced concrete, experimental tests of the specimens were modelled with MIDAS program to reproduce the flexural breaking behaviour. To simulate post - cracking behaviour was used the method σ — ε based on the relationship stress - strain, according to RILEM TC 162-TDF. For the specimens tested were plotted F — δ diagrams, which have been superimposed for comparison with the similar diagrams of experimental tests. The comparison of experimental results with those obtained from numerical simulation leads to the following conclusions: - the maximum forces obtained by numerical calculation have higher values than the experimental values for the same tensile stresses; - forces corresponding of residual strengths have very similar values between the experimental and numerical calculations; - generally the numerical model estimates a breaking force greater
Analysis of control rod behavior based on numerical simulation
International Nuclear Information System (INIS)
Ha, D. G.; Park, J. K.; Park, N. G.; Suh, J. M.; Jeon, K. L.
2010-01-01
The main function of a control rod is to control core reactivity change during operation associated with changes in power, coolant temperature, and dissolved boron concentration by the insertion and withdrawal of control rods from the fuel assemblies. In a scram, the control rod assemblies are released from the CRDMs (Control Rod Drive Mechanisms) and, due to gravity, drop rapidly into the fuel assemblies. The control rod insertion time during a scram must be within the time limits established by the overall core safety analysis. To assure the control rod operational functions, the guide thimbles shall not obstruct the insertion and withdrawal of the control rods or cause any damage to the fuel assembly. When fuel assembly bow occurs, it can affect both the operating performance and the core safety. In this study, the drag forces of the control rod are estimated by a numerical simulation to evaluate the guide tube bow effect on control rod withdrawal. The contact condition effects are also considered. A full scale 3D model is developed for the evaluation, and ANSYS - commercial numerical analysis code - is used for this numerical simulation. (authors)
Numerical simulation of ultrasonic wave propagation in elastically anisotropic media
International Nuclear Information System (INIS)
Jacob, Victoria Cristina Cheade; Jospin, Reinaldo Jacques; Bittencourt, Marcelo de Siqueira Queiroz
2013-01-01
The ultrasonic non-destructive testing of components may encounter considerable difficulties to interpret some inspections results mainly in anisotropic crystalline structures. A numerical method for the simulation of elastic wave propagation in homogeneous elastically anisotropic media, based on the general finite element approach, is used to help this interpretation. The successful modeling of elastic field associated with NDE is based on the generation of a realistic pulsed ultrasonic wave, which is launched from a piezoelectric transducer into the material under inspection. The values of elastic constants are great interest information that provide the application of equations analytical models, until small and medium complexity problems through programs of numerical analysis as finite elements and/or boundary elements. The aim of this work is the comparison between the results of numerical solution of an ultrasonic wave, which is obtained from transient excitation pulse that can be specified by either force or displacement variation across the aperture of the transducer, and the results obtained from a experiment that was realized in an aluminum block in the IEN Ultrasonic Laboratory. The wave propagation can be simulated using all the characteristics of the material used in the experiment valuation associated to boundary conditions and from these results, the comparison can be made. (author)
Two-fluid Numerical Simulations of Solar Spicules
Energy Technology Data Exchange (ETDEWEB)
Kuźma, Błażej; Murawski, Kris; Kayshap, Pradeep; Wójcik, Darek [Group of Astrophysics, University of Maria Curie-Skłodowska, ul. Radziszewskiego 10, 20-031 Lublin (Poland); Srivastava, Abhishek Kumar; Dwivedi, Bhola N., E-mail: blazejkuzma1@gmail.com [Department of Physics, Indian Institute of Technology (BHU), Varanasi-221005 (India)
2017-11-10
We aim to study the formation and evolution of solar spicules by means of numerical simulations of the solar atmosphere. With the use of newly developed JOANNA code, we numerically solve two-fluid (for ions + electrons and neutrals) equations in 2D Cartesian geometry. We follow the evolution of a spicule triggered by the time-dependent signal in ion and neutral components of gas pressure launched in the upper chromosphere. We use the potential magnetic field, which evolves self-consistently, but mainly plays a passive role in the dynamics. Our numerical results reveal that the signal is steepened into a shock that propagates upward into the corona. The chromospheric cold and dense plasma lags behind this shock and rises into the corona with a mean speed of 20–25 km s{sup −1}. The formed spicule exhibits the upflow/downfall of plasma during its total lifetime of around 3–4 minutes, and it follows the typical characteristics of a classical spicule, which is modeled by magnetohydrodynamics. The simulated spicule consists of a dense and cold core that is dominated by neutrals. The general dynamics of ion and neutral spicules are very similar to each other. Minor differences in those dynamics result in different widths of both spicules with increasing rarefaction of the ion spicule in time.
A simplified model for TIG-dressing numerical simulation
Ferro, P.; Berto, F.; James, M. N.
2017-04-01
Irrespective of the mechanical properties of the alloy to be welded, the fatigue strength of welded joints is primarily controlled by the stress concentration associated with the weld toe or weld root. In order to reduce the effects of such notch defects in welds, which are influenced by tensile properties of the alloy, post-weld improvement techniques have been developed. The two most commonly used techniques are weld toe grinding and TIG dressing, which are intended to both remove toe defects such as non-metallic intrusions and to re-profile the weld toe region to give a lower stress concentration. In the case of TIG dressing the weld toe is re-melted to provide a smoother transition between the plate and the weld crown and to beneficially modify the residual stress redistribution. Assessing the changes to weld stress state arising from TIG-dressing is most easily accomplished through a complex numerical simulation that requires coupled thermo-fluid dynamics and solid mechanics. However, this can be expensive in terms of computational cost and time needed to reach a solution. The present paper therefore proposes a simplified numerical model that overcomes such drawbacks and which simulates the remelted toe region by means of the activation and deactivation of elements in the numerical model.
NUMERICAL SIMULATION OF TOXIC CHEMICAL DISPERSION AFTER ACCIDENT AT RAILWAY
Directory of Open Access Journals (Sweden)
M. M. Biliaiev
2016-04-01
Full Text Available Purpose. This research focuses on the development of an applied numerical model to calculate the dynamics of atmospheric pollution in the emission of dangerous chemical substances in the event of transportation by railway. Methodology. For the numerical simulation of transport process of the dangerous chemical substance in the atmosphere the equation of convection-diffusion pollutant transport is used. This equation takes into account the effect of wind, atmospheric diffusion, the power of emission source, as well as the movement of the source of emission (depressurized tank on the process of pollutant dispersion. When carrying out computing experiment one also takes into account the profile of the speed of the wind flow. For the numerical integration of pollutant transport in the atmosphere implicit finite-difference splitting scheme is used. The numerical calculation is divided into four steps of splitting and at each step of splitting the unknown value of the concentration of hazardous substance is determined by the explicit running account scheme. On the basis of the numerical model it was created the code using the algorithmic language FORTRAN. One conducted the computational experiments to assess the level of air pollution near the railway station «Illarionovo» in the event of a possible accident during transportation of ammonia. Findings. The proposed model allows you to quickly calculate the air pollution after the emission of chemically hazardous substance, taking into account the motion of the emission source. The model makes it possible to determine the size of the land surface pollution zones and the amount of pollutants deposited on a specific area. Using the developed numerical model it was estimated the environmental damage near the railway station «Illarionovo». Originality. One can use the numerical model to calculate the size and intensity of the chemical contamination zones after accidents on transport. Practical value
Numerical simulation of fluid flow in microporous media
International Nuclear Information System (INIS)
Xu Ruina; Jiang Peixue
2008-01-01
The flow characteristics of water and air in microporous media with average diameters of 200 μm, 125 μm, 90 μm, 40 μm, 20 μm, and 10 μm were studied numerically. The calculated friction factors for water and air in the non-slip-flow regime in the microporous media agree well with the known correlation suitable for normal size porous media. The numerically predicted friction factors for air in the slip-flow regime in the microporous media with 90 μm, 40 μm, 20 μm, and 10 μm diameter particles were less than the correlation for normal size porous media but close to experimental data and a modified correlation that accounts for rarefaction. Comparisons of the numerical results with the experimental data and the modified correlations show that rarefaction effects occur in air flows in the microporous media with particle diameters less than 90 μm and that the numerical calculations with velocity slip on the boundary can properly simulate the fluid flow in microporous media
Study and simulation of a parallel numerical processing machine
International Nuclear Information System (INIS)
Bel Hadj, Slaheddine
1981-12-01
This study has been carried out in the perspective of the implementation on a minicomputer of the NEPTUNIX package (software for the resolution of very large algebra-differential equation systems). Aiming at increasing the system performance, a previous research work has shown the necessity of reducing the execution time of certain numerical computation tasks, which are of frequent use. It has also demonstrated the feasibility of handling these tasks with efficient algorithms of parallel type. The present work deals with the study and simulation of a parallel architecture processor adapted to the fast execution of these algorithms. A minicomputer fitted with a connection to such a parallel processor, has a greatly extended computing power. Then the architecture of a parallel numerical processor, based on the use of VLSI microprocessors and co-processors, is described. Its design aims at the best cost / performance ratio. The last part deals with the simulation processor with the 'CHAMBOR' program. Results show an increasing factor of 30 in speed, in comparison with the execution on a MITRA 15 minicomputer. Moreover the conflicts importance, mainly at the level of access to a shared resource is evaluated. Although this implementation has been designed having in mind a dedicated application, other uses could be envisaged, particularly for the simulation of nuclear reactors: operator guiding system, the behavioural study under accidental circumstances, etc. (author) [fr
Numerical Simulation of Flood Levels for Tropical Rivers
International Nuclear Information System (INIS)
Mohammed, Thamer Ahmed; Said, Salim; Bardaie, Mohd Zohadie; Basri, Shah Nor
2011-01-01
Flood forecasting is important for flood damage reduction. As a result of advances in the numerical methods and computer technologies, many mathematical models have been developed and used for hydraulic simulation of the flood. These simulations usually include the prediction of the flood width and depth along a watercourse. Results obtained from the application of hydraulic models will help engineers to take precautionary measures to minimize flood damage. Hydraulic models were used to simulate the flood can be classified into dynamic hydraulic models and static hydraulic models. The HEC-2 static hydraulic model was used to predict water surface profiles for Linggi river and Langat river in Malaysia. The model is based on the numerical solution of the one dimensional energy equation of the steady gradually varied flow using the iteration technique. Calibration and verification of the HEC-2 model were conducted using the recorded data for both rivers. After calibration, the model was applied to predict the water surface profiles for Q10, Q30, and Q100 along the watercourse of the Linggi river. The water surface profile for Q200 for Langat river was predicted. The predicted water surface profiles were found in agreement with the recorded water surface profiles. The value of the maximum computed absolute error in the predicted water surface profile was found to be 500 mm while the minimum absolute error was 20 mm only.
Numerical simulation on coolant flow and heat transfer in core
International Nuclear Information System (INIS)
Yao Zhaohui; Wang Xuefang; Shen Mengyu
1997-01-01
To simulate the coolant flow and the heat transfer characteristics of a core, a computer code, THAPMA (Thermal Hydraulic Analysis Porous Medium Analysis) has been developed. In THAPMA code, conservation equations are based on a porous-medium formulation, which uses four parameters, i.e, volume porosity, directional surface porosity, distributed resistance, and distributed heat source (sink), to model the effects of fuel rods and other internal solid structures on flow and heat transfer. Because the scheme and the solution are very important in accuracy and speed of calculation, a new difference scheme (WSUC) has been used in the energy equation, and a modified PISO solution method have been employed to simulate the steady/transient states. The code has been proved reliable and can effectively solve the transient state problem by several numerical tests. According to the design of Qinshan NPP-II, the flow and heat transfer phenomena in reactor core have been numerically simulated. The distributions of the velocity and the temperature can provide a theoretical basis for core design and safety analysis
Direct numerical simulation of bluff-body-stabilized premixed flames
Arias, Paul G.
2014-01-10
To enable high fidelity simulation of combustion phenomena in realistic devices, an embedded boundary method is implemented into direct numerical simulations (DNS) of reacting flows. One of the additional numerical issues associated with reacting flows is the stable treatment of the embedded boundaries in the presence of multicomponent species and reactions. The implemented method is validated in two test con gurations: a pre-mixed hydrogen/air flame stabilized in a backward-facing step configuration, and reactive flows around a square prism. The former is of interest in practical gas turbine combustor applications in which the thermo-acoustic instabilities are a strong concern, and the latter serves as a good model problem to capture the vortex shedding behind a bluff body. In addition, a reacting flow behind the square prism serves as a model for the study of flame stabilization in a micro-channel combustor. The present study utilizes fluid-cell reconstruction methods in order to capture important flame-to-solid wall interactions that are important in confined multicomponent reacting flows. Results show that the DNS with embedded boundaries can be extended to more complex geometries without loss of accuracy and the high fidelity simulation data can be used to develop and validate turbulence and combustion models for the design of practical combustion devices.
NUMERICAL SIMULATION OF AN AGRICULTURAL SOIL SHEAR STRESS TEST
Directory of Open Access Journals (Sweden)
Andrea Formato
2007-03-01
Full Text Available In this work a numerical simulation of agricultural soil shear stress tests was performed through soil shear strength data detected by a soil shearometer. We used a soil shearometer available on the market to measure soil shear stress and constructed special equipment that enabled automated detection of soil shear stress. It was connected to an acquisition data system that displayed and recorded soil shear stress during the full field tests. A soil shearometer unit was used to the in situ measurements of soil shear stress in full field conditions for different types of soils located on the right side of the Sele river, at a distance of about 1 km from each other, along the perpendicular to the Sele river in the direction of the sea. Full field tests using the shearometer unit were performed alongside considered soil characteristic parameter data collection. These parameter values derived from hydrostatic compression and triaxial tests performed on considered soil samples and repeated 4 times and we noticed that the difference between the maximum and minimum values detected for every set of performed tests never exceeded 4%. Full field shear tests were simulated by the Abaqus program code considering three different material models of soils normally used in the literature, the Mohr-Coulomb, Drucker-Prager and Cam-Clay models. We then compared all data outcomes obtained by numerical simulations with those from the experimental tests. We also discussed any further simulation data results obtained with different material models and selected the best material model for each considered soil to be used in tyre/soil contact simulation or in soil compaction studies.
International Nuclear Information System (INIS)
Vosegaard, T.; Malmendal, A.; Nielsen, N.C.
2002-01-01
Addressing the need for numerical simulations in the design and interpretation of advanced solid- and liquid-state NMR experiments, we present a number of novel features for numerical simulations based on the SIMPSON and SIMMOL open source software packages. Major attention is devoted to the flexibility of these Tcl-interfaced programs for numerical simulation of NMR experiments being complicated by demands for efficient powder averaging, large spin systems, and multiple-pulse rf irradiation. These features are exemplified by fast simulation of second-order quadrupolar powder patterns using crystallite interpolation, analysis of rotary resonance triple-quantum excitation for quadrupolar nuclei, iterative fitting of MQ-MAS spectra by combination of SIMIPSON and MINUIT, simulation of multiple-dimensional PISEMA-type correlation experiments for macroscopically oriented membrane proteins, simulation of Hartman-Hahn polarization transfers in liquid-state NMR, and visualization of the spin evolution under complex composite broad-band excitation pulses. (author)
Numerical Simulations of a Multiscale Model of Stratified Langmuir Circulation
Malecha, Ziemowit; Chini, Gregory; Julien, Keith
2012-11-01
Langmuir circulation (LC), a prominent form of wind and surface-wave driven shear turbulence in the ocean surface boundary layer (BL), is commonly modeled using the Craik-Leibovich (CL) equations, a phase-averaged variant of the Navier-Stokes (NS) equations. Although surface-wave filtering renders the CL equations more amenable to simulation than are the instantaneous NS equations, simulations in wide domains, hundreds of times the BL depth, currently earn the ``grand challenge'' designation. To facilitate simulations of LC in such spatially-extended domains, we have derived multiscale CL equations by exploiting the scale separation between submesoscale and BL flows in the upper ocean. The numerical algorithm for simulating this multiscale model resembles super-parameterization schemes used in meteorology, but retains a firm mathematical basis. We have validated our algorithm and here use it to perform multiscale simulations of the interaction between LC and upper ocean density stratification. ZMM, GPC, KJ gratefully acknowledge funding from NSF CMG Award 0934827.
A numerical simulation of VIV on a flexible circular cylinder
International Nuclear Information System (INIS)
Xie Fangfang; Deng Jian; Zheng Yao; Xiao Qing
2012-01-01
In this paper, numerical simulations of a flexible circular cylinder subjected to a vortex-induced vibration (VIV) are conducted. The Reynolds number for simulations is fixed at 1000. The finite volume method is applied for modeling fluid flow with the moving meshes feature. The dynamic response of a flexible cylinder fixed at both ends is modeled by the Euler–Bernoulli beam theory. The comparison between two-dimensional (2D) simulations and 3D simulations for the flexible cylinder shows that the maximum response amplitude of the cross-flow oscillation is about 0.57D for 2D rigid cylinders (modeled by a spring–damper–mass model) and 1.03D for flexible cylinders, respectively. The results from 3D simulations are closer to previous experimental results. Furthermore, the results obtained with various frequency ratios show that different wake patterns exist according to the frequency ratio, such as 2S mode, 2P mode and some more complicated modes. The wake pattern is different at various sections along the cylinder length, due to the fact that the two ends of the beam are fixed. The vibration of the flexible cylinder can also greatly alter the three dimensionality in the wake, which is our research in future work, especially in the transition region for Reynolds number ranging from 170 to 300. (paper)
Numerical simulations of seepage flow in rough single rock fractures
Directory of Open Access Journals (Sweden)
Qingang Zhang
2015-09-01
Full Text Available To investigate the relationship between the structural characteristics and seepage flow behavior of rough single rock fractures, a set of single fracture physical models were produced using the Weierstrass–Mandelbrot functions to test the seepage flow performance. Six single fractures, with various surface roughnesses characterized by fractal dimensions, were built using COMSOL multiphysics software. The fluid flow behavior through the rough fractures and the influences of the rough surfaces on the fluid flow behavior was then monitored. The numerical simulation indicates that there is a linear relationship between the average flow velocity over the entire flow path and the fractal dimension of the rough surface. It is shown that there is good a agreement between the numerical results and the experimental data in terms of the properties of the fluid flowing through the rough single rock fractures.
Numerical simulation of superheated vapor bubble rising in stagnant liquid
Samkhaniani, N.; Ansari, M. R.
2017-09-01
In present study, the rising of superheated vapor bubble in saturated liquid is simulated using volume of fluid method in OpenFOAM cfd package. The surface tension between vapor-liquid phases is considered using continuous surface force method. In order to reduce spurious current near interface, Lafaurie smoothing filter is applied to improve curvature calculation. Phase change is considered using Tanasawa mass transfer model. The variation of saturation temperature in vapor bubble with local pressure is considered with simplified Clausius-Clapeyron relation. The couple velocity-pressure equation is solved using PISO algorithm. The numerical model is validated with: (1) isothermal bubble rising and (2) one-dimensional horizontal film condensation. Then, the shape and life time history of single superheated vapor bubble are investigated. The present numerical study shows vapor bubble in saturated liquid undergoes boiling and condensation. It indicates bubble life time is nearly linear proportional with bubble size and superheat temperature.
Numerical simulation of heat exchangers elliptical tubes and corrugated fins
International Nuclear Information System (INIS)
Borrajo Pérez, Rubén; González Bayón, Juan José; Menéndez Pérez, Alberto
2015-01-01
The intensified heat exchangers fins are widely used in the automotive and domestic industry. The low heat transfer coefficients on the air side are the main reason why these fins of heat exchangers need to be intensified. In this paper, the numerical simulation of a wavy fin type is made with elliptical tubes. The dimensions of the fin is in the range of those used in air conditioning equipment. The friction factor and the mass transfer coefficient as a function of the Reynolds number for this type of fin, always within the laminar regime is determined. The numerical model against experimental results published in the literature is validated. In addition the mechanisms that produce intensified heat transfer fin in such occur. (full text)
Numerical simulation of a liquid propellant rocket motor
Salvador, Nicolas M. C.; Morales, Marcelo M.; Migueis, Carlos E. S. S.; Bastos-Netto, Demétrio
2001-03-01
This work presents a numerical simulation of the flow field in a liquid propellant rocket engine chamber and exit nozzle using techniques to allow the results to be taken as starting points for designing those propulsive systems. This was done using a Finite Volume method simulating the different flow regimes which usually take place in those systems. As the flow field has regions ranging from the low subsonic to the supersonic regimes, the numerical code used, initially developed for compressible flows only, was modified to work proficiently in the whole velocity range. It is well known that codes have been developed in CFD, for either compressible or incompressible flows, the joint treatment of both together being complex even today, given the small number of references available in this area. Here an existing code for compressible flow was used and primitive variables, the pressure, the Cartesian components of the velocity and the temperature instead of the conserved variables were introduced in the Euler and Navier-Stokes equations. This was done to permit the treatment at any Mach number. Unstructured meshes with adaptive refinements were employed here. The convective terms were treated with upwind first and second order methods. The numerical stability was kept with artificial dissipation and in the spatial coverage one used a five stage Runge-Kutta scheme for the Fluid Mechanics and the VODE (Value of Ordinary Differential Equations) scheme along with the Chemkin II in the chemical reacting solution. During the development of this code simulating the flow in a rocket engine, comparison tests were made with several different types of internal and external flows, at different velocities, seeking to establish the confidence level of the techniques being used. These comparisons were done with existing theoretical results and with other codes already validated and well accepted by the CFD community.
2D numerical simulation of the resistive reconnection layer
International Nuclear Information System (INIS)
Uzdensky, D. A.; Kulsrud, R. M.
2000-01-01
In this paper the authors present a two-dimensional numerical simulation of a reconnection current layer in incompressible resistive magnetohydrodynamics with uniform resistivity in the limit of very large Lundquist numbers. They use realistic boundary conditions derived consistently from the outside magnetic field, and they also take into account the effect of the backpressure from flow into the separatrix region. They find that within a few Alfven times the system reaches a steady state consistent with the Sweet-Parker model, even if the initial state is Petschek-like
Numerical simulation of Rayleigh-Taylor turbulent mixing layers
International Nuclear Information System (INIS)
Poujade, O.; Lardjane, N.; Peybernes, M.; Boulet, M.
2009-01-01
Accelerations in actual Rayleigh-Taylor instabilities are often variable. This article focuses on a particular class of variable accelerations where g(t) ∝ t n . A reference database is built from high resolution hydrodynamic numerical simulations. The successful comparison with a simple OD analytical model and the statistical 2SFK (2-Structure, 2-Fluid, 2-Turbulence) turbulence model is provided. Moreover, we show the difference between the mechanism at play in the Rayleigh-Taylor turbulent mixing zone and Kolmogorov's in the self similar developed turbulent regime. (authors)
Numerical simulation of the unsteady progress in centrifuge
International Nuclear Information System (INIS)
Wei Chunlin; Zeng Shi
2006-01-01
Unsteady flow equations for the centrifuge are solved on a staggered grid by a finite volume method. The transient process that the axial flow in the centrifuge is established under a steady thermal driving. It can be concluded that the influence which causes the perturbing fluid is different at the beginning and the end of the processing. The flow is caused by the imbalance of temperature which turns to be caused by the imbalance of pressure. The results show that the numerical simulation is effective at the unsteady fluid in a centrifuge. (authors)
Modelisation and numerical simulation for bulk crystal growth processes
International Nuclear Information System (INIS)
Duffar, F.; Dusserre, P.; Barat, C.; Nabot, J.P.
1993-01-01
The aim of this work is to study the relevance of numerical simulation for improving the process control in the field of crystal growth. This investigation focused on the growth of semiconductor and halide crystals by the Bridgman solidification technique, the principle of which is to cool a seeded feed material contained in a crucible, either by pulling the crucible or by decreasing the temperature in the furnace. Calculations are performed with the finite element method, and for comparison, experiments are carried out on Bridgman pulling machines operating either in a laboratory or in industrial plants. Calculations and experimental data have shown a good agreement and a satisfactory reliability
Numerical simulation of laser filamentation in underdense plasma
International Nuclear Information System (INIS)
Yu Lichun; Chen Zhihua; Tu Qinfen
2000-01-01
Developing process of filamentation and effect of characteristic parameters in underdense plasma have been studied using numerical simulation method. Production and development of two-dimensional cylinder filamentation instability were presented clearly. The results indicate incidence laser intensity and plasma background density are important factors affecting convergent intensity. At the same time, it was showed that different laser wavelength or different electron background density could affect filamentation process. The results are consistent with theory and experiments of alien reports. It can provide reference for restraining filamentation
Numerical simulation design of nuclear safety related expansion muffler
International Nuclear Information System (INIS)
Huang Bingchen; Shen Wei; Yang Tieming; Luo Jianping; Jing Feng
2014-01-01
According to the working conditions and technical requirements for pipe discharge muffler in passive nuclear power plant, the numerical simulation was used in analyzing sound transmission loss and fluid pressure loss of multi-section expansion muffler by finite element analysis (FEA) software ANSYS. The effect of different muffler structural parameters on sound transmission loss, passing frequency and pressure loss was also analyzed. Based on the analysis results, a reasonable combination of the muffler structural parameters was determined, and a pipe discharge muffler with good performance was obtained. (authors)
Achieving better cooling of turbine blades using numerical simulation methods
Inozemtsev, A. A.; Tikhonov, A. S.; Sendyurev, C. I.; Samokhvalov, N. Yu.
