Numerical simulation of the fast dense gas Ludwieg tube experiment
Zamfirescu, C.; Guerdone, A.; Collona, P.
2006-01-01
The preliminary design of a Ludwieg tube experiment for the verification of the existence of nonclassical rarefaction shock waves in dense vapors is here critically analyzed by means of real gas numerical simulations of the experimental setup. The Flexible Asymmetric Shock Tube (FAST) setup is a
Agglomeration processes in carbonaceous dusty plasmas, experiments and numerical simulations
Energy Technology Data Exchange (ETDEWEB)
Dap, S; Hugon, R; De Poucques, L; Bougdira, J [Nancy Universite-Institut Jean Lamour, Dpt CP2S UMR 7198 CNRS, Faculte des Sciences et Technologies, BP 70239, 54506 Vandoeuvre-les-Nancy cedex (France); Lacroix, D [Nancy Universite-LEMTA, UMR 7563 CNRS, Faculte des Sciences et Technologies, BP 70239, 54506 Vandoeuvre-les-Nancy cedex (France); Patisson, F, E-mail: david.lacroix@lemta.uhp-nancy.f [Nancy Universite-Institut Jean Lamour, Dpt SI2M UMR 7198 CNRS, Ecole des Mines de Nancy, Parc de Saurupt-CS 14234, 54042 Nancy cedex (France)
2010-09-15
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.
Framatome-ANP experience in numerical simulation of welding
Energy Technology Data Exchange (ETDEWEB)
Gilles, P. [FRAMATOME ANP SAS, NFPM, 92 - Paris-La-Defence (France); Pont, D. [FRAMATOME ANP SAS, NFVED, 69 - Lyon (France); Keim, E. [Framatome ANP GmbH -NGTM, Erlangen (Germany); Devaux, J. [ESI France, 69 - Lyon (France)
2004-07-01
For nuclear reactor manufacturers, ensuring a high quality of welded joints is one of the basic design rules. Qualification of welders, specific procedures, stress relief heat treatments serve efficiently this goal. Numerical simulation of welding adds the capability of assessing residual stresses, distortions, and in a near future quality of welds. Since almost 25 years, Framatome-ANP has been working on numerical simulation of welding to improve predictions and efficiency of computational tools, namely using the worldwide known SYSWELD. The largest part of Framatome-ANP experience in this field relies in the numerous studies performed by German and French teams on industrial components. This paper tries to account for all these efforts, following a presentation oriented on types of problem. (authors)
Vortex phenomena in sidewall aneurysm hemodynamics: experiment and numerical simulation.
Le, Trung B; Troolin, Daniel R; Amatya, Devesh; Longmire, Ellen K; Sotiropoulos, Fotis
2013-10-01
We carry out high-resolution laboratory experiments and numerical simulations to investigate the dynamics of unsteady vortex formation across the neck of an anatomic in vitro model of an intracranial aneurysm. A transparent acrylic replica of the aneurysm is manufactured and attached to a pulse duplicator system in the laboratory. Time-resolved three-dimensional three-component velocity measurements are obtained inside the aneurysm sac under physiologic pulsatile conditions. High-resolution numerical simulations are also carried out under conditions replicating as closely as possible those of the laboratory experiment. Comparison of the measured and computed flow fields shows very good agreement in terms of instantaneous velocity fields and three-dimensional coherent structures. Both experiments and numerical simulations show that a well-defined vortical structure is formed near the proximal neck at early systole. This vortical structure is advected by the flow across the aneurysm neck and impinges on the distal wall. The results underscore the complexity of aneurysm hemodynamics and point to the need for integrating high-resolution, time-resolved three-dimensional experimental and computational techniques. The current work emphasizes the importance of vortex formation phenomena at aneurysmal necks and reinforces the findings of previous computational work and recent clinical studies pointing to links between flow pulsatility and aneurysm growth and rupture.
Tritium release experiments with CATS and numerical simulation
Energy Technology Data Exchange (ETDEWEB)
Munakata, Kenzo, E-mail: kenzo@gipc.akita-u.ac.jp [Faculty of Engineering and Resource Sciences, Akita University, Tegata-gakuen-cho 1-1, Akita 010-8502 (Japan); Wajima, Takaaki; Hara, Keisuke; Wada, Kohei [Faculty of Engineering and Resource Sciences, Akita University, Tegata-gakuen-cho 1-1, Akita 010-8502 (Japan); Takeishi, Toshiharu; Shinozaki, Yohei; Mochizuki, Kazuhiro; Katekari, Kenichi [Interdisciplinary Graduate School of Engineering Science, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581 (Japan); Kobayashi, Kazuhiro; Iwai, Yasunori; Hayashi, Takumi; Yamanishi, Toshihiko [Tritium Technology Group, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)
2010-12-15
In D-T fusion power plants, large amounts of tritium would be handled. Tritium is the radioisotope of protium, and is easily taken into the human body, and thus the behavior of tritium accidentally released in fusion power plants should be studied for the safety design and radioprotection of workers. Therefore, it is necessary to investigate the behavior of tritium released into large rooms with objectives, since complex flow fields should exist in such rooms and they could influence the ventilation of the air containing released tritium. Thus, tritium release experiments were conducted using Caisson Assembly for Tritium Safety Study (CATS) in TPL/JAEA. Some data were taken for tritium behavior in the ventilated area and response of tritium monitors. In the experiments, approximately 17 GBq of tritium was released into Caisson with the total volume of 12 m{sup 3}, and the room was ventilated at the rate of 12 m{sup 3}/h after release of tritium. It was found that placement of an objective in the vessel substantially affects decontamination efficiency. With regard to an experimental result, numerical calculation was performed and the experimental result and the result of numerical calculation were compared, which indicates that experimental results are qualitatively reproduced by numerical calculation. However, further R and D needs to be carried out for quantitative reproduction of the experimental results.
Nucleation and solidification of thin walled ductile iron - Experiments and numerical simulation
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels Skat
2005-01-01
Investigation of solidification of thin walled ductile cast iron has been performed based on experiments and numerical simulation. The experiments were based on temperature and microstructure examination. Results of the experiments have been compared with a 1-D numerical solidification model...
Experiments and Numerical Simulation of Mixing under Supercritical Conditions (PREPRINT)
2011-02-08
equation of state. Ind. Eng. Chem. Fundam., 15:59–64, 1976. [46] T. Poinsot and S. Lele . Boundary conditions for direct simulations of compressible...and liquids. McGraw-Hill, fifth edition, 2001. [48] L. Pons , N. Darabiha, S. Candel, T. Schmitt, and B. Cuenot. The structure of multidimensional
Laboratory experiments and numerical simulations on magnetic instabilities
Stefani, F; Kasprzyk, Ch; Paredes, A; Ruediger, G; Seilmayer, M
2016-01-01
Magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both hydromagnetic dynamo action as well as magnetically triggered flow instabilities had been the subject of purely theoretical research. Meanwhile, however, the dynamo effect has been observed in large-scale liquid sodium experiments in Riga, Karlsruhe and Cadarache. In this paper, we summarize the results of some smaller liquid metal experiments devoted to various magnetic instabilities such as the helical and the azimuthal magnetorotational instability, the Tayler instability, and the different instabilities that appear in a magnetized spherical Couette flow. We conclude with an outlook on a large scale Tayler-Couette experiment using liquid sodium, and on the prospects to observe magnetically triggered ...
Numerical simulation and experiment on multilayer stagger-split die.
Liu, Zhiwei; Li, Mingzhe; Han, Qigang; Yang, Yunfei; Wang, Bolong; Sui, Zhou
2013-05-01
A novel ultra-high pressure device, multilayer stagger-split die, has been constructed based on the principle of "dividing dies before cracking." Multilayer stagger-split die includes an encircling ring and multilayer assemblages, and the mating surfaces of the multilayer assemblages are mutually staggered between adjacent layers. In this paper, we investigated the stressing features of this structure through finite element techniques, and the results were compared with those of the belt type die and single split die. The contrast experiments were also carried out to test the bearing pressure performance of multilayer stagger-split die. It is concluded that the stress distributions are reasonable and the materials are utilized effectively for multilayer stagger-split die. And experiments indicate that the multilayer stagger-split die can bear the greatest pressure.
Numerical Simulation and Experiment for Underwater Shock Wave in Newly Designed Pressure Vessel
Directory of Open Access Journals (Sweden)
M Shibuta
2016-09-01
Full Text Available Modern eating habits depend in large part on the development of food processing technology. Thermal treatments are often performed in the conventional food processing, but it can cause discoloration and loss of nutrients of the food by thermal processing or treatment. On the other hand, food processing using an underwater shock wave has little influence of heat and its processing time is very short, preventing the loss of nutrients. In this research optical observation experiment and the numerical simulation were performed, in order to understand and control the behavior of the underwater shock wave in the development of the processing container using an underwater shock wave for the factory and home. In this experiment a rectangular container was used to observe the behavior of the underwater shock wave. In the experiment, the shock wave was generated by using explosive on the shock wave generation side. The shock wave, which passed through the phosphor bronze and propagated from the aluminum sidewall, was observed on the processing container side. Numerical simulation of an analogous experimental model was investigated, where LS-DYNA software was used for the numerical simulation. The comparative study of the experiment and the numerical simulation was investigated. The behavior of a precursor shock wave from the device wall was able to be clarified. This result is used for development of the device in numerical simulation.
Energy Technology Data Exchange (ETDEWEB)
Rider, William; Kamm, J. R. (James R.); Zoldi, C. A. (Cindy A.); Tomkins, C. D. (Chris D.)
2002-01-01
We present detailed spatial analysis comparing experimental data and numerical simulation results for Richtmyer-Meshkov instability experiments of Prestridge et al. and Tomkins et al. These experiments consist, respectively, of one and two diffuse cylinders of sulphur hexafluoride (SF{sub 6}) impulsively accelerated by a Mach 1.2 shockwave in air. The subsequent fluid evolution and mixing is driven by the deposition of baroclinic vorticity at the interface between the two fluids. Numerical simulations of these experiments are performed with three different versions of high resolution finite volume Godunov methods, including a new weighted adaptive Runge-Kutta (WARK) scheme. We quantify the nature of the mixing using using integral measures as well as fractal analysis and continuous wavelet transforms. Our investigation of the gas cylinder configurations follows the path of our earlier studies of the geometrically and dynamically more complex gas 'curtain' experiment. In those studies, we found significant discrepancies in the details of the experimentally measured mixing and the details of the numerical simulations. Here we evaluate the effects of these hydrodynamic integration techniques on the diffuse gas cylinder simulations, which we quantitatively compare with experimental data.
Comparison of flow and transport experiments on 3D printed 'rocks' with direct numerical simulations
Watson, F. E.; Geiger, S.; Mackay, E.; Singleton, M.; McGravie, T.; Anouilh, T.; Jobe, D.; Zhang, S.; Agar, S. M.; Ishutov, S.; Hasiuk, F.; Chalaturnyk, R. J.
2016-12-01
3D printing technology has the potential to revolutionise modelling of fluid flow and mass transport in porous media. Using 3D printing to replicate pore geometries from real rocks quickly and cheaply, and being able to assign specific properties to the samples, would enable us to repeat experiments where things such as permeability, porosity, reactivity, or wettability are known a priori. Destructive tests, such as reactive transport experiments, could then be performed using the same, realistic, initial geometry, in a repeatable fashion; in addition, specific properties of the porous media (e.g. the reactivity of individual grains) could be altered in a controlled way. Similarly, two-phase flow experiments could be carried out where relevant properties (e.g. individual grain wettability) are modified between experiments. Results from such experiments would shed new light on key physio-chemical processes occurring at the pore-scale during multi-phase reactive flow and would allow us to validate the suite of emerging direct numerical simulation techniques (e.g. Lattice Boltzman, Volume of Fluid) currently used to model pore-scale flow and transport. We have developed a novel experimental setup to investigate single-phase flow and transport through translucent 3D printed and Perspex samples and to visualise the experiments for comparison with numerical simulations. Dyed fluid is injected at one end of the sample and the behaviour of the system is recorded using a digital camera situated directly above it. Image processing techniques are employed to quantify dye concentration and location through time. We use the finite volume method to simulate the flow experiments in OpenFOAM, using the same input geometry that was used to print the sample. Comparison of experimental results with simulations enables us to identify similarities and differences between flow and transport observed in the 3D printed samples and behaviour expected from the numerical simulations.
Experiments and numerical simulation of stress-state-dependent damage in sheet metal forming
Brünig, M.; Gerke, S.; Schmidt, M.
2017-09-01
Experiments and corresponding numerical simulations with new biaxially loaded specimens taken from thin metal sheets are discussed. Inelastic deformations as well as damage and fracture behavior of the specimens are investigated under different biaxial loading conditions covering a wide range of stress states to analyze the stress-state-dependent damage and failure mechanisms in ductile metals. During the experiments strain fields in critical regions of the specimens are analyzed by digital image correlation. Corresponding numerical simulations deliver information on stress states in tested specimens. The results are used to propose stress-state-dependent damage and failure criteria corresponding to various damage mechanisms depending on stress triaxiality and the Lode parameter. They are validated by series of biaxial experiments with newly developed specimens and corresponding numerical simulations. This demonstrates the efficiency of the new specimens’ geometries covering a wide range of stress states in the shear-tension and shear-compression regime allowing validation of stress-state-dependent functions for the damage criteria and damage evolution laws.
New method of processing heat treatment experiments with numerical simulation support
Kik, T.; Moravec, J.; Novakova, I.
2017-08-01
In this work, benefits of combining modern software for numerical simulations of welding processes with laboratory research was described. Proposed new method of processing heat treatment experiments leading to obtaining relevant input data for numerical simulations of heat treatment of large parts was presented. It is now possible, by using experiments on small tested samples, to simulate cooling conditions comparable with cooling of bigger parts. Results from this method of testing makes current boundary conditions during real cooling process more accurate, but also can be used for improvement of software databases and optimization of a computational models. The point is to precise the computation of temperature fields for large scale hardening parts based on new method of temperature dependence determination of the heat transfer coefficient into hardening media for the particular material, defined maximal thickness of processed part and cooling conditions. In the paper we will also present an example of the comparison standard and modified (according to newly suggested methodology) heat transfer coefficient data’s and theirs influence on the simulation results. It shows how even the small changes influence mainly on distribution of temperature, metallurgical phases, hardness and stresses distribution. By this experiment it is also possible to obtain not only input data and data enabling optimization of computational model but at the same time also verification data. The greatest advantage of described method is independence of used cooling media type.
Energy Technology Data Exchange (ETDEWEB)
Pruess, K.
1996-05-01
Water seepage has been numerically simulated in heterogeneous fractures, which were conceptualized as two-dimensional heterogeneous porous media. Flow was found to proceed in dendritic patterns along preferential paths, giving rise to such features as localized ponding and bypassing. Limited parameter variation studies have shown strong dependence of seepage patterns on fracture permeability and applied flow rate. The temporal evolution of seeps proceeds on a vast range of time scales. This casts doubt on the applicability of steady-state concepts for water migration in thick unsaturated zones of fractured rock where infiltration is episodic. An approximate invariance of seepage behavior was derived for simultaneous space-and-time scaling. Numerical simulation experiments have confirmed this invariance, as well as its limits of applicability.
A study on experiment and numerical simulation of heat exchanger in heating furnace
Directory of Open Access Journals (Sweden)
Z. C. Lv
2018-01-01
Full Text Available In this paper, air preheater is used the research object and its heat transfer law is studied by experiment and numerical simulation. The experimental data showed that with the increases of inlet air velocity, the comprehensive heat transfer coefficient and heat transfer efficiency increase, but the temperature efficiency decreases and the resistance loss on the air side increases. The numerical simulation results showed that the larger the diameter of the tube, the better the heat transfer effect. When horizontal spacing in the range of 290 - 305 mm and longitudinal spacing is 70 - 90 mm, the heat transfer effect is best. The optimized heat exchanger structure is that diameter is 60 mm, horizontal spacing is 300 mm, longitudinal spacing is 90 mm. As the inlet air flow rate increases, the heat transfer efficiency increases, but the temperature efficiency decreases and the resistance loss on the air side increases.
Directory of Open Access Journals (Sweden)
Rubaiyet Iftekharul Haque
2015-04-01
Full Text Available Optimization of the acoustic resonant sensor requires a clear understanding of how the output responses of the sensor are affected by the variation of different factors. During this work, output responses of a capacitive acoustic transducer, such as membrane displacement, quality factor, and capacitance variation, are considered to evaluate the sensor design. The six device parameters taken into consideration are membrane radius, backplate radius, cavity height, air gap, membrane tension, and membrane thickness. The effects of factors on the output responses of the transducer are investigated using an integrated methodology that combines numerical simulation and design of experiments (DOE. A series of numerical experiments are conducted to obtain output responses for different combinations of device parameters using finite element methods (FEM. Response surface method is used to identify the significant factors and to develop the empirical models for the output responses. Finally, these results are utilized to calculate the optimum device parameters using multi-criteria optimization with desirability function. Thereafter, the validating experiments are designed and deployed using the numerical simulation to crosscheck the responses.
Directory of Open Access Journals (Sweden)
Vlček V.
2013-04-01
Full Text Available The work is devoted to comparing measured data with the results of numerical simulations. As mathematical model was used mathematical model whitout turbulence for incompressible flow In the experiment was observed the behavior of designed NACA0015 airfoil in airflow. For the numerical solution was used OpenFOAM computational package, this is open-source software based on finite volume method. In the numerical solution is prescribed displacement of the airfoil, which corresponds to the experiment. The velocity at a point close to the airfoil surface is compared with the experimental data obtained from interferographic measurements of the velocity field. Numerical solution is computed on a 3D mesh composed of about 1 million ortogonal hexahedron elements. The time step is limited by the Courant number. Parallel computations are run on supercomputers of the CIV at Technical University in Prague (HAL and FOX and on a computer cluster of the Faculty of Mechatronics of Liberec (HYDRA. Run time is fixed at five periods, the results from the fifth periods and average value for all periods are then be compared with experiment.
Energy Technology Data Exchange (ETDEWEB)
Figueroa, Aldo [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209 (Mexico); Meunier, Patrice; Villermaux, Emmanuel [Aix-Marseille Univ., CNRS, Centrale Marseille, IRPHE, Marseille F-13384 (France); Cuevas, Sergio; Ramos, Eduardo [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, A.P. 34, Temixco, Morelos 62580 (Mexico)
2014-01-15
We present a combination of experiment, theory, and modelling on laminar mixing at large Péclet number. The flow is produced by oscillating electromagnetic forces in a thin electrolytic fluid layer, leading to oscillating dipoles, quadrupoles, octopoles, and disordered flows. The numerical simulations are based on the Diffusive Strip Method (DSM) which was recently introduced (P. Meunier and E. Villermaux, “The diffusive strip method for scalar mixing in two-dimensions,” J. Fluid Mech. 662, 134–172 (2010)) to solve the advection-diffusion problem by combining Lagrangian techniques and theoretical modelling of the diffusion. Numerical simulations obtained with the DSM are in reasonable agreement with quantitative dye visualization experiments of the scalar fields. A theoretical model based on log-normal Probability Density Functions (PDFs) of stretching factors, characteristic of homogeneous turbulence in the Batchelor regime, allows to predict the PDFs of scalar in agreement with numerical and experimental results. This model also indicates that the PDFs of scalar are asymptotically close to log-normal at late stages, except for the large concentration levels which correspond to low stretching factors.
Field experiment and numerical simulation of point source irrigation with multiple tracers.
Selim, Tarek; Bouksila, Fethi; Hamed, Yasser; Berndtsson, Ronny; Bahri, Akissa; Persson, Magnus
2018-01-01
Dyes like Brilliant Blue have similar adsorptive behaviour as some organic contaminants, e.g., pesticides. Bromide ions, on the other hand, move much like NO3-N (fertilizer) in soil. Consequently, by using these two tracers, it is possible to in a general way mimic how organic contaminants and fertilizers may move through soils. Three plots with sandy soil in semiarid Tunisia were irrigated during three successive hours using a single irrigation dripper and high-saline solution (10.50 dS m-1) containing dye and bromide. Fifteen hours after cease of infiltration, horizontal 5 cm trenches were dug in the soil and dye pattern, bromide concentration, and soil water content were recorded. Preferential flow occurred to some degree, however, it did not dominate the solute transport process. Therefore, drip irrigation can be recommended to improve plant culture for a better water and soil nutrient adsorption. Numerical simulation using HYDRUS-2D/3D was performed to replicate the field experiments. Observed soil water contents before and after infiltration were used to run an inverse parameter estimation procedure to identify soil hydraulic parameters. It was found that for both field experiments and numerical simulations the mobility of bromide is different from the mobility of dye. The dye was retarded approximately twice by volume as compared to bromide. The simulation results support the use of HYDRUS-2D/3D as a rapid and labor saving tool for investigating tracers' mobility in sandy soil under point source irrigation.
Comparison of numerical simulations to experiments for atomization in a jet nebulizer.
Lelong, Nicolas; Vecellio, Laurent; Sommer de Gélicourt, Yann; Tanguy, Christian; Diot, Patrice; Junqua-Moullet, Alexandra
2013-01-01
The development of jet nebulizers for medical purposes is an important challenge of aerosol therapy. The performance of a nebulizer is characterized by its output rate of droplets with a diameter under 5 µm. However the optimization of this parameter through experiments has reached a plateau. The purpose of this study is to design a numerical model simulating the nebulization process and to compare it with experimental data. Such a model could provide a better understanding of the atomization process and the parameters influencing the nebulizer output. A model based on the Updraft nebulizer (Hudson) was designed with ANSYS Workbench. Boundary conditions were set with experimental data then transient 3D calculations were run on a 4 µm mesh with ANSYS Fluent. Two air flow rate (2 L/min and 8 L/min, limits of the operating range) were considered to account for different turbulence regimes. Numerical and experimental results were compared according to phenomenology and droplet size. The behavior of the liquid was compared to images acquired through shadowgraphy with a CCD Camera. Three experimental methods, laser diffractometry, phase Doppler anemometry (PDA) and shadowgraphy were used to characterize the droplet size distributions. Camera images showed similar patterns as numerical results. Droplet sizes obtained numerically are overestimated in relation to PDA and diffractometry, which only consider spherical droplets. However, at both flow rates, size distributions extracted from numerical image processing were similar to distributions obtained from shadowgraphy image processing. The simulation then provides a good understanding and prediction of the phenomena involved in the fragmentation of droplets over 10 µm. The laws of dynamics apply to droplets down to 1 µm, so we can assume the continuity of the distribution and extrapolate the results for droplets between 1 and 10 µm. So, this model could help predicting nebulizer output with defined geometrical and
Comparison of numerical simulations to experiments for atomization in a jet nebulizer.