2013-02-01
A new design of the first-stage nozzle vane for the turbine of a prospective gas-turbine engine is considered. The blade's thermal state is numerically simulated in conjugate statement using the ANSYS CFX 13.0 software package. Critical locations in the blade design are determined from the distribution of heat fluxes, and measures aimed at achieving more efficient cooling are analyzed. Essentially lower (by 50-100°C) maximal temperature of metal has been achieved owing to the results of the performed work.
Numerical simulation of compact intracloud discharge and generated electromagnetic pulse
Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.
2015-06-01
Using the concept of the relativistic runaway electron avalanche, numerical simulation of compact intracloud discharge as a generator of powerful natural electromagnetic pulses (EMPs) in the HF-UHF range was conducted. We evaluated the numbers of electrons initiating the avalanche, with which the calculated EMP characteristics are consistent with measured ones. The discharge capable of generating EMPs produces runaway electrons in numbers close to those in the source of terrestrial γ-flashes (TGF) registered in the nearest space, which may be an argument for a joint EMP and TGF source.
Numerical Simulation of Plasma Antenna with FDTD Method
International Nuclear Information System (INIS)
Chao, Liang; Yue-Min, Xu; Zhi-Jiang, Wang
2008-01-01
We adopt cylindrical-coordinate FDTD algorithm to simulate and analyse a 0.4-m-long column configuration plasma antenna. FDTD method is useful for solving electromagnetic problems, especially when wave characteristics and plasma properties are self-consistently related to each other. Focus on the frequency from 75 MHz to 400 MHz, the input impedance and radiation efficiency of plasma antennas are computed. Numerical results show that, different from copper antenna, the characteristics of plasma antenna vary simultaneously with plasma frequency and collision frequency. The property can be used to construct dynamically reconBgurable antenna. The investigation is meaningful and instructional for the optimization of plasma antenna design
Numerical simulation of plasma antenna with FDTD method
International Nuclear Information System (INIS)
Liang Chao; Xu Yuemin; Wang Zhijiang
2008-01-01
We adopt cylindrical-coordinate FDTD algorithm to simulate and analyse a 0.4-m-long column configuration plasma antenna. FDTD method is useful for solving electromagnetic problems, especially when wave characteristics and plasma properties are self-consistently related to each other. Focus on the frequency from 75 MHz to 400 MHz, the input impedance and radiation efficiency of plasma antennas are computed. Numerical results show that, different from copper antenna, the characteristics of plasma antenna vary simultaneously with plasma frequency and collision frequency. The property can be used to construct dynamically reconfigurable antenna. The investigation is meaningful and instructional for the optimization of plasma antenna design. (authors)
Numerical simulation for HT-6M tokamak electrical transient behaviours
International Nuclear Information System (INIS)
Yu Yuanqi; Liu Baohua; Pan Yuan
1991-02-01
The following main points are concerned: (1) State equations used for dynamic analysis of all electrical parameters of the tokamak are derived. (2) In order to increase plasma volt-seconds and to get plasma current with longer sustainment phase, a power supply scheme for HT-6M and its numerical simulation are studied. (3) The distribution of energy flow in coupling loops of the tokamak is discussed, and the energy transfer ratio from the OH loop and vertical field loop to the plasma is also analyzed
Efficient Parallel Algorithm For Direct Numerical Simulation of Turbulent Flows
Moitra, Stuti; Gatski, Thomas B.
1997-01-01
A distributed algorithm for a high-order-accurate finite-difference approach to the direct numerical simulation (DNS) of transition and turbulence in compressible flows is described. This work has two major objectives. The first objective is to demonstrate that parallel and distributed-memory machines can be successfully and efficiently used to solve computationally intensive and input/output intensive algorithms of the DNS class. The second objective is to show that the computational complexity involved in solving the tridiagonal systems inherent in the DNS algorithm can be reduced by algorithm innovations that obviate the need to use a parallelized tridiagonal solver.
Numerical simulation of realistic high-temperature superconductors
International Nuclear Information System (INIS)
1997-01-01
One of the main obstacles in the development of practical high-temperature superconducting (HTS) materials is dissipation, caused by the motion of magnetic flux quanta called vortices. Numerical simulations provide a promising new approach for studying these vortices. By exploiting the extraordinary memory and speed of massively parallel computers, researchers can obtain the extremely fine temporal and spatial resolution needed to model complex vortex behavior. The results may help identify new mechanisms to increase the current-capability capabilities and to predict the performance characteristics of HTS materials intended for industrial applications
Numerical simulation of bosonic-superconducting-string interactions
International Nuclear Information System (INIS)
Laguna, P.; Matzner, R.A.
1990-01-01
Numerical simulations show that bosonic superconducting U(1) gauge cosmic strings interact by reconnecting and chopping off in a fashion similar to nonconducting strings. Cancellation of the electromagnetic current occurs when, in one of the strings, the direction of the U(1) gauge magnetic field is opposite to the electromagnetic current flow. Electric charge accumulates on the segments of the reconnected strings where the current is discontinuous or vanishes. A virtual photon appears after the collision and intercommutation, and a bubble of electromagnetic radiation emerges as the currents in the reconnected strings equalize. These phenomena suggest new possible mechanisms for void production in the large-scale distribution of galaxies
Numerical simulation of systems of shear bands in ductile metal with inclusions
Energy Technology Data Exchange (ETDEWEB)
Plohr, JeeYeon N., E-mail: jplohr@lanl.gov; Plohr, Bradley J. [Los Alamos National Laboratory, Theoretical Division, Los Alamos, NM 87545 (United States)
2016-02-15
We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands). This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.
Numerical simulation of systems of shear bands in ductile metal with inclusions
Directory of Open Access Journals (Sweden)
JeeYeon N. Plohr
2016-02-01
Full Text Available We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands. This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.
Numerical simulation of systems of shear bands in ductile metal with inclusions
Plohr, Jeeyeon
2017-06-01
We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation. This method employs the Generalized Method of Cells to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.
Cohesive Zone Model Based Numerical Analysis of Steel-Concrete Composite Structure Push-Out Tests
Directory of Open Access Journals (Sweden)
J. P. Lin
2014-01-01
Full Text Available Push-out tests were widely used to determine the shear bearing capacity and shear stiffness of shear connectors in steel-concrete composite structures. The finite element method was one efficient alternative to push-out testing. This paper focused on a simulation analysis of the interface between concrete slabs and steel girder flanges as well as the interface of the shear connectors and the surrounding concrete. A cohesive zone model was used to simulate the tangential sliding and normal separation of the interfaces. Then, a zero-thickness cohesive element was implemented via the user-defined element subroutine UEL in the software ABAQUS, and a multiple broken line mode was used to define the constitutive relations of the cohesive zone. A three-dimensional numerical analysis model was established for push-out testing to analyze the load-displacement curves of the push-out test process, interface relative displacement, and interface stress distribution. This method was found to accurately calculate the shear capacity and shear stiffness of shear connectors. The numerical results showed that the multiple broken lines mode cohesive zone model could describe the nonlinear mechanical behavior of the interface between steel and concrete and that a discontinuous deformation numerical simulation could be implemented.
Numerical simulation of the knotted nylon netting panel
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Li Yuwei
2016-01-01
Full Text Available A piece of netting, consists of the 8 8 meshes, fixed on a square frame, was simulated and the tensions and their distribution, the positions of knots and netting shape were calculated by means of MATLAB in computer. The dynamic mathematic model was developed based on lumped mass method, the netting was treated as spring-mass system, the Runge-Kutta fifth-order and sixth-order method was used to solve the differential equations for every step, then the displacement and tension of each mass point were obtained. For verify this model, the tests have been carried out in a flume tank. The results of the numerical simulation fully agreed with the experiments.
Reliability of numerical wind tunnels for VAWT simulation
International Nuclear Information System (INIS)
Castelli, M. Raciti; Masi, M.; Battisti, L.; Benini, E.; Brighenti, A.; Dossena, V.; Persico, G.
2016-01-01
Computational Fluid Dynamics (CFD) based on the Unsteady Reynolds Averaged Navier Stokes (URANS) equations have long been widely used to study vertical axis wind turbines (VAWTs). Following a comprehensive experimental survey on the wakes downwind of a troposkien-shaped rotor, a campaign of bi-dimensional simulations is presented here, with the aim of assessing its reliability in reproducing the main features of the flow, also identifying areas needing additional research. Starting from both a well consolidated turbulence model (k-ω SST) and an unstructured grid typology, the main simulation settings are here manipulated in a convenient form to tackle rotating grids reproducing a VAWT operating in an open jet wind tunnel. The dependence of the numerical predictions from the selected grid spacing is investigated, thus establishing the less refined grid size that is still capable of capturing some relevant flow features such as integral quantities (rotor torque) and local ones (wake velocities). (paper)
Reliability of numerical wind tunnels for VAWT simulation
Raciti Castelli, M.; Masi, M.; Battisti, L.; Benini, E.; Brighenti, A.; Dossena, V.; Persico, G.
2016-09-01
Computational Fluid Dynamics (CFD) based on the Unsteady Reynolds Averaged Navier Stokes (URANS) equations have long been widely used to study vertical axis wind turbines (VAWTs). Following a comprehensive experimental survey on the wakes downwind of a troposkien-shaped rotor, a campaign of bi-dimensional simulations is presented here, with the aim of assessing its reliability in reproducing the main features of the flow, also identifying areas needing additional research. Starting from both a well consolidated turbulence model (k-ω SST) and an unstructured grid typology, the main simulation settings are here manipulated in a convenient form to tackle rotating grids reproducing a VAWT operating in an open jet wind tunnel. The dependence of the numerical predictions from the selected grid spacing is investigated, thus establishing the less refined grid size that is still capable of capturing some relevant flow features such as integral quantities (rotor torque) and local ones (wake velocities).
Numerical simulation of long-term radiation effects for MOSFETs
International Nuclear Information System (INIS)
Wei Yuan; Xie Honggang; Gong Ding; Zhu Jinhui; Niu Shengli; Huang Liuxing
2013-01-01
A coupled algorithm is introduced to simulate the long-term radiation effects of MOSFETs, which combines particle transport with semiconductor governing equations. The former is dealt with Monte-Carlo method, and the latter is solved by finite-volume method. The trapped charge in SiO 2 and the free charge in Si are both described by the drift-diffusion model, and the deposited energy by incident particles can be coupled with the continuous equations of charge, acting as a source item. The discrete form of governing equations is obtained using the finite-volume method, and the numerical solutions of these equations are the long-term radiation response result of MOSFETs. The threshold voltage shift and off-state leakage current of an irradiated MOSFET are simulated with the coupled algorithm respectively, showing a good accordance with results by other calculations. (authors)
CASTING IMPROVEMENT BASED ON METAHEURISTIC OPTIMIZATION AND NUMERICAL SIMULATION
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Radomir Radiša
2017-12-01
Full Text Available This paper presents the use of metaheuristic optimization techniques to support the improvement of casting process. Genetic algorithm (GA, Ant Colony Optimization (ACO, Simulated annealing (SA and Particle Swarm Optimization (PSO have been considered as optimization tools to define the geometry of the casting part’s feeder. The proposed methodology has been demonstrated in the design of the feeder for casting Pelton turbine bucket. The results of the optimization are dimensional characteristics of the feeder, and the best result from all the implemented optimization processes has been adopted. Numerical simulation has been used to verify the validity of the presented design methodology and the feeding system optimization in the casting system of the Pelton turbine bucket.
Convective Self-Aggregation in Numerical Simulations: A Review
Wing, Allison A.; Emanuel, Kerry; Holloway, Christopher E.; Muller, Caroline
Organized convection in the tropics occurs across a range of spatial and temporal scales and strongly influences cloud cover and humidity. One mode of organization found is ``self-aggregation,'' in which moist convection spontaneously organizes into one or several isolated clusters despite spatially homogeneous boundary conditions and forcing. Self-aggregation is driven by interactions between clouds, moisture, radiation, surface fluxes, and circulation, and occurs in a wide variety of idealized simulations of radiative-convective equilibrium. Here we provide a review of convective self-aggregation in numerical simulations, including its character, causes, and effects. We describe the evolution of self-aggregation including its time and length scales and the physical mechanisms leading to its triggering and maintenance, and we also discuss possible links to climate and climate change.
DualSPHysics: A numerical tool to simulate real breakwaters
Zhang, Feng; Crespo, Alejandro; Altomare, Corrado; Domínguez, José; Marzeddu, Andrea; Shang, Shao-ping; Gómez-Gesteira, Moncho
2018-02-01
The open-source code DualSPHysics is used in this work to compute the wave run-up in an existing dike in the Chinese coast using realistic dimensions, bathymetry and wave conditions. The GPU computing power of the DualSPHysics allows simulating real-engineering problems that involve complex geometries with a high resolution in a reasonable computational time. The code is first validated by comparing the numerical free-surface elevation, the wave orbital velocities and the time series of the run-up with physical data in a wave flume. Those experiments include a smooth dike and an armored dike with two layers of cubic blocks. After validation, the code is applied to a real case to obtain the wave run-up under different incident wave conditions. In order to simulate the real open sea, the spurious reflections from the wavemaker are removed by using an active wave absorption technique.
Numerical simulation of a DC double anode arc plasma torch
International Nuclear Information System (INIS)
Chen Lunjiang; Tang Deli; Zhu Hailong
2012-01-01
A 2D axisymmetric numerical simulation of DC double anode plasma torch was done by the computational fluid dynamics (CFD) software FLUENT to improve the efficiency of the waste treatment, which is on the basis of the magnetic fluid dynamics (MHD) theory and uses the method of magnetic vector potential, and the simulation method is based on SIMPLE algorithm. The temperature and speed distributions of the plasma, and so on were obtained. The results show that the temperature of plasma decreases with increasing the axial distance, and increases with increasing the amplitude of the arc current. The velocity first increases and then decreases with the axial distance increase, and increase with the arc current increase. The temperature and the speed at the export of the plasma torch both decrease when the radial distance increases. Those results are in agreement with the experimental results. (authors)
Numerical simulation of low pressure die-casting aluminum wheel
Directory of Open Access Journals (Sweden)
Mi Guofa
2009-02-01
Full Text Available The FDM numerical simulation software, ViewCast system, was employed to simulate the low pressure die casting (LPDC of an aluminum wheel. By analyzing the mold-fi lling and solidifi cation stage of the LPDC process, the distribution of liquid fraction, temperature field and solidification pattern of castings were studied. The potential shrinkage defects were predicted to be formed at the rim/spoke junctions, which is in consistence with the X-ray detection result. The distribution pattern of the defects has also been studied. A solution towards reducing such defects has been presented. The cooling capacity of the mold was improved by installing water pipes both in the side mold and the top mold. Analysis on the shrinkage defects under forced cooling mode proved that adding the cooling system in the mold is an effective method for reduction of shrinkage defects.
Numerical Simulation of Flow Behavior within a Venturi Scrubber
Directory of Open Access Journals (Sweden)
M. M. Toledo-Melchor
2014-01-01
Full Text Available The present work details the three-dimensional numerical simulation of single-phase and two-phase flow (air-water in a venturi scrubber with an inlet and throat diameters of 250 and 122.5 mm, respectively. The dimensions and operating parameters correspond to industrial applications. The mass flow rate conditions were 0.483 kg/s, 0.736 kg/s, 0.861 kg/s, and 0.987 kg/s for the gas only simulation; the mass flow rate for the liquid was 0.013 kg/s and 0.038 kg/s. The gas flow was simulated in five geometries with different converging and diverging angles while the two-phase flow was only simulated for one geometry. The results obtained were validated with experimental data obtained by other researchers. The results show that the pressure drop depends significantly on the gas flow rate and that water flow rate does not have significant effects neither on the pressure drop nor on the fluid maximum velocity within the scrubber.
Real-time numerical simulation of the Carnot cycle
International Nuclear Information System (INIS)
Hurkala, J; Gall, M; Kutner, R; Maciejczyk, M
2005-01-01
We developed a highly interactive, multi-windows Java applet which made it possible to simulate and visualize within any platform and internet the Carnot cycle (or engine) in a real-time computer experiment. We extended our previous model and algorithm (Galant et al 2003 Heat Transfer, Newton's Law of Cooling and the Law of Entropy Increase Simulated by the Real-Time Computer Experiments in Java (Lecture Notes in Computer Science vol 2657) pp 45-53, Gall and Kutner 2005 Molecular mechanisms of heat transfer: Debye relaxation versus power-law Physica A 352 347-78) to simulate not only the heat flow but also the macroscopic movement of the piston. Since in reality it is impossible to construct a reversible Carnot engine, the question arises whether it is possible to simulate it at least in a numerical experiment? The positive answer to this question which we found is related to our model and algorithm which make it possible to omit the many-body problem arising when many gas particles simultaneously interact with the mobile piston. As usual, the considerations of phenomenological thermodynamics began with a study of the basic properties of heat engines, hence our approach, besides intrinsic physical significance, is also important from the educational, technological and even environmental points of view
Numerical simulation and experimental validation of aircraft ground deicing model
Directory of Open Access Journals (Sweden)
Bin Chen
2016-05-01
Full Text Available Aircraft ground deicing plays an important role of guaranteeing the aircraft safety. In practice, most airports generally use as many deicing fluids as possible to remove the ice, which causes the waste of the deicing fluids and the pollution of the environment. Therefore, the model of aircraft ground deicing should be built to establish the foundation for the subsequent research, such as the optimization of the deicing fluid consumption. In this article, the heat balance of the deicing process is depicted, and the dynamic model of the deicing process is provided based on the analysis of the deicing mechanism. In the dynamic model, the surface temperature of the deicing fluids and the ice thickness are regarded as the state parameters, while the fluid flow rate, the initial temperature, and the injection time of the deicing fluids are treated as control parameters. Ignoring the heat exchange between the deicing fluids and the environment, the simplified model is obtained. The rationality of the simplified model is verified by the numerical simulation and the impacts of the flow rate, the initial temperature and the injection time on the deicing process are investigated. To verify the model, the semi-physical experiment system is established, consisting of the low-constant temperature test chamber, the ice simulation system, the deicing fluid heating and spraying system, the simulated wing, the test sensors, and the computer measure and control system. The actual test data verify the validity of the dynamic model and the accuracy of the simulation analysis.
Direct numerical simulation of water droplet coalescence in the oil
International Nuclear Information System (INIS)
Mohammadi, Mehdi; Shahhosseini, Shahrokh; Bayat, Mahmoud
2012-01-01
Highlights: ► VOF computational technique has been used to simulate coalescence of two water droplets in oil. ► The model was validated with the experimental data for binary droplet coalescence. ► Based on the CFD simulation results a correlation has been proposed to predict the coalescence time. - Abstract: Coalescence of two water droplets in the oil was simulated using Computational Fluid Dynamics (CFD) techniques. The finite volume numerical method was applied to solve the Navier–Stokes equations in conjunction with the Volume of Fluid (VOF) approach for interface tracking. The effects of some parameters consisting of the collision velocity, off-center collision parameter, oil viscosity and water–oil interfacial tension on the coalescence time were investigated. The simulation results were validated against the experimental data available in the literature. The results revealed that quicker coalescence could be achieved if the head-on collisions occur or the droplets approach each other with a high velocity. In addition, low oil viscosities or large water–oil interfacial tensions cause less coalescence time. Moreover, a correlation was developed to predict coalescence efficiency as a function of the mentioned parameters.
Hassoon, O. H.; Tarfaoui, M.; El Moumen, A.; Benyahia, H.; Nachtane, M.
2018-06-01
The deformable composite structures subjected to water-entry impact can be caused a phenomenon called hydroelastic effect, which can modified the fluid flow and estimated hydrodynamic loads comparing with rigid body. This is considered very important for ship design engineers to predict the global and the local hydrodynamic loads. This paper presents a numerical model to simulate the slamming water impact of flexible composite panels using an explicit finite element method. In order to better describe the hydroelastic influence and mechanical properties, composite materials panels with different stiffness and under different impact velocities with deadrise angle of 100 have been studied. In the other hand, the inertia effect was observed in the early stage of the impact that relative to the loading rate. Simulation results have been indicated that the lower stiffness panel has a higher hydroelastic effect and becomes more important when decreasing of the deadrise angle and increasing the impact velocity. Finally, the simulation results were compared with the experimental data and the analytical approaches of the rigid body to describe the behavior of the hydroelastic influence.
Numerical simulation of a passive scalar transport from thermal power plants
Issakhov, Alibek; Baitureyeva, Aiymzhan
2017-06-01
The active development of the industry leads to an increase in the number of factories, plants, thermal power plants, nuclear power plants, thereby increasing the amount of emissions into the atmosphere. Harmful chemicals are deposited on the soil surface, remain in the atmosphere, which leads to a variety of environmental problems which are harmful for human health and the environment, flora and fauna. Considering the above problems, it is very important to control the emissions to keep them at an acceptable level for the environment. In order to do that it is necessary to investigate the spread of harmful emissions. The best way to assess it is the creating numerical simulation of gaseous substances' motion. In the present work the numerical simulation of the spreading of emissions from the thermal power plant chimney is considered. The model takes into account the physical properties of the emitted substances and allows to calculate the distribution of the mass fractions, depending on the wind velocity and composition of emissions. The numerical results were performed using the ANSYS Fluent software package. As a result, the results of numerical simulations and the graphs are given.
Numerical simulation of a DFB - fiber laser sensor (part 1
Directory of Open Access Journals (Sweden)
Dan SAVASTRU
2010-06-01
Full Text Available This paper presents the preliminary results obtained in developing a numerical simulationanalysis of fiber optic bending sensitivity aiming to improve the design of fiber lasers. The developednumerical simulation method relies on an analysis of both the fundamental mode propagation alongan optical fiber and of how bending of this fiber influence the optical radiation losses. The cases ofsimple, undoped and of doped with Er3+ ions optical fibers are considered. The presented results arebased on numerical simulation of eigen-modes of a laser intensity distribution by the use of finiteelement method (FEM developed in the frame of COMSOL software package. The numericalsimulations are performed by considering the cases of both normal, non-deformed optic fiber and ofsymmetrically deformed optic fiber resembling micro-bending of it. Both types of fiber optic bendinglosses are analyzed, namely: the transition loss, associated with the abrupt or rapid change incurvature at the beginning and the end of a bend, and pure bend loss is associated with the loss fromthe bend of constant curvature in between.
Numerical Simulation for Mechanism of Airway Narrowing in Asthma
Bando, Kiyoshi; Yamashita, Daisuke; Ohba, Kenkichi
A calculation model is proposed to examine the generation mechanism of the numerous lobes on the inner-wall of the airway in asthmatic patients and to clarify luminal occlusion of the airway inducing breathing difficulties. The basement membrane in the airway wall is modeled as a two-dimensional thin-walled shell having inertia force due to the mass, and the smooth muscle contraction effect is replaced by uniform transmural pressure applied to the basement membrane. A dynamic explicit finite element method is used as a numerical simulation method. To examine the validity of the present model, simulation of an asthma attack is performed. The number of lobes generated in the basement membrane increases when transmural pressure is applied in a shorter time period. When the remodeling of the basement membrane occurs characterized by thickening and hardening, it is demonstrated that the number of lobes decreases and the narrowing of the airway lumen becomes severe. Comparison of the results calculated by the present model with those measured for animal experiments of asthma will be possible.
Modelling and numerical simulation of liquid-vapor phase transitions
International Nuclear Information System (INIS)
Caro, F.