Directory of Open Access Journals (Sweden)
Nicolas Lelong
Full Text Available The development of jet nebulizers for medical purposes is an important challenge of aerosol therapy. The performance of a nebulizer is characterized by its output rate of droplets with a diameter under 5 µm. However the optimization of this parameter through experiments has reached a plateau. The purpose of this study is to design a numerical model simulating the nebulization process and to compare it with experimental data. Such a model could provide a better understanding of the atomization process and the parameters influencing the nebulizer output. A model based on the Updraft nebulizer (Hudson was designed with ANSYS Workbench. Boundary conditions were set with experimental data then transient 3D calculations were run on a 4 µm mesh with ANSYS Fluent. Two air flow rate (2 L/min and 8 L/min, limits of the operating range were considered to account for different turbulence regimes. Numerical and experimental results were compared according to phenomenology and droplet size. The behavior of the liquid was compared to images acquired through shadowgraphy with a CCD Camera. Three experimental methods, laser diffractometry, phase Doppler anemometry (PDA and shadowgraphy were used to characterize the droplet size distributions. Camera images showed similar patterns as numerical results. Droplet sizes obtained numerically are overestimated in relation to PDA and diffractometry, which only consider spherical droplets. However, at both flow rates, size distributions extracted from numerical image processing were similar to distributions obtained from shadowgraphy image processing. The simulation then provides a good understanding and prediction of the phenomena involved in the fragmentation of droplets over 10 µm. The laws of dynamics apply to droplets down to 1 µm, so we can assume the continuity of the distribution and extrapolate the results for droplets between 1 and 10 µm. So, this model could help predicting nebulizer output with defined
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 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.
Numerical simulation of the operation of the GPR experiment on NETLANDER
Ciarletti, V.; Martinat, B.; Reineix, A.; Berthelier, J. J.; Ney, R.
2003-02-01
The first objective of the Ground-Penetrating Radar (GPR) experiment on NETLANDER is to investigate the geological structures of the Martian subsurface. The aim of this paper is to present initial results obtained in the first phase of a long-term effort to build a numerical model of the GPR operation on Mars and test dedicated signal-processing algorithms on the simulated data. The simulation is based on the use of a Finite Difference Time Domain method, and we have pointed out some of its advantages that allow us to take into account complex features of the underground. This model has given reliable estimates of the power budget of the radar for a simple but still representative model of the Martian subsurface. In addition, several detailed features such as gradients and roughness at the interfaces were introduced to appraise their possible influence on the GPR performances. In the frame of a simplified geometry of both the GPR antennas and the various underground interfaces, a simple and first-order method was developed and tested on simulated data to show the ability of the GPR to retrieve a three-dimensional distribution of the underground reflectors. Based on this model, and even with some rather crude hypothesis on the subsurface electromagnetic characteristics, information on the direction and distances of the reflectors has been retrieved with a satisfactory approximation.
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.
Numerical models and experiment of air flow in a simulation box for optical wireless communications
Directory of Open Access Journals (Sweden)
Latal Jan
2016-01-01
Full Text Available In this article, the authors focused on real measurements of mechanical turbulence generated by ventilators in the simulation box for Optical Wireless Communications. The mechanical turbulences disturb the optical beam that propagates along the central axis of the simulation box. The aim of authors is to show the effect of mechanical turbulence on optical beams at different heights in the simulation box. In the Ansys Fluent, we created numerical models which were then compared with real measurements. Authors compared the real and numerical models according to statistical methods.
Elkhoury, J. E.; Detwiler, R. L.; Serajian, V.; Bruno, M. S.
2012-12-01
Geothermal energy resources are more widespread than previously thought and have the potential for providing a significant amount of sustainable clean energy worldwide. In particular, hot permeable sedimentary formations provide many advantages over traditional geothermal recovery and enhanced geothermal systems in low permeability crystalline formations. These include: (1) eliminating the need for hydraulic fracturing, (2) significant reduction in risk for induced seismicity, (3) reducing the need for surface wastewater disposal, (4) contributing to decreases in greenhouse gases, and (5) potential use for CO2 sequestration. Advances in horizontal drilling, completion, and production technology from the oil and gas industry can now be applied to unlock these geothermal resources. Here, we present experimental results from a laboratory scale circulation system and numerical simulations aimed at quantifying the heat transfer capacity of sedimentary rocks. Our experiments consist of fluid flow through a saturated and pressurized sedimentary disc of 23-cm diameter and 3.8-cm thickness heated along its circumference at a constant temperature. Injection and production ports are 7.6-cm apart in the center of the disc. We used DI de-aired water and mineral oil as working fluids and explored temperatures from 20 to 150 oC and flow rates from 2 to 30 ml/min. We performed experiments on sandstone samples (Castlegate and Kirby) with different porosity, permeability and thermal conductivity to evaluate the effect of hydraulic and thermal properties on the heat transfer capacity of sediments. The producing fluid temperature followed an exponential form with time scale transients between 15 and 45 min. Steady state outflow temperatures varied between 60% and 95% of the set boundary temperature, higher percentages were observed for lower temperatures and flow rates. We used the flow and heat transport simulator TOUGH2 to develop a numerical model of our laboratory setting. Given
DEFF Research Database (Denmark)
de Souza Reboucas, Geraldo Francisco; Santos, Ilmar; Thomsen, Jon Juel
2017-01-01
The frequency response of a single degree of freedom vibro-impact oscillator is analyzed using Harmonic Linearization, Averaging and Numeric Simulation, considering three different impact force models: one given by a piecewise-linear function (Kelvin-Voigt model), another by a high-order power fu...
Comparison of results between numerical simulation and experiment for radiative ablation of CH foil
Sheng Jia Tian; Feng Ting Gui; Zhang Li; Li Meng; Yang Jia Min; Ding Yao Nan; Jiang Shao En
2002-01-01
The radiation ablation experiments of CH foils are simulated using the experiment radiation flow in the hohlraum by 1-D radiation transfer code RDMG. The results of simulation show that influence of Non-LTE radiation source on the ablation of CH foil is very obvious. The results of simulation and experiment including radiation flow total intensity and the variation of radiation temperature with time at the rear of CH foil, as well as the time delay of 400 eV photon arriving at the rear of CH foil are consistent basically
2016-02-26
numerical simulations,molecular simulations and experiments Diego Donzis TEXAS ENGINEERING EXPERIMENT STATION COLLEGE STATION Final Report 02/26/2016...PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) TEXAS ENGINEERING EXPERIMENT STATION COLLEGE STATION 1470 WILLIAM D FITCH PKY COLLEGE STATION, TX...TERMS Aerothermodynamics and Nonequillibrium, Hypersonic and Gas-surface Interaction 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18
Internal wave attractors examined using laboratory experiments and 3D numerical simulations
Brouzet, Christophe; Scolan, H; Ermanyuk, E V; Dauxois, Thierry
2016-01-01
In the present paper, we combine numerical and experimental approaches to study the dynamics of stable and unstable internal wave attractors. The problem is considered in a classic trapezoidal setup filled with a uniformly stratified fluid. Energy is injected into the system at global scale by the small-amplitude motion of a vertical wall. Wave motion in the test tank is measured with the help of conventional synthetic schlieren and PIV techniques. The numerical setup closely reproduces the experimental one in terms of geometry and the operational range of the Reynolds and Schmidt numbers. The spectral element method is used as a numerical tool to simulate the nonlinear dynamics of a viscous salt-stratified fluid. We show that the results of three-dimensional calculations are in excellent qualitative and quantitative agreement with the experimental data, including the spatial and temporal parameters of the secondary waves produced by triadic resonance instability. Further, we explore experimentally and numeri...
Sotiropoulos, Fotis; Angelidis, Dionysios; Mendelson, Leah; Techet, Alexandra
2017-11-01
Evolution has enabled fish to develop a range of thrust producing mechanisms to allow skillful movement and give them the ability to catch prey or avoid danger. Several experimental and numerical studies have been performed to investigate how complex maneuvers are executed and develop bioinspired strategies for aquatic robot design. We will discuss recent numerical advances toward the development of a computational framework for performing turbulent, two-phase flow, fluid-structure-interaction (FSI) simulations to investigate the dynamics of aquatic jumpers. We will also discuss the integration of such numerics with high-speed imaging and particle image velocimetry data to reconstruct anatomic fish models and prescribe realistic kinematics of fish motion. The capabilities of our method will be illustrated by applying it to simulate the motion of a small scale archer fish jumping out of the water to capture prey. We will discuss the rich vortex dynamics emerging during the hovering, rapid upward and gliding phases. The simulations will elucidate the thrust production mechanisms by the movement of the pectoral and anal fins and we will show that the fins significantly contribute to the rapid acceleration.
Esau, Igor
2010-01-01
Micrometeorology, city comfort, land use management and air quality monitoring increasingly become important environmental issues. To serve the needs, meteorology needs to achieve a serious advance in representation and forecast on micro-scales (meters to 100 km) called meteorological terra incognita. There is a suitable numerical tool, namely, the large-eddy simulation modelling (LES) to support the development. However, at present, the LES is of limited utility for applications. The study addresses two problems. First, the data assimilation problem on micro-scales is investigated as a possibility to recover the turbulent fields consistent with the mean meteorological profiles. Second, the methods to incorporate of the unresolved surface structures are investigated in a priopi numerical experiments. The numerical experiments demonstrated that the simplest nudging or Newtonian relaxation technique for the data assimilation is applicable on the turbulence scales. It is also shown that the filtering property of...
Numerical Propulsion System Simulation
Naiman, Cynthia
2006-01-01
The NASA Glenn Research Center, in partnership with the aerospace industry, other government agencies, and academia, is leading the effort to develop an advanced multidisciplinary analysis environment for aerospace propulsion systems called the Numerical Propulsion System Simulation (NPSS). NPSS is a framework for performing analysis of complex systems. The initial development of NPSS focused on the analysis and design of airbreathing aircraft engines, but the resulting NPSS framework may be applied to any system, for example: aerospace, rockets, hypersonics, power and propulsion, fuel cells, ground based power, and even human system modeling. NPSS provides increased flexibility for the user, which reduces the total development time and cost. It is currently being extended to support the NASA Aeronautics Research Mission Directorate Fundamental Aeronautics Program and the Advanced Virtual Engine Test Cell (AVETeC). NPSS focuses on the integration of multiple disciplines such as aerodynamics, structure, and heat transfer with numerical zooming on component codes. Zooming is the coupling of analyses at various levels of detail. NPSS development includes capabilities to facilitate collaborative engineering. The NPSS will provide improved tools to develop custom components and to use capability for zooming to higher fidelity codes, coupling to multidiscipline codes, transmitting secure data, and distributing simulations across different platforms. These powerful capabilities extend NPSS from a zero-dimensional simulation tool to a multi-fidelity, multidiscipline system-level simulation tool for the full development life cycle.
Numerical simulation of stratified flows from laboratory experiments to coastal ocean
Fraunie, Philippe
2014-05-01
Numeric modeling of a flow past vertical strip uniformly towing with permanent velocity in horizontal direction in a linearly stratified talk which was based on a finite differences solver adapted to the low Reynolds Navier-Stokes equation with transport equation for salinity (LES simulation [6]) has demonstrated reasonable agreement with data of schlieren visualization, density marker and probe measurements of internal wave fields. Another approach based on two different numerical methods for one specific case of stably stratified incompressible flow was developed, using the compact finite-difference discretizations. The numerical scheme itself follows the principle of semi-discretisation, with high order compact discretisation in space, while the time integration is carried out by the Strong Stability Preserving Runge-Kutta scheme. Results were compared against the reference solution obtained by the AUSM finite volume method [7]. The test case allowed demonstrating the ability of selected numerical methods to represent stably stratified flows over horizontal strip [4] and hill type 2D obstacles [1, 3] with generation of internal waves. From previous LES [4] and RANS [8] realistic simulations code, the ability of research codes to reproduce field observations is discussed. ACKNOWLEDGMENTS This research work was supported by Region Provence Alpes Côte d'Azur - Modtercom project, the Research Plan MSM 6840770010 of the Ministry of education of Czech Republic and the Russian Foundation for Basic Research (grant 12-01-00128). REFERENCES 1. Chashechkin Yu.D., Mitkin V.V. Experimental study of a fine structure of 2D wakes and mixing past an obstacle in a continuously stratified fluid // Dynamics of Atmosphere and Oceans. 2001. V. 34. P. 165-187. 2. Chashechkin, Yu. D. Hydrodynamics of a sphere in a stratified fluid // Fluid Dyn. 1989. V.24(1) P. 1-7. 3. Mitkin V. V., Chashechkin Yu. D. Transformation of hanging discontinuities into vortex systems in a stratified flow
Synchronization of two bubble trains in a viscous fluid: experiment and numerical simulation.
Pereira, Felipe Augusto Cardoso; Colli, Eduardo; Sartorelli, José Carlos
2013-02-01
We investigate the interactions of two trains of bubbles, ejected by nozzles immersed in a viscous fluid, due only to the solution's circulation. The air fluxes (Q(1),Q(2)) are controlled independently, and we constructed parameter spaces of the periodicity of the attractors. We have observed complex behavior and many modes of phase synchronization that depend on these airflows as well as on the height (H) of the solution above the tops of the nozzles. Such synchronizations are shown in details in the parameter space (Q(1),Q(2)) and also in the (Q(1),H) space. We also observed that the coupling strength between the two trains of bubbles increases when the solution height increases. The experimental results were reasonably explained by numerical simulations of a model combining a simple bubble growth model for each bubble train and a coupling term between them, which was assumed symmetrical and proportional to the growth velocities.
Numerical simulation of reactive processes in an experiment with partially saturated bentonite.
Xie, Mingliang; Bauer, Sebastian; Kolditz, Olaf; Nowak, Thomas; Shao, Hua
2006-02-01
Bentonites are preferred materials for use as engineered barriers for high-level nuclear waste repositories. Simulation of geochemical processes in bentonite is therefore important for long-term safety assessment of those repositories. In this work, the porewater chemistry of a bentonite sample subject to simultaneous heating and hydration, as studied by Cuevas et al. [Cuevas, J., Villar, M., Fernández, A., Gómez, P., Martín, P., 1997. Porewaters extracted from compacted bentonite subjected to simultaneous heating and hydration. Applied Geochemistry 12, 473-481.], was assessed with a non-isothermal reactive transport model by coupling the geochemical software PHREEQC2 with the object-oriented FEM simulator GeoSys/RockFlow. Reactive transport modelling includes heat transport, two-phase flow, multicomponent transport and geochemical reactions in the liquid phase, i.e. ion exchange, mineral dissolution/precipitation and equilibrium reactions. Simulations show that the easily soluble minerals in bentonite determine the porewater chemistry. Temperature affects both two-phase flow and geochemical reactions. Porosity change due to dissolution/precipitation is low during the experiment. However, changes of the effective porosity caused by bentonite swelling can be very large. The simulated results agree well with the experimental data.
Numerical simulation of reactive processes in an experiment with partially saturated bentonite
Xie, Mingliang; Bauer, Sebastian; Kolditz, Olaf; Nowak, Thomas; Shao, Hua
2006-02-01
Bentonites are preferred materials for use as engineered barriers for high-level nuclear waste repositories. Simulation of geochemical processes in bentonite is therefore important for long-term safety assessment of those repositories. In this work, the porewater chemistry of a bentonite sample subject to simultaneous heating and hydration, as studied by Cuevas et al. [Cuevas, J., Villar, M., Fernández, A., Gómez, P., Martín, P., 1997. Porewaters extracted from compacted bentonite subjected to simultaneous heating and hydration. Applied Geochemistry 12, 473-481.], was assessed with a non-isothermal reactive transport model by coupling the geochemical software PHREEQC2 with the object-oriented FEM simulator GeoSys/RockFlow. Reactive transport modelling includes heat transport, two-phase flow, multicomponent transport and geochemical reactions in the liquid phase, i.e. ion exchange, mineral dissolution/precipitation and equilibrium reactions. Simulations show that the easily soluble minerals in bentonite determine the porewater chemistry. Temperature affects both two-phase flow and geochemical reactions. Porosity change due to dissolution/precipitation is low during the experiment. However, changes of the effective porosity caused by bentonite swelling can be very large. The simulated results agree well with the experimental data.
Directory of Open Access Journals (Sweden)
Hong Zhao
2016-10-01
Full Text Available Abstract A remote-control tether-less isolation tool is a mechanical device that is normally used in pipelines to block the flow at a given position by transforming a blocking module. In this study, the interactions between the fluid and the plug module of the isolation tool were investigated. Simulations of the plug process and particle image velocimetry measurements were performed to study the flow characteristics. Numerical solutions for the continuity, momentum, and energy equations were obtained by using commercial software based on finite-volume techniques. Box–Behnken design was applied, and response surface methodology (RSM-based CFD simulation analysis was conducted. The dynamic model in the plug process was built by RSM and used to evaluate the influences of the main mechanical parameters on the pressure during the plug process. The diameter of the isolation tool and the diameter of the plug module have strong influences on the process, and the length of the isolation tool has only a little influence on the plug process.
Borodkin, A. A.; Khudyakov, D. V.; Vartapetov, S. K.
2015-02-01
The operation regimes of a pulsed all-normal-dispersion polarisation-maintaining fibre laser with a nonlinear optical loop mirror are studied. The use of polarisation-maintaining fibres ensures polarisation and temperature stability of output radiation. The lasing and instability thresholds of the pulsed laser are determined experimentally. A spectral filter placed in the cavity makes it possible to change the centre wavelength of laser radiation within the range 1.02 - 1.05 μm with a spectral full width at half maximum of 2 nm. The average output power is 7 mW, which corresponds to a pulse energy of 0.8 nJ. The autocorrelation function width of the output pulse is 50 ps. The minimum pulse duration achieved after compression by an external pair of diffraction gratings is 1.8 ps. The dynamics of the temporal and spectral parameters of laser pulses is studied using mathematical simulation based on numerical solution of the nonlinear Schrödinger equation. The simulation results coincide with experimental data with a high accuracy.
Energy Technology Data Exchange (ETDEWEB)
Borodkin, A A; Khudyakov, D V; Vartapetov, S K [Physics Instrumentation Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation)
2015-02-28
The operation regimes of a pulsed all-normal-dispersion polarisation-maintaining fibre laser with a nonlinear optical loop mirror are studied. The use of polarisation-maintaining fibres ensures polarisation and temperature stability of output radiation. The lasing and instability thresholds of the pulsed laser are determined experimentally. A spectral filter placed in the cavity makes it possible to change the centre wavelength of laser radiation within the range 1.02 – 1.05 μm with a spectral full width at half maximum of 2 nm. The average output power is 7 mW, which corresponds to a pulse energy of 0.8 nJ. The autocorrelation function width of the output pulse is 50 ps. The minimum pulse duration achieved after compression by an external pair of diffraction gratings is 1.8 ps. The dynamics of the temporal and spectral parameters of laser pulses is studied using mathematical simulation based on numerical solution of the nonlinear Schrödinger equation. The simulation results coincide with experimental data with a high accuracy. (lasers)
Kube, Ralph; Garcia, Odd Erik; Theodorsen, Audun; Brunner, Dan; Labombard, Brian; Terry, James; Wiesenberger, Matthias
2017-10-01
Particle density time series, sampled in the outboard mid-plane scrape-off layer, are interspersed by large amplitude bursts due to radial propagation of plasma blobs. GPI and Langmuir probe time series measured in the Alcator C-Mod tokamak suggest that conditionally averaged wave forms of large amplitude bursts are well described by a double exponential function. Furthermore remains the ratio of the rise and fall e-folding time of the conditionally averaged wave form constant over a range of line-averaged plasma densities. In this contribution we compare this finding to results from numerical simulations. A two-dimensional drift-fluid model has been used to simulate the propagation of seeded plasma blobs in scrape-off layer plasmas for various initial amplitudes and cross-field sizes. Time traces of the particle density, sampled at a single point, are compared to the conditionally averaged waveform of the experimental data time series. The results are interpreted in the framework of a stochastic model which relates the statistical properties of the SOL fluctuations to the profile scale length.
Experiments and Numerical Simulations of Dike Erosion due to a Wave Impact
Directory of Open Access Journals (Sweden)
Stefania Evangelista
2015-10-01
Full Text Available Dike erosion is a crucial issue in coastal and fluvial flood risk management. These defense structures appear vulnerable to extreme hydrological events, whose potential occurrence risk seems to be recently increased due to climate change. Their design and reinforcement is, however, a complex task, and although numerical models are very powerful nowadays, real processes cannot be accurately predicted; therefore, physical models constitute a useful tool to investigate different features under controlled conditions. This paper presents some laboratory experimental results of erosion of a sand dike produced by the impact of a dam break wave. Experiments have been conducted in the Water Engineering Laboratory at the University of Cassino and Southern Lazio, Italy, in a rectangular channel: here, the sudden opening of a gate forming the reservoir generates the wave impacting the dike, made in turn of two different, almost uniform sands. The physical evidence proves that the erosion process is strongly unsteady and significantly different from a gradual overtopping and highlights the importance of apparent cohesion for the fine sand dike. The experimental results have also been compared against the ones obtained through the numerical integration of a two-phase model, which shows the reasonable predictive capability of the temporal free surface and dike profile evolution.
Dunstan, Jocelyn; Lee, Kyoung Jin; Park, Simon; Goldstein, Raymond E.
A novel form of convection was observed in a suspension of non-motile Photobacterium phosphoreum bacteria. The pattern resembles classical bioconvection, however this strain has limited if any motility, which excludes this possible explanation. After performing a series of control experiments we found that the convection was actually driven by the evaporation of the salty bacterial medium, and the same kind of plumes were observed using polystyrene beads suspended in water with salt added. A mathematical model was formulated for the process and studied using a linear stability analysis and finite element method simulations, reproducing most of the observed experimental features. From the linear stability analysis, a threshold in salt concentration to observe convective motion was obtained, as well as the wavelength of the pattern at the onset of the instability. This was complemented by finite element simulations, which produced plume dynamics remarkably similar to the experimental observations. Evaporation-driven convection on the millimeter scale has not been studied extensively, and its effect may have been underestimated in other experiments.
Apsilidis, Nikolaos; Raben, Sam; Diplas, Panayiotis; Dancey, Clinton; Vlachos, Pavlos; Khosronejad, Ali; Sotiropoulos, Fotis
2009-11-01
Turbulent flows past wall-mounted obstacles are dominated by dynamically rich, slowly evolving coherent structures producing most of the turbulence in the junction region. Numerical simulations [Paik et al., Phys. of Fluids 2007] elucidated the large-scale instabilities but important questions still remain unexplored. One such question is with regard to the effect of the Reynolds number on the dynamics of the turbulent horseshoe vortex (THV). We carry out high-resolution laboratory experiments for the flow past a wall mounted cylinder in a laboratory water tunnel for ReD= 26000, 48000 and 117000. We employ the Time-Resolved Particle Image Velocimetry technique to resolve the dynamics of the flow at the symmetry plane of the cylinder and analyze the instantaneous velocity fields using the Proper Orthogonal Decomposition technique. The experimental study is integrated with coherent-structure-resolving numerical simulations providing the first comprehensive investigation of Reynolds number effects on the dynamics of the THV.