2004-11-01
This work deals with the modelling and numerical simulation of liquid-vapor phase transition phenomena. The study is divided into two part: first we investigate phase transition phenomena with a Van Der Waals equation of state (non monotonic equation of state), then we adopt an alternative approach with two equations of state. In the first part, we study the classical viscous criteria for selecting weak solutions of the system used when the equation of state is non monotonic. Those criteria do not select physical solutions and therefore we focus a more recent criterion: the visco-capillary criterion. We use this criterion to exactly solve the Riemann problem (which imposes solving an algebraic scalar non linear equation). Unfortunately, this step is quite costly in term of CPU which prevent from using this method as a ground for building Godunov solvers. That is why we propose an alternative approach two equations of state. Using the least action principle, we propose a phase changing two-phase flow model which is based on the second thermodynamic principle. We shall then describe two equilibrium submodels issued from the relaxations processes when instantaneous equilibrium is assumed. Despite the weak hyperbolicity of the last sub-model, we propose stable numerical schemes based on a two-step strategy involving a convective step followed by a relaxation step. We show the ability of the system to simulate vapor bubbles nucleation. (author)
Numerical Simulation of Oil Jet Lubrication for High Speed Gears
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Tommaso Fondelli
2015-01-01
Full Text Available The Geared Turbofan technology is one of the most promising engine configurations to significantly reduce the specific fuel consumption. In this architecture, a power epicyclical gearbox is interposed between the fan and the low pressure spool. Thanks to the gearbox, fan and low pressure spool can turn at different speed, leading to higher engine bypass ratio. Therefore the gearbox efficiency becomes a key parameter for such technology. Further improvement of efficiency can be achieved developing a physical understanding of fluid dynamic losses within the transmission system. These losses are mainly related to viscous effects and they are directly connected to the lubrication method. In this work, the oil injection losses have been studied by means of CFD simulations. A numerical study of a single oil jet impinging on a single high speed gear has been carried out using the VOF method. The aim of this analysis is to evaluate the resistant torque due to the oil jet lubrication, correlating the torque data with the oil-gear interaction phases. URANS calculations have been performed using an adaptive meshing approach, as a way of significantly reducing the simulation costs. A global sensitivity analysis of adopted models has been carried out and a numerical setup has been defined.
Review of numerical simulation of capillary tube using refrigerant mixtures
Energy Technology Data Exchange (ETDEWEB)
Garcia-Valladares, O. [Centro de Investigacion en Energia de la UNAM, Morelos (Mexico)
2004-05-01
A detailed one-dimensional steady and transient state numerical simulation of the thermal and fluid-dynamic behaviour of capillary tube expansion devices considering metastable region and working with pure and mixed refrigerants has been developed and presented in previous works [Appl. Therm. Eng. 22 (2002) 173; Appl. Therm. Eng. 22 (2002) 379]. The discretized governing equations are coupled using an implicit step-by-step method. Due to the changes observed in the thermo-physical properties of mixtures using REFPROP v7.0 [Reference Fluid Thermodynamic and Transport Properties, NIST Standard Reference Database 23, Gaithersburg, MD 20899, USA, 2002] compared to REFPROP v5.0 [NIST Thermodynamic Properties of Refrigerants and Refrigerant Mixtures Database, Standard Reference Data Program, Gaithersburg, MD 20899, USA (February 1996)]; an extensive comparison of the numerical simulation developed with experimental data presented in the technical literature will be shown in order to demonstrate the accuracy of this detailed model. Finally, refrigerant-specific rating charts to predict in an easy way R-407C flow rates through adiabatic capillary tube are shown and used. (author)
Numerical Simulation of the Coagulation Dynamics of Blood
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T. Bodnár
2008-01-01
Full Text Available The process of platelet activation and blood coagulation is quite complex and not yet completely understood. Recently, a phenomenological meaningful model of blood coagulation and clot formation in flowing blood that extends existing models to integrate biochemical, physiological and rheological factors, has been developed. The aim of this paper is to present results from a computational study of a simplified version of this coupled fluid-biochemistry model. A generalized Newtonian model with shear-thinning viscosity has been adopted to describe the flow of blood. To simulate the biochemical changes and transport of various enzymes, proteins and platelets involved in the coagulation process, a set of coupled advection–diffusion–reaction equations is used. Three-dimensional numerical simulations are carried out for the whole model in a straight vessel with circular cross-section, using a finite volume semi-discretization in space, on structured grids, and a multistage scheme for time integration. Clot formation and growth are investigated in the vicinity of an injured region of the vessel wall. These are preliminary results aimed at showing the validation of the model and of the numerical code.
Numerical simulation system for environmental studies: SPEEDI-MP
International Nuclear Information System (INIS)
Nagai, Haruyasu; Chino, Masamichi; Terada, Hiroaki; Harayama, Takaya; Kobayashi, Takuya; Tsuduki, Katsunori; Kim, Keyong-Ok; Furuno, Akiko
2006-09-01
A numerical simulation system SPEEDI-MP has been developed to apply for various environmental studies. SPEEDI-MP consists of dynamical models and material transport models for the atmospheric, terrestrial, and oceanic environments, meteorological and geographical database for model inputs, and system utilities for file management, visualization, analysis, etc., using graphical user interfaces (GUIs). As a numerical simulation tool, a model coupling program (model coupler) has been developed. It controls parallel calculations of several models and data exchanges among them to realize the dynamical coupling of the models. A coupled model system for water circulation has been constructed with atmosphere, ocean, wave, hydrology, and land-surface models using the model coupler. System utility GUIs are based on the Web technology, allowing users to manipulate all the functions on the system using their own PCs via the internet. In this system, the source estimation function in the atmospheric transport model can be executed on the grid computer system. Performance tests of the coupled model system for water circulation were also carried out for the flood event at Saudi Arabia in January 2005 and the storm surge case by the hurricane KATRINA in August 2005. (author)
Review of numerical simulation of capillary tube using refrigerant mixtures
International Nuclear Information System (INIS)
Garcia-Valladares, O.
2004-01-01
A detailed one-dimensional steady and transient state numerical simulation of the thermal and fluid-dynamic behaviour of capillary tube expansion devices considering metastable region and working with pure and mixed refrigerants has been developed and presented in previous works [Appl. Therm. Eng. 22 (2002) 173; Appl. Therm. Eng. 22 (2002) 379]. The discretized governing equations are coupled using an implicit step-by-step method. Due to the changes observed in the thermo-physical properties of mixtures using REFPROP v7.0 [Reference Fluid Thermodynamic and Transport Properties, NIST Standard Reference Database 23, Gaithersbug, MD 20899, USA, 2002] compared to REFPROP v5.0 [NIST Thermodynamic Properties of Refrigerants and Refrigerant Mixtures Database, Standard Reference Data Program, Gaithersbug, MD 20899, USA (February 1996)]; an extensive comparison of the numerical simulation developed with experimental data presented in the technical literature will be shown in order to demonstrate the accuracy of this detailed model. Finally, refrigerant-specific rating charts to predict in an easy way R-407C flow rates through adiabatic capillary tube are shown and used
Numerical Simulation of Nanofluid Suspensions in a Geothermal Heat Exchanger
Directory of Open Access Journals (Sweden)
Xiao-Hui Sun
2018-04-01
Full Text Available It has been shown that using nanofluids as heat carrier fluids enhances the conductive and convective heat transfer of geothermal heat exchangers. In this paper, we study the stability of nanofluids in a geothermal exchanger by numerically simulating nanoparticle sedimentation during a shut-down process. The nanofluid suspension is modeled as a non-linear complex fluid; the nanoparticle migration is modeled by a particle flux model, which includes the effects of Brownian motion, gravity, turbulent eddy diffusivity, etc. The numerical results indicate that when the fluid is static, the nanoparticle accumulation appears to be near the bottom borehole after many hours of sedimentation. The accumulated particles can be removed by the fluid flow at a relatively high velocity. These observations indicate good suspension stability of the nanofluids, ensuring the operational reliability of the heat exchanger. The numerical results also indicate that a pulsed flow and optimized geometry of the bottom borehole can potentially improve the suspension stability of the nanofluids further.
Numerical simulation of nonlinear dynamical systems driven by commutative noise
International Nuclear Information System (INIS)
Carbonell, F.; Biscay, R.J.; Jimenez, J.C.; Cruz, H. de la
2007-01-01
The local linearization (LL) approach has become an effective technique for the numerical integration of ordinary, random and stochastic differential equations. One of the reasons for this success is that the LL method achieves a convenient trade-off between numerical stability and computational cost. Besides, the LL method reproduces well the dynamics of nonlinear equations for which other classical methods fail. However, in the stochastic case, most of the reported works has been focused in Stochastic Differential Equations (SDE) driven by additive noise. This limits the applicability of the LL method since there is a number of interesting dynamics observed in equations with multiplicative noise. On the other hand, recent results show that commutative noise SDEs can be transformed into a random differential equation (RDE) by means of a random diffeomorfism (conjugacy). This paper takes advantages of such conjugacy property and the LL approach for defining a LL scheme for SDEs driven by commutative noise. The performance of the proposed method is illustrated by means of numerical simulations
Numerical Simulation of Wind Turbine Blade-Tower Interaction
Institute of Scientific and Technical Information of China (English)
Qiang Wang; Hu Zhou; Decheng Wan
2012-01-01
Numerical simulations of wind turbine blade-tower interaction by using the open source OpenFOAM tools coupled with arbitrary mesh interface (AMI) method were presented.The governing equations were the unsteady Reynolds-averaged Navier-Stokes (PANS) which were solved by the pimpleDyMFoam solver,and the AMI method was employed to handle mesh movements.The National Renewable Energy Laboratory (NREL) phase Ⅵ wind turbine in upwind configuration was selected for numerical tests with different incoming wind speeds (5,10,15,and 25 m/s) at a fixed blade pitch and constant rotational speed.Detailed numerical results of vortex structure,time histories of thrust,and pressure distribution on the blade and tower were presented.The findings show that the wind turbine tower has little effect on the whole aerodynamic performance of an upwind wind turbine,while the rotating rotor will induce an obvious cyclic drop in the front pressure of the tower.Also,strong interaction of blade tip vortices with separation from the tower was observed.
Numerical simulation of double-pipe condensers and evaporators
Energy Technology Data Exchange (ETDEWEB)
Garcia-Valladares, O. [Universidad Nacional Autonoma de Mexico, Morelos (Mexico). Centro de Investigacion en Energia; Perez-Segarra, C.D.; Rigola, J. [Universitat Politecnica de Catalunya, Terrassa (Spain). Centre Tecnologic de Transferencia de Calor, Lab. de Termotecnia i Energetica
2004-09-01
A detailed one-dimensional steady and transient numerical simulation of the thermal and fluid-dynamic behaviour of double-pipe heat exchangers (evaporators and condensers) has been carried out. The governing equations (continuity, momentum and energy) inside the internal tube and the annulus, together with the energy equation in the internal tube wall, external tube wall and insulation, are solved iteratively in a segregated manner. The discretized governing equations in the zones with fluid flow are efficiently coupled using an implicit step by step method. This formulation requires the use of empirical correlations for the evaluation of convective heat transfer, shear stress and void fraction. An implicit central difference numerical scheme and a line-by-line solver was used in the internal and external tube walls and insulation. A special treatment has been implemented in order to consider transitions (single-phase/two-phase, dry-out,...). All the flow variables (enthalpies, temperatures, pressures, mass fractions, velocities, heat fluxes,...) together with the thermophysical properties are evaluated at each point of the grid in which the domain is discretized. Different numerical aspects and comparisons with analytical and experimental results are presented in order to verify and validate the model. (author)
Numerical simulation of triple concentric-tube heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Garcia-Valladares, O. [Centro de Investigacion en Energia (CIE), Universidad Nacional Autonoma de Mexico (UNAM), Privada Xochicalco S/N, Temixco, 62580, Morelos (Mexico)
2004-10-01
A detailed one-dimensional steady and transient numerical simulation of the thermal and fluid-dynamic behaviour of triple concentric-tube heat exchangers has been developed. The governing equations (continuity, momentum and energy) inside the inner tube and the annulus (inner and outer), together with the energy equations in the inner, intermediate and outermost tube wall and insulation, are solved iteratively in a segregated manner. The discretized governing equations in the zones with fluid flow are coupled using an implicit step by step method. This formulation requires the use of empirical information for the evaluation of convective heat transfer, shear stress and void fraction. An implicit central difference numerical scheme and a line-by-line solver was used in the inner and intermediate tube walls and the outermost tube wall with insulation. All the flow variables (enthalpies, temperatures, pressures, mass fractions, velocities, heat fluxes, etc.) together with the thermophysical properties are evaluated at each point of the grid in which the domain is discretized. Different numerical aspects and comparisons with results obtained from the technical literature are presented in order to verify and validate the model. (authors)
Numerical simulation of impact tests on reinforced concrete beams
International Nuclear Information System (INIS)
Jiang, Hua; Wang, Xiaowo; He, Shuanhai
2012-01-01
Highlights: ► Predictions using advanced concrete model compare well with the impact test results. ► Several important behavior of concrete is discussed. ► Two mesh ways incorporating rebar into concrete mesh is also discussed. ► Gives a example of using EPDC model and references to develop new constitutive models. -- Abstract: This paper focuses on numerical simulation of impact tests of reinforced concrete (RC) beams by the LS-DYNA finite element (FE) code. In the FE model, the elasto-plastic damage cap (EPDC) model, which is based on continuum damage mechanics in combination with plasticity theory, is used for concrete, and the reinforcement is assumed to be elasto-plastic. The numerical results compares well with the experimental values reported in the literature, in terms of impact force history, mid-span deflection history and crack patterns of RC beams. By comparing the numerical and experimental results, several important behavior of concrete material is investigated, which includes: damage variable to describe the strain softening section of stress–strain curve; the cap surface to describe the plastic volume change; the shape of the meridian and deviatoric plane to describe the yield surface as well as two methods of incorporating rebar into concrete mesh. This study gives a good example of using EPDC model and can be utilized for the development new constitutive models for concrete in future.
Taylor bubbles at high viscosity ratios: experiments and numerical simulations
Hewakandamby, Buddhika; Hasan, Abbas; Azzopardi, Barry; Xie, Zhihua; Pain, Chris; Matar, Omar
2015-11-01
The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube, often occurring in gas-liquid slug flows in many industrial applications, particularly oil and gas production. The objective of this study is to investigate the fluid dynamics of three-dimensional Taylor bubble rising in highly viscous silicone oil in a vertical pipe. An adaptive unstructured mesh modelling framework is adopted here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rising and reduce computational effort without sacrificing accuracy. The numerical framework consists of a mixed control volume and finite element formulation, a `volume of fluid'-type method for the interface-capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Experimental results for the Taylor bubble shape and rise velocity are presented, together with numerical results for the dynamics of the bubbles. A comparison of the simulation predictions with experimental data available in the literature is also presented to demonstrate the capabilities of our numerical method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.
Numerical Simulation of Non-Thermal Food Preservation
Rauh, C.; Krauss, J.; Ertunc, Ö.; Delgado, a.
2010-09-01
Food preservation is an important process step in food technology regarding product safety and product quality. Novel preservation techniques are currently developed, that aim at improved sensory and nutritional value but comparable safety than in conventional thermal preservation techniques. These novel non-thermal food preservation techniques are based for example on high pressures up to one GPa or pulsed electric fields. in literature studies the high potential of high pressures (HP) and of pulsed electric fields (PEF) is shown due to their high retention of valuable food components as vitamins and flavour and selective inactivation of spoiling enzymes and microorganisms. for the design of preservation processes based on the non-thermal techniques it is crucial to predict the effect of high pressure and pulsed electric fields on the food components and on the spoiling enzymes and microorganisms locally and time-dependent in the treated product. Homogenous process conditions (especially of temperature fields in HP and PEF processing and of electric fields in PEF) are aimed at to avoid the need of over-processing and the connected quality loss and to minimize safety risks due to under-processing. the present contribution presents numerical simulations of thermofluiddynamical phenomena inside of high pressure autoclaves and pulsed electric field treatment chambers. in PEF processing additionally the electric fields are considered. Implementing kinetics of occurring (bio-) chemical reactions in the numerical simulations of the temperature, flow and electric fields enables the evaluation of the process homogeneity and efficiency connected to different process parameters of the preservation techniques. Suggestions to achieve safe and high quality products are concluded out of the numerical results.
Hybrid numerical methods for multiscale simulations of subsurface biogeochemical processes
International Nuclear Information System (INIS)
Scheibe, T D; Tartakovsky, A M; Tartakovsky, D M; Redden, G D; Meakin, P
2007-01-01
Many subsurface flow and transport problems of importance today involve coupled non-linear flow, transport, and reaction in media exhibiting complex heterogeneity. In particular, problems involving biological mediation of reactions fall into this class of problems. Recent experimental research has revealed important details about the physical, chemical, and biological mechanisms involved in these processes at a variety of scales ranging from molecular to laboratory scales. However, it has not been practical or possible to translate detailed knowledge at small scales into reliable predictions of field-scale phenomena important for environmental management applications. A large assortment of numerical simulation tools have been developed, each with its own characteristic scale. Important examples include 1. molecular simulations (e.g., molecular dynamics); 2. simulation of microbial processes at the cell level (e.g., cellular automata or particle individual-based models); 3. pore-scale simulations (e.g., lattice-Boltzmann, pore network models, and discrete particle methods such as smoothed particle hydrodynamics); and 4. macroscopic continuum-scale simulations (e.g., traditional partial differential equations solved by finite difference or finite element methods). While many problems can be effectively addressed by one of these models at a single scale, some problems may require explicit integration of models across multiple scales. We are developing a hybrid multi-scale subsurface reactive transport modeling framework that integrates models with diverse representations of physics, chemistry and biology at different scales (sub-pore, pore and continuum). The modeling framework is being designed to take advantage of advanced computational technologies including parallel code components using the Common Component Architecture, parallel solvers, gridding, data and workflow management, and visualization. This paper describes the specific methods/codes being used at each
Carbon Dioxide Dispersion in the Combustion Integrated Rack Simulated Numerically
Wu, Ming-Shin; Ruff, Gary A.
2004-01-01
When discharged into an International Space Station (ISS) payload rack, a carbon dioxide (CO2) portable fire extinguisher (PFE) must extinguish a fire by decreasing the oxygen in the rack by 50 percent within 60 sec. The length of time needed for this oxygen reduction throughout the rack and the length of time that the CO2 concentration remains high enough to prevent the fire from reigniting is important when determining the effectiveness of the response and postfire procedures. Furthermore, in the absence of gravity, the local flow velocity can make the difference between a fire that spreads rapidly and one that self-extinguishes after ignition. A numerical simulation of the discharge of CO2 from PFE into the Combustion Integrated Rack (CIR) in microgravity was performed to obtain the local velocity and CO2 concentration. The complicated flow field around the PFE nozzle exits was modeled by sources of equivalent mass and momentum flux at a location downstream of the nozzle. The time for the concentration of CO2 to reach a level that would extinguish a fire anywhere in the rack was determined using the Fire Dynamics Simulator (FDS), a computational fluid dynamics code developed by the National Institute of Standards and Technology specifically to evaluate the development of a fire and smoke transport. The simulation shows that CO2, as well as any smoke and combustion gases produced by a fire, would be discharged into the ISS cabin through the resource utility panel at the bottom of the rack. These simulations will be validated by comparing the results with velocity and CO2 concentration measurements obtained during the fire suppression system verification tests conducted on the CIR in March 2003. Once these numerical simulations are validated, portions of the ISS labs and living areas will be modeled to determine the local flow conditions before, during, and after a fire event. These simulations can yield specific information about how long it takes for smoke and
Numerical simulations of the IPPE target geometry flows
International Nuclear Information System (INIS)
Prakash, Akshay; Kakarantzas, Sotiris; Bernardi, Davide; Micciche, Gioacchino; Massaut, Vincent; Knaepen, Bernard
2013-01-01
Highlights: ► We performed numerical simulation of flow over IPPE geometry using turbulence models in FLUENT. ► Stable free surface profile well within the required design limits was predicted by the models. ► Velocity profiles across the liquid jet and jet thickness different for different models. ► There were some 3D effects noticeable for the velocity profiles but the predicted jet thickness similar to 2D models. ► TKE predicted by different models close to each other and compare will with published data. -- Abstract: A high speed water and liquid lithium (Li) flow is computed over the IPPE geometry to evaluate the performance of different turbulence models in 2D and 3D simulations. Results reported are the thickness of the liquid jet, irregularities in the surface, transient phenomena at the wall which can affect fluid surface and effect of the variation in bulk velocity on these quantities. All models show good near wall resolution of the boundary layer and expected profiles for the free surface flow. Predicted turbulent kinetic energy compare well with published data. Fluctuations of the flow surface at the control location (center of the curved section) and elsewhere are well within 1 mm for all models. However it was observed that the predictions are strongly dependent on the model used. Overall, the predictions of RANS models are close to each other whereas predictions of laminar simulations are close to those obtained with LES models
Numerical Simulation of a Solar Domestic Hot Water System
International Nuclear Information System (INIS)
Mongibello, L; Graditi, G; Bianco, N; Di Somma, M; Naso, V
2014-01-01
An innovative transient numerical model is presented for the simulation of a solar Domestic Hot Water (DHW) system. The solar collectors have been simulated by using a zerodimensional analytical model. The temperature distributions in the heat transfer fluid and in the water inside the tank have been evaluated by one-dimensional models. The reversion elimination algorithm has been used to include the effects of natural convection among the water layers at different heights in the tank on the thermal stratification. A finite difference implicit scheme has been implemented to solve the energy conservation equation in the coil heat exchanger, and the energy conservation equation in the tank has been solved by using the finite difference Euler implicit scheme. Energy conservation equations for the solar DHW components models have been coupled by means of a home-made implicit algorithm. Results of the simulation performed using as input data the experimental values of the ambient temperature and the solar irradiance in a summer day are presented and discussed
Color Gradients Within Globular Clusters: Restricted Numerical Simulation
Directory of Open Access Journals (Sweden)
Young-Jong Sohn
1997-06-01
Full Text Available The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salpeter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpeter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.
Numerical simulation of metallic wire arc additive manufacturing (WAAM)
Graf, M.; Pradjadhiana, K. P.; Hälsig, A.; Manurung, Y. H. P.; Awiszus, B.
2018-05-01
Additive-manufacturing technologies have been gaining tremendously in popularity for some years in the production of single-part series with complex, close-to-final-contour geometries and the processing of special or hybrid materials. In principle, the processes can be subdivided into wire-based and powder-based processes in accordance with the Association of German Engineers (VDI) Guideline 3405. A further subdivision is made with respect to the smelting technology. In all of the processes, the base material is applied in layers at the points where it is needed in accordance with the final contour. The process that was investigated was wire-based, multi-pass welding by means of gas-metal arc welding. This was accomplished in the present study by determining the material parameters (thermo-mechanical and thermo-physical characteristics) of the welding filler G3Si1 (material number: 1.5125) that were necessary for the numerical simulation and implementing them in a commercial FE program (MSC Marc Mentat). The focus of this paper was on simulation and validation with respect to geometry and microstructural development in the welding passes. The resulting minimal deviation between reality and simulation was a result of the measurement inertia of the thermocouples. In general, however, the FE model can be used to make a very good predetermination of the cooling behaviour, which affects the microstructural development and thus the mechanical properties of the joining zone, as well as the geometric design of the component (distortion, etc.).
Numerical Simulation of Density Current Evolution in a Diverging Channel
Directory of Open Access Journals (Sweden)
Mitra Javan
2012-01-01
Full Text Available When a buoyant inflow of higher density enters a reservoir, it sinks below the ambient water and forms an underflow. Downstream of the plunge point, the flow becomes progressively diluted due to the fluid entrainment. This study seeks to explore the ability of 2D width-averaged unsteady Reynolds-averaged Navier-Stokes (RANS simulation approach for resolving density currents in an inclined diverging channel. 2D width-averaged unsteady RANS equations closed by a buoyancy-modified − turbulence model are integrated in time with a second-order fractional step approach coupled with a direct implicit method and discretized in space on a staggered mesh using a second-order accurate finite volume approach incorporating a high-resolution semi-Lagrangian technique for the convective terms. A series of 2D width-averaged unsteady simulations is carried out for density currents. Comparisons with the experimental measurements and the other numerical simulations show that the predictions of velocity and density field are with reasonable accuracy.
Numerical Simulation of a Solar Domestic Hot Water System
Mongibello, L.; Bianco, N.; Di Somma, M.; Graditi, G.; Naso, V.
2014-11-01
An innovative transient numerical model is presented for the simulation of a solar Domestic Hot Water (DHW) system. The solar collectors have been simulated by using a zerodimensional analytical model. The temperature distributions in the heat transfer fluid and in the water inside the tank have been evaluated by one-dimensional models. The reversion elimination algorithm has been used to include the effects of natural convection among the water layers at different heights in the tank on the thermal stratification. A finite difference implicit scheme has been implemented to solve the energy conservation equation in the coil heat exchanger, and the energy conservation equation in the tank has been solved by using the finite difference Euler implicit scheme. Energy conservation equations for the solar DHW components models have been coupled by means of a home-made implicit algorithm. Results of the simulation performed using as input data the experimental values of the ambient temperature and the solar irradiance in a summer day are presented and discussed.
Intensification of transesterification via sonication numerical simulation and sensitivity study
International Nuclear Information System (INIS)
Janajreh, Isam; ElSamad, Tala; Noorul Hussain, Mohammed
2017-01-01
Highlights: • 3D numerical simulation of transesterification is accomplished. • A non-isothermal, reactive Navier–stokes was carried out. • Conventional and sonicated process was compared as far as reaction kinetics and yield. • Higher kinetic rates are achieved at lower molar ratios in sonicated process. • It validates feasibility of numerical simulation for transesterification assessment. - Abstract: Transesterification is known as slow reaction that can take over several hours to complete. The process involves two immiscible reactants to produce the biodiesel and the byproduct glycerol. Biodiesel commercialization has always been hindered by the long process times of the transesterification reaction. Catalyzing the process and increasing the agitation rate is the mode of intensifying the process additional to the increase of the molar ratio, temperature, circulation that all penalize the overall process metrics. Finding shorter path by reducing the reaction into a few minutes and ensures high quality biodiesel, in economically viable way is coming along with sonication. This drastic reduction moves the technology from the slow batch process into the high throughput continuous process. In a practical sense this means a huge optimization for the biodiesel production process which opens pathways for faster, voluminous and cheaper production. The mechanism of sonication assisted reaction is explained by the creation of microbubbles which increases the interfacial surface reaction areas and the presence of high localized temperature and turbulence as these microbubbles implode. As a result the reaction kinetics of sonicated transesterification as inferred by several authors is much faster. The aim of this work is to implement the inferred rates in a high fidelity numerical reactive flow simulation model while considering the reactor geometry. It is based on Navier–Stokes equations coupled with energy equation for non-isothermal flow and the transport
Numerical simulation of runaway electron effect on Plasma Facing Components
International Nuclear Information System (INIS)
Ezato, Koichiro; Suzuki, Satoshi; Akiba, Masato; Kunugi, Tomoaki
1998-07-01
The runaway electron effects on Plasma Facing Components (PFCs) are studied by the numerical analyses. The present study is the first investigation of time-dependent thermal response of PFCs caused by runaway electron impact. For this purpose, we developed a new integrated numerical code, which consists of the Monte Carlo code for the coupled electrons and photons transport analysis and the finite element code for the thermo-mechanical analysis. In this code, we apply the practical incident parameters and distribution of runaway electrons recently proposed by S. Putvinski, which can express the time-dependent behavior of runaway electrons impact. The incident parameters of electrons in this study are the energy density ranging from 10 to 75 MJ/m 2 , the average electrons' energy of 12.5 MeV, the incident angle of 0.01deg and the characteristic time constant for decay of runaway electrons event of 0.15sec. The numerical results showed that the divertor with CFC (Carbon-Fiber-Composite) armor did not suffer serious damage. On the other hand, maximum temperatures at the surface of the divertor with tungsten armor and the first wall with beryllium armor exceed the melting point in case of the incident energy density of 20 and 50 MJ/m 2 . Within the range of the incident condition of runaway electrons, the cooling pipe of each PFCs can be prevented from the melting or burn-out caused by runaway electrons impact, which is one of the possible consequences of runaway electrons event so far. (author)
Comparing Numerical Spall Simulations with a Nonlinear Spall Formation Model
Ong, L.; Melosh, H. J.
2012-12-01
Spallation accelerates lightly shocked ejecta fragments to speeds that can exceed the escape velocity of the parent body. We present high-resolution simulations of nonlinear shock interactions in the near surface. Initial results show the acceleration of near-surface material to velocities up to 1.8 times greater than the peak particle velocity in the detached shock, while experiencing little to no shock pressure. These simulations suggest a possible nonlinear spallation mechanism to produce the high-velocity, low show pressure meteorites from other planets. Here we pre-sent the numerical simulations that test the production of spall through nonlinear shock interactions in the near sur-face, and compare the results with a model proposed by Kamegai (1986 Lawrence Livermore National Laboratory Report). We simulate near-surface shock interactions using the SALES_2 hydrocode and the Murnaghan equation of state. We model the shock interactions in two geometries: rectangular and spherical. In the rectangular case, we model a planar shock approaching the surface at a constant angle phi. In the spherical case, the shock originates at a point below the surface of the domain and radiates spherically from that point. The angle of the shock front with the surface is dependent on the radial distance of the surface point from the shock origin. We model the target as a solid with a nonlinear Murnaghan equation of state. This idealized equation of state supports nonlinear shocks but is tem-perature independent. We track the maximum pressure and maximum velocity attained in every cell in our simula-tions and compare them to the Hugoniot equations that describe the material conditions in front of and behind the shock. Our simulations demonstrate that nonlinear shock interactions in the near surface produce lightly shocked high-velocity material for both planar and cylindrical shocks. The spall is the result of the free surface boundary condi-tion, which forces a pressure gradient
Numerical simulation for cyclic steam injection at Santa Clara field
International Nuclear Information System (INIS)
Rodriguez, Edwin; Barrios, Wilson; Sandoval, Roy; Santos, Nicolas; Cortes, Ingrid
2008-01-01
This article presents the methodology used and the results obtained in the construction, match and prediction of the first thermal composition simulation model done in Colombia by employing advanced thermal process commercial software, globally recognized because of its effectiveness in modeling these types of processes (CMG-STARS, 2005). The Santa Clara and Palermo fields were modeled and an excellent history match was achieved. All in all 28 wells and 17 years of production were matched. Two production scenes were proposed. The first involved primary production from existing wells, in other words: primary production; and a second scene where all the wells in the field are converted into injectors and producers, to simulate cyclic steam injection. This injection process included a series of sensitivity studies for several of the parameters involved in this technology, such as: pressure and temperature injection, time and rate of injection, heat injected, soaking period, steam quality, and injection cycles. This sensitivity study was focused on optimizing the processes to obtain the maximum end recovery possible. The information entered into the simulator was validated by laboratory tests developed at the Instituto Colombiano del Petroleo (ICP). Among the tests performed the following were assessed: rock compressibility, relative permeability curve behavior at different temperatures, formation sensitivity to injection fluids, DRX analysis and residual saturation of crude oil for steam injection. The aforementioned results are documented in this paper
Advances in Integrated Vehicle Thermal Management and Numerical Simulation
Directory of Open Access Journals (Sweden)
Yan Wang
2017-10-01
Full Text Available With the increasing demands for vehicle dynamic performance, economy, safety and comfort, and with ever stricter laws concerning energy conservation and emissions, vehicle power systems are becoming much more complex. To pursue high efficiency and light weight in automobile design, the power system and its vehicle integrated thermal management (VITM system have attracted widespread attention as the major components of modern vehicle technology. Regarding the internal combustion engine vehicle (ICEV, its integrated thermal management (ITM mainly contains internal combustion engine (ICE cooling, turbo-charged cooling, exhaust gas recirculation (EGR cooling, lubrication cooling and air conditioning (AC or heat pump (HP. As for electric vehicles (EVs, the ITM mainly includes battery cooling/preheating, electric machines (EM cooling and AC or HP. With the rational effective and comprehensive control over the mentioned dynamic devices and thermal components, the modern VITM can realize collaborative optimization of multiple thermodynamic processes from the aspect of system integration. Furthermore, the computer-aided calculation and numerical simulation have been the significant design methods, especially for complex VITM. The 1D programming can correlate multi-thermal components and the 3D simulating can develop structuralized and modularized design. Additionally, co-simulations can virtualize simulation of various thermo-hydraulic behaviors under the vehicle transient operational conditions. This article reviews relevant researching work and current advances in the ever broadening field of modern vehicle thermal management (VTM. Based on the systematic summaries of the design methods and applications of ITM, future tasks and proposals are presented. This article aims to promote innovation of ITM, strengthen the precise control and the performance predictable ability, furthermore, to enhance the level of research and development (R&D.
Single Stage To Orbit Minimum Requirements Through Numerical Simulation
Teixeira, E.
It is widely known that producing a single stage to orbit spacecraft is no easy task. It is also understood that it will be the first steady step towards spacecraft that operate in much the same way as today's airliners. This, in turn is believed to decrease the economical cost of reaching space through more efficient use of a single vehicle and higher launch rates. Space is then open to the common man, either through tourism or as a transportation medium. This paper is yet another study on the physical requirements of a SSTO spacecraft. It will begin with simple assumptions and gradually build up accuracy until reaching the use of a numerical simulation tool, so as to provide the necessary insight into it. The curvature of the Earth, its gravitational field, the exhaust pressure loss and atmospheric drag are a few of the considerations that the simulation takes into account. No attention was give to the actual details of the spacecraft such as propulsion type(s), winged or lifting body (aerodynamics), active or passive cooling (thermodynamics), stability and control. All these subsystems are considered to be included into the construction mass. The drag model is a simple textbook approximation and the propulsion force is given by a hypothetical propellant and engine so as to produce the assumed range of specific impulse. Even the construction mass is supposed to be futuristic so as to reach the lowest specified values. Not only vertical take-off will be simulated but also horizontal launching from altitude (from a towing aircraft, for example). The result of the paper shows the relationship between the construction mass and the specific impulse of a given spacecraft if it is to reach low earth orbit. This paper thus aims at bringing some light to the controversial discussion of how to make these vehicles a reality. The simulation program (Matlab) is available to students.
Numerical simulation of boron injection in a BWR
Energy Technology Data Exchange (ETDEWEB)
Tinoco, Hernan, E-mail: htb@forsmark.vattenfall.s [Forsmarks Kraftgrupp AB, SE-742 03 Osthammar (Sweden); Buchwald, Przemyslaw [Reactor Technology, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Frid, Wiktor, E-mail: wiktor@reactor.sci.kth.s [Reactor Technology, Royal Institute of Technology, SE-100 44 Stockholm (Sweden)
2010-02-15
The present study constitutes a first step to understand the process of boron injection, transport and mixing in a BWR. It consists of transient CFD simulations of boron injection in a model of the downcomer of Forsmark's Unit 3 containing about 6 million elements. The two cases studied are unintentional start of boron injection under normal operation and loss of offsite power with partial ATWS leaving 10% of the core power uncontrolled. The flow conditions of the second case are defined by means of an analysis with RELAP5, assuming boron injection start directly after the first ECCS injection. Recent publications show that meaningful conservative results may be obtained for boron or thermal mixing in PWRs with grids as coarse as that utilized here, provided that higher order discretization schemes are used to minimize numerical diffusion. The obtained results indicate an apparently strong influence of the scenario in the behavior of the injection process. The normal operation simulation shows that virtually all boron solution flows down to the Main Recirculation Pump inlet located directly below the boron inlet nozzle. The loss of offsite power simulation shows initially a spread of the boron solution over the entire sectional area of the lower part of the downcomer filled with colder water. This remaining effect of the ECCS injection lasts until all this water has left the downcomer. Above this region, the boron injection jet develops in a vertical streak, eventually resembling the injection of the normal operation scenario. Due to the initial spread, this boron injection will probably cause larger temporal and spatial concentration variations in the core. In both cases, these variations may cause reactivity transients and fuel damage due to local power escalation. To settle this issue, an analysis using an extended model containing the downcomer, the MRPs and the Lower Plenum will be carried out. Also, the simulation time will be extended to a scale of
Numerical simulation of boron injection in a BWR
International Nuclear Information System (INIS)
Tinoco, Hernan; Buchwald, Przemyslaw; Frid, Wiktor
2010-01-01
The present study constitutes a first step to understand the process of boron injection, transport and mixing in a BWR. It consists of transient CFD simulations of boron injection in a model of the downcomer of Forsmark's Unit 3 containing about 6 million elements. The two cases studied are unintentional start of boron injection under normal operation and loss of offsite power with partial ATWS leaving 10% of the core power uncontrolled. The flow conditions of the second case are defined by means of an analysis with RELAP5, assuming boron injection start directly after the first ECCS injection. Recent publications show that meaningful conservative results may be obtained for boron or thermal mixing in PWRs with grids as coarse as that utilized here, provided that higher order discretization schemes are used to minimize numerical diffusion. The obtained results indicate an apparently strong influence of the scenario in the behavior of the injection process. The normal operation simulation shows that virtually all boron solution flows down to the Main Recirculation Pump inlet located directly below the boron inlet nozzle. The loss of offsite power simulation shows initially a spread of the boron solution over the entire sectional area of the lower part of the downcomer filled with colder water. This remaining effect of the ECCS injection lasts until all this water has left the downcomer. Above this region, the boron injection jet develops in a vertical streak, eventually resembling the injection of the normal operation scenario. Due to the initial spread, this boron injection will probably cause larger temporal and spatial concentration variations in the core. In both cases, these variations may cause reactivity transients and fuel damage due to local power escalation. To settle this issue, an analysis using an extended model containing the downcomer, the MRPs and the Lower Plenum will be carried out. Also, the simulation time will be extended to a scale of several
Finite element simulation of a novel composite light-weight microporous cladding panel
Tian, Lida; Wang, Dongyan
2018-04-01
A novel composite light-weight microporous cladding panel with matched connection detailing is developed. Numerical simulation on the experiment is conducted by ABAQUS. The accuracy and rationality of the finite element model is verified by comparison between the simulation and the experiment results. It is also indicated that the novel composite cladding panel is of desirable bearing capacity, stiffness and deformability under out-of-plane load.
A calculation method for RF couplers design based on numerical simulation by microwave studio
International Nuclear Information System (INIS)
Wang Rong; Pei Yuanji; Jin Kai
2006-01-01
A numerical simulation method for coupler design is proposed. It is based on the matching procedure for the 2π/3 structure given by Dr. R.L. Kyhl. Microwave Studio EigenMode Solver is used for such numerical simulation. the simulation for a coupler has been finished with this method and the simulation data are compared with experimental measurements. The results show that this numerical simulation method is feasible for coupler design. (authors)
Numerical Simulation of A Right-moving Storm Over France
Chancibault, K.; Ducrocq, V.; Lafore, J.-Ph.
A three-dimensional non-hydrostatic mesoscale model is used to simulate the right- moving storm produced through storm splitting, on 30 may 1999, over northern France. The initial state is provided by the French 3D-var ARPEGE analysis and the simuation is performed with two interactive nested domains. The aim of this study is to improve our understanding of such storm dynamics. A vor- ticity analysis has been carried out, with emphasis on stretching and tilting terms of the vertical vorticity equation, thanks to the backward trajectories. The baroclinic produc- tion and stretching terms of the horizontal vorticity equation have also been studied to understand the interaction between the horizontal vorticity and a mesoscale thermal line. Finally, the spatial and temporal variation of the Storm Relative Environmental Helicity has been examined. Most of the results compare well with previous results on right-moving storms ob- tained from theoritical or numerical studies from idealized homogeneous base state.
Numerical simulation for design of biped locomotion robots
International Nuclear Information System (INIS)
Kume, Etsuo; Takanishi, Atsuo
1993-01-01
A mechanical design study of anthropomorphic walking robots for patrol and inspection in nuclear facilities is being performed at Computing and Information Systems Center (CISC) of JAERI. We mainly focus on developing a software system to find a stable walking pattern, given robot models described by links, joints and so on. One of the features of our software is that some of the body elements, such as actuators and sensors, can be modeled as material particles as well as rigid bodies. The other is that our software has the cabability of obtaining unknown part of robot motions under given part of robot motions, satisfying a stable constraint. In this paper, we present the numerical models and the simulated results. (orig.)
Numerical simulation of transient moisture transfer into an electronic enclosure
International Nuclear Information System (INIS)
Nasirabadi, P. Shojaee; Jabbari, M.; Hattel, J. H.
2016-01-01
Electronic systems are sometimes exposed to harsh environmental conditions of temperature and humidity. Moisture transfer into electronic enclosures and condensation can cause several problems such as corrosion and alteration in thermal stresses. It is therefore essential to study the local climate inside the enclosures to be able to protect the electronic systems. In this work, moisture transfer into a typical electronic enclosure is numerically studied using CFD. In order to reduce the CPU-time and make a way for subsequent factorial design analysis, a simplifying modification is applied in which the real 3D geometry is approximated by a 2D axial symmetry one. The results for 2D and 3D models were compared in order to calibrate the 2D representation. Furthermore, simulation results were compared with experimental data and good agreement was found.
Numerical simulation of the RF ion source RIG-10
International Nuclear Information System (INIS)
Arzt, T.
1988-01-01
A two-dimensional model for the numerical simulation of the inductively coupled radio-frequency (RF) ion source RIG-10 is presented. Due to the ambipolar characteristics of a discharge operating with hydrogen gas, the model consists of an equation for the space charge imbalance, Poisson's equation for the self-consistent presheath potential and the ion momentum transport equation. For a relatively broad range of operation and design parameters, the model allows the reproduction and prediction of the RF discharge behaviour in a systematic way and, hence, computes the 2D distribution of the ion current density within the source. By implementing relevant discharge physics, the model can provide an appropriate tool for ion source design with respect to an application in the field of neutral beam injection. (author)
Direct numerical simulation of turbulent channel flow with deformed bubbles
International Nuclear Information System (INIS)
Yamamoto, Yoshinobu; Kunugi, Tomoaki
2010-01-01
In this study, the direct numerical simulation of a fully-developed turbulent channel flow with deformed bubbles were conducted by means of the refined MARS method, turbulent Reynolds number 150, and Bubble Reynolds number 120. As the results, large-scale wake motions were observed round the bubbles. At the bubble located region, mean velocity was degreased and turbulent intensities and Reynolds shear stress were increased by the effects of the large-scale wake motions round bubbles. On the other hands, near wall region, bubbles might effect on the flow laminarlize and drag reduction. Two types of drag coefficient of bubble were estimated from the accelerated velocity of bubble and correlation equation as a function of Particle Reynolds number. Empirical correlation equation might be overestimated the drag effects in this Particle Reynolds number range. (author)
Numerical simulation of a battlefield Nd:YAG laser
Henriksson, Markus; Sjoqvist, Lars; Uhrwing, Thomas
2005-11-01
A numeric model has been developed to identify the critical components and parameters in improving the output beam quality of a flashlamp pumped Q-switched Nd:YAG laser with a folded Porro-prism resonator and polarization output coupling. The heating of the laser material and accompanying thermo-optical effects are calculated using the finite element partial differential equations package FEMLAB allowing arbitrary geometries and time distributions. The laser gain and the cavity are modeled with the physical optics simulation code GLAD including effects such as gain profile, thermal lensing and stress-induced birefringence, the Pockels cell rise-time and component aberrations. The model is intended to optimize the pumping process of an OPO providing radiation to be used for ranging, imaging or optical countermeasures.
Numerical simulation of effect of laser nonuniformity in interior interface
International Nuclear Information System (INIS)
Yu Xiaojin; Wu Junfeng; Ye Wenhua
2007-01-01
Using the LARED-S code and referring to the NIF direct-drive DT ignition target, the effect of laser nonuniformity on the interior interface in direct-drive spherical implosion with high convergence ratio was numerically studied. The two-dimensional results show that the implosion with high convergence ratio is sensitive to the nonuniformity of driving laser, and the growth of hydrodynamic instability on interior interface destroys the symmetric-drive and reduces the volume of central hot spot observably. Taking the limit that perturbation amplitude is equal to 1/3 radius of central hot spot, the simulation also gives that the requirements for the laser uniformity for different mode number(less than 12) on simple physical model are between 2.5% -0.25%, and the modes between 8-10 have the most rigorous requirement which is about 0.25%. (authors)
Numerical simulation of transient moisture transfer into an electronic enclosure
Energy Technology Data Exchange (ETDEWEB)
Nasirabadi, P. Shojaee; Jabbari, M.; Hattel, J. H. [Process Modelling Group, Department of Mechanical Engineering, Technical University of Denmark, Nils Koppels Allé, 2800 Kgs. Lyngby (Denmark)
2016-06-08
Electronic systems are sometimes exposed to harsh environmental conditions of temperature and humidity. Moisture transfer into electronic enclosures and condensation can cause several problems such as corrosion and alteration in thermal stresses. It is therefore essential to study the local climate inside the enclosures to be able to protect the electronic systems. In this work, moisture transfer into a typical electronic enclosure is numerically studied using CFD. In order to reduce the CPU-time and make a way for subsequent factorial design analysis, a simplifying modification is applied in which the real 3D geometry is approximated by a 2D axial symmetry one. The results for 2D and 3D models were compared in order to calibrate the 2D representation. Furthermore, simulation results were compared with experimental data and good agreement was found.
Numerical simulation of hydrodynamic performance of ship under oblique conditions
Directory of Open Access Journals (Sweden)
CHEN Zhiming
2018-02-01
Full Text Available [Objectives] This paper is intended to study the viscous flow field around a ship under oblique conditions and provide a research basis for ship maneuverability. [Methods] Using commercial software STRA-CCM+, the SST k-ω turbulence model is selected to predict the hydrodynamic performance of the KVLCC2 model at different drift angles, and predict the hull flow field. The pressure distribution of the ship model at different drift angles is observed and the vortex shedding of the ship's hull and constraint streamlines on the hull's surface are also observed. [Results] The results show that numerical simulation can satisfy the demands of engineering application in the prediction of the lateral force, yaw moment and hull surface pressure distribution of a ship. [Conclusions] The research results of this paper can provide valuable references for the study of the flow separation phenomenon under oblique conditions.
Direct Numerical Simulations for Combustion Science: Past, Present, and Future
Im, Hong G.
2017-01-01
Direct numerical simulations (DNS) of turbulent combustion have evolved tremendously in the past decades, thanks to the rapid advances in high performance computing technology. Today’s DNS is capable of incorporating detailed reaction mechanisms and transport properties, with physical parameter ranges approaching laboratory scale flames, thereby allowing direct comparison and cross-validation against laser diagnostic measurements. While these developments have led to significantly improved understanding of fundamental turbulent flame characteristics, there are increasing demands to explore combustion regimes at higher levels of turbulent Reynolds (Re) and Karlovitz (Ka) numbers, with a practical interest in new combustion engines driving towards higher efficiencies and lower emissions. This chapter attempts to provide a brief historical review of the progress in DNS of turbulent combustion during the past decades. Major scientific accomplishments and contributions towards fundamental understanding of turbulent combustion will be summarized and future challenges and research needs will be proposed.
Numerical simulation of dimples in airfoil using MATLAB
Booma Devi, P.; Shah, Dilip A.
2017-05-01
The Aircraft wing is a point of important research which poses greater challenge in terms of aerodynamic efficiency. The flow separation control method is addressed in classical aerodynamics methods. This study focuses on influence of dimples on controlling the flow and also increasing the aerodynamic efficiency. The periodic process of placing the cavities on the wing starting from root to tip controls the flow separation. The linear variation of characteristic curve provides the information about the flow separation and control of flow on upper surface of the airfoil.These different shapes are utilized viz., Square, Rectangle and Triangle. The numerical simulation is carried out in using MATLAB package. Preliminary analysis on the flow separation is carried out focuses on laminar flow separation, which has the influence on the overall lift generation and drag generation.
Parallelization of a numerical simulation code for isotropic turbulence
International Nuclear Information System (INIS)
Sato, Shigeru; Yokokawa, Mitsuo; Watanabe, Tadashi; Kaburaki, Hideo.
1996-03-01
A parallel pseudospectral code which solves the three-dimensional Navier-Stokes equation by direct numerical simulation is developed and execution time, parallelization efficiency, load balance and scalability are evaluated. A vector parallel supercomputer, Fujitsu VPP500 with up to 16 processors is used for this calculation for Fourier modes up to 256x256x256 using 16 processors. Good scalability for number of processors is achieved when number of Fourier mode is fixed. For small Fourier modes, calculation time of the program is proportional to NlogN which is ideal complexity of calculation for 3D-FFT on vector parallel processors. It is found that the calculation performance decreases as the increase of the Fourier modes. (author)
An example of numerical simulation in causal set dynamics
International Nuclear Information System (INIS)
Krugly, Alexey L; Tserkovnikov, Ivan A
2013-01-01
The model of a discrete pregeometry on a microscopic scale is an x-graph. This is a directed acyclic graph. An outdegree and an indegree of each vertex are not more than 2. The sets of vertices and edges of x-graph are particular cases of causal sets. The sequential growth of a graph is an addition of new vertices one by one. A simple stochastic algorithm of sequential growth of x-graph are considered. It is based on a random walk at the x-graph. The particles in this model must be self-organized repetitive structures. We introduce the method of search of such repetitive structures. It is based on a discrete Fourier transformation. An example of numerical simulation is introduced.
Turbulent diffusion of chemically reacting flows: Theory and numerical simulations.
Elperin, T; Kleeorin, N; Liberman, M; Lipatnikov, A N; Rogachevskii, I; Yu, R
2017-11-01
The theory of turbulent diffusion of chemically reacting gaseous admixtures developed previously [T. Elperin et al., Phys. Rev. E 90, 053001 (2014)PLEEE81539-375510.1103/PhysRevE.90.053001] is generalized for large yet finite Reynolds numbers and the dependence of turbulent diffusion coefficient on two parameters, the Reynolds number and Damköhler number (which characterizes a ratio of turbulent and reaction time scales), is obtained. Three-dimensional direct numerical simulations (DNSs) of a finite-thickness reaction wave for the first-order chemical reactions propagating in forced, homogeneous, isotropic, and incompressible turbulence are performed to validate the theoretically predicted effect of chemical reactions on turbulent diffusion. It is shown that the obtained DNS results are in good agreement with the developed theory.