Directory of Open Access Journals (Sweden)
Xiaocui Wu
2015-11-01
Full Text Available Fluid–structure interaction is an important issue for non-rigid airships with inflated envelopes. In this study, a wind tunnel test is conducted, and a loosely coupled procedure is correspondingly established for numerical simulation based on computational fluid dynamics and nonlinear finite element analysis methods. The typical results of the numerical simulation and wind tunnel experiment, including the overall lift and deformation, are in good agreement with each other. The results obtained indicate that the effect of fluid–structure interaction is noticeable and should be considered for non-rigid airships. Flow-induced deformation can further intensify the upward lift force and pitching moment, which can lead to a large deformation. Under a wind speed of 15 m/s, the lift force of the non-rigid model is increased to approximately 60% compared with that of the rigid model under a high angle of attack.
14N overtone NMR spectra under magic angle spinning: Experiments and numerically exact simulations
O'Dell, Luke A.; Brinkmann, Andreas
2013-02-01
It was recently shown that high resolution 14N overtone NMR spectra can be obtained directly under magic angle spinning (MAS) conditions [L. A. O'Dell and C. I. Ratcliffe, Chem. Phys. Lett. 514, 168 (2011)], 10.1016/j.cplett.2011.08.030. Preliminary experimental results showed narrowed powder pattern widths, a frequency shift that is dependent on the MAS rate, and an apparent absence of spinning sidebands, observations which appeared to be inconsistent with previous theoretical treatments. Herein, we reproduce these effects using numerically exact simulations that take into account the full nuclear spin Hamiltonian. Under sample spinning, the 14N overtone signal is split into five (0, ±1, ±2) overtone sidebands separated by the spinning frequency. For a powder sample spinning at the magic angle, the +2ωr sideband is dominant while the others show significantly lower signal intensities. The resultant MAS powder patterns show characteristic quadrupolar lineshapes from which the 14N quadrupolar parameters and isotropic chemical shift can be determined. Spinning the sample at other angles is shown to alter both the shapes and relative intensities of the five overtone sidebands, with MAS providing the benefit of averaging dipolar couplings and shielding anisotropy. To demonstrate the advantages of this experimental approach, we present the 14N overtone MAS spectrum obtained from L-histidine, in which powder patterns from all three nitrogen sites are clearly resolved.
Experiment and numerical simulation for laser ultrasonic measurement of residual stress.
Zhan, Yu; Liu, Changsheng; Kong, Xiangwei; Lin, Zhongya
2017-01-01
Laser ultrasonic is a most promising method for non-destructive evaluation of residual stress. The residual stress of thin steel plate is measured by laser ultrasonic technique. The pre-stress loading device is designed which can easily realize the condition of the specimen being laser ultrasonic tested at the same time in the known stress state. By the method of pre-stress loading, the acoustoelastic constants are obtained and the effect of different test directions on the results of surface wave velocity measurement is discussed. On the basis of known acoustoelastic constants, the longitudinal and transverse welding residual stresses are measured by the laser ultrasonic technique. The finite element method is used to simulate the process of surface wave detection of welding residual stress. The pulsed laser is equivalent to the surface load and the relationship between the physical parameters of the laser and the load is established by the correction coefficient. The welding residual stress of the specimen is realized by the ABAQUS function module of predefined field. The results of finite element analysis are in good agreement with the experimental method. The simple and effective numerical and experimental methods for laser ultrasonic measurement of residual stress are demonstrated. Copyright © 2016. Published by Elsevier B.V.
Ghamlouch, T.; Roux, S.; Bailleul, J.-L.; Lefèvre, N.; Sobotka, V.
2017-10-01
Today's aerospace industrial first priority is the quality improvement of the composite material parts with the reduction of the manufacturing time in order to increase their quality/cost ratio. A fabrication method that could meet these specifications especially for large parts is the autoclave curing process. In fact the autoclave molding ensures the thermal control of the composite parts during the whole curing cycle. However the geometry of the tools as well as their positioning in the autoclave induce non uniform and complex flows around composite parts. This heterogeneity implies non-uniform heat transfers which can directly impact on part quality. One of the main challenges is therefore to describe the flow field inside an autoclave as well as the convective heat transfer from the heated pressurized gas to the composite part and the mold. For this purpose, and given the technical issues associated with instrumentation and measurements in actual autoclaves, an autoclave model was designed and then manufactured based on similarity laws. This tool allows the measurement of the flow field around representative real industrial molds using the PIV technique and the characterization of the heat transfer thanks to thermal instrumentation. The experimental results are then compared with those derived from numerical simulations using a commercial RANS CFD code. This study aims at developing a semi-empirical approach for the prediction of the heat transfer coefficient around the parts and therefore predicts its thermal history during the process with a view of optimization.
Bosilovich, Michael G.; Sud, Yogesh; Schubert, Siegfried D.; Walker, Gregory K.
2003-01-01
There are several important research questions that the Global Energy and Water Cycle Experiment (GEWEX) is actively pursuing, namely: What is the intensity of the water cycle and how does it change? And what is the sustainability of water resources? Much of the research to address these questions is directed at understanding the atmospheric water cycle. In this paper, we have used a new diagnostic tool, called Water Vapor Tracers (WVTs), to quantify the how much precipitation originated as continental or oceanic evaporation. This shows how long water can remain in the atmosphere and how far it can travel. The model-simulated data are analyzed over regions of interest to the GEWEX community, specifically, their Continental Scale Experiments (CSEs) that are in place in the United States, Europe, Asia, Brazil, Africa and Canada. The paper presents quantitative data on how much each continent and ocean on Earth supplies water for each CSE. Furthermore, the analysis also shows the seasonal variation of the water sources. For example, in the United States, summertime precipitation is dominated by continental (land surface) sources of water, while wintertime precipitation is dominated by the Pacific Ocean sources of water. We also analyze the residence time of water in the atmosphere. The new diagnostic shows a longer residence time for water (9.2 days) than more traditional estimates (7.5 days). We emphasize that the results are based on model simulations and they depend on the model s veracity. However, there are many potential uses for the new diagnostic tool in understanding weather processes and large and small scales.
Directory of Open Access Journals (Sweden)
L. J. Yu
2007-12-01
Full Text Available A high-temperature molten carbonate fuel cell stack was studied experimentally and computationally. Experimental data for fuel cell temperature was obtained when the stack was running under given operational conditions. A 3-D CFD numerical model was set up and used to simulate the central fuel cell in the stack. It includes the mass, momentum and energy conservation equations, the ideal gas law and an empirical equation for cell voltage. The model was used to simulate the transient behavior of the fuel cell under the same operational conditions as those of the experiment. Simulation results show that the transient temperature and current and power densities reach their maximal values at the channel outlet. A comparison of the modeling results and the experimental data shows the good agreement.
Directory of Open Access Journals (Sweden)
Lei Zhang
2010-01-01
Full Text Available The importance of wind observations has been recognized for many years. However, wind observations—especially three-dimensional global wind measurements—are very limited. A satellite-based Doppler Wind Lidar (DWL is proposed to measure three-dimensional wind profiles using remote sensing techniques. Assimilating these observations into a mesoscale model is expected to improve the performance of the numerical weather prediction (NWP models. In order to examine the potential impact of the DWL three-dimensional wind profile observations on the numerical simulation and prediction of tropical cyclones, a set of observing simulation system experiments (OSSEs is performed using the advanced research version of the Weather Research and Forecasting (WRF model and its three-dimensional variational (3DVAR data assimilation system. Results indicate that assimilating the DWL wind observations into the mesoscale numerical model has significant potential for improving tropical cyclone track and intensity forecasts.
Zaussinger, F.; Plesa, A.; Egbers, C.; Breuer, D.
2012-04-01
Convection in not directly observable fluids or objects with a central symmetry buoyancy field in spherical shells plays an important role in geophysical and astrophysical research. The main focus of this study is to compare two different numerical approaches based on two Navier-Stokes solvers (RESPECT code and GAIA code) with the 'on orbit' experiments called GeoFlowI and GeoFlowII. The numerical simulation of flows in the spherical gap geometry is challenging and requests high accuracy to resolve all relevant scales. Beside isoviscous Rayleigh-B'enard convection the influence of temperature dependent viscosity on the temperature field is investigated. The Simulation of Geophysical Fluid Flow under Microgravity (Geoflow) is an ESA investigation running inside the Fluid Science Laboratory (FSL) on the International Space Station ISS and has the goal to better understand the interior dynamics of our planet [1]. The GeoFlowI mission focused on the simulation of iso-viscous flows, whereas in the GeoFlowII mission the effects of temperature-dependent viscosity are investigated - the latter is more relevant for mantle material. The GAIA software package, developed at DLR, solves the conservation equations of thermal convection for an incompressible Boussinesq fluid with infinite Prandtl number. The discretization of the governing equations is based on the finite-volume method with the advantage of using fully irregular grids [2, 3]. The code can handle viscosity variations of up to 8 orders of magnitude from cell-to-cell and up to 45 orders of magnitude system wide. We further use the pseudo spectral method based code RESPECT modified after [4] to be able to handle viscosity contrast up to 10. The main property of the underlying algorithm is the implicitly treatment of the linear parts and the pseudo spectral calculation of the non-linearities. While the spectral method based code is fast and accurate for small viscosity ratios, the GAIA suite provides stable
Lipeng, Du; Ruifeng, Tian; Pengfei, Zhang; Zhongning, Sun
2011-12-01
The humidity of steam is an important parameter, but its exact measurement is difficult. The use of capacitance is a novel measurement method. On the basis of the theory of dielectric polarization and hydrodynamics and applying FLUENT UDF language, the coupling of the steam flow field and electric field within the capacitance sensor are investigated through numerical simulation. The standard k-e model, scalable wall function and SIMPLE (Semi-Implicit Method for Pressure Linked Equations) are used in the research. Additionally, steam humidity is measured according to capacitance in an experiment. The results show that the water molecule is polarized; polarized charge appears near the wall of the flow field; the radial velocity depends on whether there is an electric field within the capacitance sensor, with the dependence being greatest near the outermost board; and the electric field intensity near the electrode board is less when there is no flow field. The numerical simulation agrees with the results of the experiment. The capacitance does not depend on a change in steam flow, and the capacitance of the sensor increases linearly with humidity.
Short-Term Creep Experiment of Cement Asphalt Mortar and Its Numerical Simulation
Directory of Open Access Journals (Sweden)
Hao Xu
2016-01-01
Full Text Available In order to investigate the creep performance of cement asphalt mortar (CA mortar, the field sampling of CA mortar cylinder samples was produced, and all samples were tested on WDW series electric universal testing machine by using uniaxial static creep test at 25°C, and the load stress levels were 0.05 MPa, 0.1 MPa, 0.3 MPa, and 0.5 MPa. The greater the load is, the bigger the creep deformation is. The creep performance was simulated by using Burgers model, and the correlation coefficients between fitting results of Burgers model and experimental results are all greater than 0.9. Based on the requirements of finite element software, the Prony series of Burgers model was obtained, and the short-term creep process of CA mortar was simulated by the finite element software ANSYS. The relative error between simulation results and experimental data is not more than 2.5%, which indicates that the short-creep process of CA mortar can be simulated by ANSYS software. The study results can improve the structural design theory of slab track.
Formation of residual NAPL in three-phase systems: Experiments and numerical simulations
Hofstee, C.; Oostrom, M.
2002-01-01
The formation of residual, discontinuous nonaqueous phase liquids (NAPLs) in the vadose zone is a process that is not well understood. The simulators have conveniently implemented the Leverett concept (Leverett and Lewis, 1941) which states that in a water-wet porous media, when fluid wettabilities
A Novel Material for In Situ Construction on Mars: Experiments and Numerical Simulations
Wan, Lin; Wendner, Roman; Cusatis, Gianluca
2015-01-01
A significant step in space exploration during the 21st century will be human settlement on Mars. Instead of transporting all the construction materials from Earth to the red planet with incredibly high cost, using Martian soil to construct a site on Mars is a superior choice. Knowing that Mars has long been considered a "sulfur-rich planet", a new construction material composed of simulated Martian soil and molten sulfur is developed. In addition to the raw material availability for producin...
Klein, Max; Sharma, Rati; Bohrer, Chris H; Avelis, Cameron M; Roberts, Elijah
2017-01-15
Data-parallel programming techniques can dramatically decrease the time needed to analyze large datasets. While these methods have provided significant improvements for sequencing-based analyses, other areas of biological informatics have not yet adopted them. Here, we introduce Biospark, a new framework for performing data-parallel analysis on large numerical datasets. Biospark builds upon the open source Hadoop and Spark projects, bringing domain-specific features for biology. Source code is licensed under the Apache 2.0 open source license and is available at the project website: https://www.assembla.com/spaces/roberts-lab-public/wiki/Biospark CONTACT: eroberts@jhu.eduSupplementary information: Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Is Cu involved in prion oligopeptide stability? Experiments and numerical simulations
Minicozzi, V.; Morante, S.
The high-sociological impact of neurodegenerative diseases (like Alzheimer disease, Transmissible Spongiform Encephalopathies, Parkinson disease, etc.) has renewed the interest of researchers in the study of misfolding processes and in particular of the rôle played by metals in plaque formation as their unbalanced concentration can be regarded as a possible concurrent cause of protein aggregation. Metals are essential players in many of the fundamental activities of cells. Storing, metabolism, and trafficking of metals through the cellular membrane and within the cytoplasm are mediated by many proteins via well-tuned mechanisms because of the toxicity of free ions. In this review article, we summarize the results of the most recent experimental and numerical investigations aimed at understanding the possible rôle of Cu in stabilizing the Prion protein structure and in the formation of protein polymers.
Short-Term Creep Experiment of Cement Asphalt Mortar and Its Numerical Simulation
Xu, Hao; Wang, Ping; Lin, Hong-song; Yan, Hua
2016-01-01
In order to investigate the creep performance of cement asphalt mortar (CA mortar), the field sampling of CA mortar cylinder samples was produced, and all samples were tested on WDW series electric universal testing machine by using uniaxial static creep test at 25°C, and the load stress levels were 0.05 MPa, 0.1 MPa, 0.3 MPa, and 0.5 MPa. The greater the load is, the bigger the creep deformation is. The creep performance was simulated by using Burgers model, and the correlation coefficients ...
Combining Narrative and Numerical Simulation
DEFF Research Database (Denmark)
Hansen, Mette Sanne; Ladeby, Klaes Rohde; Rasmussen, Lauge Baungaard
2011-01-01
Strategic simulation is the combination of narrative and numerical simulation and can be used as a tool to support strategic decision making by providing different scenarios in combination with computer modelling. The core of the combined simulation approach (CSA) is to make it possible for decis......Strategic simulation is the combination of narrative and numerical simulation and can be used as a tool to support strategic decision making by providing different scenarios in combination with computer modelling. The core of the combined simulation approach (CSA) is to make it possible...... 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...
Numerical simulation and experiment on split tungsten carbide cylinder of high pressure apparatus.
Yang, Yunfei; Li, Mingzhe; Liu, Zhiwei; Wang, Bolong
2015-12-01
A new high pressure device with a split cylinder was investigated on the basis of the belt-type apparatus. The belt-type die is subjected to excessive tangential tensile stress and the tungsten carbide cylinder is easily damaged in the running process. Taking into account the operating conditions and material properties of the tungsten carbide cylinder, it is divided into 6 blocks to eliminate the tangential tensile stress. We studied two forms of the split type: radial split and tangential split. Simulation results indicate that the split cylinder has more uniform stress distribution and smaller equivalent stress compared with the belt-type cylinder. The inner wall of the tangential split cylinder is in the situation that compressive stress is distributed in the axial, radial, and tangential directions. It is similar to the condition of hydrostatic pressure, and it is the best condition for tungsten carbide materials. The experimental results also verify that the tangential split die can bear the highest chamber pressure. Therefore, the tangential split structure can increase the pressure bearing capacity significantly.
Numerical Simulation and Experiment Study on Extrusion of AZ31 Magnesium Alloy Tube
Directory of Open Access Journals (Sweden)
SUN Ying-di
2017-06-01
Full Text Available The extrusion process of typical AZ31 magnesium alloy tube was simulated by using the constitutive model of AZ31 alloys and ALE-based HyperXtrude software. The changes of stress distribution and velocity distribution were analyzed under different conditions, through the adjustment of three structural parameters, including the height, big round corner and gradient of weld chamber. The results show that the pressure near the work zone in the weld chamber decrease with the increase of the height of weld chamber, the maximum value and average value of the pressure in the weld chamber are decreasing with the increase of big round corner of weld chamber, and the pressure in the port holes and weld chamber increases with the increase of the gradient of weld chamber. The minimum variance of metal flow rate is achieved in the height of weld chamber with 16mm, big round corner with 18mm and gradient of weld chamber with 15°. The optimized structure alleviates the issues of stress concentration and non-homogeneous flowing velocity. The final die is proved to be capable of producing the qualified products and the microstructure after extrusion is uniform and fine.
Dippold, Vance F., III; Friedlander, David
2017-01-01
NASA and industry partners desire to reintroduce commercial supersonic airliners to the air transportation system. There are a number of technical challenges that must be overcome by future commercial supersonic airliners to make them viable solutions in society. NASA is specifically concerned with the challenges of reducing boom during supersonic cruise, maximizing range, and reducing airport community noise to acceptable levels. Concepts for commercial supersonic transports, such as the concept aircraft by Lockheed Martin pictured in Figure 1, place the engine nozzles in close proximity to wing and tail surfaces. However, the effects of noise shielding and noise radiation are not fully understood for installed propulsion systems. A series of acoustic tests were conducted on the NASA Glenn Research Centers Nozzle Acoustic Test Rig (NATR) to address the challenge of reducing airport community noise, which is often dominated by jet noise. To best represent the conceptual aircraft in the acoustic tests, noise measurements were taken of the jet in close proximity of simulated aerodynamic surfaces, not simply of an isolated jet.
Numerical simulation and experiment on split tungsten carbide cylinder of high pressure apparatus
Energy Technology Data Exchange (ETDEWEB)
Yang, Yunfei; Li, Mingzhe, E-mail: limz@jlu.edu.cn; Wang, Bolong [Dieless Forming Technology Center, Jilin University, Changchun 130025 (China); Liu, Zhiwei [School of Mechanical Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China)
2015-12-15
A new high pressure device with a split cylinder was investigated on the basis of the belt-type apparatus. The belt-type die is subjected to excessive tangential tensile stress and the tungsten carbide cylinder is easily damaged in the running process. Taking into account the operating conditions and material properties of the tungsten carbide cylinder, it is divided into 6 blocks to eliminate the tangential tensile stress. We studied two forms of the split type: radial split and tangential split. Simulation results indicate that the split cylinder has more uniform stress distribution and smaller equivalent stress compared with the belt-type cylinder. The inner wall of the tangential split cylinder is in the situation that compressive stress is distributed in the axial, radial, and tangential directions. It is similar to the condition of hydrostatic pressure, and it is the best condition for tungsten carbide materials. The experimental results also verify that the tangential split die can bear the highest chamber pressure. Therefore, the tangential split structure can increase the pressure bearing capacity significantly.
Wang, Ping; Pozdniakov, Sergey P.; Vasilevskiy, Peter Yu.
2017-12-01
Surface water infiltration from ephemeral dryland streams is particularly important in hyporheic exchange and biogeochemical processes in arid and semi-arid regions. However, streamflow transmission losses can vary significantly, partly due to spatiotemporal variations in streambed permeability. To extend our understanding of changes in streambed hydraulic properties, field investigations of streambed hydraulic conductivity were conducted in an ephemeral dryland stream in north-western China during high and low streamflow periods. Additionally, streamflow transmission losses were numerically estimated using combined stream and groundwater hydraulic head data and stream and streambed temperature data. An analysis of slug test data at two different river flow stages (one test was performed at a low river stage with clean water and the other at a high river stage with muddy water) suggested that sedimentation from fine-grained particles, i.e., physical clogging processes, likely led to a reduction in streambed hydraulic properties. To account for the effects of streambed clogging on changes in hydraulic properties, an iteratively increasing total hydraulic resistance during the slug test was considered to correct the estimation of streambed hydraulic conductivity. The stream and streambed temperature can also greatly influence the hydraulic properties of the streambed. One-dimensional coupled water and heat flux modelling with HYDRUS-1D was used to quantify the effects of seasonal changes in stream and streambed temperature on streamflow losses. During the period from 6 August 2014 to 4 June 2015, the total infiltration estimated using temperature-dependent hydraulic conductivity accounted for approximately 88% of that using temperature-independent hydraulic conductivity. Streambed clogging processes associated with fine particle settling/wash up cycles during flow events, and seasonal changes in streamflow temperature are two considerable factors that affect water
DEFF Research Database (Denmark)
Hagsäter, Melker; Jensen, Thomas Glasdam; Bruus, Henrik
2007-01-01
to different aqueous phases in two-phase systems. This separation process may be enhanced or extended by applying an electric field perpendicular to the phase boundary. In this context, microsystems offer new possibilities, as interfacial forces usually dominate over volume forces, thus allowing a superior......This work reports on protein transport phenomena discovered in partitioning experiments with a novel setup for continuous-flow two-phase electrophoresis consisting of a microchannel in which a phase boundary is formed in flow direction. Proteins can be partitioned exploiting their affinity...... control of the formation and arrangement of liquid/liquid phase boundaries. The two immiscible phases which are injected separately into the microchannel are taken from a polyethylene glycol (PEG)–dextran system. The side walls of the channel are partially made of gel material which serves as an ion...
Directory of Open Access Journals (Sweden)
Nikki C. Privé
2013-11-01
Full Text Available A series of experiments that explore the roles of model and initial condition error in numerical weather prediction are performed using an observing system simulation experiment (OSSE framework developed at the National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO. The use of an OSSE allows the analysis and forecast errors to be explicitly calculated, and different hypothetical observing networks can be tested with ease. In these experiments, both a full global OSSE framework and an ‘identical twin’ OSSE setup are used to compare the behaviour of the data assimilation system (DAS and evolution of forecast skill with and without model error. The initial condition error is manipulated by varying the distribution and quality of the observing network and the magnitude of observation errors. The results show that model error has a strong impact on both the quality of the analysis field and the evolution of forecast skill, including both systematic and unsystematic model error components. With a realistic observing network, the analysis state retains a significant quantity of error due to systematic model error. If errors of the analysis state are minimised, model error acts to rapidly degrade forecast skill during the first 24–48 hours of forward integration. In the presence of model error, the impact of observation errors on forecast skill is small, but in the absence of model error, observation errors cause a substantial degradation of the skill of medium-range forecasts.
Beyer, C.; Ballarini, E.; Bauer, R.; Griebler, C.; Bauer, S.
2011-12-01
profiles perpendicular to the flow direction along the plume. Simulated microbial growth was strongest near the central tank inlet, where both, oxygen and ethylbenzene were available at high concentrations, and along the transverse mixing zone at the fringe of the developed ethylbenzene plume. Model based interpretation of the aerobic/anaerobic phase with competitive biodegradation proved to be ambiguous due to uncertainties regarding the actual stoichiometry of the specific denitrification reaction. Also, the simulated isotopic patterns were very sensitive to the assumed initial distribution of the A. aromaticum EbN1 biomass. Ethylbenzene concentrations and isotopic patterns predicted by the numerical model match the measurements quite well for the first half of the aerobic/anaerobic phase. A distinct increase in biodegradation dynamics later on hints at a change in biodegradation dynamics during the course of the experiment.
Charogiannis, Alexandros; Denner, Fabian; van Wachem, Berend G. M.; Kalliadasis, Serafim; Markides, Christos N.
2017-12-01
We scrutinize the statistical characteristics of liquid films flowing over an inclined planar surface based on film height and velocity measurements that are recovered simultaneously by application of planar laser-induced fluorescence (PLIF) and particle tracking velocimetry (PTV), respectively. Our experiments are complemented by direct numerical simulations (DNSs) of liquid films simulated for different conditions so as to expand the parameter space of our investigation. Our statistical analysis builds upon a Reynolds-like decomposition of the time-varying flow rate that was presented in our previous research effort on falling films in [Charogiannis et al., Phys. Rev. Fluids 2, 014002 (2017), 10.1103/PhysRevFluids.2.014002], and which reveals that the dimensionless ratio of the unsteady term to the mean flow rate increases linearly with the product of the coefficients of variation of the film height and bulk velocity, as well as with the ratio of the Nusselt height to the mean film height, both at the same upstream PLIF/PTV measurement location. Based on relations that are derived to describe these results, a methodology for predicting the mass-transfer capability (through the mean and standard deviation of the bulk flow speed) of these flows is developed in terms of the mean and standard deviation of the film thickness and the mean flow rate, which are considerably easier to obtain experimentally than velocity profiles. The errors associated with these predictions are estimated at ≈1.5 % and 8% respectively in the experiments and at flow characteristics based on simple flow information, the data provided can be used to design improved heat- and mass-transfer equipment reactors or other process operation units which exploit film flows, but also to develop and validate multiphase flow models in other physical and technological settings.
Directory of Open Access Journals (Sweden)
Lávička D.
2010-07-01
Full Text Available This paper describes the topic of measurement using a modern laser method (PIV in an annular channel of very small dimensions. The annular channel simulates the flow area around a model of a fuel rod in the VVER nuclear reactor. The annular channel holds spacers which create obstacles to fluid flow. The spacers serve a number of important purposes. In the real nuclear reactor, the spacer holds a fuel rod in the fuel rod bundle. Another important function of the spacer is to influence the flow field characteristics, especially turbulence size, by the shape of the spacer. The value of the turbulence regulates the intensity of heat transfer between the fuel rod and the fluid. Therefore, it is very important to provide a correct description and analysis of the flow field behind the obstacle the spacer generates. The paper further looks into the solution of the same task using numerical simulation. The solution of this task consisted of setting the suitable boundary conditions and of setting the turbulence model for the numerical simulation. The result is a comparison of the flow field characteristics from the experimental measurement and the findings of the numerical simulation. The numerical simulation was carried out using commercial CFD software package, FLUENT.
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 Japan Sea effect snowfall
Estoque, M.A.; Ninomiya, K.
2011-01-01
Snowfall associated with the modification of cold air-mass outbreaks by the Sea of Japan is simulated with a simple numerical model. The model incorporates the effects of momentum, heat, and moisture fluxes across the air-sea interface as well as the effects of orography. The simulated distributions of snowfall, temperature, wind, and moisture are compared with observations and reasonable agreement is found. Numerical experiments were made in order to determine the dependence of the snowfall ...
Direct numerical simulation of supercritical annular electroconvection
Tsai, Peichun Amy; Daya, Zahir A.; Deyirmenjian, Vatche B.; Morris, Stephen W.
2007-01-01
We use direct numerical simulation to study electrically driven convection in an annular thin film. The simulation models a laboratory experiment that consists of a weakly conducting, submicron thick liquid crystal film suspended between two concentric electrodes. The film is driven to convect by
Hot-blade cutting of EPS foam for double-curved surfaces—numerical simulation and experiments
DEFF Research Database (Denmark)
Petkov, Kiril P.; Hattel, Jesper Henri
2017-01-01
In the present paper, experimental and numerical studies of a newly developed process of Hot-Blade Cutting used for free forming of double-curved surfaces and cost effective rapid prototyping of expanded polystyrene foam is carried out. The experimental part of the study falls in two parts......-Blade Cutting similar to the one previously proposed by Petkov and Hattel (Int J Machine Tools Manuf 107:50–59 2016) for Hot-Wire Cutting of Polystyrene foam is used to simulate the process and describe the effects taking place within the hot-blade during different cutting procedures. The obtained results...
Energy Technology Data Exchange (ETDEWEB)
Molenkamp, C.R.; Grossman, A.
1999-12-20
A network of small balloon-borne transponders which gather very high resolution wind and temperature data for use by modern numerical weather predication models has been proposed to improve the reliability of long-range weather forecasts. The global distribution of an array of such transponders is simulated using LLNL's atmospheric parcel transport model (GRANTOUR) with winds supplied by two different general circulation models. An initial study used winds from CCM3 with a horizontal resolution of about 3 degrees in latitude and longitude, and a second study used winds from NOGAPS with a 0.75 degree horizontal resolution. Results from both simulations show that reasonable global coverage can be attained by releasing balloons from an appropriate set of launch sites.
Simulation of Numerical Distance Relays
Sherwali, Hamid; Abdlrahem, Abdlmnam
2010-01-01
As modern numerical relays are widely employed in protection systems nowadays and modeling of these types of relays is important to adjust and settle protection equipment in electrical facilities and to train protection personnel, the simulation of distance relays using MATLAB offers a good opportunity to perform these activities efficiently and with minimum cost. Another advantages is that, as MATLAB is a powerful tool rich with component models, any shape of relay characteristic (Impedance,...
Numerical Simulations of Granular Processes
Richardson, Derek C.; Michel, Patrick; Schwartz, Stephen R.; Ballouz, Ronald-Louis; Yu, Yang; Matsumura, Soko
2014-11-01
Spacecraft images and indirect observations including thermal inertia measurements indicate most small bodies have surface regolith. Evidence of granular flow is also apparent in the images. This material motion occurs in very low gravity, therefore in a completely different gravitational environment than on the Earth. Understanding and modeling these motions can aid in the interpretation of imaged surface features that may exhibit signatures of constituent material properties. Also, upcoming sample-return missions to small bodies, and possible future manned missions, will involve interaction with the surface regolith, so it is important to develop tools to predict the surface response. We have added new capabilities to the parallelized N-body gravity tree code pkdgrav [1,2] that permit the simulation of granular dynamics, including multi-contact physics and friction forces, using the soft-sphere discrete-element method [3]. The numerical approach has been validated through comparison with laboratory experiments (e.g., [3,4]). Ongoing and recently completed projects include: impacts into granular materials using different projectile shapes [5]; possible tidal resurfacing of asteroid Apophis during its 2029 encounter [6]; the Brazil-nut effect in low gravity [7]; and avalanche modeling.Acknowledgements: DCR acknowledges NASA (grants NNX08AM39G, NNX10AQ01G, NNX12AG29G) and NSF (AST1009579). PM acknowledges the French agency CNES. SRS works on the NEOShield Project funded under the European Commission’s FP7 program agreement No. 282703. SM acknowledges support from the Center for Theory and Computation at U Maryland and the Dundee Fellowship at U Dundee. Most simulations were performed using the YORP cluster in the Dept. of Astronomy at U Maryland and on the Deepthought High-Performance Computing Cluster at U Maryland.References: [1] Richardson, D.C. et al. 2000, Icarus 143, 45; [2] Stadel, J. 2001, Ph.D. Thesis, U Washington; [3] Schwartz, S.R. et al. 2012, Gran
Numerical Propulsion System Simulation Architecture
Naiman, Cynthia G.
2004-01-01
The Numerical Propulsion System Simulation (NPSS) is a framework for performing analysis of complex systems. Because the NPSS was developed using the object-oriented paradigm, the resulting architecture is an extensible and flexible framework that is currently being used by a diverse set of participants in government, academia, and the aerospace industry. NPSS is being used by over 15 different institutions to support rockets, hypersonics, power and propulsion, fuel cells, ground based power, and aerospace. Full system-level simulations as well as subsystems may be modeled using NPSS. The NPSS architecture enables the coupling of analyses at various levels of detail, which is called numerical zooming. The middleware used to enable zooming and distributed simulations is the Common Object Request Broker Architecture (CORBA). The NPSS Developer's Kit offers tools for the developer to generate CORBA-based components and wrap codes. The Developer's Kit enables distributed multi-fidelity and multi-discipline simulations, preserves proprietary and legacy codes, and facilitates addition of customized codes. The platforms supported are PC, Linux, HP, Sun, and SGI.
Numerical simulations of Lake Vostok
Curchitser, E.; Tremblay, B.
2003-04-01
Numerical simulations of Lake Vostok We present a systematic approach towards a realistic hydrodynamic model of lake Vostok. The lake is characterized by the unusual combination of size (permitting significant geostrophic motion) and an overlying ice sheet several kilometers thick. A priori estimates of the circulation in the deep lake predict a mostly geostrophic circulation driven by horizontal temperature gradients produced by the pressure-dependent freezing point at the base of the (non-uniform) ice sheet. Further preliminary (remote) research has revealed the steep topography and the elliptical geometry of the lake. A three dimensional, primitive equation, free surface, model is used as a starting point for the Lake configuration. We show how the surface pressure gradient forces are modified to permit a simulation that includes the hydrostatic effects of the overlying ice sheet. A thermodynamic ice model is coupled with the circulation component to simulate the ice accretion/melting at the base of the ice sheet. A stretching of the terrain following vertical coordinate is used to resolve the boundary layer in the ice/water interface. Furthermore, the terrain-following coordinate evolves in time, and is used to track the evolution of the ice sheet due to ice accretion/melting. Both idealized and realistic ice sheet bottom topographies (from remote radar data) are used to drive the simulations. Steady state and time evolving simulations (i.e., constant and evolving ice sheet geometry) will be descirbed, as well as a comparison to an idealized box model (Tremblay, Clarke, and Hohman). The coastline and lake bathymetry used in the simulation are derived from radar data and are accurately represented in our model.
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 Unravel the Cosmic Web
Faucher-Giguere, C. -A.; Lidz, A.; Hernquist, L.
2008-01-01
The universe is permeated by a network of filaments, sheets, and knots collectively forming a "cosmic web.'' The discovery of the cosmic web, especially through its signature of absorption of light from distant sources by neutral hydrogen in the intergalactic medium, exemplifies the interplay between theory and experiment that drives science, and is one of the great examples in which numerical simulations have played a key and decisive role. We recount the milestones in our understanding of c...
Relativistic Positioning Systems: Numerical Simulations
Puchades, Neus
2014-01-01
The motion of satellite constellations similar to GPS and Galileo is numerically simulated and, then, the region where bifurcation (double positioning) occurs is appropriately represented. In the cases of double positioning, the true location may be found using additional information (angles or times). The zone where the Jacobian, J, of the transformation from inertial to emission coordinates vanishes is also represented and interpreted. It is shown that the uncertainties in the satellite world lines produce positioning errors, which depend on the value of |J|. The smaller this quantity the greater the expected positioning errors. Among all the available 4-tuples of satellites, the most appropriate one -for a given location- should minimize positioning errors (large enough |J| values) avoiding bifurcation. Our study is particularly important to locate objects which are far away from Earth, e.g., satellites.
Simulation - modeling - experiment; Simulation - modelisation - experience
Energy Technology Data Exchange (ETDEWEB)
NONE
2004-07-01
After two workshops held in 2001 on the same topics, and in order to make a status of the advances in the domain of simulation and measurements, the main goals proposed for this workshop are: the presentation of the state-of-the-art of tools, methods and experiments in the domains of interest of the Gedepeon research group, the exchange of information about the possibilities of use of computer codes and facilities, about the understanding of physical and chemical phenomena, and about development and experiment needs. This document gathers 18 presentations (slides) among the 19 given at this workshop and dealing with: the deterministic and stochastic codes in reactor physics (Rimpault G.); MURE: an evolution code coupled with MCNP (Meplan O.); neutronic calculation of future reactors at EdF (Lecarpentier D.); advance status of the MCNP/TRIO-U neutronic/thermal-hydraulics coupling (Nuttin A.); the FLICA4/TRIPOLI4 thermal-hydraulics/neutronics coupling (Aniel S.); methods of disturbances and sensitivity analysis of nuclear data in reactor physics, application to VENUS-2 experimental reactor (Bidaud A.); modeling for the reliability improvement of an ADS accelerator (Biarotte J.L.); residual gas compensation of the space charge of intense beams (Ben Ismail A.); experimental determination and numerical modeling of phase equilibrium diagrams of interest in nuclear applications (Gachon J.C.); modeling of irradiation effects (Barbu A.); elastic limit and irradiation damage in Fe-Cr alloys: simulation and experiment (Pontikis V.); experimental measurements of spallation residues, comparison with Monte-Carlo simulation codes (Fallot M.); the spallation target-reactor coupling (Rimpault G.); tools and data (Grouiller J.P.); models in high energy transport codes: status and perspective (Leray S.); other ways of investigation for spallation (Audoin L.); neutrons and light particles production at intermediate energies (20-200 MeV) with iron, lead and uranium targets (Le Colley F
suk O, Jin; Jeen, Sung-Wook; Gillham, Robert W; Gui, Lai
2009-01-26
Column experiments and numerical simulation were conducted to test the hypothesis that iron material having a high corrosion rate is not beneficial for the long-term performance of iron permeable reactive barriers (PRBs) because of faster passivation of iron and greater porosity loss close to the influent face of the PRBs. Four iron materials (Connelly, Gotthart-Maier, Peerless, and ISPAT) were used for the column experiments, and the changes in reactivity toward cis-dichloroethene (cis-DCE) degradation in the presence of dissolved CaCO3 were evaluated. The experimental results showed that the difference in distribution of the accumulated precipitates, resulting from differences in iron corrosion rate, caused a difference in the migration rate of the cis-DCE profiles and a significant difference in the pattern of passivation, indicating a faster passivation in the region close to the influent end for the material having a higher corrosion rate. For the numerical simulation, the accumulation of secondary minerals and reactivity loss of iron were coupled using an empirically-derived relationship that was incorporated into a multi-component reactive transport model. The simulation results provided a reasonable representation of the evolution of iron reactivity toward cis-DCE treatment and the changes in geochemical conditions for each material, consistent with the observed data. The simulations for long-term performance were also conducted to further test the hypothesis and predict the differences in performance over a period of 40 years under typical groundwater conditions. The predictions showed that the cases of higher iron corrosion rates had earlier cis-DCE breakthrough and more reduction in porosity starting from near the influent face, due to more accumulation of carbonate minerals in that region. Therefore, both the experimental and simulation results appear to support the hypothesis and suggest that reactivity changes of iron materials resulting from
Baviskar, S.M.; Heimovaara, T.J.
2015-01-01
We believe the unsaturated and heterogeneous nature of landfills leads to the emergence of preferential pathways of water and dissolved compounds through the waste body. In this research we explore the origin of preferential flow in a porous media with a deterministic numerical model. In this model
Leckey, Cara A C; Wheeler, Kevin R; Hafiychuk, Vasyl N; Hafiychuk, Halyna; Timuçin, Doğan A
2017-11-04
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.
Numerical Simulation of GFRP Reinforced Concrete Beams
National Research Council Canada - National Science Library
Xia Zhao; Xiong-Jun He; Yong-Chao Yang
2017-01-01
.... The finite element numerical simulation of GFRP fiber reinforced concrete beam was carried out, and the load deflection nephogram of fiber reinforced concrete beam, strain nephogram, crack nephogram...
Energy Technology Data Exchange (ETDEWEB)
Kwicklis, E.M.; Healy, R.W. [Geological Survey, Denver, CO (United States); Thamir, F. [AMX International, Inc., Denver, CO (United States); Hampson, D. [EQE International, Evergreen, CO (United States)
1998-11-01
Numerical models of water movement through variably saturated, fractured tuff have undergone little testing against experimental data collected from relatively well-controlled and characterized experiments. This report used the results of a multistage experiment on a block of variably saturated, fractured, welded tuff and associated core samples to investigate if those results could be explained using models and concepts currently used to simulate water movement in variably saturated, fractured tuff at Yucca Mountain, Nevada, the potential location of a high-level nuclear-waste repository. Aspects of the experiment were modeled with varying degrees of success. Imbibition experiments performed on cores of various lengths and diameters were adequately described by models using independently measured permeabilities and moisture-characteristic curves, provided that permeability reductions resulting from the presence of entrapped air were considered. Entrapped gas limited maximum water saturations during imbibition to approximately 0.70 to 0,80 of the fillable porosity values determined by vacuum saturation. A numerical simulator developed for application to fluid flow problems in fracture networks was used to analyze the results of air-injection tests conducted within the tuff block through 1.25-cm-diameter boreholes. These analyses produced estimates of transmissivity for selected fractures within the block. Transmissivities of other fractures were assigned on the basis of visual similarity to one of the tested fractures. The calibrated model explained 53% of the observed pressure variance at the monitoring boreholes (with the results for six outliers omitted) and 97% of the overall pressure variance (including monitoring and injection boreholes) in the subset of air-injection tests examined.
Numerical simulations unravel the cosmic web.
Faucher-Giguère, Claude-André; Lidz, Adam; Hernquist, Lars
2008-01-04
The universe is permeated by a network of filaments, sheets, and knots collectively forming a "cosmic web." The discovery of the cosmic web, especially through its signature of absorption of light from distant sources by neutral hydrogen in the intervening intergalactic medium, exemplifies the interplay between theory and experiment that drives science and is one of the great examples in which numerical simulations have played a key and decisive role. We recount the milestones in our understanding of cosmic structure; summarize its impact on astronomy, cosmology, and physics; and look ahead by outlining the challenges faced as we prepare to probe the cosmic web at new wavelengths.
Numerical simulations of regolith sampling processes
Schäfer, Christoph M.; Scherrer, Samuel; Buchwald, Robert; Maindl, Thomas I.; Speith, Roland; Kley, Wilhelm
2017-07-01
We present recent improvements in the simulation of regolith sampling processes in microgravity using the numerical particle method smooth particle hydrodynamics (SPH). We use an elastic-plastic soil constitutive model for large deformation and failure flows for dynamical behaviour of regolith. In the context of projected small body (asteroid or small moons) sample return missions, we investigate the efficiency and feasibility of a particular material sampling method: Brushes sweep material from the asteroid's surface into a collecting tray. We analyze the influence of different material parameters of regolith such as cohesion and angle of internal friction on the sampling rate. Furthermore, we study the sampling process in two environments by varying the surface gravity (Earth's and Phobos') and we apply different rotation rates for the brushes. We find good agreement of our sampling simulations on Earth with experiments and provide estimations for the influence of the material properties on the collecting rate.
Energy Technology Data Exchange (ETDEWEB)
Gokaltun, Seckin [Florida International Univ., Miami, FL (United States); Munroe, Norman [Florida International Univ., Miami, FL (United States); Subramaniam, Shankar [Iowa State Univ., Ames, IA (United States)
2014-12-31
This study presents a new drag model, based on the cohesive inter-particle forces, implemented in the MFIX code. This new drag model combines an existing standard model in MFIX with a particle-based drag model based on a switching principle. Switches between the models in the computational domain occur where strong particle-to-particle cohesion potential is detected. Three versions of the new model were obtained by using one standard drag model in each version. Later, performance of each version was compared against available experimental data for a fluidized bed, published in the literature and used extensively by other researchers for validation purposes. In our analysis of the results, we first observed that standard models used in this research were incapable of producing closely matching results. Then, we showed for a simple case that a threshold is needed to be set on the solid volume fraction. This modification was applied to avoid non-physical results for the clustering predictions, when governing equation of the solid granular temperate was solved. Later, we used our hybrid technique and observed the capability of our approach in improving the numerical results significantly; however, improvement of the results depended on the threshold of the cohesive index, which was used in the switching procedure. Our results showed that small values of the threshold for the cohesive index could result in significant reduction of the computational error for all the versions of the proposed drag model. In addition, we redesigned an existing circulating fluidized bed (CFB) test facility in order to create validation cases for clustering regime of Geldart A type particles.
Finsterbusch, Jürgen
2010-12-01
Double- or two-wave-vector diffusion-weighting experiments with short mixing times in which two diffusion-weighting periods are applied in direct succession, are a promising tool to estimate cell sizes in the living tissue. However, the underlying effect, a signal difference between parallel and antiparallel wave vector orientations, is considerably reduced for the long gradient pulses required on whole-body MR systems. Recently, it has been shown that multiple concatenations of the two wave vectors in a single acquisition can double the modulation amplitude if short gradient pulses are used. In this study, numerical simulations of such experiments were performed with parameters achievable with whole-body MR systems. It is shown that the theoretical model yields a good approximation of the signal behavior if an additional term describing free diffusion is included. More importantly, it is demonstrated that the shorter gradient pulses sufficient to achieve the desired diffusion weighting for multiple concatenations, increase the signal modulation considerably, e.g. by a factor of about five for five concatenations. Even at identical echo times, achieved by a shortened diffusion time, a moderate number of concatenations significantly improves the signal modulation. Thus, experiments on whole-body MR systems may benefit from multiple concatenations. Copyright © 2010 Elsevier Inc. All rights reserved.