Numerical Simulations for a Typical Train Fire in China
Directory of Open Access Journals (Sweden)
W. K. Chow
2011-01-01
Full Text Available Railway is the key transport means in China including the Mainland, Taiwan, and Hong Kong. Consequent to so many big arson and accidental fires in the public transport systems including trains and buses, fire safety in passenger trains is a concern. Numerical simulations with Computational Fluid Dynamics on identified fire scenarios with typical train compartments in China will be reported in this paper. The heat release rate of the first ignited item was taken as the input parameter. The mass lost rate of fuel vapor of other combustibles was estimated to predict the resultant heat release rates by the combustion models in the software. Results on air flow, velocity vectors, temperature distribution, smoke layer height, and smoke spread patterns inside the train compartment were analyzed. The results are useful for working out appropriate fire safety measures for train vehicles and determining the design fire for subway stations and railway tunnels.
Numerical simulation of abutment pressure redistribution during face advance
Klishin, S. V.; Lavrikov, S. V.; Revuzhenko, A. F.
2017-12-01
The paper presents numerical simulation data on the abutment pressure redistribution in rock mass during face advance, including isolines of maximum shear stress and pressure epures. The stress state of rock in the vicinity of a breakage heading is calculated by the finite element method using a 2D nonlinear model of a structurally heterogeneous medium with regard to plasticity and internal self-balancing stress. The thus calculated stress field is used as input data for 3D discrete element modeling of the process. The study shows that the abutment pressure increases as the roof span extends and that the distance between the face breast and the peak point of this pressure depends on the elastoplastic properties and internal self-balancing stress of a rock medium.
Modelization and numerical simulation of atmospheric aerosols dynamics
International Nuclear Information System (INIS)
Debry, Edouard
2004-01-01
Chemical-transport models are now able to describe in a realistic way gaseous pollutants behavior in the atmosphere. Nevertheless atmospheric pollution also exists as a fine suspended particles, called aerosols which interact with gaseous phase, solar radiation, and have their own dynamic behavior. The goal of this thesis is the modelization and numerical simulation of the General Dynamic Equation of aerosols (GDE). Part I deals with some theoretical aspects of aerosol modelization. Part II is dedicated to the building of one size resolved aerosol model (SIREAM). In part III we perform the reduction of this model in order to use it in dispersion models as POLAIR3D. Several modelization issues are still opened: organic aerosol matter, externally mixed aerosols, coupling with turbulent mixing, and nano-particles. (author) [fr
Developing a numerical simulation for fading in feldspar
International Nuclear Information System (INIS)
Larsen, A.; Greilich, S.; Jain, M.; Murray, A.S.
2009-01-01
Most models describing anomalous fading in feldspars are based on analytical solutions. As an alternative approach we present an entirely numerical model based on statistical sampling that simulates stepwise the charge creation/trapping and recombination in a given phosphor. We assume the number density of electrons and holes at any time to be equal, although the model is not bound to that assumption. The model is flexible enough to be used on any combination of geological and laboratory timescales and for any defined configuration of defects. Using this approach we observed reorganization of nearest-neighbor distances with time. The best agreement with experimental data is achieved if we assume the crystal to consist of small subvolumes (nanocrystals) only within which charge carriers are allowed to recombine.
Numerical Simulation of Cylindrical Solitary Waves in Periodic Media
Quezada de Luna, Manuel; Ketcheson, David I.
2013-01-01
We study the behavior of nonlinear waves in a two-dimensional medium with density and stress relation that vary periodically in space. Efficient approximate Riemann solvers are developed for the corresponding variable-coefficient first-order hyperbolic system. We present direct numerical simulations of this multiscale problem, focused on the propagation of a single localized perturbation in media with strongly varying impedance. For the conditions studied, we find little evidence of shock formation. Instead, solutions consist primarily of solitary waves. These solitary waves are observed to be stable over long times and to interact in a manner approximately like solitons. The system considered has no dispersive terms; these solitary waves arise due to the material heterogeneity, which leads to strong reflections and effective dispersion.
Direct numerical simulation of homogeneous stratified rotating turbulence
Energy Technology Data Exchange (ETDEWEB)
Iida, O.; Tsujimura, S.; Nagano, Y. [Nagoya Institute of Technology, Department of Mech. Eng., Nagoya (Japan)
2005-12-01
The effects of the Prandtl number on stratified rotating turbulence have been studied in homogeneous turbulence by using direct numerical simulations and a rapid distortion theory. Fluctuations under strong stable-density stratification can be theoretically divided into the WAVE and the potential vorticity (PV) modes. In low-Prandtl-number fluids, the WAVE mode deteriorates, while the PV mode remains. Imposing rotation on a low-Prandtl-number fluid makes turbulence two-dimensional as well as geostrophic; it is found from the instantaneous turbulent structure that the vortices merge to form a few vertically-elongated vortex columns. During the period toward two-dimensionalization, the vertical vortices become asymmetric in the sense of rotation. (orig.)
Direct Numerical Simulations for Combustion Science: Past, Present, and Future
Im, Hong G.
2017-12-12
Direct numerical simulations (DNS) of turbulent combustion have evolved tremendously in the past decades, thanks to the rapid advances in high performance computing technology. Today’s DNS is capable of incorporating detailed reaction mechanisms and transport properties, with physical parameter ranges approaching laboratory scale flames, thereby allowing direct comparison and cross-validation against laser diagnostic measurements. While these developments have led to significantly improved understanding of fundamental turbulent flame characteristics, there are increasing demands to explore combustion regimes at higher levels of turbulent Reynolds (Re) and Karlovitz (Ka) numbers, with a practical interest in new combustion engines driving towards higher efficiencies and lower emissions. This chapter attempts to provide a brief historical review of the progress in DNS of turbulent combustion during the past decades. Major scientific accomplishments and contributions towards fundamental understanding of turbulent combustion will be summarized and future challenges and research needs will be proposed.
Numerical simulation of high Reynolds number bubble motion
Energy Technology Data Exchange (ETDEWEB)
McLaughlin, J.B. [Clarkson Univ., Potsdam, NY (United States)
1995-12-31
This paper presents the results of numerical simulations of bubble motion. All the results are for single bubbles in unbounded fluids. The liquid phase is quiescent except for the motion created by the bubble, which is axisymmetric. The main focus of the paper is on bubbles that are of order 1 mm in diameter in water. Of particular interest is the effect of surfactant molecules on bubble motion. Results for the {open_quotes}insoluble surfactant{close_quotes} model will be presented. These results extend research by other investigators to finite Reynolds numbers. The results indicate that, by assuming complete coverage of the bubble surface, one obtains good agreement with experimental observations of bubble motion in tap water. The effect of surfactant concentration on the separation angle is discussed.
Numerical simulation of flow fields and particle trajectories
DEFF Research Database (Denmark)
Mayer, Stefan
2000-01-01
. The time-dependent flow is approximated with a continuous sequence of steady state creeping flow fields, where metachronously beating ciliary bands are modelled by linear combinations of singularity solutions to the Stokes equations. Generally, the computed flow fields can be divided into an unsteady......A model describing the ciliary driven flow and motion of suspended particles in downstream suspension feeders is developed. The quasi-steady Stokes equations for creeping flow are solved numerically in an unbounded fluid domain around cylindrical bodies using a boundary integral formulation...... in the simulated unsteady ciliary driven flow. A fraction of particles appear to follow trajectories, that resemble experimentally observed particle capture events in the downstream feeding system of the polycheate Sabella penicillus, indicating that particles can be captured by ciliary systems without mechanical...
Numerical Simulation of Cylindrical Solitary Waves in Periodic Media
Quezada de Luna, Manuel
2013-07-14
We study the behavior of nonlinear waves in a two-dimensional medium with density and stress relation that vary periodically in space. Efficient approximate Riemann solvers are developed for the corresponding variable-coefficient first-order hyperbolic system. We present direct numerical simulations of this multiscale problem, focused on the propagation of a single localized perturbation in media with strongly varying impedance. For the conditions studied, we find little evidence of shock formation. Instead, solutions consist primarily of solitary waves. These solitary waves are observed to be stable over long times and to interact in a manner approximately like solitons. The system considered has no dispersive terms; these solitary waves arise due to the material heterogeneity, which leads to strong reflections and effective dispersion.
Numerical simulation of electron beam welding with beam oscillations
Trushnikov, D. N.; Permyakov, G. L.
2017-02-01
This research examines the process of electron-beam welding in a keyhole mode with the use of beam oscillations. We study the impact of various beam oscillations and their parameters on the shape of the keyhole, the flow of heat and mass transfer processes and weld parameters to develop methodological recommendations. A numerical three-dimensional mathematical model of electron beam welding is presented. The model was developed on the basis of a heat conduction equation and a Navier-Stokes equation taking into account phase transitions at the interface of a solid and liquid phase and thermocapillary convection (Marangoni effect). The shape of the keyhole is determined based on experimental data on the parameters of the secondary signal by using the method of a synchronous accumulation. Calculations of thermal and hydrodynamic processes were carried out based on a computer cluster, using a simulation package COMSOL Multiphysics.
Holistic simulation of geotechnical installation processes numerical and physical modelling
2015-01-01
The book provides suitable methods for the simulations of boundary value problems of geotechnical installation processes with reliable prediction for the deformation behavior of structures in static or dynamic interaction with the soil. It summarizes the basic research of a research group from scientists dealing with constitutive relations of soils and their implementations as well as contact element formulations in FE-codes. Numerical and physical experiments are presented providing benchmarks for future developments in this field. Boundary value problems have been formulated and solved with the developed tools in order to show the effectivity of the methods. Parametric studies of geotechnical installation processes in order to identify the governing parameters for the optimization of the process are given in such a way that the findings can be recommended to practice for further use. For many design engineers in practice the assessment of the serviceability of nearby structures due to geotechnical installat...
Chrystal and Proudman resonances simulated with three numerical models
Bubalo, Maja; Janeković, Ivica; Orlić, Mirko
2018-05-01
The aim of this work was to study Chrystal and Proudman resonances in a simple closed basin and to explore and compare how well the two resonant mechanisms are reproduced with different, nowadays widely used, numerical ocean models. The test case was based on air pressure disturbances of two commonly used shapes (a sinusoidal and a boxcar), having various wave lengths, and propagating at different speeds. Our test domain was a closed rectangular basin, 300 km long with a uniform depth of 50 m, with the theoretical analytical solution available for benchmark. In total, 2250 simulations were performed for each of the three different numerical models: ADCIRC, SCHISM and ROMS. During each of the simulations, we recorded water level anomalies and computed the integral of the energy density spectrum for a number of points distributed along the basin. We have successfully documented the transition from Proudman to Chrystal resonance that occurs for a sinusoidal air pressure disturbance having a wavelength between one and two basin lengths. An inter-model comparison of the results shows that different models represent the two resonant phenomena in a slightly different way. For Chrystal resonance, all the models showed similar behavior; however, ADCIRC model providing slightly higher values of the mean resonant period than the other two models. In the case of Proudman resonance, the most consistent results, closest to the analytical solution, were obtained using ROMS model, which reproduced the mean resonant speed equal to 22.00 m/s— i.e., close to the theoretical value of 22.15 m/s. ADCIRC and SCHISM models showed small deviations from that value, with the mean speed being slightly lower—21.97 m/s (ADCIRC) and 21.93 m/s (SCHISM). The findings may seem small but could play an important role when resonance is a crucial process producing enhancing effects by two orders of magnitude (i.e., meteotsunamis).
Numerical simulation of travelling wave induced electrothermal fluid flow
International Nuclear Information System (INIS)
Perch-Nielsen, Ivan R; Green, Nicolas G; Wolff, Anders
2004-01-01
Many microdevices for manipulating particles and cells use electric fields to produce a motive force on the particles. The movement of particles in non-uniform electric fields is called dielectrophoresis, and the usual method of applying this effect is to pass the particle suspension over a microelectrode structure. If the suspension has a noticeable conductivity, one important side effect is that the electric field drives a substantial conduction current through the fluid, causing localized Joule-heating. The resulting thermal gradient produces local conductivity and permittivity changes in the fluid. Dielectrophoretic forces acting upon these pockets of fluid will then produce motion of both the fluid and the particles. This paper presents a numerical solution of the electrical force and the resulting electrothermal driven fluid flow on a travelling wave structure. This common electrode geometry consists of interdigitated electrodes laid down in a long array, with the phase of the applied potential shifted by 90 0 on each subsequent electrode. The resulting travelling electric field was simulated and the thermal field and electrical body force on the fluid calculated, for devices constructed from two typical materials: silicon and glass. The electrothermal fluid flow in the electrolyte over the electrode array was then numerically simulated. The model predicts that the thermal field depends on the conductivity and applied voltage, but more importantly on the geometry of the system and the material used in the construction of the device. The velocity of the fluid flow depends critically on the same parameters, with slight differences in the thermal field for glass and silicon leading to diametrically opposite flow direction with respect to the travelling field for the two materials. In addition, the imposition of slight external temperature gradients is shown to have a large effect on the fluid flow in the device, under certain conditions leading to a reversal of
Numerical Simulation of Dispersion from Urban Greenhouse Gas Sources
Nottrott, Anders; Tan, Sze; He, Yonggang; Winkler, Renato
2017-04-01
Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant source distributions. These features create a scale separation between local sources and urban scale emissions estimates known as the Grey-Zone. Modern computational fluid dynamics (CFD) techniques provide a quasi-deterministic, physically based toolset to bridge the scale separation gap between source level dynamics, local measurements, and urban scale emissions inventories. CFD has the capability to represent complex building topography and capture detailed 3D turbulence fields in the urban boundary layer. This presentation discusses the application of OpenFOAM to urban CFD simulations of natural gas leaks in cities. OpenFOAM is an open source software for advanced numerical simulation of engineering and environmental fluid flows. When combined with free or low cost computer aided drawing and GIS, OpenFOAM generates a detailed, 3D representation of urban wind fields. OpenFOAM was applied to model scalar emissions from various components of the natural gas distribution system, to study the impact of urban meteorology on mobile greenhouse gas measurements. The numerical experiments demonstrate that CH4 concentration profiles are highly sensitive to the relative location of emission sources and buildings. Sources separated by distances of 5-10 meters showed significant differences in vertical dispersion of plumes, due to building wake effects. The OpenFOAM flow fields were combined with an inverse, stochastic dispersion model to quantify and visualize the sensitivity of point sensors to upwind sources in various built environments. The Boussinesq approximation was applied to investigate the effects of canopy layer temperature gradients and convection on sensor footprints.
Direct Numerical Simulation of Low Capillary Number Pore Scale Flows
Esmaeilzadeh, S.; Soulaine, C.; Tchelepi, H.
2017-12-01
The arrangement of void spaces and the granular structure of a porous medium determines multiple macroscopic properties of the rock such as porosity, capillary pressure, and relative permeability. Therefore, it is important to study the microscopic structure of the reservoir pores and understand the dynamics of fluid displacements through them. One approach for doing this, is direct numerical simulation of pore-scale flow that requires a robust numerical tool for prediction of fluid dynamics and a detailed understanding of the physical processes occurring at the pore-scale. In pore scale flows with a low capillary number, Eulerian multiphase methods are well-known to produce additional vorticity close to the interface. This is mainly due to discretization errors which lead to an imbalance of capillary pressure and surface tension forces that causes unphysical spurious currents. At the pore scale, these spurious currents can become significantly stronger than the average velocity in the phases, and lead to unphysical displacement of the interface. In this work, we first investigate the capability of the algebraic Volume of Fluid (VOF) method in OpenFOAM for low capillary number pore scale flow simulations. Afterward, we compare VOF results with a Coupled Level-Set Volume of Fluid (CLSVOF) method and Iso-Advector method. It has been shown that the former one reduces the VOF's unphysical spurious currents in some cases, and both are known to capture interfaces sharper than VOF. As the conclusion, we will investigate that whether the use of CLSVOF or Iso-Advector will lead to less spurious velocities and more accurate results for capillary driven pore-scale multiphase flows or not. Keywords: Pore-scale multiphase flow, Capillary driven flows, Spurious currents, OpenFOAM
Numerical Simulation of In Situ Combustion of Oil Shale
Directory of Open Access Journals (Sweden)
Huan Zheng
2017-01-01
Full Text Available This paper analyzes the process of in situ combustion of oil shale, taking into account the transport and chemical reaction of various components in porous reservoirs. The physical model is presented, including the mass and energy conservation equations and Darcy’s law. The oxidation reactions of oil shale combustion are expressed by adding source terms in the conservation equations. The reaction rate of oxidation satisfies the Arrhenius law. A numerical method is established for calculating in situ combustion, which is simulated numerically, and the results are compared with the available experiment. The profiles of temperature and volume fraction of a few components are presented. The temperature contours show the temperature variation in the combustion tube. It is found that as combustion reaction occurs in the tube, the concentration of oxygen decreases rapidly, while the concentration of carbon dioxide and carbon monoxide increases contrarily. Besides, the combustion front velocity is consistent with the experimental value. Effects of gas injection rate, permeability of the reservoir, initial oil content, and injected oxygen content on the ISC process were investigated in this study. Varying gas injection rate and oxygen content is important in the field test of ISC.
Numerical Simulation of rivulet build up via lubrication equations
Suzzi, N.; Croce, G.
2017-11-01
A number of engineering problems involve the evolution of a thin layer of liquid over a non-wettable substrate. For example, CO2 chemical absorption is carried out in packed columns, where post-combustion CO2 flows up while liquid solvent falls down through a collection of corrugated sheets. Further application include, among others, in-flight icing simulations, moisture condensation on de-humidifier fins, fogging build up and removal. Here, we present a development of an in-house code solving numerically the 2D lubrication equation for a film flowing down an inclined plate. The disjoining pressure approach is followed, in order to model both the contact line discontinuity and the surface wettability. With respect to the original implementation, the full modeling of capillary pressure terms according to Young- Laplace relation allows to investigate contact angles close to π/2. The code is thus validated with literature numerical results, obtained by a fully 3D approach (VOF), showing satisfying agreement despite a strong reduction in terms of computational cost. Steady and unsteady wetting dynamics of a developing rivulet are investigated (and validated) under different load conditions and for different values of the contact angles.
Numerical simulations of downward convective overshooting in giants
Tian, Chun-Lin; Deng, Li-Cai; Chan, Kwing-Lam
2009-09-01
An attempt at understanding downward overshooting in the convective envelopes of post-main-sequence stars has been made on the basis of three-dimensional large-eddy simulations, using artificially modified OPAL opacity and taking into account radiation and ionization in the equation of state. Two types of star, an intermediate-mass star and a massive star, were considered. To avoid a long thermal relaxation time of the intermediate-mass star, we increased the stellar energy flux artificially while trying to maintain a structure close to the one given by a 1D stellar model. A parametric study of the flux factor was performed. For the massive star, no such process was necessary. Numerical results were analysed when the system reached the statistical steady state. It was shown that the penetration distance in pressure scaleheights is of the order of unity. The scaling relations between penetration distance, input flux and vertical velocity fluctuations studied by Singh et al. were checked. The anisotropy of the turbulent convection and the diffusion models of the third-order moments representing the non-local transport were also investigated. These models are dramatically affected by the velocity fields and no universal constant parameters seem to exist. The limitations of the numerical results were also discussed.
Direct Numerical Simulations of Statistically Stationary Turbulent Premixed Flames
Im, Hong G.
2016-07-15
Direct numerical simulations (DNS) of turbulent combustion have evolved tremendously in the past decades, thanks to the rapid advances in high performance computing technology. Today’s DNS is capable of incorporating detailed reaction mechanisms and transport properties of hydrocarbon fuels, with physical parameter ranges approaching laboratory scale flames, thereby allowing direct comparison and cross-validation against laser diagnostic measurements. While these developments have led to significantly improved understanding of fundamental turbulent flame characteristics, there are increasing demands to explore combustion regimes at higher levels of turbulent Reynolds (Re) and Karlovitz (Ka) numbers, with a practical interest in new combustion engines driving towards higher efficiencies and lower emissions. The article attempts to provide a brief overview of the state-of-the-art DNS of turbulent premixed flames at high Re/Ka conditions, with an emphasis on homogeneous and isotropic turbulent flow configurations. Some important qualitative findings from numerical studies are summarized, new analytical approaches to investigate intensely turbulent premixed flame dynamics are discussed, and topics for future research are suggested. © 2016 Taylor & Francis.
Numerical Simulation on Zonal Disintegration in Deep Surrounding Rock Mass
Directory of Open Access Journals (Sweden)
Xuguang Chen
2014-01-01
Full Text Available Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the generating condition and forming process of zonal disintegration. Via comparing the results with the geomechanical model test, the zonal disintegration phenomenon was confirmed and its mechanism is revealed. It is found to be the result of circular fracture which develops within surrounding rock mass under the high geostress. The fractured shape of zonal disintegration was determined, and the radii of the fractured zones were found to fulfill the relationship of geometric progression. The numerical results were in accordance with the model test findings. The mechanism of the zonal disintegration was revealed by theoretical analysis based on fracture mechanics. The fractured zones are reportedly circular and concentric to the cavern. Each fracture zone ruptured at the elastic-plastic boundary of the surrounding rocks and then coalesced into the circular form. The geometric progression ratio was found to be related to the mechanical parameters and the ground stress of the surrounding rocks.
Numerical simulation on zonal disintegration in deep surrounding rock mass.
Chen, Xuguang; Wang, Yuan; Mei, Yu; Zhang, Xin
2014-01-01
Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the generating condition and forming process of zonal disintegration. Via comparing the results with the geomechanical model test, the zonal disintegration phenomenon was confirmed and its mechanism is revealed. It is found to be the result of circular fracture which develops within surrounding rock mass under the high geostress. The fractured shape of zonal disintegration was determined, and the radii of the fractured zones were found to fulfill the relationship of geometric progression. The numerical results were in accordance with the model test findings. The mechanism of the zonal disintegration was revealed by theoretical analysis based on fracture mechanics. The fractured zones are reportedly circular and concentric to the cavern. Each fracture zone ruptured at the elastic-plastic boundary of the surrounding rocks and then coalesced into the circular form. The geometric progression ratio was found to be related to the mechanical parameters and the ground stress of the surrounding rocks.
Numerical simulation of a cross flow Marine Hydrokinetic turbine.
Hall, Taylor; Aliseda, Alberto
2011-11-01
In the search for alternative sources of energy, the kinetic energy of water currents in oceans, rivers and estuaries is being explored as predictable and environmentally benign. We are investigating the flow past a cross flow turbine in which a helical blade under hydrodynamic forces turns around a shaft perpendicular to the free stream. This type of turbine, while very different from the classical horizontal axis turbine commonly used in the wind energy field, presents advantages for stacking in very narrow constricted channels where the water currents are consistently high and therefore turbine installation may be economically feasible. We use a model of a helical four-bladed turbine in cross flow to investigate the efficiency of the energy capture and the dynamics of the turbulent wake. Scale model experiments in a flume are used to validate the numerical results on a stationary configuration as an initial step towards creating an accurate numerical model of the turbine. The simulation of the rotating turbine provides a full perspective on the effect of angular position on flow detachment and vortex shedding from the blade, as well as on the fluctuations of the shaft torque produced (a problematic feature of this type of turbine). The results are analyzed in terms of hydrodynamic optimization of the blade and its structural loading. Supported by DOE through the Northwest National Marine Renewable Energy Center.
Direct numerical simulation of axisymmetric laminar low-density jets
Gomez Lendinez, Daniel; Coenen, Wilfried; Sevilla, Alejandro
2017-11-01
The stability of submerged laminar axisymmetric low-density jets has been investigated experimentally (Kyle & Sreenivasan 1993, Hallberg & Strykowski 2006) and with linear analysis (Jendoubi & Strykowski 1994, Coenen & Sevilla 2012, Coenen et al. 2017). These jets become globally unstable when the Reynolds number is larger than a certain critical value which depends on the density ratio and on the velocity profile at the injector outlet. In this work, Direct Numerical Simulations using FreeFEM + + (Hecht 2012) with P1 elements for pressure and P2 for velocity and density are performed to complement the above mentioned studies. Density and velocity fields are analyzed at long time showing the unforced space-time evolution of nonlinear disturbances propagating along the jet. Using the Stuart-Landau model to fit the numerical results for the self-excited oscillations we have computed a neutral stability curve that shows good agreement with experiments and stability theory. Thanks to Spanish MINECO under projects DPI2014-59292-C3-1-P and DPI2015-71901-REDT for financial support.
Numerical Simulations of Particle Deposition in Metal Foam Heat Exchangers
Sauret, Emilie; Saha, Suvash C.; Gu, Yuantong
2013-01-01
Australia is a high-potential country for geothermal power with reserves currently estimated in the tens of millions of petajoules, enough to power the nation for at least 1000 years at current usage. However, these resources are mainly located in isolated arid regions where water is scarce. Therefore, wet cooling systems for geothermal plants in Australia are the least attractive solution and thus air-cooled heat exchangers are preferred. In order to increase the efficiency of such heat exchangers, metal foams have been used. One issue raised by this solution is the fouling caused by dust deposition. In this case, the heat transfer characteristics of the metal foam heat exchanger can dramatically deteriorate. Exploring the particle deposition property in the metal foam exchanger becomes crucial. This paper is a numerical investigation aimed to address this issue. Two-dimensional (2D) numerical simulations of a standard one-row tube bundle wrapped with metal foam in cross-flow are performed and highlight preferential particle deposition areas.
Korte, M. C.; Wardinski, I.; Brown, M. C.
2016-12-01
Paleomagnetic results from sediments and lava flows provide observational evidence of numerous geomagnetic excursions throughout Earth's history. Two new spherical harmonic geomagnetic field models covering 50-30 ka, including the Laschamp ( 41ka) and Mono Lake ( 32-35 ka) excursions allow us to characterize the global behaviour of these events, both at Earth's surface and the core-mantle boundary. We investigate the evolution of dipole and large-scale non-dipole power throughout the duration of the model and the morphology of the large-scale radial field at the core-mantle boundary. The models suggest clear differences in both the decrease in axial dipole strength and dipole tilt between the two excursions and unlike the previously published model by Leonhardt et al. (2009), they suggest some increase of non-dipole power during the early and late stages of the Laschamp excursion. Global characteristics from the models can be directly compared with results from numerical simulations. We do so for several excursions generated by a numerical simulation driven by purely compositional convection, which appears Earth-like in terms of excursion and reversal occurrence frequency. Excursions from this simulation show differing characteristics, including differences in spectral power evolution. Some cases show similarities to the Laschamp and Mono Lake excursions in the spherical harmonic models. In particular they all indicate that excursions are mainly governed by the axial dipole term and equatorial dipole terms play a minor role.
Finite-difference numerical simulations of underground explosion cavity decoupling
Aldridge, D. F.; Preston, L. A.; Jensen, R. P.
2012-12-01
Earth models containing a significant portion of ideal fluid (e.g., air and/or water) are of increasing interest in seismic wave propagation simulations. Examples include a marine model with a thick water layer, and a land model with air overlying a rugged topographic surface. The atmospheric infrasound community is currently interested in coupled seismic-acoustic propagation of low-frequency signals over long ranges (~tens to ~hundreds of kilometers). Also, accurate and efficient numerical treatment of models containing underground air-filled voids (caves, caverns, tunnels, subterranean man-made facilities) is essential. In support of the Source Physics Experiment (SPE) conducted at the Nevada National Security Site (NNSS), we are developing a numerical algorithm for simulating coupled seismic and acoustic wave propagation in mixed solid/fluid media. Solution methodology involves explicit, time-domain, finite-differencing of the elastodynamic velocity-stress partial differential system on a three-dimensional staggered spatial grid. Conditional logic is used to avoid shear stress updating within the fluid zones; this approach leads to computational efficiency gains for models containing a significant proportion of ideal fluid. Numerical stability and accuracy are maintained at air/rock interfaces (where the contrast in mass density is on the order of 1 to 2000) via a finite-difference operator "order switching" formalism. The fourth-order spatial FD operator used throughout the bulk of the earth model is reduced to second-order in the immediate vicinity of a high-contrast interface. Current modeling efforts are oriented toward quantifying the amount of atmospheric infrasound energy generated by various underground seismic sources (explosions and earthquakes). Source depth and orientation, and surface topography play obvious roles. The cavity decoupling problem, where an explosion is detonated within an air-filled void, is of special interest. A point explosion
Direct Numerical Simulations of Particle-Laden Turbulent Channel Flow
Jebakumar, Anand Samuel; Premnath, Kannan; Abraham, John
2017-11-01
In a recent experimental study, Lau and Nathan (2014) reported that the distribution of particles in a turbulent pipe flow is strongly influenced by the Stokes number (St). At St lower than 1, particles migrate toward the wall and at St greater than 10 they tend to migrate toward the axis. It was suggested that this preferential migration of particles is due to two forces, the Saffman lift force and the turbophoretic force. Saffman lift force represents a force acting on the particle as a result of a velocity gradient across the particle when it leads or lags the fluid flow. Turbophoretic force is induced by turbulence which tends to move the particle in the direction of decreasing turbulent kinetic energy. In this study, the Lattice Boltzmann Method (LBM) is employed to simulate a particle-laden turbulent channel flow through Direct Numerical Simulations (DNS). We find that the preferential migration is a function of particle size in addition to the St. We explain the effect of the particle size and St on the Saffman lift force and turbophoresis and present how this affects particle concentration at different conditions.
Equilibrium statistical mechanics of strongly coupled plasmas by numerical simulation
International Nuclear Information System (INIS)
DeWitt, H.E.
1977-01-01
Numerical experiments using the Monte Carlo method have led to systematic and accurate results for the thermodynamic properties of strongly coupled one-component plasmas and mixtures of two nuclear components. These talks are intended to summarize the results of Monte Carlo simulations from Paris and from Livermore. Simple analytic expressions for the equation of state and other thermodynamic functions have been obtained in which there is a clear distinction between a lattice-like static portion and a thermal portion. The thermal energy for the one-component plasma has a simple power dependence on temperature, (kT)/sup 3 / 4 /, that is identical to Monte Carlo results obtained for strongly coupled fluids governed by repulsive l/r/sup n/ potentials. For two-component plasmas the ion-sphere model is shown to accurately represent the static portion of the energy. Electron screening is included in the Monte Carlo simulations using linear response theory and the Lindhard dielectric function. Free energy expressions have been constructed for one and two component plasmas that allow easy computation of all thermodynamic functions
Optimizing switching frequency of the soliton transistor by numerical simulation
Energy Technology Data Exchange (ETDEWEB)
Izadyar, S., E-mail: S_izadyar@yahoo.co [Department of Electronics, Khaje Nasir Toosi University of Technology, Shariati Ave., Tehran (Iran, Islamic Republic of); Niazzadeh, M.; Raissi, F. [Department of Electronics, Khaje Nasir Toosi University of Technology, Shariati Ave., Tehran (Iran, Islamic Republic of)
2009-10-15
In this paper, by numerical simulations we have examined different ways to increase the soliton transistor's switching frequency. Speed of the solitons in a soliton transistor depends on various parameters such as the loss of the junction, the applied bias current, and the transmission line characteristics. Three different ways have been examined; (i) decreasing the size of the transistor without losing transistor effect. (ii) Decreasing the amount of loss of the junction to increase the soliton speed. (iii) Optimizing the bias current to obtain maximum possible speed. We have obtained the shortest possible length to have at least one working soliton inside the transistor. The dimension of the soliton can be decreased by changing the inductance of the transmission line, causing a further decrease in the size of the transistor, however, a trade off between the size and the inductance is needed to obtain the optimum switching speed. Decreasing the amount of loss can be accomplished by increasing the characteristic tunneling resistance of the device, however, a trade off is again needed to make soliton and antisoliton annihilation possible. By increasing the bias current, the forces acting the solitons increases and so does their speed. Due to nonuniform application of bias current a self induced magnetic field is created which can result in creation of unwanted solitons. Optimum bias current application can result in larger bias currents and larger soliton speed. Simulations have provided us with such an arrangement of bias current paths.
Optimizing switching frequency of the soliton transistor by numerical simulation
International Nuclear Information System (INIS)
Izadyar, S.; Niazzadeh, M.; Raissi, F.
2009-01-01
In this paper, by numerical simulations we have examined different ways to increase the soliton transistor's switching frequency. Speed of the solitons in a soliton transistor depends on various parameters such as the loss of the junction, the applied bias current, and the transmission line characteristics. Three different ways have been examined; (i) decreasing the size of the transistor without losing transistor effect. (ii) Decreasing the amount of loss of the junction to increase the soliton speed. (iii) Optimizing the bias current to obtain maximum possible speed. We have obtained the shortest possible length to have at least one working soliton inside the transistor. The dimension of the soliton can be decreased by changing the inductance of the transmission line, causing a further decrease in the size of the transistor, however, a trade off between the size and the inductance is needed to obtain the optimum switching speed. Decreasing the amount of loss can be accomplished by increasing the characteristic tunneling resistance of the device, however, a trade off is again needed to make soliton and antisoliton annihilation possible. By increasing the bias current, the forces acting the solitons increases and so does their speed. Due to nonuniform application of bias current a self induced magnetic field is created which can result in creation of unwanted solitons. Optimum bias current application can result in larger bias currents and larger soliton speed. Simulations have provided us with such an arrangement of bias current paths.
Numerical simulation of nonequilibrium effects in an argon plasma jet
International Nuclear Information System (INIS)
Chang, C.H.; Ramshaw, J.D.
1994-01-01
Departures from thermal (translational), ionization, and excitation equilibrium in an axisymmetric argon plasma jet have been studied by two-dimensional numerical simulations. Electrons, ions, and excited and ground states of neutral atoms are represented as separate chemical species in the mixture. Transitions between excited states, as well as ionization/recombination reactions due to both collisional and radiative processes, are treated as separate chemical reactions. Resonance radiation transport is represented using Holstein escape factors to simulate both the optically thin and optically thick limits. The optically thin calculation showed significant underpopulation of excited species in the upstream part of the jet core, whereas in the optically thick calculation this region remains close to local thermodynamic equilibrium, consistent with previous experimental observations. Resonance radiation absorption is therefore an important effect. The optically thick calculation results also show overpopulations (relative to equilibrium) of excited species and electron densities in the fringes and downstream part of the jet core. In these regions, however, the electrons and ions are essentially in partial local thermodynamic equilibrium with the excited state at the electron temperature, even though the ionized and excited states are no longer in equilibrium with the ground state. Departures from partial local thermodynamic equilibrium are observed in the outer fringes and far downstream part of the jet. These results are interpreted in terms of the local relative time scales for the various physical and chemical processes occurring in the plasma
Parametric Optimization Through Numerical Simulation of VCR Diesel Engine
Ganji, Prabhakara Rao; Mahmood, Al-Qarttani Abdulrahman Shakir; Kandula, Aasrith; Raju, Vysyaraju Rajesh Khana; Rao, Surapaneni Srinivasa
2017-08-01
In the present study, the Variable Compression Ratio (VCR) engine was analyzed numerically using CONVERGE™ Computational Fluid Dynamics code in order to optimize the design/operating parameters such as Compression Ratio (CR), Start of Injection (SOI) and Exhaust Gas Recirculation (EGR). VCR engine was run for 100 % load to test its performance and it was validated for standard configuration. Simulations were performed by varying the design/operating parameters such as CR (18-14), SOI (17°-26° bTDC) and EGR (0-15 %) at constant fuel injection pressure of 230 bar and speed of 1500 rpm. The effect of each of these parameters on pressure, oxides of nitrogen (NOx) and soot are presented. Finally, regression equations were developed for pressure, NOx and soot by using the simulation results. The regression equations were solved for multi objective criteria in order to reduce the NOx and soot while maintaining the baseline performance. The optimized configuration was tested for validation and found satisfactory.
Direct Numerical Simulation of heat transfer in a turbulent flume
International Nuclear Information System (INIS)
Bergant, R.; Tiselj, I.
2001-01-01
Direct Numerical Simulation (DNS) can be used for the description of turbulent heat transfer in the fluid at low Reynolds numbers. DNS means precise solving of Navier-Stoke's equations without any extra turbulent models. DNS should be able to describe all relevant length scales and time scales in observed turbulent flow. The largest length scale is actually dimension of system and the smallest length and time scale is equal to Kolmogorov scale. In the present work simulations of fully developed turbulent velocity and temperature fields were performed in a turbulent flume (open channel) with pseudo-spectral approach at Reynolds number 2670 (friction Reynolds number 171) and constant Prandtl number 5.4, considering the fluid temperature as a passive scalar. Two ideal thermal boundary conditions were taken into account on the heated wall. The first one was an ideal isothermal boundary condition and the second one an ideal isoflux boundary condition. We observed different parameters like mean temperature and velocity, fluctuations of temperature and velocity, and auto-correlation functions.(author)
Numerical simulation of NQR/NMR: Applications in quantum computing.
Possa, Denimar; Gaudio, Anderson C; Freitas, Jair C C
2011-04-01
A numerical simulation program able to simulate nuclear quadrupole resonance (NQR) as well as nuclear magnetic resonance (NMR) experiments is presented, written using the Mathematica package, aiming especially applications in quantum computing. The program makes use of the interaction picture to compute the effect of the relevant nuclear spin interactions, without any assumption about the relative size of each interaction. This makes the program flexible and versatile, being useful in a wide range of experimental situations, going from NQR (at zero or under small applied magnetic field) to high-field NMR experiments. Some conditions specifically required for quantum computing applications are implemented in the program, such as the possibility of use of elliptically polarized radiofrequency and the inclusion of first- and second-order terms in the average Hamiltonian expansion. A number of examples dealing with simple NQR and quadrupole-perturbed NMR experiments are presented, along with the proposal of experiments to create quantum pseudopure states and logic gates using NQR. The program and the various application examples are freely available through the link http://www.profanderson.net/files/nmr_nqr.php. Copyright © 2011 Elsevier Inc. All rights reserved.
Direct Numerical Simulation of Transition Due to Traveling Crossflow Vortices
Li, Fei; Choudhari, Meelan M.; Duan, Lian
2016-01-01
Previous simulations of laminar breakdown mechanisms associated with stationary crossflow instability over a realistic swept-wing configuration are extended to investigate the alternate scenario of transition due to secondary instability of traveling crossflow modes. Earlier analyses based on secondary instability theory and parabolized stability equations have shown that this alternate scenario is viable when the initial amplitude of the most amplified mode of the traveling crossflow instability is greater than approximately 0.03 times the initial amplitude of the most amplified stationary mode. The linear growth predictions based on the secondary instability theory and parabolized stability equations agree well with the direct numerical simulation. Nonlinear effects are initially stabilizing but subsequently lead to a rapid growth followed by the onset of transition when the amplitude of the secondary disturbance exceeds a threshold value. Similar to the breakdown of stationary vortices, the transition zone is rather short and the boundary layer becomes completely turbulent across a distance of less than 15 times the boundary layer thickness at the completion of transition.
Direct numerical simulation of fractal-generated turbulence
International Nuclear Information System (INIS)
Suzuki, H; Hasegawa, Y; Ushijima, T; Nagata, K; Sakai, Y; Hayase, T
2013-01-01
We simulate fractal-generated turbulence (Hurst and Vassilicos 2007 Phys. Fluids 19 035103)) by means of a direct numerical simulation and address its fundamental characteristics. We examine whether the fractal-generated turbulence in the upstream region has a nature similar to that of a wake. We propose an equation for predicting peak values of the velocity fluctuation intensity and devise a method for formulating the functional form of the quantity of interest by focusing on the time scale of decaying turbulence, and we examine those forms for the turbulent kinetic energy and rms of pressure fluctuation through this method. By using the method, both of these functional forms are found to be power-law functions in the downstream region, even though these profiles follow exponential functions around these peaks. In addition, decay exponents of these quantities are estimated. The integral length scales of velocity fluctuations for transverse as well as streamwise directions are essentially constant in the downstream direction. Decaying turbulence having both these characteristics conflicts with decaying turbulence described by the theory predicting exponential decay. We discuss a factor causing the difference by focusing on the functional form of the transfer function of homogeneous, isotropic turbulence. (paper)
Direct numerical simulations of evaporating droplets in turbulence
Palmore, John; Desjardins, Olivier
2015-11-01
This work demonstrates direct numerical simulations of evaporating two phase flows, with applications to studying combustion in aircraft engines. Inside the engine, liquid fuel is injected into the combustion chamber where it atomizes into droplets and evaporates. Combustion occurs as the fuel vapor mixes with the surrounding flow of turbulent gas. Understanding combustion, therefore, requires studying evaporation in a turbulent flow and the resulting vapor distribution. We study the problem using a finite volume framework to solve the Navier-Stokes and scalar transport equations under a low-Mach assumption [Desjardins et al., J. Comp. Phys., 2008]. The liquid-gas interface is tracked using a conservative level-set method [Desjardins et al., J. Comp. Phys., 2008] which allows for a sharp reconstruction of the discontinuity across the interface. Special care is taken in the discretization of cells near the liquid-gas interface to ensure the stability and accuracy of the solution. Results are discussed for non-reacting simulations of liquid droplets evaporating into a turbulent field of inert gas.
Numerical relativity simulations of precessing binary neutron star mergers
Dietrich, Tim; Bernuzzi, Sebastiano; Brügmann, Bernd; Ujevic, Maximiliano; Tichy, Wolfgang
2018-03-01
We present the first set of numerical relativity simulations of binary neutron mergers that include spin precession effects and are evolved with multiple resolutions. Our simulations employ consistent initial data in general relativity with different spin configurations and dimensionless spin magnitudes ˜0.1 . They start at a gravitational-wave frequency of ˜392 Hz and cover more than 1 precession period and about 15 orbits up to merger. We discuss the spin precession dynamics by analyzing coordinate trajectories, quasilocal spin measurements, and energetics, by comparing spin aligned, antialigned, and irrotational configurations. Gravitational waveforms from different spin configuration are compared by calculating the mismatch between pairs of waveforms in the late inspiral. We find that precession effects are not distinguishable from nonprecessing configurations with aligned spins for approximately face-on binaries, while the latter are distinguishable from nonspinning configurations. Spin precession effects are instead clearly visible for approximately edge-on binaries. For the parameters considered here, precession does not significantly affect the characteristic postmerger gravitational-wave frequencies nor the mass ejection. Our results pave the way for the modeling of spin precession effects in the gravitational waveform from binary neutron star events.
Numerical simulation of linear fiction welding (LFW) processes
Fratini, L.; La Spisa, D.
2011-05-01
Solid state welding processes are becoming increasingly important due to a large number of advantages related to joining "unweldable" materials and in particular light weight alloys. Linear friction welding (LFW) has been used successfully to bond non-axisymmetric components of a range of materials including titanium alloys, steels, aluminum alloys, nickel, copper, and also dissimilar material combinations. The technique is useful in the research of quality of the joints and in reducing costs of components and parts of the aeronautic and automotive industries. LFW involves parts to be welded through the relative reciprocating motion of two components under an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and proper bonding conditions due to both the temperature increase and the local pressure of the two edges to be welded. This paper is a comparative test between the numerical model in two dimensions, i.e. in plane strain conditions, and in three dimensions of a LFW process of AISI1045 steel specimens. It must be observed that the 3D model assures a faithful simulation of the actual threedimensional material flow, even if the two-dimensional simulation computational times are very short, a few hours instead of several ones as the 3D model. The obtained results were compared with experimental values found out in the scientific literature.
Numerical simulation of linear fiction welding (LFW) processes
International Nuclear Information System (INIS)
Fratini, L.; La Spisa, D.
2011-01-01
Solid state welding processes are becoming increasingly important due to a large number of advantages related to joining ''unweldable'' materials and in particular light weight alloys. Linear friction welding (LFW) has been used successfully to bond non-axisymmetric components of a range of materials including titanium alloys, steels, aluminum alloys, nickel, copper, and also dissimilar material combinations. The technique is useful in the research of quality of the joints and in reducing costs of components and parts of the aeronautic and automotive industries.LFW involves parts to be welded through the relative reciprocating motion of two components under an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and proper bonding conditions due to both the temperature increase and the local pressure of the two edges to be welded. This paper is a comparative test between the numerical model in two dimensions, i.e. in plane strain conditions, and in three dimensions of a LFW process of AISI1045 steel specimens. It must be observed that the 3D model assures a faithful simulation of the actual threedimensional material flow, even if the two-dimensional simulation computational times are very short, a few hours instead of several ones as the 3D model. The obtained results were compared with experimental values found out in the scientific literature.
Direct numerical simulation of stratified gas-liquid flow
International Nuclear Information System (INIS)
Lombardi, P.; De Angelis, V.; Banerjee, S.
1996-01-01
Interactions through an interface between two turbulent flows play an important role in many environmental and industrial problems, e.g. in determining the coupling fluxes of heat mass and momentum, between the ocean and atmosphere, and in the design of gas-liquid contractors for the chemical industry, as well as in determining interactions between phases in nuclear transients that are accompanied by system voiding e.g. LOCAs. Here, the Direct Numerical Simulation (DNS) of the interaction of two turbulent fluids through a flat interface has been simulated. The flow and the temperature fields are computed using a pseudospectral method. This study shows that shear stress at the interface correlates well with the heat flux. Extensive analysis of the near interface turbulence structure has been performed using quadrant analysis. From this it is clear that gas-side sweeps dominate over the high shear stress regions. This suggests that simple parameterizations based on sweep frequency may be adequate for predictions of scalar transport rates
Direct numerical simulation of turbulent, chemically reacting flows
Doom, Jeffrey Joseph
This dissertation: (i) develops a novel numerical method for DNS/LES of compressible, turbulent reacting flows, (ii) performs several validation simulations, (iii) studies auto-ignition of a hydrogen vortex ring in air and (iv) studies a hydrogen/air turbulent diffusion flame. The numerical method is spatially non-dissipative, implicit and applicable over a range of Mach numbers. The compressible Navier-Stokes equations are rescaled so that the zero Mach number equations are discretely recovered in the limit of zero Mach number. The dependent variables are co--located in space, and thermodynamic variables are staggered from velocity in time. The algorithm discretely conserves kinetic energy in the incompressible, inviscid, non--reacting limit. The chemical source terms are implicit in time to allow for stiff chemical mechanisms. The algorithm is readily applicable to complex chemical mechanisms. Good results are obtained for validation simulations. The algorithm is used to study auto-ignition in laminar vortex rings. A nine species, nineteen reaction mechanism for H2/air combustion proposed by Mueller et al. [37] is used. Diluted H 2 at ambient temperature (300 K) is injected into hot air. The simulations study the effect of fuel/air ratio, oxidizer temperature, Lewis number and stroke ratio (ratio of piston stroke length to diameter). Results show that auto--ignition occurs in fuel lean, high temperature regions with low scalar dissipation at a 'most reactive' mixture fraction, zeta MR (Mastorakos et al. [32]). Subsequent evolution of the flame is not predicted by zetaMR; a most reactive temperature TMR is defined and shown to predict both the initial auto-ignition as well as subsequent evolution. For stroke ratios less than the formation number, ignition in general occurs behind the vortex ring and propagates into the core. At higher oxidizer temperatures, ignition is almost instantaneous and occurs along the entire interface between fuel and oxidizer. For stroke
Numerical simulation of progressive BWR fuel inlet orifices
International Nuclear Information System (INIS)
Sara Lundgren; Hernan Tinoco; Aleksander Pohl; Wiktor Frid
2005-01-01
Full text of publication follows: A 'progressive' orifice is characterized by an edge-shaped hole that gives a Reynolds number dependent resistance coefficient. For Reynolds numbers smaller than a critical one, the resistance coefficient has a high constant value that drops to a much lower value for Reynolds numbers greater than this critical value. A similar effect is widely known for external flows around bodies of different shapes, i. e. spheres, cylinders, etc., and the sudden drop in drag coefficient is due to the shift from laminar to turbulent boundary-layer flow. Experimentally, progressive orifices have been investigated under high-pressure and high-temperature conditions by Akiba et al. (2001) for a reduced set of geometrical parameters. Using the sparse experimental data, a core stability study was carried out by Forsmaks Kraftgrupp AB that showed an improvement in core stability but without the expected reduction in pump power at normal operation. The reason for this partial success was the impossibility of optimizing the fuel inlet pressure drop owing to the limited amount of available data. Due to the high costs associated with the experimental generation of high-pressure, high-temperature data, it was considered that, if possible, the lacking data could be generated numerically at much lower cost. Therefore, the present work deals with the possibility of numerically simulate the flow through progressive orifices, and with the conditions under which to reproduce and generate resistance coefficient data by means of a commercial CFD-code. The results obtained with a two-dimensional, axisymmetric approximation show that Reynolds Averaged Navier-Stokes (RANS) turbulence models are able to qualitatively capture the physics of the phenomenon but with an earlier transition to turbulent boundary-layer flow and with an underestimation of the resistance coefficient by approximately 20 %. This underestimation of the resistance coefficient is related to the two
Numerical simulation of progressive BWR fuel inlet orifices
Energy Technology Data Exchange (ETDEWEB)
Sara Lundgren; Hernan Tinoco [Forsmarks Kraftgrupp AB, 742 03 Oesthammar (Sweden); Aleksander Pohl; Wiktor Frid [The Royal Institute of Technology, Dept. Energy Technology, SE-100 44 Stockholm (Sweden)
2005-07-01
Full text of publication follows: A 'progressive' orifice is characterized by an edge-shaped hole that gives a Reynolds number dependent resistance coefficient. For Reynolds numbers smaller than a critical one, the resistance coefficient has a high constant value that drops to a much lower value for Reynolds numbers greater than this critical value. A similar effect is widely known for external flows around bodies of different shapes, i. e. spheres, cylinders, etc., and the sudden drop in drag coefficient is due to the shift from laminar to turbulent boundary-layer flow. Experimentally, progressive orifices have been investigated under high-pressure and high-temperature conditions by Akiba et al. (2001) for a reduced set of geometrical parameters. Using the sparse experimental data, a core stability study was carried out by Forsmaks Kraftgrupp AB that showed an improvement in core stability but without the expected reduction in pump power at normal operation. The reason for this partial success was the impossibility of optimizing the fuel inlet pressure drop owing to the limited amount of available data. Due to the high costs associated with the experimental generation of high-pressure, high-temperature data, it was considered that, if possible, the lacking data could be generated numerically at much lower cost. Therefore, the present work deals with the possibility of numerically simulate the flow through progressive orifices, and with the conditions under which to reproduce and generate resistance coefficient data by means of a commercial CFD-code. The results obtained with a two-dimensional, axisymmetric approximation show that Reynolds Averaged Navier-Stokes (RANS) turbulence models are able to qualitatively capture the physics of the phenomenon but with an earlier transition to turbulent boundary-layer flow and with an underestimation of the resistance coefficient by approximately 20 %. This underestimation of the resistance coefficient is related to
Direct numerical simulation of droplet-laden isotropic turbulence
Dodd, Michael S.