Numerical aspects of compressible turbulence simulations
Honein, Albert Edward
Nonlinear instabilities present a long standing hurdle for compact, high order, non dissipative, finite difference computation of compressible turbulence. The spectral-like accuracy of these schemes, while attractive, results in significant aliasing errors that corrupt the solution. As a result, successful simulations have been limited to moderate Reynolds numbers ( Re) and low-order or upwind schemes with inherent numerical dissipation. However, resorting to dissipative schemes in discretizing the nonlinear terms was shown to have a detrimental effect on turbulence. A recent LES approach is to abandon the subgrid model altogether and rely on the scheme dissipation to mimic the effect of small scales. A dissipative monotone integrated LES (MILES) algorithm based on a multidimensional flux-corrected transport (FCT) algorithm has been developed and tested for decaying compressible isotropic turbulence. Agreement with the benchmark experiments of Comte-Bellot and Corrsin is very sensitive to the parameters involved in the FCT algorithm, while the evolution of thermodynamic fluctuations do not compare well with direct numerical simulations. An under-resolved simulation of inviscid, compressible, isotropic turbulence at low Mach number is chosen as a severe benchmark to investigate the nonlinear stability properties of nondissipative schemes. The behavior of this benchmark is predicted by performing a fully de-aliased spectral simulation on a 32 3 grid with turbulent Mach number of Mto = 0.07. The kinetic energy and thermodynamic fluctuations are found to decay for finite Re, and remain constant at infinite Re for a long time before the occurrence of numerical shocks. Extending the proof of Kraichnan (Journal of the Acoustical Society of America, 27(3), 1955), this inviscid statistical equilibrium is demonstrated to be a consequence of the discrete equivalent of the Liouville theorem of classical statistical mechanics. Several existing non-dissipative methods are
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 simulations of pulsejet engines
Geng, Tao
The pulsejet has recently received more research interests due to its simple design, which can be developed into low-cost micro-scale propulsion devices for use in many of today's new applications such as UAVs. However, the relatively low thermal efficiency of pulsejets has always been the major obstacle in their development. The goal of this research is to investigate the possibility of using pulsejets in certain applications where the pulsejet can trade its low efficiency with low cost, simple design, and light weight. This work investigates pulsejet operation in a combined experimental and numerical approach, although the focus here is on the computational research. The fluid mechanics, acoustics, and chemical kinetics are studied numerically to understand the physics behind pulsejets and their operations. The research objectives include miniaturization of valveless pulsejets, acoustics model developments for both valved and valveless pulsejets, obtaining preliminary thrust performance data on micro-scale pulsejets, and finally, the formation of the starting vortex ring and its effect on pulsejet thrust.
Numerical Implementation and Computer Simulation of Tracer ...
African Journals Online (AJOL)
, was most dependent on the source definition and the hydraulic conductivity K of the porous medium. The 12000mg/l chloride tracer source was almost completely dispersed within 34 hours. Keywords: Replication, Numerical simulation, ...
Collisionless microinstabilities in stellarators II - numerical simulations
Proll, Josefine Henriette Elise; Helander, Per
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 (NCSX) 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 reduce...
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...
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.
Numerical simulations of dissipationless disk accretion
Bogovalov, S. V.; Tronin, I. V.
2017-09-01
Our goal is to study the regime of disk accretion in which almost all of the angular momentum and energy is carried away by the wind outflowing from the disk in numerical experiments. For this type of accretion the kinetic energy flux in the outflowing wind can exceed considerably the bolometric luminosity of the accretion disk, what is observed in the plasma flow from galactic nuclei in a number of cases. In this paper we consider the nonrelativistic case of an outflow from a cold Keplerian disk. All of the conclusions derived previously for such a system in the self-similar approximation are shown to be correct. The numerical results agree well with the analytical predictions. The inclination angle of the magnetic field lines in the disk is less than 60°, which ensures a free wind outflow from the disk, while the energy flux per wind particle is greater than the particle rotation energy in its Keplerian orbit by several orders of magnitude, provided that the ratio r A/ r ≫ 1, where r A is the Alfvénic radius and r is the radius of the Keplerian orbit. In this case, the particle kinetic energy reaches half the maximum possible energy in the simulation region. The magnetic field collimates the outflowing wind near the rotation axis and decollimates appreciably the wind outflowing from the outer disk periphery.
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.
Boundary acquisition for setup of numerical simulation
Energy Technology Data Exchange (ETDEWEB)
Diegert, C. [Sandia National Lab., Albuquerque, NM (United States)
1997-12-31
The author presents a work flow diagram that includes a path that begins with taking experimental measurements, and ends with obtaining insight from results produced by numerical simulation. Two examples illustrate this path: (1) Three-dimensional imaging measurement at micron scale, using X-ray tomography, provides information on the boundaries of irregularly-shaped alumina oxide particles held in an epoxy matrix. A subsequent numerical simulation predicts the electrical field concentrations that would occur in the observed particle configurations. (2) Three-dimensional imaging measurement at meter scale, again using X-ray tomography, provides information on the boundaries fossilized bone fragments in a Parasaurolophus crest recently discovered in New Mexico. A subsequent numerical simulation predicts acoustic response of the elaborate internal structure of nasal passageways defined by the fossil record. The author must both add value, and must change the format of the three-dimensional imaging measurements before the define the geometric boundary initial conditions for the automatic mesh generation, and subsequent numerical simulation. The author applies a variety of filters and statistical classification algorithms to estimate the extents of the structures relevant to the subsequent numerical simulation, and capture these extents as faceted geometries. The author will describe the particular combination of manual and automatic methods used in the above two examples.
Study of Cardiac Defibrillation Through Numerical Simulations
Bragard, J.; Marin, S.; Cherry, E. M.; Fenton, F. H.
Three-dimensional numerical simulations of the defibrillation problem are presented. In particular, in this study we use the rabbit ventricular geometry as a realistic model system for evaluating the efficacy of defibrillatory shocks. Statistical data obtained from the simulations were analyzed in term of a dose-response curve. Good quantitative agreement between our numerical results and clinically relevant values is obtained. An electric field strength of about 6.6 V/cm indicates a fifty percent probability of successful defibrillation for a 12-ms monophasic shock. Our validated model will be useful for optimizing defibrillation protocols.
Numerical simulation of transverse jet flow field under supersonic inflow
Directory of Open Access Journals (Sweden)
Qian Li
2017-01-01
Full Text Available Transverse jet flow field under supersonic inflow is simulated numerically for studying the characteristic of fuel transverse jet and fuel mixing in scramjet combustion chamber. Comparison is performed between simulated results and the results of references and experiments. Results indicate that the CFD code in this paper is applicable for simulation of transverse jut flow field under supersonic inflow, but in order to providing more effective numerical predictive method, CFD code should be modified through increasing mesh density and adding LES module.
Directory of Open Access Journals (Sweden)
Himr D.
2013-04-01
Full Text Available Article describes simulation of unsteady flow during water hammer with two programs, which use different numerical approaches to solve ordinary one dimensional differential equations describing the dynamics of hydraulic elements and pipes. First one is Matlab-Simulink-SimHydraulics, which is a commercial software developed to solve the dynamics of general hydraulic systems. It defines them with block elements. The other software is called HYDRA and it is based on the Lax-Wendrff numerical method, which serves as a tool to solve the momentum and continuity equations. This program was developed in Matlab by Brno University of Technology. Experimental measurements were performed on a simple test rig, which consists of an elastic pipe with strong damping connecting two reservoirs. Water hammer is induced with fast closing the valve. Physical properties of liquid and pipe elasticity parameters were considered in both simulations, which are in very good agreement and differences in comparison with experimental data are minimal.
Numerical Simulation of SLD Ice Accretions
Hospers, Jacco; Hoeijmakers, Hendrik Willem Marie
2011-01-01
In this study, computational methods are presented that compute ice accretion on multiple-element airfoils in specified icing conditions. The ¿Droplerian¿ numerical simulation method used is based on an Eulerian method for predicting droplet trajectories and the resulting droplet catching efficiency
Numerical Simulations of a Vibrating Elasticum
DEFF Research Database (Denmark)
Sinclair, Robert
1999-01-01
Two robust numerical algorithms for simulating the dynamics of a clamped, massless, incompressibleelasticum with a unit point mass at the free end are presented, along with some first results concerning various modes of oscillation, and further data with some relevance to the question of whether...
Direct numerical simulations of aeolian sand ripples
Durán, Orencio; Claudin, Philippe; Andreotti, Bruno
2014-01-01
Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873
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 ...
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...
Numerical simulations of flux flow in stacked Josephson junctions
DEFF Research Database (Denmark)
Madsen, Søren Peder; Pedersen, Niels Falsig
2005-01-01
We numerically investigate Josephson vortex flux flow states in stacked Josephson junctions, motivated by recent experiments trying to observe the vortices in a square vortex lattice when a magnetic field is applied to layered high-Tc superconductors of the Bi2Sr2CaCu2Ox type. By extensive...... numerical simulations, we are able to clearly distinguish between triangular and square vortex lattices and to identify the parameters leading to an in-phase vortex configuration....
Numerical Simulation of Piston Ring Lubrication
DEFF Research Database (Denmark)
Felter, Christian Lotz
2006-01-01
is extended to include also the oil film outside the piston rings. The numerical model consists of a 2D free surface code that solves the time dependent compressible Navier-Stokes equations. The equations are cast in Lagrangian form and discretized by a meshfree moving least squares method using the primitive...... and the angle between the normals of the solid and the free surface. The numerical model is compared with the results from an analytical solution of Reynolds equation for a fixed incline slider bearing. Then results from a more compli- cated simulation of piston ring lubrication is given and discussed....
High Rayleigh number convection numerical experiments
Verzicco, Roberto
2002-03-01
Numerical experiments on the flow developing in a cylindrical cell of aspect ratio Γ = 1/2 heated from below and cooled from above, are conducted for Rayleigh numbers (Ra) ranging from 2 x 10^6 up to 2 x 10^11. The aim of the present study is to numerically replicate the experiments by Roche et al. (2001) and Niemela et al. (2000) performed using gaseous helium close to the critical point as working fluid (Pr = 0.7). The numerical simulation permitted us to generate a large data base which was validated by the experimental results and, on the other hand, provided physical insights which are missed by the experimental approaches usually limited to pointwise temperature and global heat exchange measurements. Attention is focussed on the presence of large-scale structures whose characterization is important owing to the introduction of constant `winds' sweeping the plates and generating viscous and thermal boundary layers. The analysis of instantaneous snapshots clearly indicates that the topology of the recirculating large scale structures is quite different with respect to what is commonly observed in Γ = 1 cells where a unique large scale recirculation structure completely fills the fluid volume (e.g. Verzicco & Camussi, 1999). It is shown that a transition occurs at about Ra = 10^9; at lower Ra the flow is characterized by the presence of two counter-rotating toroidal rings attached to the horizontal plates. At larger Ra, in contrast, the most intense structure consists of two counter-rotating rolls of unitary aspect ratio. The two types of flow, which co-exists in the range 10^9 thermal and the viscous boundary layers. Indeed, even if the limited range of Ra analyzed in the present simulation does not allow the presence of a transition to be clearly observed in the Nu vs Ra diagram, the proposed scenario is confirmed by the direct analysis of the boundary layer thicknesses and of the kinetic energy and temperature variance dissipations. The achieved results
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.
Issues in Numerical Simulation of Fire Suppression
Energy Technology Data Exchange (ETDEWEB)
Tieszen, S.R.; Lopez, A.R.
1999-04-12
This paper outlines general physical and computational issues associated with performing numerical simulation of fire suppression. Fire suppression encompasses a broad range of chemistry and physics over a large range of time and length scales. The authors discuss the dominant physical/chemical processes important to fire suppression that must be captured by a fire suppression model to be of engineering usefulness. First-principles solutions are not possible due to computational limitations, even with the new generation of tera-flop computers. A basic strategy combining computational fluid dynamics (CFD) simulation techniques with sub-grid model approximations for processes that have length scales unresolvable by gridding is presented.
Numerical simulation of orbiting black holes.
Brügmann, Bernd; Tichy, Wolfgang; Jansen, Nina
2004-05-28
We present numerical simulations of binary black hole systems which for the first time last for about one orbital period for close but still separate black holes as indicated by the absence of a common apparent horizon. An important part of the method is the construction of comoving coordinates, in which both the angular and the radial motion are minimized through a dynamically adjusted shift condition. We use fixed mesh refinement for computational efficiency.
Energy Technology Data Exchange (ETDEWEB)
Tsuboi, N. [Tokyo Univ. (Japan)] Hayashi, K. [Aoyama Gakuin Univ., Tokyo (Japan)] Fujiwara, T. [Nagoya Univ. (Japan)] Arashi, K. [Kumamoto Inst. of Tech., Kumamoto (Japan); Kodama, M. [Mitsubishi Heavy Industries Ltd., Tokyo (Japan)
1998-09-05
A large-sized rocket, such as the H-II rocket used in recent years ejects a high-temperature high-pressure jet from the jet nozzle of the rocket to obtain a required level of thrust at the launching. Therefore, the protection of objects such as the rocket body, reflectors and the launcher against the high-temperature high-pressure jet is a problem. In this study, the clarification of the physical phenomenon is attempted by both numerical analysis and experiments in regard to the problem of the impingement of the axisymmetric supersonic jet upon the plate under the atmospheric and non-high-temperature underexpansion conditions. In this report, and analysis of a non-viscous flow which was made so as to examine the effect of the compressibility of a shock wave structure is described. Experiments were then conducted so as to qualitatively and quantitatively examine the results of the numerical analysis. A stagnation bubble forming and breaking mechanism and a complicated structure of the shock-shock interaction were then studied by a numerical analysis by changing the position of the plate. 14 refs., 20 figs., 2 tabs.
2001 Numerical Propulsion System Simulation Review
Lytle, John; Follen, Gregory; Naiman, Cynthia; Veres, Joseph; Owen, Karl; Lopez, Isaac
2002-01-01
The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective, high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. Major accomplishments include the first formal release of the NPSS object-oriented architecture (NPSS Version 1) and the demonstration of a one order of magnitude reduction in computing cost-to-performance ratio using a cluster of personal computers. The paper also describes the future NPSS milestones, which include the simulation of space transportation propulsion systems in response to increased emphasis on safe, low cost access to space within NASA's Aerospace Technology Enterprise. In addition, the paper contains a summary of the feedback received from industry partners on the fiscal year 2000 effort and the actions taken over the past year to
2000 Numerical Propulsion System Simulation Review
Lytle, John; Follen, Greg; Naiman, Cynthia; Veres, Joseph; Owen, Karl; Lopez, Isaac
2001-01-01
The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia, and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective. high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. Major accomplishments include the first formal release of the NPSS object-oriented architecture (NPSS Version 1) and the demonstration of a one order of magnitude reduction in computing cost-to-performance ratio using a cluster of personal computers. The paper also describes the future NPSS milestones, which include the simulation of space transportation propulsion systems in response to increased emphasis on safe, low cost access to space within NASA'S Aerospace Technology Enterprise. In addition, the paper contains a summary of the feedback received from industry partners on the fiscal year 1999 effort and the actions taken over the past year to
Numerical simulation of a natural circulation loop
Energy Technology Data Exchange (ETDEWEB)
Verissimo, Gabriel L.; Moreira, Maria de Lourdes; Faccini, Jose Luiz H., E-mail: gabrielverissimo@poli.ufrj.b, E-mail: malu@ien.gov.b, E-mail: faccini@ien.gov.b [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)
2011-07-01
This work presents a numerical simulation of a natural circulation loop using computational fluid dynamics. The simulated loop is an experimental model in a reduced scale of 1:10 of a passive heat removal system typical of advanced PWR reactors. The loop is composed of a heating vessel containing 52 electric heaters, a vertical shell-tube heat exchanger and a column of expansion. The working fluid is distilled water. Initially it was created a tridimensional geometric model of the loop components. After that, it was generated a tridimensional mesh of finite elements in order to calculate the variables of the problem. The boundaries of the numerical simulation were the power of the electric resistances and the cooling flow in the secondary side of the heat exchanger. The initial conditions were the temperature, the pressure and the fluid velocity at the time just before the power has been switched on. The results of this simulation were compared with the experimental data, in terms of the evolution of the temperatures in different locations of the loop, and of the average natural circulation flow as a function of time for a given power. (author)
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.
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 Solidification Microstructure based on Adaptive Octree Grids
Directory of Open Access Journals (Sweden)
Yin Y.
2016-06-01
Full Text Available The main work of this paper focuses on the simulation of binary alloy solidification using the phase field model and adaptive octree grids. Ni-Cu binary alloy is used as an example in this paper to do research on the numerical simulation of isothermal solidification of binary alloy. Firstly, the WBM model, numerical issues and adaptive octree grids have been explained. Secondary, the numerical simulation results of three dimensional morphology of the equiaxed grain and concentration variations are given, taking the efficiency advantage of the adaptive octree grids. The microsegregation of binary alloy has been analysed emphatically. Then, numerical simulation results of the influence of thermophysical parameters on the growth of the equiaxed grain are also given. At last, a simulation experiment of large scale and long-time has been carried out. It is found that increases of initial temperature and initial concentration will make grain grow along certain directions and adaptive octree grids can effectively be used in simulations of microstructure.
Seafloor weathering buffering climate: numerical experiments
Farahat, N. X.; Archer, D. E.; Abbot, D. S.
2013-12-01
Continental silicate weathering is widely held to consume atmospheric CO2 at a rate controlled in part by temperature, resulting in a climate-weathering feedback [Walker et al., 1981]. It has been suggested that weathering of oceanic crust of warm mid-ocean ridge flanks also has a CO2 uptake rate that is controlled by climate [Sleep and Zahnle, 2001; Brady and Gislason, 1997]. Although this effect might not be significant on present-day Earth [Caldeira, 1995], seafloor weathering may be more pronounced during snowball states [Le Hir et al., 2008], during the Archean when seafloor spreading rates were faster [Sleep and Zahnle, 2001], and on waterworld planets [Abbot et al., 2012]. Previous studies of seafloor weathering have made significant contributions using qualitative, generally one-box, models, and the logical next step is to extend this work using a spatially resolved model. For example, experiments demonstrate that seafloor weathering reactions are temperature dependent, but it is not clear whether the deep ocean temperature affects the temperature at which the reactions occur, or if instead this temperature is set only by geothermal processes. Our goal is to develop a 2-D numerical model that can simulate hydrothermal circulation and resulting alteration of oceanic basalts, and can therefore address such questions. A model of diffusive and convective heat transfer in fluid-saturated porous media simulates hydrothermal circulation through porous oceanic basalt. Unsteady natural convection is solved for using a Darcy model of porous media flow that has been extensively benchmarked. Background hydrothermal circulation is coupled to mineral reaction kinetics of basaltic alteration and hydrothermal mineral precipitation. In order to quantify seafloor weathering as a climate-weathering feedback process, this model focuses on hydrothermal reactions that influence carbon uptake as well as ocean alkalinity: silicate rock dissolution, calcium and magnesium leaching
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...... 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....
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......, compressible flow in one space dimension is presented. The implementation produces models where all the equations, which are on a form that should be understandable to someone with a background in engineering thermodynamics, can be accessed and modified individually. The implementation was designed to make...
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 flow through biofluid devices
Energy Technology Data Exchange (ETDEWEB)
Rogers, S.E.; Kwak, D. (NASA Ames Research Center, Moffett Field, CA (US)); Kiris, C.; Chang, I.D. (Stanford Univ., Stanford, CA (US))
1990-01-01
The results of a numerical simulation on a Cray-2 supercomputer of flow through an artificial heart and through an artificial tilting-disk heart valve are presented. The simulation involves solving the incompressible Navier-Stokes equations; the solution process is described. The details and difficulties of modeling these particular geometries are discussed. The artificial heart geometry uses a single moving grid, and the valve computation uses an overlaid-grid approach with one moving grid and one stationary grid. The equations must be solved iteratively for each discrete time step of the computations, requiring a significant amount of computing time. It is particularly difficult to analyze and present the fluid physics represented by these calculations because of the time-varying nature of the flow, and because the flows are internal. The use of three-dimensional graphics and scientific visualization techniques have become instrumental in solving these problems.
Direct Numerical Simulations of Transient Dispersion
Porter, M.; Valdes-Parada, F.; Wood, B.
2008-12-01
Transient dispersion is important in many engineering applications, including transport in porous media. A common theoretical approach involves upscaling the micro-scale mass balance equations for convection- diffusion to macro-scale equations that contain effective medium quantities. However, there are a number of assumptions implicit in the various upscaling methods. For example, results obtained from volume averaging are often dependent on a given set of length and time scale constraints. Additionally, a number of the classical models for dispersion do not fully capture the early-time dispersive behavior of the solute for a general set of initial conditions. In this work, we present direct numerical simulations of micro-scale transient mass balance equations for convection-diffusion in both capillary tubes and porous media. Special attention is paid to analysis of the influence of a new time- decaying coefficient that filters the effects of the initial conditions. The direct numerical simulations were compared to results obtained from solving the closure problem associated with volume averaging. These comparisons provide a quantitative measure of the significance of (1) the assumptions implicit in the volume averaging method and (2) the importance of the early-time dispersive behavior of the solute due to various initial conditions.
Directory of Open Access Journals (Sweden)
Dańko R.
2015-12-01
Full Text Available Experiments of filling the model moulds cavity of various inner shapes inserted in rectangular cavity of the casting die (dimensions: 280 mm (height × 190 mm (width × 10 mm (depth by applying model liquids of various density and viscosity are presented in the paper. Influence of die venting as well as inlet system area and inlet velocity on the volumetric rate of filling of the model liquid - achieved by means of filming the process in the system of a cold-chamber casting die was tested. Experiments compared with the results of simulation performed by means of the calculation module Novacast (Novaflow&Solid for the selected various casting conditions - are also presented in the paper.
Direct numerical simulation of dynamo transition for nonhelical MHD
Energy Technology Data Exchange (ETDEWEB)
Nath, Dinesh; Verma, Mahendra K [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Lessinnes, Thomas; Carati, Daniele [Physique Statistique et Plasmas, Universite Libre de Bruxellers, B-1050 Bruxelles (Belgium); Sarris, Ioannis [Department of Mechanical and Industrial Engineering, University of Thessaly, Volos (Greece)
2010-02-01
Pseudospectral Direct Numerical Simulation (DNS) has been performed to simulate dynamo transition for nonhelical magnetohydrodynamics turbulence. The numerical results are compared with a recent low-dimensional model [Verma et al. [13
Mechanical Contact Experiments and Simulations
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Martins, P; Zhang, W.
2011-01-01
Mechanical contact is studied under dynamic development by means of a combined numerical and experimental investigation. The experiments are designed to allow dynamical development of non-planar contact areas with significant expansion in all three directions as the load is increased. Different....... The overall investigation serves for testing and validating the numerical implementation of the mechanical contact, which is one of the main contributions to a system intended for 3D simulation of resistance welding. Correct modelling of contact between parts to be welded, as well as contact with electrodes......, is crucial for satisfactory modelling of the resistance welding process. The resistance heating at the contact interfaces depends on both contact area and pressure, and as the contact areas develop dynamically, the presented tests are relevant for assessing the validity and accuracy of the mechanical contact...
Numerical experiments on unstructured PIC stability.
Energy Technology Data Exchange (ETDEWEB)
Day, David Minot
2011-04-01
Particle-In-Cell (PIC) is a method for plasmas simulation. Particles are pushed with Verlet time integration. Fields are modeled using finite differences on a tensor product mesh (cells). The Unstructured PIC methods studied here use instead finite element discretizations on unstructured (simplicial) meshes. PIC is constrained by stability limits (upper bounds) on mesh and time step sizes. Numerical evidence (2D) and analysis will be presented showing that similar bounds constrain unstructured PIC.