Interaction of liquid droplets with turbulence is important in numerous applications ranging from rain formation to oil spills to spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown, especially when compared to that of solid particles. Compared to solid particles, droplets can deform, break up, coalesce and have internal fluid circulation. The main goal of this work is to investigate using direct numerical simulation (DNS) the physical mechanisms of droplet-turbulence interaction, both for non-evaporating and evaporating droplets. To achieve this objective, we develop and couple a new pressure-correction method with the volume-of-fluid (VoF) method for simulating incompressible two-fluid flows. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation. This equation can then be solved directly using, e.g., the FFT-based parallel Poisson solver. For a 10243 mesh, our new pressure-correction method using a fast Poisson solver is ten to forty times faster than the standard pressure-correction method using multigrid. Using the coupled pressure-correction and VoF method, we perform direct numerical simulations (DNS) of 3130 finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale and with 5% droplet volume fraction in decaying isotropic turbulence at initial Taylor-scale Reynolds number Relambda = 83. In the droplet-laden cases, we vary one of the following three parameters: the droplet Weber number based on the r.m.s. velocity of turbulence (0.1 ≤ Werms ≤ 5), the droplet- to carrier-fluid density ratio (1 ≤ rhod/rho c ≤ 100) or the droplet- to carrier-fluid viscosity ratio (1 ≤ mud/muc ≤ 100). We derive the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. These equations allow
International Nuclear Information System (INIS)
Aadmi, Moussa; Karkri, Mustapha; El Hammouti, Mimoun
2014-01-01
In the present study, phase change materials based on epoxy resin paraffin wax with the melting point 27 °C were used as a new energy storage system. Thermophysical properties and the process of melting of a PCM (phase change material) composite were investigated numerically and experimentally. DSC (differential scanning calorimetry) has been used for measurement of melting enthalpy and determination of PCM heat capacity. The thermophysical properties of the prepared composite have been characterized by using a new transient hot plate apparatus. The results have shown that the most important thermal properties of these composites at the solid and liquid states are like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. These experimental results have been simulated by using numerical Comsol ® Multiphysiques 4.3 based models with success. The results of the experimental investigation compare favorably with the numerical results and thus serve to validate the numerical approach. - Highlights: • Phase change materials based on paraffin spheres used as new energy storage system. • Thermophysical properties and the melting process of composites were investigated. • All experimental results have been simulated using Comsol ® Multiphysiques. • The ability to store and release the thermal energy were investigated. • A very thin molten PCM (phase change material) exists which is apparently visible in the spheres
Numerical simulation of turbulent forced convection in liquid metals
International Nuclear Information System (INIS)
Vodret, S; Di Maio, D Vitale; Caruso, G
2014-01-01
In the frame of the future generation of nuclear reactors, liquid metals are foreseen to be used as a primary coolant. Liquid metals are characterized by a very low Prandtl number due to their very high heat diffusivity. As such, they do not meet the so-called Reynolds analogy which assumes a complete similarity between the momentum and the thermal boundary layers via the use of the turbulent Prandtl number. Particularly, in the case of industrial fluid-dynamic calculations where a resolved computation near walls could be extremely time consuming and could need very large computational resources, the use of the classical wall function approach could lead to an inaccurate description of the temperature profile close to the wall. The first aim of the present study is to investigate the ability of a well- established commercial code (ANSYS FLUENT v.14) to deal with this issue, validating a suitable expression for the turbulent Prandtl number. Moreover, a thermal wall-function developed at Universite Catholique de Louvain has been implemented in FLUENT and validated, overcoming the limits of the solver to define it directly. Both the resolved and unresolved approaches have been carried out for a channel flow case and assessed against available direct numerical and large eddy simulations. A comparison between the numerically evaluated Nusselt number and the main correlations available in the literature has been also carried out. Finally, an application of the proposed methodology to a typical sub-channel case has been performed, comparing the results with literature correlations for tube banks
Numerical Forming Simulations and Optimisation in Advanced Materials
International Nuclear Information System (INIS)
Huetink, J.; Boogaard, A. H. van den; Geijselears, H. J. M.; Meinders, T.
2007-01-01
With the introduction of new materials as high strength steels, metastable steels and fibre reinforced composites, the need for advanced physically valid constitutive models arises. In finite deformation problems constitutive relations are commonly formulated in terms the Cauchy stress as a function of the elastic Finger tensor and an objective rate of the Cauchy stress as a function of the rate of deformation tensor. For isotropic materials models this is rather straightforward, but for anisotropic material models, including elastic anisotropy as well as plastic anisotropy, this may lead to confusing formulations. It will be shown that it is more convenient to define the constitutive relations in terms of invariant tensors referred to the deformed metric. Experimental results are presented that show new combinations of strain rate and strain path sensitivity. An adaptive through- thickness integration scheme for plate elements is developed, which improves the accuracy of spring back prediction at minimal costs. A procedure is described to automatically compensate the CAD tool shape numerically to obtain the desired product shape. Forming processes need to be optimized for cost saving and product improvement. Until recently, a trial-and-error process in the factory primarily did this optimization. An optimisation strategy is proposed that assists an engineer to model an optimization problem that suits his needs, including an efficient algorithm for solving the problem
Dobson, Patrick F.; Kneafsey, Timothy J.; Sonnenthal, Eric L.; Spycher, Nicolas; Apps, John A.
2003-05-01
Plugging of flow paths caused by mineral precipitation in fractures above the potential repository at Yucca Mountain, Nevada could reduce the probability of water seeping into the repository. As part of an ongoing effort to evaluate thermal-hydrological-chemical (THC) effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation under anticipated temperature and pressure conditions in the repository. To replicate mineral dissolution by vapor condensate in fractured tuff, water was flowed through crushed Yucca Mountain tuff at 94 °C. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/l; silica was the dominant dissolved constituent. A portion of the steady-state mineralized water was flowed into a vertically oriented planar fracture in a block of welded Topopah Spring Tuff that was maintained at 80 °C at the top and 130 °C at the bottom. The fracture began to seal with amorphous silica within 5 days. A 1-D plug-flow numerical model was used to simulate mineral dissolution, and a similar model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents for the tuff dissolution were within a factor of 2 of the measured average steady-state compositions. The mineral precipitation simulations predicted the precipitation of amorphous silica at the base of the boiling front, leading to a greater than 50-fold decrease in fracture permeability in 5 days, consistent with the laboratory experiment. These results help validate the use of a numerical model to simulate THC processes at Yucca Mountain. The experiment and simulations indicated that boiling and concomitant precipitation of amorphous silica could cause significant reductions in fracture porosity and permeability on a local scale. However
Numerical simulation of turbulent buoyant flows in horizontal channels
International Nuclear Information System (INIS)
Seiter, C.
1995-09-01
A numerical method is presented, to calculate the three-dimensional, time-dependent large scale structure of turbulent buoyant flows. The subject of the study is the Rayleigh-Benard-convection with air (Pr=0.71, Ra=2.5 10 6 , 10 7 ) and sodium (Pr=0.006, Ra=8.4 10 4 , 2.5 10 5 , 10 6 , 10 7 ) and a fluid layer with water and an internal heat source (Pr=7.0, Ra I =1.5 10 10 ) at moderate and high Rayleigh-numbers. The goal of the work is both, the analysis of structures of instantaneous as well as the statistical analysis of spatially and/or time averaged data, to give a contribution to the investigation of the characteristics of turbulent natural convection mainly in fluids with small Prandtl-numbers. The large eddy simulation of natural convection requires the development of appropriate momentum and heat subgrid scale models and the formulation of new boundary conditions. The used energy-length-models in the computer code TURBIT are extended methodically by modification of the characteristic length scales of the sub scale turbulence. The reduction or the increase of the sub scale turbulence correlations, caused by the influence of solid boundaries or the stratification, is considered. In the same way the new boundary conditions for the diffusive terms of the conservation equations are seen to be necessary, when the thermal or in the case of liquid metals the more critical hydrodynamic boundary layer is resolved insufficiently or not at all. The extended and new methods, models and boundary conditions, which enabled the realization of the planned simulations, are presented. (orig.)
Direct numerical simulation of free and forced square jets
International Nuclear Information System (INIS)
Gohil, Trushar B.; Saha, Arun K.; Muralidhar, K.
2015-01-01
Highlights: • Free square jet at Re = 500–2000 is studied using DNS. • Forced square jet at Re = 1000 subjected to varicose perturbation is also investigated at various forcing frequencies. • Vortex interactions within the jet and jet spreading are affected both for free and forced jets. • Perturbation at higher frequency shows axis-switching. - Abstract: Direct numerical simulation (DNS) of incompressible, spatially developing square jets in the Reynolds number range of 500–2000 is reported. The three-dimensional unsteady Navier–Stokes equations are solved using high order spatial and temporal discretization. The objective of the present work is to understand the evolution of free and forced square jets by examining the formation of large-scale structures. Coherent structures and related interactions of free jets suggest control strategies that can be used to achieve enhanced spreading and mixing of the jet with the surrounding fluid. The critical Reynolds number for the onset on unsteadiness in an unperturbed free square jet is found to be 875–900 while it reduces to the range 500–525 in the presence of small-scale perturbations. Disturbances applied at the flow inlet cause saturation of KH-instability and early transition to turbulence. Forced jet calculations have been carried out using varicose perturbation with amplitude of 15%, while frequency is independently varied. Simulations show that the initial development of the square jet is influenced by the four corners leading to the appearance hairpin structures along with the formation of vortex rings. Farther downstream, adjacent vortices strongly interact leading to their rapid breakup. Excitation frequencies in the range 0.4–0.6 cause axis-switching of the jet cross-section. Results show that square jets achieve greater spreading but are less controllable in comparison to the circular ones
Numerical Simulation of Explosive Forming Using Detonating Fuse
Directory of Open Access Journals (Sweden)
H Iyama
2017-09-01
Full Text Available The explosive forming is a characteristic method. An underwater shock wave is generated by underwater explosion of an explosive. A metal plate is affected high strain rate by the shock loading and is formed along a metal die. Although this method has the advantage of mirroring the shape of the die, a free forming was used in this paper. An expensive metal die is not necessary for this free forming. It is possible that a metal plate is formed with simple supporting parts. However, the forming shape is depend on the shock pressure distribution act on the metal plate. This pressure distribution is able to change by the shape of explosive, a mass of explosive and a shape of pressure vessel. On the other hand, we need the pressure vessel for food processing by the underwater shock wave. Therefore, we propose making the pressure vessel by this explosive forming. One design suggestion of pressure vessel made of stainless steel was considered. However, we cannot decide suitable conditions, the mass of the explosive and the distance between the explosive and the metal plate to make the pressure vessel. In order to decide these conditions, we have tried the numerical simulation on this explosive forming. The basic simulation method was ALE (Arbitrary Laglangian Eulerian method including with Mie-Grümeisen EOS (equation of state, JWL EOS, Johnson-Cook constitutive equation for a material model. In this paper, the underwater pressure contours to clear the propagations of the underwater shock wave, forming processes and deformation velocity of the metal plate is shown and it will be discussed about those results.
Numerical simulations of the stratified oceanic bottom boundary layer
Taylor, John R.
Numerical simulations are used to consider several problems relevant to the turbulent oceanic bottom boundary layer. In the first study, stratified open channel flow is considered with thermal boundary conditions chosen to approximate a shallow sea. Specifically, a constant heat flux is applied at the free surface and the lower wall is assumed to be adiabatic. When the surface heat flux is strong, turbulent upwellings of low speed fluid from near the lower wall are inhibited by the stable stratification. Subsequent studies consider a stratified bottom Ekman layer over a non-sloping lower wall. The influence of the free surface is removed by using an open boundary condition at the top of the computational domain. Particular attention is paid to the influence of the outer layer stratification on the boundary layer structure. When the density field is initialized with a linear profile, a turbulent mixed layer forms near the wall, which is separated from the outer layer by a strongly stable pycnocline. It is found that the bottom stress is not strongly affected by the outer layer stratification. However, stratification reduces turbulent transport to the outer layer and strongly limits the boundary layer height. The mean shear at the top of the boundary layer is enhanced when the outer layer is stratified, and this shear is strong enough to cause intermittent instabilities above the pycnocline. Turbulence-generated internal gravity waves are observed in the outer layer with a relatively narrow frequency range. An explanation for frequency content of these waves is proposed, starting with an observed broad-banded turbulent spectrum and invoking linear viscous decay to explain the preferential damping of low and high frequency waves. During the course of this work, an open-source computational fluid dynamics code has been developed with a number of advanced features including scalar advection, subgrid-scale models for large-eddy simulation, and distributed memory
Numerical simulation of ventilation air movement in partitioned offices
Energy Technology Data Exchange (ETDEWEB)
Plett, E.G.; Soultogiannis, A.A.; Jouini, D.B. (Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Ontario (Canada))
1993-01-01
Good air quality can only be assured throughout an office complex if each workspace receives an adequate supply of ventilation air. The likelihood of achieving this situation would be increased if the building engineer had a means of easily predicting the air movement in each office configuration. A simple computer-based solution to this need is proposed. To this end, the development and validation testing of a numerical solution technique to simulate the ventilation air movement in a room or office is described. The predictions of the two-dimensional, isothermal, inviscid formulation are seen to be in good agreement with experimentally measured airflows in configurations of interest. The computer code is then used to illustrate the airflow in offices served by a single row of supply air diffusers, when partitions are used to divide the space into smaller workspaces. It is observed that the partitions distort the airflow patterns to the extent that it would be difficult to provide desirable ventilation airflows to all the workspaces formed by the partitions. (au) (26 refs.)
Direct Numerical Simulation of Flow Over Passive Geometric Disturbances
Vizard, Alexander
It is well understood that delaying flow separation on a bluff body allows significant drag reduction, which is attractive in many applications. With this in mind, many separation control mechanisms, both active and passive, have been developed and tested to optimize the effects of this phenomenon. Although this idea is generally accepted, the physical occurrences in the near-wall region during transition that lead to separation delay are not well understood. The current study evaluates the impact of both spherical dimples, and sandgrain style roughness on downstream flow by performing direct numerical simulations over such geometries on a zero pressure gradient flat plate. It is shown that although dimples and random roughness of similar characteristic length scales exhibit similar boundary layer characteristics, dimples are more successful in developing high momentum in the vicinity of the wall. Additionally it is shown that increasing the relative size of the rough elements does not increase the near-wall momentum, and is undesirable in controlling separation. Finally, it is shown that the impact of roughness elements on the flow is more immediate, and that, for the case of one row of dimples and an equivalent area of roughness, the roughness patch is more successful in transitioning the near-wall region to a non-laminar state. It can be concluded from variation in the span of the flowfield for a single row of dimples that the size and orientation of the disturbance region is significant to the results.
Numerical Simulation of Particle Distribution in Capillary Membrane during Backwash
Directory of Open Access Journals (Sweden)
Anik Keller
2013-09-01
Full Text Available The membrane filtration with inside-out dead-end driven UF-/MF- capillary membranes is an effective process for particle removal in water treatment. Its industrial application increased in the last decade exponentially. To date, the research activities in this field were aimed first of all at the analysis of filtration phenomena disregarding the influence of backwash on the operation parameters of filtration plants. However, following the main hypothesis of this paper, backwash has great potential to increase the efficiency of filtration. In this paper, a numerical approach for a detailed study of fluid dynamic processes in capillary membranes during backwash is presented. The effect of particle size and inlet flux on the backwash process are investigated. The evaluation of these data concentrates on the analysis of particle behavior in the cross sectional plane and the appearance of eventually formed particle plugs inside the membrane capillary. Simulations are conducted in dead-end filtration mode and with two configurations. The first configuration includes a particle concentration of 10% homogeneously distributed within the capillary and the second configuration demonstrates a cake layer on the membrane surface with a packing density of 0:6. Analyzing the hydrodynamic forces acting on the particles shows that the lift force plays the main role in defining the particle enrichment areas. The operation parameters contribute in enhancing the lift force and the heterogeneity to anticipate the clogging of the membrane.
[New approaches in pharmacology: numerical modelling and simulation].
Boissel, Jean-Pierre; Cucherat, Michel; Nony, Patrice; Dronne, Marie-Aimée; Kassaï, Behrouz; Chabaud, Sylvie
2005-01-01
The complexity of pathophysiological mechanisms is beyond the capabilities of traditional approaches. Many of the decision-making problems in public health, such as initiating mass screening, are complex. Progress in genomics and proteomics, and the resulting extraordinary increase in knowledge with regard to interactions between gene expression, the environment and behaviour, the customisation of risk factors and the need to combine therapies that individually have minimal though well documented efficacy, has led doctors to raise new questions: how to optimise choice and the application of therapeutic strategies at the individual rather than the group level, while taking into account all the available evidence? This is essentially a problem of complexity with dimensions similar to the previous ones: multiple parameters with nonlinear relationships between them, varying time scales that cannot be ignored etc. Numerical modelling and simulation (in silico investigations) have the potential to meet these challenges. Such approaches are considered in drug innovation and development. They require a multidisciplinary approach, and this will involve modification of the way research in pharmacology is conducted.
Developments in numerical simulation of IFE target and chamber physics
International Nuclear Information System (INIS)
Velarde, G.; Minguez, E.; Alonso, E.; Gil, J.M.; Malerba, L.; Marian, J.; Martel, P.; Martinez-Val, J.M.; Munoz, R.; Ogando, F.; Perlado, J.M.; Piera, M.; Reyes, S.; Rubiano, J.G.; Sanz, J.; Sauvan, P.; Velarde, M.; Velarde, P.
2000-01-01
The work presented outlines the global frame given at the Institute of Nuclear Fusion (DENIM) for having an integral perspective of the different research areas with the development of Inertial Fusion for energy generation. The coupling of a new radiation transport (RT) solver with an existing multi-material fluid dynamics code using Adaptive Mesh Refinement (ARM) is presented in Section 2, including improvements and additional information about the solver precision. In Section 3, new developments in the atomic physics codes under target conditions, to determine populations, opacity data and emissivities have been performed. Exotic and innovative ideas about Inertial Fusion Energy (IFE), as catalytic fuels and Z-pinches have been explored, and they are explained in Section 4. Numerical simulations demonstrate important reductions in the tritium inventory. Section 5 is devoted to safety and environment of the IFE. Uncertainties analysis in activation calculations have been included in the ACAB activation code, and also calculations on pulse activation in IFE reactors and on the activation of target debris in NIF are presented. A comparison of the accidental releases of tritium from some IFE reactors computed using MACCS2 code is explained. Finally, Section 6 contains the research on the basic mechanisms of neutron damage in SiC (low-activation material) and FeCu alloy using the DENIM/LLNL molecular dynamics code MDCASK. (authors)
Direct numerical simulation of incompressible multiphase flow with phase change
Lee, Moon Soo; Riaz, Amir; Aute, Vikrant
2017-09-01
Simulation of multiphase flow with phase change is challenging because of the potential for unphysical pressure oscillations, spurious velocity fields and mass flux errors across the interface. The resulting numerical errors may become critical when large density contrasts are present. To address these issues, we present a new approach for multiphase flow with phase change that features, (i) a smooth distribution of sharp velocity jumps and mass flux within a narrow region surrounding the interface, (ii) improved mass flux projection from the implicit interface onto the uniform Cartesian grid and (iii) post-advection velocity correction step to ensure accurate velocity divergence in interfacial cells. These new features are implemented in combination with a sharp treatment of the jumps in pressure and temperature gradient. A series of 1-D, 2-D, axisymmetric and 3-D problems are solved to verify the improvements afforded by the new approach. Axisymmetric film boiling results are also presented, which show good qualitative agreement with heat transfer correlations as well as experimental observations of bubble shapes.
Numerical simulation of carbon dioxide effects in geothermal reservoirs
Energy Technology Data Exchange (ETDEWEB)
Moya, S.L.; Iglesias, E.R. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1995-03-01
We developed and coded a new equation of state (EOS) for water-carbon dioxide mixtures and coupled it to the TOUGH numerical simulator. This EOS is valid up to 350{degrees}C and 500 bar. Unlike previous thermodynamical models, it rigorously considers the non-ideal behavior of both components in the gaseous mixture and formally includes the effect of the compressibility of the liquid phase. We refer to the coupling of this EOS with TOUGH as TOUGH-DIOX. To complement this enhancement of TOUGH, we added indexed output files for easy selection and interpretation of results. We validated TOUGH-DIOX against published results. Furthermore we used TOUGH-DIOX to explore and compare mass and energy inflow performance relationships of geothermal wells with/without carbon dioxide (CO{sub 2}). Our results include the effects of a broad range of fluid and formation properties, initial conditions and history of reservoir production. This work contributes with generalized dimensionless inflow performance relationships appropriate for geothermal use.
Optimization and Numerical Simulation of Outlet of Twin Screw Extruder
Directory of Open Access Journals (Sweden)
Zhang Yuan
2018-01-01
Full Text Available In view of the unreasonable design of non-intermeshing counter-rotating twin screw extruder die, the problem of productivity reduction was discussed. Firstly, the mathematical model of extruder productivity was established. The extruder die model was improved. Secondly, the force analysis of twin screw extruder physical model was carried out. Meanwhile, A combination of mechanical analysis and numerical simulation was adopted. The velocity field, pressure field and viscosity field were calculated by Mini-Element interpolation method, linear interpolation method and Picard iterative convergence method respectively. The influence of die model on the quantity of each field before and after improvement was analyzed. The results show that the improved model had increased the rheological parameters of the flow field, the leakage and reverse flow decreased. Through post-processing calculation, the productivity of the third dies extruder was 10% higher than before. The research results provide a theoretical basis for the design and optimization of die model of non intermeshing counter-rotating twin screw extruder.
Direct numerical simulation of vector-controlled free jets
International Nuclear Information System (INIS)
Tsujimoto, K; Ao, K; Shakouchi, T; Ando, T
2011-01-01
We conduct DNS (direct numerical simulation) of vector controlled free jets. The inflow velocity of jet is periodically oscillated perpendicular to the jet axis. In order to realize the high accurate computation, a discretization in space is performed with hybrid scheme in which Fourier spectral and 6th order compact scheme are adopted. From visualized instantaneous vortex structures, it is found that the flow pattern considerably changes according to the oscillating frequency, i.e., according to the increasing the frequency, wave, bifurcating and flapping modes appear in turn. In order to quantify mixing efficiency under the vector control, as the mixing measure, statistical entropy is investigated. Compared to the uncontrolled jet, the mixing efficiency is improved in order of wavy, flapping and bifurcating modes. Thus the vector control can be expected for the improvement of mixing efficiency. Further to make clear the reason for the mixing enhancement, Snapshot POD and DMD method are applied. The primary flow structures under the vector control are demonstrated.
Direct Numerical Simulation of Fingering Instabilities in Coating Flows
Eres, Murat H.; Schwartz, Leonard W.
1998-11-01
We consider stability and finger formation in free surface flows. Gravity driven downhill drainage and temperature gradient driven climbing flows are two examples of such problems. The former situation occurs when a mound of viscous liquid on a vertical wall is allowed to flow. Constant surface shear stress due to temperature gradients (Marangoni stress) can initiate the latter problem. The evolution equations are derived using the lubrication approximation. We also include the effects of finite-contact angles in the evolution equations using a disjoining pressure model. Evolution equations for both problems are solved using an efficient alternating-direction-implicit method. For both problems a one-dimensional base state is established, that is steady in a moving reference frame. This base state is unstable to transverse perturbations. The transverse wavenumbers for the most rapidly growing modes are found through direct numerical solution of the nonlinear evolution equations, and are compared with published experimental results. For a range of finite equilibrium contact angles, the fingers can grow without limit leading to semi-finite steady fingers in a moving coordinate system. A computer generated movie of the nonlinear simulation results, for several sets of input parameters, will be shown.
DIPOLE COLLAPSE AND DYNAMO WAVES IN GLOBAL DIRECT NUMERICAL SIMULATIONS
Energy Technology Data Exchange (ETDEWEB)
Schrinner, Martin; Dormy, Emmanuel [MAG (ENS/IPGP), LRA, Ecole Normale Superieure, 24 Rue Lhomond, 75252 Paris Cedex 05 (France); Petitdemange, Ludovic, E-mail: martin@schrinner.eu [Previously at Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg, Germany. (Germany)
2012-06-20
Magnetic fields of low-mass stars and planets are thought to originate from self-excited dynamo action in their convective interiors. Observations reveal a variety of field topologies ranging from large-scale, axial dipoles to more structured magnetic fields. In this article, we investigate more than 70 three-dimensional, self-consistent dynamo models in the Boussinesq approximation obtained by direct numerical simulations. The control parameters, the aspect ratio, and the mechanical boundary conditions have been varied to build up this sample of models. Both strongly dipolar and multipolar models have been obtained. We show that these dynamo regimes in general can be distinguished by the ratio of a typical convective length scale to the Rossby radius. Models with a predominantly dipolar magnetic field were obtained, if the convective length scale is at least an order of magnitude larger than the Rossby radius. Moreover, we highlight the role of the strong shear associated with the geostrophic zonal flow for models with stress-free boundary conditions. In this case the above transition disappears and is replaced by a region of bistability for which dipolar and multipolar dynamos coexist. We interpret our results in terms of dynamo eigenmodes using the so-called test-field method. We can thus show that models in the dipolar regime are characterized by an isolated 'single mode'. Competing overtones become significant as the boundary to multipolar dynamos is approached. We discuss how these findings relate to previous models and to observations.
Numerical simulation of transitions between back discharge regimes
International Nuclear Information System (INIS)
Jansky, Jaroslav; Lemont, Florent; Bessieres, Delphine; Paillol, Jean
2014-01-01
This paper presents numerical simulations of transitions between back discharge regimes. Back discharge refers to any discharge initiated at or near a dielectric layer covering a passive electrode. In this work, a pinhole in a dielectric layer on a plane anode serves as a model for back discharge activity. We have studied transitions between back discharge regimes by varying the surface charge density on the dielectric layer and the electric field in front of the pinhole. From the variation of these two independent parameters, the back discharge regimes have been depicted as a mode diagram inspired by the experimental study of Masuda and Mizuno. The resulting diagram includes the different discharge regimes that are commonly observed in experiments. The propagation of a positive ionizing wave inside the pinhole toward its edge, and the resulting formation of a plasma zone at its exit constitute the onset stage of back discharge. From this stage, the transitions to volume discharge or surface discharge can occur. The volume discharge regime consists of the propagation of a discharge in space toward the cathode which can be superimposed with the propagation of a discharge above the dielectric layer surface. The diagram reveals the conditions for transitions between back discharge regimes. (authors)
Numerical simulation of responses for cased-hole density logging
International Nuclear Information System (INIS)
Wu, Wensheng; Fu, Yaping; Niu, Wei
2013-01-01
Stabilizing or stimulating oil production in old oil fields requires density logging in cased holes where open-hole logging data are either missing or of bad quality. However, measured values from cased-hole density logging are more severely influenced by factors such as fluid, casing, cement sheath and the outer diameter of the open-hole well compared with those from open-hole logging. To correctly apply the cased-hole formation density logging data, one must eliminate these influences on the measured values and study the characteristics of how the cased-hole density logging instrument responds to these factors. In this paper, a Monte Carlo numerical simulation technique was used to calculate the responses of the far detector of a cased-hole density logging instrument to in-hole fluid, casing wall thickness, cement sheath density and the formation and thus to obtain influence rules and response coefficients. The obtained response of the detector is a function of in-hole liquid, casing wall thickness, the casing's outer diameter, cement sheath density, open-hole well diameter and formation density. The ratio of the counting rate of the detector in the calibration well to that in the measurement well was used to get a fairly simple detector response equation and the coefficients in the equation are easy to acquire. These provide a new way of calculating cased-hole density through forward modelling methods. (paper)
Numerical simulations of turbulent jet ignition and combustion
Validi, Abdoulahad; Irannejad, Abolfazl; Jaberi, Farhad
2013-11-01
The ignition and combustion of a homogeneous lean hydrogen-air mixture by a turbulent jet flow of hot combustion products injected into a colder gas mixture are studied by a high fidelity numerical model. Turbulent jet ignition can be considered as an efficient method for starting and controlling the reaction in homogeneously charged combustion systems used in advanced internal combustion and gas turbine engines. In this work, we study in details the physics of turbulent jet ignition in a fundamental flow configuration. The flow and combustion are modeled with the hybrid large eddy simulation/filtered mass density function (LES/FMDF) approach, in which the filtered form the compressible Navier-Stokes equations are solved with a high-order finite difference scheme for the turbulent velocity and the FMDF transport equations are solved with a Lagrangian stochastic method to obtain the scalar (temperature and species mass fractions) field. The hydrogen oxidation is described by a detailed reaction mechanism with 37 elementary reactions and 9 species.
Numerical simulation of ion confinement in the Phaedrus plugs
International Nuclear Information System (INIS)
Horne, S.F.
1984-01-01
Neutral beams of up to 60 amps were injected into the plugs of the tandem mirror Phaedrus. Substantial heating of the target RF-sustained plasma has been observed, but fueling has been negligible. In order to understand the lack of significant fueling, a model of the trapping and loss processes occurring in the Phaedrus plug was developed, and is presented in this thesis. The model includes neutral beam effects, RF trapping, Coulomb losses, and charge exchange on background gas, in a framework which includes finite gyro-orbit effects. A numerical simulation based on the model is compared to data from 2XIIB and TMX, and shows good agreement. The model is then applied to the Phaedrus plugs, and compared to RF-sustained and neutral-beam data obtained during machine operation in hydrogen and deuterium. The modeling of the Phaedrus plugs indicates that during beam injection, a two-step process occurs that results in the rapid loss of ions. Charge exchange of trapped plasma on the energetic neutral beam causes rapid radial diffusion of the plasma, which then charge exchanges on the background gas, or is lost to the limiter. Because this is a finite gyro-orbit effect, increasing the plug magnetic field should improve the net beam fueling by reducing this diffusion. Results from the model indicate that increasing the plug midplane field from 2600 to 4000 gauss will improve the beam fueling significantly
Numerical Simulation of Tower Rotor Interaction for Downwind Wind Turbine
Directory of Open Access Journals (Sweden)
Isam Janajreh
2010-01-01
Full Text Available Downwind wind turbines have lower upwind rotor misalignment, and thus lower turning moment and self-steered advantage over the upwind configuration. In this paper, numerical simulation to the downwind turbine is conducted to investigate the interaction between the tower and the blade during the intrinsic passage of the rotor in the wake of the tower. The moving rotor has been accounted for via ALE formulation of the incompressible, unsteady, turbulent Navier-Stokes equations. The localized CP, CL, and CD are computed and compared to undisturbed flow evaluated by Panel method. The time history of the CP, aerodynamic forces (CL and CD, as well as moments were evaluated for three cross-sectional tower; asymmetrical airfoil (NACA0012 having four times the rotor's chord length, and two circular cross-sections having four and two chords lengths of the rotor's chord. 5%, 17%, and 57% reductions of the aerodynamic lift forces during the blade passage in the wake of the symmetrical airfoil tower, small circular cross-section tower and large circular cross-section tower were observed, respectively. The pronounced reduction, however, is confined to a short time/distance of three rotor chords. A net forward impulsive force is also observed on the tower due to the high speed rotor motion.
Numerical simulation of natural convection in annuli with internal fins
International Nuclear Information System (INIS)
Ha, Man Yeong; Kim, Joo Goo
2004-01-01
The solution for the natural convection in internally finned horizontal annuli is obtained by using a numerical simulation of time-dependent and two-dimensional governing equations. The fins existing in annuli influence the flow pattern, temperature distribution and heat transfer rate. The variations of the fin configuration suppress or accelerate the free convective effects compared to those of the smooth tubes. The effects of fin configuration, number of fins and ratio of annulus gap width to the inner cylinder radius on the fluid flow and heat transfer in annuli are demonstrated by the distribution of the velocity vector, isotherms and streamlines. The governing equations are solved efficiently by using a parallel implementation. The technique is adopted for reduction of the computation cost. The parallelization is performed with the domain decomposition technique and message passing between sub-domains on the basis of the MPI library. The results from parallel computation reveal in consistency with those of the sequential program. Moreover, the speed-up ratio shows linearity with the number of processor
Numerical simulation of pulverized coal combustion to reduce pollutants
International Nuclear Information System (INIS)
Mohammad Bagher Ayani; Behnam Rahmanian
2010-01-01
Full text: In this research, the numerical simulation of pollutant reduction and in a pulverized coal combustion at 2D combustion chamber have been studied. Finite volume method using structured grid arrangement was utilized for modeling the pulverized coal combustion. The pressure base algorithm and implicit solver has been employed to simulate non-premix combustion model. The air was diluted by some participative gaseous such as whose percentages varied from 0 % to 20 %. Participative gases and air were preheated by a high-temperature gas generator, and the preheated oxidizer temperature could achieve. The combustion simulation with the generalized finite rate chemistry model, referred to as the Magnussen model and the reacting flow with the mixture fraction PDF/ equilibrium chemistry model, referred to as the PDF model are studied. Quick scheme was adopted for the discretization of all convective terms of the advective transport equations. So, as a result of addition participative gases into oxidizer the rate of formation of pollutants as well as NO x suppressed. The addition only a few percent of halogen components can make some systems nonflammable. The effects of addition halogen components and non-reaction gaseous such as Helium and Argon are fuel dilution and its acts as catalysts in reducing the H atom concentration necessary for the chain branching reaction sequence. Moreover, they act like surface and they make the increment of surface ratio versus volume. Because of this, the number of radical conflicts and hence destruction them will be increase. Furthermore, the rate of formation of pollutants will be decreased if the halogen components and non-reaction gaseous injection will be increased. However, as a result of this research, in the case of injection in pulverized coal combustion the flame temperature is lower than Steam, Argon and Helium. So, the emission levels of carbon dioxide is significantly lower than other participative gases, but in this
Adaptive and dynamic meshing methods for numerical simulations
Acikgoz, Nazmiye
For the numerical simulation of many problems of engineering interest, it is desirable to have an automated mesh adaption tool capable of producing high quality meshes with an affordably low number of mesh points. This is important especially for problems, which are characterized by anisotropic features of the solution and require mesh clustering in the direction of high gradients. Another significant issue in meshing emerges in the area of unsteady simulations with moving boundaries or interfaces, where the motion of the boundary has to be accommodated by deforming the computational grid. Similarly, there exist problems where current mesh needs to be adapted to get more accurate solutions because either the high gradient regions are initially predicted inaccurately or they change location throughout the simulation. To solve these problems, we propose three novel procedures. For this purpose, in the first part of this work, we present an optimization procedure for three-dimensional anisotropic tetrahedral grids based on metric-driven h-adaptation. The desired anisotropy in the grid is dictated by a metric that defines the size, shape, and orientation of the grid elements throughout the computational domain. Through the use of topological and geometrical operators, the mesh is iteratively adapted until the final mesh minimizes a given objective function. In this work, the objective function measures the distance between the metric of each simplex and a target metric, which can be either user-defined (a-priori) or the result of a-posteriori error analysis. During the adaptation process, one tries to decrease the metric-based objective function until the final mesh is compliant with the target within a given tolerance. However, in regions such as corners and complex face intersections, the compliance condition was found to be very difficult or sometimes impossible to satisfy. In order to address this issue, we propose an optimization process based on an ad
Numerical simulation of binary black hole and neutron star mergers
Energy Technology Data Exchange (ETDEWEB)
Kastaun, W.; Rezzolla, L. [Albert Einstein Institut, Potsdam-Golm (Germany)
2016-11-01
One of the last predictions of general relativity that still awaits direct observational confirmation is the existence of gravitational waves. Those fluctuations of the geometry of space and time are expected to travel with the speed of light and are emitted by any accelerating mass. Only the most violent events in the universe, such as mergers of two black holes or neutron stars, produce gravitational waves strong enough to be measured. Even those waves are extremely weak when arriving at Earth, and their detection is a formidable technological challenge. In recent years sufficiently sensitive detectors became operational, such as GEO600, Virgo, and LIGO. They are expected to observe around 40 events per year. To interpret the observational data, theoretical modeling of the sources is a necessity, and requires numerical simulations of the equations of general relativity and relativistic hydrodynamics. Such computations can only be carried out on large scale supercomputers, given that many scenarios need to be simulated, each of which typically occupies hundreds of CPU cores for a week. Our main goal is to predict the gravitational wave signal from the merger of two compact objects. Comparison with future observations will provide important insights into the fundamental forces of nature in regimes that are impossible to recreate in laboratory experiments. The waveforms from binary black hole mergers would allow one to test the correctness of general relativity in previously inaccessible regimes. The signal from binary neutron star mergers will provide input for nuclear physics, because the signal depends strongly on the unknown properties of matter at the ultra high densities inside neutron stars, which cannot be observed in any other astrophysical scenario. Besides mergers, we also want to improve the theoretical models of close encounters between black holes. A gravitational wave detector with even higher sensitivity, the Einstein Telescope, is already in the
Multi-physics modeling and numerical simulation of weld pool in GTA welding
International Nuclear Information System (INIS)
Nguyen, Minh-Chien
2015-01-01
In this work, we develop a 3D physical and numerical model of the GTA (Gas Tungsten Arc) welding process in order to predict, for given welding parameters, useful quantities for the designer of welded assembly: weld bead shape, fluid flow in the weld pool as well as thermal distribution in the work piece. The model is developed in the Cast3M (http://www-cast3m.cea.fr/) finite element software and takes into account the main physical phenomena acting in the work piece and particularly in the weld pool, subject to source terms modeling the arc part of the welding process. A steady solution of this model is thought for and involves the coupling of the nonlinear thermohydraulics and electromagnetic equations together with the displacement of the deformable free surface of the weld pool. A first step in the development consisted in modeling the electromagnetic phenomena with two different numerical methods, in comparing the numerical results obtained with those of the literature and in quantifying the importance of the Lorentz force and the Joule effect compared to the other mechanical and thermal sources by computing power balances. Then, in order to assess the predictive capability of the model, simulations of various welding configurations are performed: variation in the chemical composition of the material, of the welding speed, of the prescribed arc pressure and of the welding positions, which is a focus of this work, are studied. A good agreement is obtained between the results of our model and other experimental and numerical results of the literature. Eventually, a model accounting for metal filling is proposed and its results are discussed. Thus, our complete model can be seen as a solid foundation towards future totally-coupled 3D welding models including the arc and it will be included in WPROCESS the in-house CEA software dedicated to the numerical simulation of welding. (author) [fr
Numerical simulation of collision-free plasma using Vlasov hybrid simulation
International Nuclear Information System (INIS)
Nunn, D.
1990-01-01
A novel scheme for the numerical simulation of wave particle interactions in space plasmas has been developed. The method, termed VHS or Vlasov Hybrid Simulation, is applicable to hot collision free plasmas in which the unperturbed distribution functions is smooth and free of delta function singularities. The particle population is described as a continuous Vlasov fluid in phase space-granularity and collisional effects being ignored. In traditional PIC/CIC codes the charge/current due to each simulation particle is assigned to a fixed spatial grid. In the VHS method the simulation particles sample the Vlasov fluid and provide information about the value of distribution function (F(r,v) at random points in phase space. Values of F are interpolated from the simulation particles onto a fixed grid in velocity/position or phase space. With distribution function defined on a phase space grid the plasma charge/current field is quickly calculated. The simulation particles serve only to provide information, and thus the particle population may be dynamic. Particles no longer resonant with the wavefield may be discarded from the simulation, and new particles may be inserted into the Vlasov fluid where required
Girolamo, Donato; Davila, Carlos G.; Leone, Frank A.; Lin, Shih-Yung
2015-01-01
The results of an experimental/numerical campaign aimed to develop progressive damage analysis (PDA) tools for predicting the strength of a composite bonded joint under tensile loads are presented. The PDA is based on continuum damage mechanics (CDM) to account for intralaminar damage, and cohesive laws to account for interlaminar and adhesive damage. The adhesive response is characterized using standard fracture specimens and digital image correlation (DIC). The displacement fields measured by DIC are used to calculate the J-integrals, from which the associated cohesive laws of the structural adhesive can be derived. A finite element model of a sandwich conventional splice joint (CSJ) under tensile loads was developed. The simulations, in agreement with experimental tests, indicate that the model is capable of predicting the interactions of damage modes that lead to the failure of the joint.
Lacoste, Eric; Arvieu, Corinne; Mantaux, Olivier
2018-04-01
One of the technologies used to produce metal matrix composites (MMCs) is liquid route processing. One solution is to inject a liquid metal under pressure or at constant rate through a fibrous preform. This foundry technique overcomes the problem of the wettability of ceramic fibers by liquid metal. The liquid route can also be used to produce semiproducts by coating a filament with a molten metal. These processes involve physical phenomena combined with mass and heat transfer and phase change. The phase change phenomena related to solidification and also to the melting of the metal during the process notably result in modifications to the permeability of porous media, in gaps in impregnation, in the appearance of defects (porosities), and in segregation in the final product. In this article, we provide a state-of-the-art review of numerical models and simulation developed to study these physical phenomena involved in MMC processing by the liquid route.
A Numerical Approach for Hybrid Simulation of Power System Dynamics Considering Extreme Icing Events
DEFF Research Database (Denmark)
Chen, Lizheng; Zhang, Hengxu; Wu, Qiuwei
2017-01-01
numerical simulation scheme integrating icing weather events with power system dynamics is proposed to extend power system numerical simulation. A technique is developed to efficiently simulate the interaction of slow dynamics of weather events and fast dynamics of power systems. An extended package for PSS...
International Nuclear Information System (INIS)
Kazuyuki, Takase; Hiroyuki, Yoshida; Hidesada, Tamai; Hajime, Akimoto; Yasuo, Ose
2003-01-01
Fluid flow characteristics in a fuel bundle of a reduced-moderation light water reactor (RMWR) with a tight-lattice core were analyzed numerically using a newly developed two-phase flow analysis code under the full bundle size condition. Conventional analysis methods such as sub-channel codes need composition equations based on the experimental data. In case that there are no experimental data regarding to the thermal-hydraulics in the tight-lattice core, therefore, it is difficult to obtain high prediction accuracy on the thermal design of the RMWR. Then the direct numerical simulations with the earth simulator were chosen. The axial velocity distribution in a fuel bundle changed sharply around a grid spacer and its quantitative evaluation was obtained from the present preliminary numerical study. The high prospect was acquired on the possibility of establishment of the thermal design procedure of the RMWR by large-scale direct simulations. (authors)
Numerical Simulation of Recycled Concrete Using Convex Aggregate Model and Base Force Element Method
Directory of Open Access Journals (Sweden)
Yijiang Peng
2016-01-01
Full Text Available By using the Base Force Element Method (BFEM on potential energy principle, a new numerical concrete model, random convex aggregate model, is presented in this paper to simulate the experiment under uniaxial compression for recycled aggregate concrete (RAC which can also be referred to as recycled concrete. This model is considered as a heterogeneous composite which is composed of five mediums, including natural coarse aggregate, old mortar, new mortar, new interfacial transition zone (ITZ, and old ITZ. In order to simulate the damage processes of RAC, a curve damage model was adopted as the damage constitutive model and the strength theory of maximum tensile strain was used as the failure criterion in the BFEM on mesomechanics. The numerical results obtained in this paper which contained the uniaxial compressive strengths, size effects on strength, and damage processes of RAC are in agreement with experimental observations. The research works show that the random convex aggregate model and the BFEM with the curve damage model can be used for simulating the relationship between microstructure and mechanical properties of RAC.
Direct numerical simulation of turbulent mixing in grid-generated turbulence
International Nuclear Information System (INIS)
Nagata, Kouji; Suzuki, Hiroki; Sakai, Yasuhiko; Kubo, Takashi; Hayase, Toshiyuki
2008-01-01
Turbulent mixing of passive scalar (heat) in grid-generated turbulence (GGT) is simulated by means of direct numerical simulation (DNS). A turbulence-generating grid, on which the velocity components are set to zero, is located downstream of the channel entrance, and it is numerically constructed on the staggered mesh arrangement using the immersed boundary method. The grid types constructed are: (a) square-mesh biplane grid, (b) square-mesh single-plane grid, (c) composite grid consisting of parallel square-bars and (d) fractal grid. Two fluids with different temperatures are provided separately in the upper and lower streams upstream of the turbulence-generating grids, generating the thermal mixing layer behind the grids. For the grid (a), simulations for two different Prandtl numbers of 0.71 and 7.1, corresponding to air and water flows, are conducted to investigate the effect of the Prandtl number. The results show that the typical grid turbulence and shearless mixing layer are generated downstream of the grids. The results of the scalar field show that a typical thermal mixing layer is generated as well, and the effects of the Prandtl numbers on turbulent heat transfer are observed.
Direct numerical simulation of turbulent mixing in grid-generated turbulence
Energy Technology Data Exchange (ETDEWEB)
Nagata, Kouji; Suzuki, Hiroki; Sakai, Yasuhiko; Kubo, Takashi [Department of Mechanical Science and Engineering, Nagoya University, Nagoya 464-8603 (Japan); Hayase, Toshiyuki [Institute of Fluid Science, Tohoku University, Sendai 980-8577 (Japan)], E-mail: nagata@nagoya-u.jp, E-mail: hsuzuki@nagoya-u.jp, E-mail: ysakai@mech.nagoya-u.ac.jp, E-mail: t-kubo@nagoya-u.jp, E-mail: hayase@ifs.tohoku.ac.jp
2008-12-15
Turbulent mixing of passive scalar (heat) in grid-generated turbulence (GGT) is simulated by means of direct numerical simulation (DNS). A turbulence-generating grid, on which the velocity components are set to zero, is located downstream of the channel entrance, and it is numerically constructed on the staggered mesh arrangement using the immersed boundary method. The grid types constructed are: (a) square-mesh biplane grid, (b) square-mesh single-plane grid, (c) composite grid consisting of parallel square-bars and (d) fractal grid. Two fluids with different temperatures are provided separately in the upper and lower streams upstream of the turbulence-generating grids, generating the thermal mixing layer behind the grids. For the grid (a), simulations for two different Prandtl numbers of 0.71 and 7.1, corresponding to air and water flows, are conducted to investigate the effect of the Prandtl number. The results show that the typical grid turbulence and shearless mixing layer are generated downstream of the grids. The results of the scalar field show that a typical thermal mixing layer is generated as well, and the effects of the Prandtl numbers on turbulent heat transfer are observed.
Numerical simulation of in-situ DNAPL remediation by alcohol flooding
Energy Technology Data Exchange (ETDEWEB)
Falta, R.W.; Brame, S.E. [Earth Science Department, Clemson, SC (United States)
1995-03-01
The removal of residual saturations of dense non-aqueous phase liquids (DNAPLs) from below the water table using alcohol solutions is under investigation as a potential remediation tool. Alcohol flooding reduces the interfacial tension (IFT) an density difference between the aqueous and DNAPL phases, and increases the chemical solubility in the aqueous phase. Depending on the partitioning behavior of the alcohol/chemical system, DNAPL can be removed by either mobilization as a separate phase or through enhanced dissolution. A new three dimensional multiphase numerical simulator has been developed for modeling this process. The code is based on the general TOUGH2 Integral Finite Difference formulation for multiphase transport with modifications to account for the complex behavior of an alcohol/water/DNAPL system. The alcohol flood code uses a special equation of state module for computing phase compositions, IFT, saturations, densities, viscosities, relative permeabilities, and capillary pressures during each time step. This equation of state is based on a numerical interpolation of experimentally determined ternary phase data. The code was designed so that it can readily be applied to other three-component, two-phase problems such as surfactant and solvent floods given appropriate ternary data. Comparisons of simulation results with column experiments performed at Clemson University were used to validate the simulator.
Local mechanical properties of LFT injection molded parts: Numerical simulations versus experiments
Desplentere, F.; Soete, K.; Bonte, H.; Debrabandere, E.
2014-05-01
In predictive engineering for polymer processes, the proper prediction of material microstructure from known processing conditions and constituent material properties is a critical step forward properly predicting bulk properties in the finished composite. Operating within the context of long-fiber thermoplastics (LFT, length Autodesk Simulation Moldflow Insight 2014 software has been used. In this software, a fiber breakage algorithm for the polymer flow inside the mold is available. Using well known micro mechanic formulas allow to combine the local fiber length with the local orientation into local mechanical properties. Different experiments were performed using a commercially available glass fiber filled compound to compare the measured data with the numerical simulation results. In this investigation, tensile tests and 3 point bending tests are considered. To characterize the fiber length distribution of the polymer melt entering the mold (necessary for the numerical simulations), air shots were performed. For those air shots, similar homogenization conditions were used as during the injection molding tests. The fiber length distribution is characterized using automated optical method on samples for which the matrix material is burned away. Using the appropriate settings for the different experiments, good predictions of the local mechanical properties are obtained.