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.
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 of electron beam welding and instrumental technique
Energy Technology Data Exchange (ETDEWEB)
Carin, M.; Rogeon, P.; Carron, D.; Le Masson, P.; Couedel, D. [Universite de Bretagne Sud, Centre de Recherche, Lab. d' Etudes Thermiques Energetique et Environnement, 56 - Lorient (France)
2004-07-01
In the present work, thermal cycles measured with thermocouples embedded in specimens are employed to validate a numerical thermo-metallurgical model of an Electron Beam welding process. The implemented instrumentation techniques aim at reducing the perturbations induced by the sensors in place. The numerical model is based on the definition of a heat source term linked to the keyhole geometry predicted by a model of pressure balance using the FEMLAB code. The heat source term is used by the thermo-metallurgical simulation carried out with the finite element code SYSWELD. Kinetics parameters are extracted from dilatometric experiments achieved in welding austenitization conditions at constant cooling rates. (authors)
Numerical simulation of pump-intake vortices
Directory of Open Access Journals (Sweden)
Rudolf Pavel
2015-01-01
Full Text Available Pump pre-swirl or uneven flow distribution in front of the pump can induce pump-intake vortices. These phenomena result in blockage of the impeller suction space, deterioration of efficiency, drop of head curve and earlier onset of cavitation. Real problematic case, where head curve drop was documented, is simulated using commercial CFD software. Computational simulation was carried out for three flow rates, which correspond to three operating regimes of the vertical pump. The domain consists of the pump sump, pump itself excluding the impeller and the delivery pipe. One-phase approach is applied, because the vortex cores were not filled with air during observation of the real pump operation. Numerical simulation identified two surface vortices and one bottom vortex. Their position and strength depend on the pump flow rate. Paper presents detail analysis of the flow field on the pump intake, discusses influence of the vortices on pump operation and suggests possible actions that should be taken to suppress the intake vortices.
Numerical simulation of pump-intake vortices
Rudolf, Pavel; Klas, Roman
2015-05-01
Pump pre-swirl or uneven flow distribution in front of the pump can induce pump-intake vortices. These phenomena result in blockage of the impeller suction space, deterioration of efficiency, drop of head curve and earlier onset of cavitation. Real problematic case, where head curve drop was documented, is simulated using commercial CFD software. Computational simulation was carried out for three flow rates, which correspond to three operating regimes of the vertical pump. The domain consists of the pump sump, pump itself excluding the impeller and the delivery pipe. One-phase approach is applied, because the vortex cores were not filled with air during observation of the real pump operation. Numerical simulation identified two surface vortices and one bottom vortex. Their position and strength depend on the pump flow rate. Paper presents detail analysis of the flow field on the pump intake, discusses influence of the vortices on pump operation and suggests possible actions that should be taken to suppress the intake vortices.
Direct numerical simulation of human phonation
Saurabh, Shakti; Bodony, Daniel
2016-11-01
A direct numerical simulation study of the generation and propagation of the human voice in a full-body domain is conducted. A fully compressible fluid flow model, anatomically representative vocal tract geometry, finite deformation model for vocal fold (VF) motion and a fully coupled fluid-structure interaction model are employed. The dynamics of the multi-layered VF tissue with varying stiffness are solved using 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 new inflow boundary condition, based upon a quasi-1D formulation with constant sub-glottal volume velocity, linked to the VF movement, has been adopted. Simulations for both child and adult phonation were performed. Acoustic characteristics obtained from these simulation are consistent with expected values. A sensitivity analysis based on VF stiffness variation is undertaken and sound pressure level/fundamental frequency trends are established. An evaluation of the data against the commonly-used quasi-1D equations suggest that the latter are not sufficient to model phonation. Phonation threshold pressures are measured for several VF stiffness variations and comparisons to clinical data are carried out. Supported by the National Science Foundation (CAREER Award Number 1150439).
Numerical Propulsion System Simulation: An Overview
Lytle, John K.
2000-01-01
The cost of implementing new technology in aerospace propulsion systems is becoming prohibitively expensive and time consuming. One of the main contributors to the high cost and lengthy time is the need to perform many large-scale hardware tests and the inability to integrate all appropriate subsystems early in the design process. The NASA Glenn Research Center is developing the technologies required to enable simulations of full aerospace propulsion systems in sufficient detail to resolve critical design issues early in the design process before hardware is built. This concept, called the Numerical Propulsion System Simulation (NPSS), is focused on the integration of multiple disciplines such as aerodynamics, structures and heat transfer with computing and communication technologies to capture complex physical processes in a timely and cost-effective manner. The vision for NPSS, as illustrated, is to be a "numerical test cell" that enables full engine simulation overnight on cost-effective computing platforms. There are several key elements within NPSS that are required to achieve this capability: 1) clear data interfaces through the development and/or use of data exchange standards, 2) modular and flexible program construction through the use of object-oriented programming, 3) integrated multiple fidelity analysis (zooming) techniques that capture the appropriate physics at the appropriate fidelity for the engine systems, 4) multidisciplinary coupling techniques and finally 5) high performance parallel and distributed computing. The current state of development in these five area focuses on air breathing gas turbine engines and is reported in this paper. However, many of the technologies are generic and can be readily applied to rocket based systems and combined cycles currently being considered for low-cost access-to-space applications. Recent accomplishments include: (1) the development of an industry-standard engine cycle analysis program and plug 'n play
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.
Automated continuous verification for numerical simulation
Directory of Open Access Journals (Sweden)
P. E. Farrell
2011-05-01
Full Text Available Verification is a process crucially important for the final users of a computational model: code is useless if its results cannot be relied upon. Typically, verification is seen as a discrete event, performed once and for all after development is complete. However, this does not reflect the reality that many geoscientific codes undergo continuous development of the mathematical model, discretisation and software implementation. Therefore, we advocate that in such cases verification must be continuous and happen in parallel with development: the desirability of their automation follows immediately. This paper discusses a framework for automated continuous verification of wide applicability to any kind of numerical simulation. It also documents a range of test cases to show the possibilities of the framework.
Numerical simulation of the pulsed Pirani gauges
Gospodinov, P.; Dankov, D.; Roussinov, V.; Mironova, M.
2017-10-01
The transient heat transfer process is studied in rarefied gas confined between two stationary concentric cylinders. The inner cylinder (filament) is subjected to a periodically heating-cooling cycle. The energy transfer is modeled with a continuous model based on Navier-Stokes-Fourier (NSF) equations of motion and energy transfer and with a statistical Direct Simulation Monte Carlo Method (DSMC). Numerical results for the temperature, thermodynamic pressure and pressure difference between thermodynamic pressure and radial stress tensor component are obtained for different circular frequencies of heating cooling cycle of filament and for different filament radii. The pressure variation at the end of any local heating stage of heating-cooling cycle is close to the value of equilibrium thermodynamic pressure. The results are applicable in designing the pulsed Pirani gauges.
Some Experiences with Numerical Modelling of Overflows
DEFF Research Database (Denmark)
Larsen, Torben; Nielsen, L.; Jensen, B.
2007-01-01
and reliable formulas for the estimation of overflows have been derived. Numerical modelling of overflows is significantly more complicated than standard 1-dimensional river or sewer modelling. The problem is usually managed by incorporating the mentioned empirical formulas in the numerical models......Overflows are commonly applied in storm sewer systems to control flow and water surface level. Therefore overflows play a central role in the control of discharges of pollutants from sewer systems to the environment. The basic hydrodynamic principle of an overflow is the so-called critical flow...... across the edge of the overflow. To ensure critical flow across the edge, the upstream flow must be subcritical whereas the downstream flow is either supercritical or a free jet. Experimentally overflows are well studied. Based on laboratory experiments and Froude number scaling, numerous accurate...
Numerical simulation of turbulent slurry flows
Haghgoo, Mohammad Reza; Spiteri, Reymond J.; Bergstrom, Donlad J.
2016-11-01
Slurry flows, i.e., the flow of an agglomeration of liquid and particles, are widely employed in many industrial applications, such as hydro-transport systems, pharmaceutical batch crystallizers, and wastewater disposal. Although there are numerous studies available in the literature on turbulent gas-particle flows, the hydrodynamics of turbulent liquid-particle flows has received much less attention. In particular, the fluid-phase turbulence modulation due to the particle fluctuating motion is not yet well understood and remains challenging to model. This study reports the results of a numerical simulation of a vertically oriented slurry pipe flow using a two-fluid model based on the kinetic theory of granular flows. The particle stress model also includes the effects of frictional contact. Different turbulence modulation models are considered, and their capability to capture the characteristic features of the turbulent flow is assessed. The model predictions are validated against published experimental data and demonstrate the significant effect of the particles on the fluid-phase turbulence.
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
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).
Numerical simulations of capillary barrier field tests
Energy Technology Data Exchange (ETDEWEB)
Morris, C.E. [Univ. of Wollongong (Australia); Stormont, J.C. [Univ. of New Mexico, Albuquerque, NM (United States)
1997-12-31
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 Simulations of the G Ring Arc
Tiscareno, Matthew S.; Hedman, M. M.; Burns, J. A.; Nicholson, P. D.
2007-07-01
We conducted numerical simulations of 3,830 massless test particles in the Saturn system near the 7:6 corotation eccentricity resonance (CER) with Mimas, in response to the recent observations of an arc in the faint and dusty G Ring (see Hedman et al, this conference). We simulated 80 years of evolution, taking into account the perturbations of Saturn's nine most massive moons, the Sun, Jupiter, and Saturn's J2 and J4 gravity harmonics. Perturber trajectories were obtained at every timestep from JPL ephemera DE414 and SAT252. We find that particles are efficiently trapped into librations about any of the six corotation sites, consistent with the observed arc which extends 30o in longitude. We find forced eccentricities that are consistent with the observed radial width of the arc, and a long libration period (1273 days) which indicates we may have yet to observe the turning point in the arc's libration. The potentially disruptive effects of inter-particle collisions were not taken into account, due to the G Ring's very low optical depth. Leakage out of the resonance is probably dominated instead by non-gravitational forces, which preferentially drive smaller (dust) grains outward, plausibly accounting for the observed radial profile of the G Ring.
High-Order Numerical Simulations of Wind Turbine Wakes
Kleusberg, E.; Mikkelsen, R. F.; Schlatter, P.; Ivanell, S.; Henningson, D. S.
2017-05-01
Previous attempts to describe the structure of wind turbine wakes and their mutual interaction were mostly limited to large-eddy and Reynolds-averaged Navier-Stokes simulations using finite-volume solvers. We employ the higher-order spectral-element code Nek5000 to study the influence of numerical aspects on the prediction of the wind turbine wake structure and the wake interaction between two turbines. The spectral-element method enables an accurate representation of the vortical structures, with lower numerical dissipation than the more commonly used finite-volume codes. The wind-turbine blades are modeled as body forces using the actuator-line method (ACL) in the incompressible Navier-Stokes equations. Both tower and nacelle are represented with appropriate body forces. An inflow boundary condition is used which emulates homogeneous isotropic turbulence of wind-tunnel flows. We validate the implementation with results from experimental campaigns undertaken at the Norwegian University of Science and Technology (NTNU Blind Tests), investigate parametric influences and compare computational aspects with existing numerical simulations. In general the results show good agreement between the experiments and the numerical simulations both for a single-turbine setup as well as a two-turbine setup where the turbines are offset in the spanwise direction. A shift in the wake center caused by the tower wake is detected similar to experiments. The additional velocity deficit caused by the tower agrees well with the experimental data. The wake is captured well by Nek5000 in comparison with experiments both for the single wind turbine and in the two-turbine setup. The blade loading however shows large discrepancies for the high-turbulence, two-turbine case. While the experiments predicted higher thrust for the downstream turbine than for the upstream turbine, the opposite case was observed in Nek5000.
NUMERICAL SIMULATION OF VISCOUS FLOW AROUND A TANKER MODEL
Directory of Open Access Journals (Sweden)
Andrea Farkas
2017-01-01
Full Text Available In this paper, numerical simulation of the viscous flow around a tanker model was carried out utilizing software package STAR-CCM+. A mathematical model based on Reynolds Averaged Navier-Stokes equations, k-ε turbulence model and Volume of Fluid method for describing the motion of two-phase media are given. Necessary boundary conditions for the mathematical model and the method of discretization are described as well. The influence of the grid density on the numerical results for the total resistance of tanker model was investigated using three different grid densities. Two different types of k-ε turbulence model are implemented and the deviations in numerical results are highlighted. Results for total resistance of tanker model, obtained by numerical simulations, were validated against experimental results. Experiments were performed in the towing tank of Brodarski Institut in Zagreb for wide range of Froude numbers. It has been shown that for all three grid densities and both types of k-ε turbulence model satisfactory agreement with experimental results can be achieved for whole range of Froude numbers. The scale effects are investigated by Computational Fluid Dynamics study for the same tanker model in three different scales. Numerically calculated scale effects on the wave resistance are reviewed.
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.
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.
Direct numerical simulation of the dynamics of sliding rough surfaces
Dang, Viet Hung; Scheibert, Julien; Bot, Alain Le
2013-01-01
The noise generated by the friction of two rough surfaces under weak contact pressure is usually called roughness noise. The underlying vibration which produces the noise stems from numerous instantaneous shocks (in the microsecond range) between surface micro-asperities. The numerical simulation of this problem using classical mechanics requires a fine discretization in both space and time. This is why the finite element method takes much CPU time. In this study, we propose an alternative numerical approach which is based on a truncated modal decomposition of the vibration, a central difference integration scheme and two algorithms for contact: The penalty algorithm and the Lagrange multiplier algorithm. Not only does it reproduce the empirical laws of vibration level versus roughness and sliding speed found experimentally but it also provides the statistical properties of local events which are not accessible by experiment. The CPU time reduction is typically a factor of 10.
Swanson, Ryan David
The advection-dispersion equation (ADE) fails to describe non-Fickian solute transport breakthrough curves (BTCs) in saturated porous media in both laboratory and field experiments, necessitating the use of other models. The dual-domain mass transfer (DDMT) model partitions the total porosity into mobile and less-mobile domains with an exchange of mass between the two domains, and this model can reproduce better fits to BTCs in many systems than ADE-based models. However, direct experimental estimation of DDMT model parameters remains elusive and model parameters are often calculated a posteriori by an optimization procedure. Here, we investigate the use of geophysical tools (direct-current resistivity, nuclear magnetic resonance, and complex conductivity) to estimate these model parameters directly. We use two different samples of the zeolite clinoptilolite, a material shown to demonstrate solute mass transfer due to a significant internal porosity, and provide the first evidence that direct-current electrical methods can track solute movement into and out of a less-mobile pore space in controlled laboratory experiments. We quantify the effects of assuming single-rate DDMT for multirate mass transfer systems. We analyze pore structures using material characterization methods (mercury porosimetry, scanning electron microscopy, and X-ray computer tomography), and compare these observations to geophysical measurements. Nuclear magnetic resonance in conjunction with direct-current resistivity measurements can constrain mobile and less-mobile porosities, but complex conductivity may have little value in relation to mass transfer despite the hypothesis that mass transfer and complex conductivity lengths scales are related. Finally, we conduct a geoelectrical monitored tracer test at the Macrodispersion Experiment (MADE) site in Columbus, MS. We relate hydraulic and electrical conductivity measurements to generate a 3D hydraulic conductivity field, and compare to
Numerical simulation of condensation on structured surfaces.
Fu, Xiaowu; Yao, Zhaohui; Hao, Pengfei
2014-11-25
Condensation of liquid droplets on solid surfaces happens widely in nature and industrial processes. This phase-change phenomenon has great effect on the performance of some microfluidic devices. On the basis of micro- and nanotechnology, superhydrophobic structured surfaces can be well-fabricated. In this work, the nucleating and growth of droplets on different structured surfaces are investigated numerically. The dynamic behavior of droplets during the condensation is simulated by the multiphase lattice Boltzmann method (LBM), which has the ability to incorporate the microscopic interactions, including fluid-fluid interaction and fluid-surface interaction. The results by the LBM show that, besides the chemical properties of surfaces, the topography of structures on solid surfaces influences the condensation process. For superhydrophobic surfaces, the spacing and height of microridges have significant influence on the nucleation sites. This mechanism provides an effective way for prevention of wetting on surfaces in engineering applications. Moreover, it suggests a way to prevent ice formation on surfaces caused by the condensation of subcooled water. For hydrophilic surfaces, however, microstructures may be submerged by the liquid films adhering to the surfaces. In this case, microstructures will fail to control the condensation process. Our research provides an optimized way for designing surfaces for condensation in engineering systems.
Proton decay: Numerical simulations confront grand unification
Energy Technology Data Exchange (ETDEWEB)
Brower, R.C.; Maturana, G.; Giles, R.C.; Moriarty, K.J.M.; Samuel, S.
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.).
Direct Numerical Simulation of Cell Printing
Qiao, Rui; He, Ping
2010-11-01
Structural cell printing, i.e., printing three dimensional (3D) structures of cells held in a tissue matrix, is gaining significant attention in the biomedical community. The key idea is to use desktop printer or similar devices to print cells into 3D patterns with a resolution comparable to the size of mammalian cells, similar to that in living organs. Achieving such a resolution in vitro can lead to breakthroughs in areas such as organ transplantation and understanding of cell-cell interactions in truly 3D spaces. Although the feasibility of cell printing has been demonstrated in the recent years, the printing resolution and cell viability remain to be improved. In this work, we investigate one of the unit operations in cell printing, namely, the impact of a cell-laden droplet into a pool of highly viscous liquids using direct numerical simulations. The dynamics of droplet impact (e.g., crater formation and droplet spreading and penetration) and the evolution of cell shape and internal stress are quantified in details.
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.
Numerical simulation and optimization of casting process for complex pump
Liu, Xueqin; Dong, Anping; Wang, Donghong; Lu, Yanling; Zhu, Guoliang
2017-09-01
The complex shape of the casting pump body has large complicated structure and uniform wall thickness, which easy give rise to casting defects. The numerical simulation software ProCAST is used to simulate the initial top gating process, after analysis of the material and structure characteristics of the high-pressure pump. The filling process was overall smooth, not there the water shortage phenomenon. But the circular shrinkage defects appear at the bottom of casting during solidification process. Then, the casting parameters were optimized and adding cold iron in the bottom. The shrinkage weight was reduced from 0.00167g to 0.0005g. The porosity volume was reduced from 1.39cm3 to 0.41cm3. The optimization scheme is simulated and actual experimented. The defect has been significantly improved.
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 ...
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 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
Energy Technology Data Exchange (ETDEWEB)
1993-08-01
This report discusses research in High Energy Physics at Florida State University. Contained in this paper are: highlights of activities during the past few years; five year summary; fixed target experiments; collider experiments; SSC preparation, detector development and detector construction; computing, networking and VAX upgrade to ALPHA; and particle theory programs.
Numerical simulation of convective boundary layer above polynyas and leads.
Debolskiy, Andrey; Stepanenko, Victor
2013-04-01
Arctic region is very important as one of drivers for global atmosphere circulation. Meanwhile, results of modern global atmospheric models, both climatic and weather forecasting differs significantly from each other and observations in this region. One of the reasons for these uncertainties can be inaccurate simulation of ice and snow cover distribution, which accuracy depends in turn on variety of factors. Among others, appropriate parameterizations of atmospheric boundary layer over inhomogeneous surface, not explicitly resolved at the atmospheric model grid, can decrease these inaccuracies. The main objective of these parameterizations is to calculate surface heat and water vapor fluxes, averaged over the whole model cell. However, due to great differences in structure of boundary layers formed over cold ice and relatively warm open water, which cause nonlinear dependencies,the parameterizations suggested to the moment can hardly be regarded as applicable for "complete" set of synoptic scenarios . The present paper attempts to improve standard mosaic method of flux aggregation, which is still common in climate models [1]. The main idea is to derive heat fluxes using data from numerical experiments, explicitly reproducing most of sub grid (for global models) turbulence motions spectra, and compare with fluxes calculated using mosaic method implying the part of model domain to be a global model cell. The study is based on idealized high resolution (~10 m) experiments with typically observed surface parameters (temperature and roughness), ice-open water distribution, initial temperature and wind profiles distribution included in Large Eddy Simulation model of Insitute of Numerical Mathematics RAS [2],[3]. Analysis of other boundary layer characteristics such as its height, eddy diffusivity profiles, kinetic energy is presented. The modeling results are compared with field experiments' data gathered at White Sea. References: 1. V.M. Stepanenko, P.M. Miranda, V
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 Simulations of the Flame of a Single Coaxial Injector
Directory of Open Access Journals (Sweden)
Victor P. Zhukov
2017-01-01
Full Text Available The processes of mixing and combustion in the jet of a shear-coaxial injector are investigated. Two test cases (nonreacting and reacting are simulated using the commercial computational fluid dynamics code ANSYS CFX. The first test case is an experiment on the mixing in a nonreacting coaxial jet carried out with the use of planar laser induced fluorescence (PLIF. The second test case is an experiment on the visualization of hydrogen-oxygen flame using PLIF of OH in a single injector combustion chamber at pressure of 53 bar. In the first test case, the two-dimensional axisymmetric simulations are performed using the shear-stress turbulence (SST model. Due to the dominant flow unsteadiness in the second test case, the turbulence is modeled using transient SAS (Scale-Adaptive Simulation model. The combustion is modeled using the burning velocity model (BVM while both two- and three-dimensional simulations are carried out. The numerical model agrees with the experimental data very well in the first test case and adequately in the second test case.
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...
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.
Optimal Taylor-Couette flow: direct numerical simulations
Mónico, Rodolfo Ostilla; Grossman, Siegfried; Verzicco, Roberto; Lohse, Detlef
2013-01-01
We numerically simulate turbulent Taylor-Couette flow for independently rotating inner and outer cylinders, focusing on the analogy with turbulent Rayleigh-B\\'enard flow. Reynolds numbers of Re_i = 8\\times10^3 and Re_o =\\pm4\\times10^3 of the inner and outer cylinders, respectively, are reached, corresponding to Taylor numbers Ta up to 10^8 . Effective scaling laws for the torque and other system responses are found. Recent experiments with the Twente turbulent Taylor-Couette (T^3C) setup at very high Reynolds numbers have vealed an optimum transport at a certain non-zero rotation rate ratio a = -{\\omega}_o/{\\omega}_i that depends on Ta. For large enough Ta in the numerically accessible range we find such an optimum at non-zero counter-rotation also in the numerics. We furthermore numerically calculate the corresponding angular velocity profiles and visualize the different flow structures for the various regimes. By writing the equations in a frame co-rotating with the outer cylinder a link is found between th...
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 free water surface in pump intake
Zhao, L. J.; Nohmi, M.
2012-11-01
The purpose of this paper is to verify the volume of fluid (VOF) method for simulating the free water surface flow in pump intake. With the increasing computer power, VOF method has been becoming a more flexible and accurate choice to replace the conventional fixed water surface method, because it does not require assumptions on the nature of air-water interface. Two examples are presented in this paper. The first example is presented for simulating the growth of air-entrained vortices. LES (Large Eddy Simulation) model, instead of RANS (Reynolds averaged Navier-Stokes) turbulence model, is used to capture the peak of circular velocity around the vortex core. Numerical result shows good agreement with the benchmark experiment carried by the Turbomachinery Society of Japan. The second example predicts the flow rate distribution in the pump intake consisting of one opened and two closed channels. VOF result is compared with the conventional fixed water surface method assuming free-slip boundary condition on the fluid interface. The difference of flow pattern in the opened channel indicates that numerical flow field is affected remarkably by the setup of boundary condition at air-water interface.
Bridging experiments, models and simulations
DEFF Research Database (Denmark)
Carusi, Annamaria; Burrage, Kevin; Rodríguez, Blanca
2012-01-01
electrophysiology. Our analysis reveals that models, simulations, and experiments are intertwined, in an assemblage that is a system itself, namely the model-simulation-experiment (MSE) system. We argue that validation is part of the whole MSE system and is contingent upon 1) understanding and coping with sources...
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.
Unsteady numerical simulations of the stability and dynamics of flames
Kailasanath, K.; Patnaik, G.; Oran, E. S.
1995-01-01
In this report we describe the research performed at the Naval Research Laboratory in support of the NASA Microgravity Science and Applications Program over the past three years (from Feb. 1992) with emphasis on the work performed since the last microgravity combustion workshop. The primary objective of our research is to develop an understanding of the differences in the structure, stability, dynamics and extinction of flames in earth gravity and in microgravity environments. Numerical simulations, in which the various physical and chemical processes can be independently controlled, can significantly advance our understanding of these differences. Therefore, our approach is to use detailed time-dependent, multi-dimensional, multispecies numerical models to perform carefully designed computational experiments. The basic issues we have addressed, a general description of the numerical approach, and a summary of the results are described in this report. More detailed discussions are available in the papers published which are referenced herein. Some of the basic issues we have addressed recently are (1) the relative importance of wall losses and gravity on the extinguishment of downward-propagating flames; (2) the role of hydrodynamic instabilities in the formation of cellular flames; (3) effects of gravity on burner-stabilized flames, and (4) effects of radiative losses and chemical-kinetics on flames near flammability limits. We have also expanded our efforts to include hydrocarbon flames in addition to hydrogen flames and to perform simulations in support of other on-going efforts in the microgravity combustion sciences program. Modeling hydrocarbon flames typically involves a larger number of species and a much larger number of reactions when compared to hydrogen. In addition, more complex radiation models may also be needed. In order to efficiently compute such complex flames recent developments in parallel computing have been utilized to develop a state
Numerical Simulation of Tyre/Road Noise
Schutte, J.H.
2011-01-01
In modern society, traffic noise has become an important issue for mental health. A significant contributor to this noise pollution is exterior tyre/road noise, which is caused by the interaction between tyre and road surface and. In order to reduce tyre/road noise at the source, accurate numerical
Numerical simulation of the hepatic circulation
Van Der Plaats, A; 'tHart, NA; Verkerke, GJ; Leuvenink, HGD; Verdonck, P; Ploeg, RJ; Rakhorst, G
Availability of donor livers and the relatively short preservation time limit the success of liver transplantation. The use of hypothermic machine perfusion could pave the way for expansion of the donor pool. To better define optimal settings of such a device, the feasibility of using a numerical
Numerical Flow Simulation for Complete Vehicle Configurations
1993-09-01
Conference of Numerical Grid Generation in Computational Fluid Dynamics, Barcelona, Spain, June 1991, edited by A. S. Arcilla , J. Hauser, P. R... Arcilla , J. Hauser, P. R. Eiseman and J. F. Thompson, North Holland, p. 143, 1991. 61. Weathenll, N. P., "Mixed Structured-Unstructured Meshes for
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 then was ca...... then was captured using scanning transmission electron microscopy (STEM) and the obtained dark field images are used to set up COMSOL simulations corresponding to actual structures....
Numerical Simulation of Oil Spill in Ocean
Directory of Open Access Journals (Sweden)
Yong-Sik Cho
2012-01-01
Full Text Available The spreading of oil in an open ocean may cause serious damage to a marine environmental system. Thus, an accurate prediction of oil spill is very important to minimize coastal damage due to unexpected oil spill accident. The movement of oil may be represented with a numerical model that solves an advection-diffusion-reaction equation with a proper numerical scheme. In this study, the spilled oil dispersion model has been established in consideration of tide and tidal currents simultaneously. The velocity components in the advection-diffusion-reaction equation are obtained from the shallow-water equations. The accuracy of the model is verified by applying it to a simple but significant problem. The results produced by the model agree with corresponding analytical solutions and field-observed data. The model is then applied to predict the spreading of an oil spill in a real coastal environment.
Numerical simulation of magmatic hydrothermal systems
Ingebritsen, S.E.; Geiger, S.; Hurwitz, S.; Driesner, T.
2010-01-01
The dynamic behavior of magmatic hydrothermal systems entails coupled and nonlinear multiphase flow, heat and solute transport, and deformation in highly heterogeneous media. Thus, quantitative analysis of these systems depends mainly on numerical solution of coupled partial differential equations and complementary equations of state (EOS). The past 2 decades have seen steady growth of computational power and the development of numerical models that have eliminated or minimized the need for various simplifying assumptions. Considerable heuristic insight has been gained from process-oriented numerical modeling. Recent modeling efforts employing relatively complete EOS and accurate transport calculations have revealed dynamic behavior that was damped by linearized, less accurate models, including fluid property control of hydrothermal plume temperatures and three-dimensional geometries. Other recent modeling results have further elucidated the controlling role of permeability structure and revealed the potential for significant hydrothermally driven deformation. Key areas for future reSearch include incorporation of accurate EOS for the complete H2O-NaCl-CO2 system, more realistic treatment of material heterogeneity in space and time, realistic description of large-scale relative permeability behavior, and intercode benchmarking comparisons. Copyright 2010 by the American Geophysical Union.
Numerical simulation of controlled large space structures
Quan, Ralph
1989-01-01
Large Space Structures do not have much damping, which necessitates the installation of a controller onto the structure. If the controller is improperly designed, the structure may become unstable and be destroyed. Since Large Space Structures are extremely expensive pieces of hardware, new controllers must not be tested first on the structure. They must first be tested in computer simulations. Until now, the usual procedure for simulating controlled Large Space Structures is to compute a reduced order modal representation of the structure and then apply the controller. However, this procedure entails modal truncation error. A new software package which is free from this error is currently under development within the Center for Space Construction. The more accurate finite element representation of the structure is used in the simulation, instead of the less accurate reduced order modal representation. This software also features an efficient matrix storage scheme, which effectively deals with the asymmetric system matrices which occur when control is added to the structure. Also, an integration algorithm was chosen so that the simulation is a reliable indicator of system stability or instability. The software package is fairly general in nature. Linearity of the finite element model and of the controller is the only assumption made. Actuator dynamics, sensor dynamics, noise, and disturbances can be handled by the package. In addition, output feedback of displacement, velocity, and/or acceleration signals can be simulated. Kalman state estimation was also implemented. This software was tested on a finite element model of a real Large Space Structure: The Mini-Mast Truss. Mini-Mast is a testbed at NASA-Langley which is currently under development. A 714 degree of freedom finite element model was computed, and a 19 state controller was designed for it. Torque wheel dynamics were added to the model, and the entire closed loop system was simulated with the software
Numerical simulations of NASA research instrumentation in hurricane environments
Albers, Cerese M.
Tropical cyclone intensity prediction is an issue at the forefront of mesoscale numerical weather prediction efforts because it is an area where historically there have been only small improvements, and yet much more progress is needed to improve advance warnings for land- falling tropical cyclones (TCs). In recent years, research instrumentation has been developed for deployment aboard aircraft that remotely study tropical cyclones in order to answer critical intensity questions about TCs. One such instrument is the NASA Hurricane Imaging Radiometer (HIRAD) that has been developed to observe hurricane surface wind speeds and rain rates. This study explores the expected benefits of this instrument's data to numerical simulations of tropical cyclones using two different data assimilation methods within the experimental framework of Observing System Simulation Experiments (OSSE). The HIRAD instrument performed its inaugural hurricane flights during the summer 2010 NASA Genesis and Rapid Intensification Processes (GRIP) field program, when it first studied Hurricane Karl undergoing Rapid Intensification (RI) during its brief transit over the southern Gulf of Mexico. RI events such as this one are particularly difficult to forecast given the short duration and distance over water between landmasses. The aims of this study are four-fold: first, the creation of two Nature Run simulations of Hurricane Karl as a strong and a weak hurricane; second, the accurate simulation of the HIRAD instrument's rain rate and wind speed observations; third, the development and use of two data assimilation schemes for use with the Weather Research and Forecasting (WRF) model using simulated HIRAD data for both Nature Runs; and fourth, the improvement of Hurricane Karl's intensity forecast at the end of the data assimilation period due to the inclusion of HIRAD observations and potential use for aiding the forecast of landfalling intensity. The two data assimilation schemes in this study
Numerical simulation of instability and transition physics
Streett, C. L.
1990-01-01
The study deals with the algorithm technology used in instability and transition simulations. Discretization methods are outlined, and attention is focused on high-order finite-difference methods and high-order centered-difference formulas. One advantage of finite-difference methods over spectral methods is thought to be in implementation of nonrigorous boundary conditions. It is suggested that the next significant advances in the understanding of transition physics and the ability to predict transition will come with more physically-realistic simulations. Compressible-flow algorithms are discussed, and it is noted that with further development, exploration of bypass mechanism on simple bodies at high speed would be possible.
Numerical Simulations of Low Mass Star Formation
Bhandare, Asmita; Kuiper, R.; Henning, T.; Fendt, C.; Koelligan, A.
2017-06-01
Stars are formed by gravitational collapse of dense cores in magnetized molecular clouds. Details of the earliest epochs of star formation process and protostellar evolution are only vaguely known and strongly depend on the accretion history. Thermodynamical modeling in terms of radiation transport and phase transitions is crucial to identify meaningful results. In this study, we use a gray treatment of radiative transfer coupled with hydrodynamics to simulate Larson's collapse. In spherically symmetric collapse simulations, we investigate properties of prestellar cores in the low mass regime.
Testing Numerical Modeling of Phase Coarsening by Microgravity Experiments
Wang, K. G.; Glicksman, M. E.
2017-12-01
Quantitative understanding of the morphological evolution that occurs during phase coarsening is crucial for optimization of processing procedures to control the final structure and properties of multiphase materials. Generally, ground-based experimental studies of phase coarsening in solids are limited to model alloy systems. Data from microgravity experiments on phase coarsening in Sn-Pb solid-liquid mixtures, executed on the International Space Station, are archived in NASA's Physical Sciences Informatics (PSI) system. In such microgravity experiments, it is expected that the rate of sedimentation will be greatly reduced compared with terrestrial conditions, allowing the kinetics of phase coarsening to be followed more carefully and accurately. In this work we tested existing numerical models of phase coarsening using NASA's PSI microgravity data. Specially, we compared the microstructures derived from phase-field and multiparticle diffusion simulations with those observed in microgravity experiments.
Numerical simulation of transient flows in a rocket propulsion nozzle
Energy Technology Data Exchange (ETDEWEB)
Lijo, Vincent [School of Mechanical Engineering, Andong National University, Andong 760-749 (Korea, Republic of); Kim, Heuy Dong, E-mail: kimhd@andong.ac.k [School of Mechanical Engineering, Andong National University, Andong 760-749 (Korea, Republic of); Setoguchi, Toshiaki; Matsuo, Shigeru [Department of Mechanical Engineering, Saga University, 1 Honjo, Saga (Japan)
2010-06-15
A numerical investigation of transient flows in an axisymmetric over-expanded thrust-optimized contour nozzle is presented. These nozzles experience side-loads during start-up and shut-down operations, because of the flow separation at nozzle walls. Two types of flow separations such as free shock separation (FSS) and restricted shock separation (RSS) shock structure occur. A two-dimensional axisymmetric numerical simulation has been carried for a thrust-optimized contour nozzle to validate present results and investigate oscillatory flow characteristics during the start-up processes. Reynolds-Averaged Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Governing equations are solved by coupled implicit scheme. The present work is concerned with comprehensive assessment of the flow features by using Reynolds stress turbulence model. Computed pressure at the nozzle wall closely matched with the experimental data. A hysteresis phenomenon has been observed between these two shock structures. The transition from FSS to RSS pattern during start-up process has shown maximum nozzle wall pressure. Nozzle wall pressure and shear stress values have shown fluctuations during the FSS to RSS transition. The oscillatory pressure has been observed on the nozzle wall for high pressure ratio. Present results have shown that magnitude of the nozzle wall pressure variation is high for the oscillatory phenomenon.
Numerical aspects of giant impact simulations
Reinhardt, Christian; Stadel, Joachim
2017-06-01
In this paper, we present solutions to three short comings of smoothed particles hydrodynamics (SPH) encountered in previous work when applying it to giant impacts. First we introduce a novel method to obtain accurate SPH representations of a planet's equilibrium initial conditions based on equal area tessellations of the sphere. This allows one to imprint an arbitrary density and internal energy profile with very low noise which substantially reduces computation because these models require no relaxation prior to use. As a consequence one can significantly increase the resolution and more flexibly change the initial bodies to explore larger parts of the impact parameter space in simulations. The second issue addressed is the proper treatment of the matter/vacuum boundary at a planet's surface with a modified SPH density estimator that properly calculates the density stabilizing the models and avoiding an artificially low-density atmosphere prior to impact. Further we present a novel SPH scheme that simultaneously conserves both energy and entropy for an arbitrary equation of state. This prevents loss of entropy during the simulation and further assures that the material does not evolve into unphysical states. Application of these modifications to impact simulations for different resolutions up to 6.4 × 106 particles show a general agreement with prior result. However, we observe resolution-dependent differences in the evolution and composition of post-collision ejecta. This strongly suggests that the use of more sophisticated equations of state also demands a large number of particles in such simulations.
NUMERICAL SIMULATION AND MODELING OF UNSTEADY FLOW ...
African Journals Online (AJOL)
2014-06-30
Jun 30, 2014 ... Aerospace, our results were in good agreement with experimental data. By simulation studies predeterminations became very easy to prepare, this gain is the result of the development of computational methods and hardware remarkable revolution. So mastery of computers has become indispensable for ...
Numerical simulation of roadway support clamping
Energy Technology Data Exchange (ETDEWEB)
Dobrocinski, S. (Akademia Marynarki Wojennej, Gdynia (Poland))
1988-01-01
Evaluates interaction of arched steel roadway supports and surrounding strata in stratified coal-bearing strata. A combination of the finite element method and boundary element method is used. A numerical model that describes interaction of supports and surrounding strata is discussed. Advantages of the calculation method developed by the authors compared to the finite element method are analyzed. The method is especially useful for description of support interaction at the junction of mine roadways or at junctions of mine roadways and mine shafts. 2 refs.
Numerical Simulations of Acoustically Driven, Burning Droplets
Kim, Heon-Chang; Karagozian, Ann R.; Smith, Owen I.
1999-11-01
The burning characteristics of fuel droplets exposed to external acoustical excitation within a microgravity environment are investigated numerically. The issue of acoustic excitation of flames in microgravity is especially pertinent to understanding the behavior of accidental fires which could occur in spacecraft crew quarters and which could be affected by pressure perturbations as result from ventilation fans or engine vibrations. Combustion of methanol fuel droplets is considered here using a full chemical reaction mechanism.(Marchese, A.J., et al., 26th Symp. (Int.) on Comb., p. 1209, 1997) The droplet and surrounding diffusion flame are situated within a cylindrical acoustic waveguide where standing waves are generated with varying frequency and amplitude. Applied sound pressure levels are limited at present to magnitudes for which the droplet shape remains spherical. A third order accurate, essentially-non-oscillatory (ENO) numerical scheme is employed to accurately resolve the spatial and temporal evolution of the flame front. Acoustically excited vs. non-excited external conditions for the burning droplet in microgravity are compared, and the effects of acoustic frequency, sound pressure level, and relative position of the droplet with respect to pressure and velocity nodes are explored.
Direct Numerical Simulation of Aeolian Tones
2005-04-15
simulation results of aeolian tones generated by a two-dimensional obstacle (circular cylinder, square cylinder, NACA0012 airfoil) in a uniform flow are...Square cylinder. M = 0.2, Re = 150. Fig. 3. Fluctuation pressure superimposed on vorticity. NACA0012 . M...0.2, Re = 300. 864 Osamu Inoue A typical example of computational results for the case of an NACA0012 airfoil is presented in Fig. 3
A new approach in the numerical simulation for the blood flow in large vessels
Directory of Open Access Journals (Sweden)
Balazs ALBERT
2013-03-01
Full Text Available In this paper we are proposing a new approach in the numerical simulation of the bloodflow in large vessels. The initial conditions are set to be compatible with the non-Newtonian modelused. Numerical experiments in stenosed artery and in artery with aneurysm (using COMSOL 3.3,are presented.
A new approach in the numerical simulation for the blood flow in large vessels
Balazs ALBERT; Titus PETRILA
2013-01-01
In this paper we are proposing a new approach in the numerical simulation of the bloodflow in large vessels. The initial conditions are set to be compatible with the non-Newtonian modelused. Numerical experiments in stenosed artery and in artery with aneurysm (using COMSOL 3.3),are presented.
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...
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 ...
Numerical simulation of the LAGEOS thermal behavior and thermal accelerations
Andrés, J.I.; Noomen, R.; Vecellio None, S.
2006-01-01
The temperature distribution throughout the LAGEOS satellites is simulated numerically with the objective to determine the resulting thermal force. The different elements and materials comprising the spacecraft, with their energy transfer, have been modeled with unprecedented detail. The radiation
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...
Solid-state electro-cumulation effect numerical simulation
Grishin, V G
2001-01-01
It is an attempt to simulate as really as possible a crystal's interatomic interaction under conditions of "Solid-state electro-cumulation (super-polarization) effect". Some theoretical and experimental reasons to believe that within solid substances an interparticles interaction could concentrate from the surface to a centre were given formerly. Now, numerical results show the conditions that could make the cumulation more effective. Another keywords: ion, current, solid, symmetry, cumulation, polarization, depolarization, ionic conductor,superionic conductor, ice, crystal, strain, V-center, V-centre, doped crystal, interstitial impurity, intrinsic color center, high pressure technology, Bridgman, anvil, experiment, crowdion, dielectric, proton, layer, defect, lattice, dynamics, electromigration, mobility, muon catalysis, concentration, doping, dopant, conductivity, pycnonuclear reaction, permittivity, dielectric constant, point defects, interstitials, polarizability, imperfection, defect centers, glass, epi...
Numerical Simulation of Wire-Coating
DEFF Research Database (Denmark)
Wapperom, Peter; Hassager, Ole
1999-01-01
A finite element program has been used to analyze the wire-coating process of an MDPE melt. The melt is modeled by a nonisothermal Carreau model. The emphasis is on predicting an accurate temperature field. Therefore, it is necessary to include the heat conduction in the metal parts. A comparison...... is made with the results of a simulation that models the heat conduction in the metal head by means of a Biot boundary condition. The influence of the wire velocity, inlet temperature and power-law index will be examined....
Numerical Simulations of Turbulence Mixing in the Northern Arabian Gulf
Li, D.; Anis, A.
2016-12-01
The Arabian Gulf (24° to 30° N, 48° to 57° E) is a large semi-enclosed and relatively shallow body of water and connects to the Indian Ocean through the Strait of Hormuz. The maximum and average water depths are 90 and 50 meters, respectively. Strong northwesterly winds, named ''Shamals'' are common in this region and are expected to lead to significant turbulence mixing processes in this relatively shallow water body. Measurements and a numerical model were used to study these processes. Observations were conducted in the vicinity of Qarooh Island, off Kuwait, from January to April, 2013. Observational data included time series of surface meteorological parameters (wind speed and direction, air temperature and humidity, short- and long-wave radiation, and barometric pressure) and hydrodynamical parameters (water-temperature and water-currents). These were used to force and verify the numerical simulations conducted with a 1-D numerical model, the General Ocean Turbulence Model (GOTM), to further study the physical mechanisms. Here we used second-moment two-equation k-ɛ turbulence models with a 300-s time step, a 0.1-m vertical grid size, and a 12-hour spin-up time for numerical experiments. The model was driven by surface momentum and heat flux. Temperature advection was computed from two nearby stations, station Sea Island (48.30° E, 29.10° N) and station Beacon (48.06° E ,29.52° N). The simulations were relaxed to the observed temperature and current speeds at 8 meters below the surface. GOTM generated bottom current velocities and temperature agreed well with observed values at our observation site. During shamal events when maximum wind speeds reach up to 13 m/s, energy input from the winds is estimated to be 0.12W/m2. GOTM generated turbulent kinetic energy (TKE) in the water-column was found to increase from 8.80 J/m2 to 12.51 J/m2 with 12-hour delay. TKE induced by the wind was estimated to be 30% of the total TKE of the water column while the rest
Large scale experiments as a tool for numerical model development
DEFF Research Database (Denmark)
Kirkegaard, Jens; Hansen, Erik Asp; Fuchs, Jesper
2003-01-01
Experimental modelling is an important tool for study of hydrodynamic phenomena. The applicability of experiments can be expanded by the use of numerical models and experiments are important for documentation of the validity of numerical tools. In other cases numerical tools can be applied for im...... hydrodynamic interaction with structures. The examples also show that numerical model development benefits from international co-operation and sharing of high quality results.......Experimental modelling is an important tool for study of hydrodynamic phenomena. The applicability of experiments can be expanded by the use of numerical models and experiments are important for documentation of the validity of numerical tools. In other cases numerical tools can be applied...... for improvement of the reliability of physical model results. This paper demonstrates by examples that numerical modelling benefits in various ways from experimental studies (in large and small laboratory facilities). The examples range from very general hydrodynamic descriptions of wave phenomena to specific...
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.
An Introduction to Observing System Simulation Experiments
Prive, Nikki C.
2017-01-01
Observing System Simulation Experiments (OSSEs) are used to estimate the potential impact of proposed new instruments and data on numerical weather prediction. OSSEs can also be used to help design new observing platforms and to investigate the behavior of data assimilation systems. A basic overview of how to design and perform an OSSE will be given, as well as best practices and pitfalls. Some examples using the OSSE framework developed at the NASA Global Modeling and Assimilation Office will be shown.
Numerical simulation of hole injection in high barrier metal ...
African Journals Online (AJOL)
Numerical simulation of hole injection in high barrier metal-semiconductor short diodes. ... Journal of the Nigerian Association of Mathematical Physics ... A numerical investigation is carried out on effects of minority carriers on the transport parameters of one-dimensional metal-semiconductor short diodes under highly ...
Gravity Currents with Convective Mixing: High-resolution Numerical Simulations
Voskov, D.; Elenius, M. T.; Tchelepi, H.
2014-12-01
Due to challenges in performing direct numerical simulations for gravity currents with convective mixing, different attempts have been made to simplify the problem. In this work, the full problem is investigated with direct numerical simulations. Our simulations employ a recently developed capability in our General Purpose Research Simulator (AD-GPRS). The compositional approach is based on K-values and a linear density model. A shared-memory parallel implementation allows for high resolution simulations in a reasonable time frame. Our results indicate that it is important to consider the reduction in the dissolution rate after the fingers begin to interact with the bottom of the aquifer. Another important observation suggests considering a reduction in the dissolution rate where the plume thickness increases in time. In addition to the large-scale simulations, we performed convective-mixing simulations in relatively small domains to support the analysis of large-scale plume migration and CO2 trapping.
Numerical Simulation of Confined Multiple Transverse Jets
2012-06-01
issuing into a fully-developed pipe flow with both fluids being air nominally at standard temperature and pressure. The purpose of this phase of...single or multiple jets, impinging on a wall or on other jets, swirling , homogeneous or heterogeneous cross flow , compressible or incompressible, etc...work performed by A. Strzelecki, et al. [2-3]. In these experiments, the mixing of eight isothermal jets issuing into a circular pipe flow is
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.
3D CFD Transient Numerical Simulation of Superfluid Helium
Bruce, R.; Reynaud, J.; Pascali, S.; Baudouy, B.
2017-12-01
Numerical simulations of superfluid helium are necessary to design the next generation of superconducting accelerator magnets at CERN. Previous studies have presented the thermodynamic equations implemented in the Fluent CFD software to model the thermal behavior of superfluid helium. Momentum and energy equations have been modified in the solver to model a simplified two-fluid model. In this model, the thermo-mechanical effect term and the Gorter-Mellink mutual friction term are the dominant terms in the momentum equation for the superfluid component. This assumption is valid for most of superfluid applications. Transient thermal and dynamic behavior of superfluid helium has been studied in this paper. The equivalent thermal conductivity in the energy equation is represented by the Gorter-Mellink term and both the theoretical and the Sato formulation of this term have been compared to unsteady helium superfluid experiments. The main difference between these two formulations is the coefficient to the power of the temperature gradient between the hot and the cold part in the equivalent thermal conductivity. The results of these unsteady simulations have been compared with two experiments. The first one is a Van Sciver experiment on a 10 m long, and 9 mm diameter tube at saturation conditions and the other, realized in our laboratory, is a 150×50×10 mm rectangular channel filled with pressurized superfluid helium. Both studies have been performed with a heating source that starts delivering power at the beginning of the experiment and many temperature sensors measure the transient thermal behavior of the superfluid helium along the length of the channel.
Numerical simulation of flow past circular duct
Directory of Open Access Journals (Sweden)
Ze-gao Yin
2010-06-01
Full Text Available The Renormalization Group (RNG k—ɛ turbulence model and Volume of Fluid (VOF method were employed to simulate the flow past a circular duct in order to obtain and analyze hydraulic parameters. According to various upper and bottom gap ratios, the force on the duct was calculated. When the bottom gap ratio is 0, the drag force coefficient, lift force coefficient, and composite force reach their maximum values, and the azimuth reaches its minimum. With an increase of the bottom gap ratio from 0 to 1, the drag force coefficient and composite force decrease sharply, and the lift force coefficient does not decreases so much, but the azimuth increases dramatically. With a continuous increase of the bottom gap ratio from 1 upward, the drag force coefficient, lift force coefficient, composite force, and azimuth vary little. Thus, the bottom gap ratio is the key factor influencing the force on the circular duct. When the bottom gap ratio is less than 1, the upper gap ratio has a remarkable influence on the force of the circular duct. When the bottom gap ratio is greater than 1, the variation of the upper gap ratio has little influence on the force of the circular duct.
Numerical simulations for terrestrial planets formation
Directory of Open Access Journals (Sweden)
Ji J.
2011-07-01
Full Text Available We investigate the formation of terrestrial planets in the late stage of planetary formation using two-planet model. At that time, the protostar has formed for about 3 Myr and the gas disk has dissipated. In the model, the perturbations from Jupiter and Saturn are considered. We also consider variations of the mass of outer planet, and the initial eccentricities and inclinations of embryos and planetesimals. Our results show that, terrestrial planets are formed in 50 Myr, and the accretion rate is about 60%–80%. In each simulation, 3–4 terrestrial planets are formed inside “Jupiter” with masses of 0.15–3.6 M⊕. In the 0.5–4 AU, when the eccentricities of planetesimals are excited, planetesimals are able to accrete material from wide radial direction. The plenty of water material of the terrestrial planet in the Habitable Zone may be transferred from the farther places by this mechanism. Accretion may also happen a few times between two giant planets only if the outer planet has a moderate mass and the small terrestrial planet could survive at some resonances over time scale of 108 yr.
Numerical simulation of flow past circular duct
Directory of Open Access Journals (Sweden)
Ze-gao YIN
2010-06-01
Full Text Available On the basis of Fluent software, Renormalization Group (RNGk-ε turbulent model and Volume of Fluid (VOF method are employed to simulate the flow past circular duct to obtain and analyze the hydraulic parameters. According to various upper and bottom gap-ratios, the force on duct is calculated. Firstly, when bottom gap-ratio is 0, drag force coefficient, lift force coefficient and composite force reach the maximum respectively and azimuth reaches the minimum. Secondly, with the increase of bottom gap-ratio from 0 to 1, drag force coefficient and composite force decrease sharply, lift force coefficient decreases a little, but azimuth increases dramatically. Thirdly, with the continuous increase of bottom gap-ratio from 1, drag force coefficient, lift force coefficient, composite force and azimuth vary little. So, bottom gap-ratio is the key factor influencing the force on circular duct. When bottom gap-ratio is less than 1, upper gap-ratio has the remarkable influence on the circular duct force. When bottom gap-ratio is greater than 1, the varation of upper gap-ratio has a little influence on the circular duct force.
Scorching heat and numerical simulation; Canicule et simulation numerique
Energy Technology Data Exchange (ETDEWEB)
Deque, M
2007-07-01
A simulation of 140 years has been realized with ARPEGE-climat using the hypothesis of the increase of the greenhouse effect gases, of the scenario called A2 by the GIEC. The summer temperature observed at Pais and simulated between 1960 and 2003, as the average temperature in France are presented and discussed. (A.L.B.)
Numerical Simulation and Optimization of Performances of a Solar ...
African Journals Online (AJOL)
Numerical Simulation and Optimization of Performances of a Solar Cell Based on CdTe. ... We will lay the stress, initially, on the essential design features of a photovoltaic module (the open-circuit tension, the short-circuit current, the fill factor, and the output of the cell), our results was simulated with the SCAPS computer ...
Transonic Flow of Wet Steam — Numerical Simulation
Directory of Open Access Journals (Sweden)
Jan Halama
2012-01-01
Full Text Available The paper presents a numerical simulation of the transonic flow of steam with a non-equilibrium phase change. The flow of steam is approximated by a mixture model complemented by transport equations for moments. Proper formulation of the problem consists of domain definition, a complete set of equations, and appropriate choice of initial and boundary conditions. This problem is then solved numerically by a numerical code, that has been developed in-house. The code is based on a fractional step method and a finite volume formulation. Important issues related to numerical solution are discussed. Results for flow in a turbine are presented.
Numerical simulation of the dynamics evolution of alluvial mining quarries
Lyubimova, T. P.; Lepikhin, A. P.; Parshakova, Ya N.
2017-07-01
Alluvial mining quarry (or placer mining) is one of the main techniques for extracting important building materials such as sand and gravels. Prediction of quarries detrimental effects on the hydraulic regimes of rivers, in particular on flow regimes, has been carried on in full details in 0, 1 and 2D problem formulations (in the latter case, a depth-averaging is applied). However, the prediction of the quarry behavior itself is unfeasible, though such information would be of paramount importance for estimating the adverse effect on the river bed. This work studies the dynamics evolution of alluvial mining quarries in the framework of two-dimensional formulation based on width-averaging. The Euler multiphase model, which allows simulating separately the behavior of several interacting phases, is implemented. The conducted numerical experiments show that the upstream part of the quarry is eroded more intensively than the downstream one, displacing the quarry up-stream. This effect was observed during numerous field case-studies.
Numerical Simulations of Thermal Convection in Rapidly Rotating Spherical Shell
Energy Technology Data Exchange (ETDEWEB)
Nenkov, Constantine; Peltier, Richard, E-mail: nenkov@atmosp.physics.utoronto.ca, E-mail: peltier@atmosp.physics.utoronto.ca [Department of Physics, University of Toronto Toronto, Ontario, M5S 1A7 (Canada)
2010-11-01
We present a novel numerical model used to simulate convection in the atmospheres of the Gas Giant planets Jupiter and Saturn. Nonlinear, three-dimensional, time-dependant solutions of the anelastic hydrodynamic equations are presented for a stratified, rotating spherical fluid shell heated from below. This new model is specified in terms of a grid-point based methodology which employs a hierarchy of tessellations of the regular icosahedron onto the sphere through the process of recurrent dyadic refinements of the spherical surface. We describe discretizations of the governing equations in which all calculations are performed in Cartesian coordinates in the local neighborhoods of the almost uniform icosahedral grid, a methodology which avoids the potential mathematical and numerical difficulties associated with the pole problem in spherical geometry. Using this methodology we have built our model in primitive equations formulation, whereas the three-dimensional vector velocity field and temperature are directly advanced in time. We show results of thermal convection in rapidly rotating spherical shell which leads to the formation of well pronounced prograde zonal jets at the equator, results which previous experiments with two-dimensional models in the limit of freely evolving turbulence were not able to achieve.
Numerical Simulation of Barotropic Tides around Taiwan
Directory of Open Access Journals (Sweden)
Chih-Kai Hu
2010-01-01
Full Text Available A 1/12°, 2-D barotropic tide model was used to examine the characteristics of barotropic tides and to improve the accuracy of predicting tidal sea levels and currents in the seas around Taiwan. The form ratio suggests that tides are predominantly semidiurnal in the northern reaches of the Taiwan Strait and mixed of diurnal and semidiurnal elsewhere around Taiwan. When the dominant M2 wave enters the Strait from the north, its amplitude is magnified to ~2 m in the middle, and then decreases rapidly toward the south end of the Strait. The predominance of diurnal tides along the southwest to the south coast of Taiwan is attributed to the quasi-resonance of diurnal waves in the South China Sea. The tidal range is small and tidal currents are weak off the east coast of Taiwan. Barotropic tidal energy is mostly dissipated on the shallow banks of the southwestern Strait. Results summarized from sensitivity tests on the bottom drag coefficient (CD and horizontal eddy viscosity (AM indicate that CD = 0.0015 - 0.00175 and AM = 150 m2 s-1 lead to the best model-data fit when compared to the observed tidal sea levels at ten reference tide-gauge stations around Taiwan. The averaged root-mean-squared (RMS differences of the simulated tidal sea level for the six principal constituents of O1, P1, K1, N2, M2, and S2 are significantly reduced to 1.3, 0.7, 2.0, 1.6, 5.1, and 3.1 cm, respectively, compared to that calculated from a 0.5° resolution global tide harmonic constant database, NAO.99b (Matsumoto et al. 2000. The averaged RMS differences of barotropic tidal currents (U, V for O1, K1, M2, and S2 are (0.92, 1.64, (1.17, 0.61, (3.88, 2.37, and (1.52, 1.20 cm s-1. A database of tidal sea levels and current harmonic constants, TWTIDE08, for Q1, O1, P1, K1, J1, OO1, 2N2, μ2, N2, ν2, M2, L2, T2, S2, and K2 is established with this study.
Numerical Simulation of Cold Dense Plasma Sputtering with VORPAL
Zhou, Chuandong; Stoltz, Peter; Veitzer, Seth
2009-10-01
Sputtering is an evaporation process that physically removes atoms from a solid target material. This process takes place under bombardment of the target surface by energetic ions. Sputtering is widely applied in material processing and coating, such as etching and thin film deposition. Numerical simulation of sputtering process requires both accurate models of nuclear stopping in materials, particle dynamics and consistent electromagnetic fields. The particle in cell code VORPAL can simulate cold dense plasma under many different electromagnetic configurations. The dynamics of both incident particles and sputtered neutral atoms are simulated in VORPAL, and the sputtering yield is calculated from a standalone numerical library for a variety of materials that are commonly used in industrial applications. Numerical simulation of the spatial distribution of sputtering resulting from a cold dense plasma under externally applied magnetic field and self-consistent electric field is presented.
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.
Numerical Simulations for Large Deformation of Geomaterials Using Molecular Dynamics
Directory of Open Access Journals (Sweden)
Ziyang Zhao
2018-01-01
Full Text Available From the microperspective, this paper presents a model based on a new type of noncontinuous theoretical mechanical method, molecular dynamics (MD, to simulate the typical soil granular flow. The Hertzian friction formula and viscous damping force are introduced in the MD governing equations to model the granular flow. To show the validity of the proposed approach, a benchmark problem of 2D viscous material flow is simulated. The calculated final flow runout distance of the viscous material agrees well with the result of constrained interpolated profile (CIP method as reported in the literature. Numerical modeling of the propagation of the collapse of three-dimensional axisymmetric sand columns is performed by the application of MD models. Comparison of the MD computational runout distance and the obtained distance by experiment shows a high degree of similarity. This indicates that the proposed MD model can accurately represent the evolution of the granular flow. The model developed may thus find applications in various problems involving dense granular flow and large deformations, such as landslides and debris flow. It provides a means for predicting fluidization characteristics of soil large deformation flow disasters and for identification and design of appropriate protective measures.
Numerical simulation of unsteady propeller/rudder interaction
Directory of Open Access Journals (Sweden)
Lei He
2017-11-01
Full Text Available A numerical approach based on a potential flow method is developed to simulate the unsteady interaction between propeller and rudder. In this approach, a panel method is used to solve the flow around the rudder and a vortex lattice method is used to solve the flow around the propeller, respectively. An iterative procedure is adopted to solve the interaction between propeller and rudder. The effects of one component on the other are evaluated by using induced velocities due to the other component at every time step. A fully unsteady wake alignment algorithm is implemented into the vortex lattice method to simulate the unsteady propeller flow. The Rosenhead-Moore core model is employed during the wake alignment procedure to avoid the singularities and instability. The Lamb-Oseen vortex model is adopted in the present method to decay the vortex strength around the rudder and to eliminate unrealistically high induced velocity. The present methods are applied to predict the performance of a cavitating horn-type rudder in the presence of a 6-bladed propeller. The predicted cavity patterns compare well with those observed from the experiments.
Numerical simulation of circular cylinders in free-fall
Energy Technology Data Exchange (ETDEWEB)
Romero-Gomez, Pedro; Richmond, Marshall C.
2016-02-01
In this work, we combined the use of (i) overset meshes, (ii) a 6 degree-of-freedom (6- DOF) motion solver, and (iii) an eddy-resolving flow simulation approach to resolve the drag and secondary movement of large-sized cylinders settling in a quiescent fluid at moderate terminal Reynolds numbers (1,500 < Re < 28,000). These three strategies were implemented in a series of computational fluid dynamics (CFD) solutions to describe the fluid-structure interactions and the resulting effects on the cylinder motion. Using the drag coefficient, oscillation period, and maximum angular displacement as baselines, the findings show good agreement between the present CFD results and corresponding data of published laboratory experiments. We discussed the computational expense incurred in using the present modeling approach. We also conducted a preceding simulation of flow past a fixed cylinder at Re = 3,900, which tested the influence of the turbulence approach (time-averaging vs eddy-resolving) and the meshing strategy (continuous vs. overset) on the numerical results. The outputs indicated a strong effect of the former and an insignificant influence of the latter. The long-term motivation for the present study is the need to understand the motion of an autonomous sensor of cylindrical shape used to measure the hydraulic conditions occurring in operating hydropower turbines.
Experiments and Numerics of Bichromatic Wave Groups
Westhuis, J.H.; van Groesen, Embrecht W.C.; Huijsmans, R.
2001-01-01
This paper reports on extensive experiments on nonlinear wave groups that evolve in a hydrodynamic laboratory over long distances (200 m) from the generation of simple bichromatic waves. The deepwater experiments show large deformations of the wave group, with large increase of wave heights,
A numerical simulation method and analysis of a complete thermoacoustic-Stirling engine.
Ling, Hong; Luo, Ercang; Dai, Wei
2006-12-22
Thermoacoustic prime movers can generate pressure oscillation without any moving parts on self-excited thermoacoustic effect. The details of the numerical simulation methodology for thermoacoustic engines are presented in the paper. First, a four-port network method is used to build the transcendental equation of complex frequency as a criterion to judge if temperature distribution of the whole thermoacoustic system is correct for the case with given heating power. Then, the numerical simulation of a thermoacoustic-Stirling heat engine is carried out. It is proved that the numerical simulation code can run robustly and output what one is interested in. Finally, the calculated results are compared with the experiments of the thermoacoustic-Stirling heat engine (TASHE). It shows that the numerical simulation can agrees with the experimental results with acceptable accuracy.
Numerical Modelling of Solitary Wave Experiments on Rubble Mound Breakwaters
Guler, H. G.; Arikawa, T.; Baykal, C.; Yalciner, A. C.
2016-12-01
Performance of a rubble mound breakwater protecting Haydarpasa Port, Turkey, has been tested under tsunami attack by physical model tests conducted at Port and Airport Research Institute (Guler et al, 2015). It is aimed to understand dynamic force of the tsunami by conducting solitary wave tests (Arikawa, 2015). In this study, the main objective is to perform numerical modelling of solitary wave tests in order to verify accuracy of the CFD model IHFOAM, developed in OpenFOAM environment (Higuera et al, 2013), by comparing results of the numerical computations with the experimental results. IHFOAM is the numerical modelling tool which is based on VARANS equations with a k-ω SST turbulence model including realistic wave generation, and active wave absorption. Experiments are performed using a Froude scale of 1/30, measuring surface elevation and flow velocity at several locations in the wave channel, and wave pressure around the crown wall of the breakwater. Solitary wave tests with wave heights of H=7.5 cm and H=10 cm are selected which represent the results of the experiments. The first test (H=7.5 cm) is the case that resulted in no damage whereas the second case (H=10 cm) resulted in total damage due to the sliding of the crown wall. After comparison of the preliminary results of numerical simulations with experimental data for both cases, it is observed that solitary wave experiments could be accurately modeled using IHFOAM focusing water surface elevations, flow velocities, and wave pressures on the crown wall of the breakwater (Figure, result of sim. at t=29.6 sec). ACKNOWLEDGEMENTSThe authors acknowledge developers of IHFOAM, further extend their acknowledgements for the partial supports from the research projects MarDiM, ASTARTE, RAPSODI, and TUBITAK 213M534. REFERENCESArikawa (2015) "Consideration of Characteristics of Pressure on Seawall by Solitary Waves Based on Hydraulic Experiments", Jour. of Japan. Soc. of Civ. Eng. Ser. B2 (Coast. Eng.), Vol 71, p I
Caprock integrity and induced seismicity from laboratory and numerical experiments
Vilarrasa, Victor; Makhnenko, Roman
2017-04-01
CO2 leakage, either across the caprock or through faults, is a major concern for geologic carbon storage. To assess the caprock sealing capacity and the strength of faults, we investigate clay-rich geomaterials in the laboratory. We focus on the thermo-hydro-mechanical coupled processes that shale may undergo during CO2 storage. Specimens of Opalinus clay - a Swiss shale - are brought to the conditions of suitable storage formations (1 km depth) and are fully saturated with in-situ brine. Poro-thermo-mechanical parameters are measured in drained, undrained, and unjacketed compression experiments. We use the measured parameters at the laboratory as input data to a numerical model that simulates CO2 injection in a deep saline aquifer bounded by a low-permeable fault. We find that the caprock sealing capacity is maintained and that even the fault may undergo a series of microseismic events, leakage is unlikely to occur through the ductile clay-rich fault.
Compressible Turbulent Flow Numerical Simulations of Tip Vortex Cavitation
Khatami, F.; van der Weide, E.; Hoeijmakers, H.
2015-12-01
For an elliptic Arndt's hydrofoil numerical simulations of vortex cavitation are presented. An equilibrium cavitation model is employed. This single-fluid model assumes local thermodynamic and mechanical equilibrium in the mixture region of the flow, is employed. Furthermore, for characterizing the thermodynamic state of the system, precomputed multiphase thermodynamic tables containing data for the appropriate equations of state for each of the phases are used and a fast, accurate, and efficient look-up approach is employed for interpolating the data. The numerical simulations are carried out using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations for compressible flow. The URANS equations of motion are discretized using an finite volume method for unstructured grids. The numerical simulations clearly show the formation of the tip vortex cavitation in the flow about the elliptic hydrofoil.
FSW Numerical Simulation of Aluminium Plates by Sysweld - Part I
Directory of Open Access Journals (Sweden)
Jančo Roland
2016-07-01
Full Text Available Friction Stir Welding (FSW is one of the most effective solid state joining processes and it has numerous potential applications in many industries. The simulation process can provide the evolution of physical quantities such as temperature, metallurgical phase proportions, stress and strain which can be easily measured during welding. The numerical modelling requires the modelling of a complex interaction between thermal, metallurgical and mechanical phenomena. The aim of this paper is to describe the thermal-fluid simulation of FSW using the finite element method. In the theoretical part of the paper heating is provided by the material flow and contact condition between the tool and the welded material. The thermal-fluid results from the numerical simulation for aluminium alloy using SYSWELD are also presented in this paper.
FSW Numerical Simulation of Aluminium Plates by SYSWELD - Part II
Directory of Open Access Journals (Sweden)
Jančo Roland
2016-11-01
Full Text Available Friction Stir Welding (FSW is one of the most effective solid state joining processes and has numerous potential applications in many industries. The simulation process can provide the evolution of physicals quantities such as temperature, metallurgical phase proportions, stress and strain which can be easily measured during welding. The numerical modelling requires the modelling of the complex interaction between thermal, metallurgical and mechanical phenomena. The aim of this paper is to describe the thermal-fluid simulation of FSW using the finite element method. In the theoretical part of paper heating is provided by the material flow and contact condition between the tool and the welded material. Thermal-mechanical results from the numerical simulation using SYSWELD are also presented for aluminium alloy.
Numerical Simulation of Multicomponent Ion Beam from Ion Sources
Alexandrov, V S; Kazarinov, Yu M; Shevtsov, V P; Shirkov, G D
1999-01-01
A program library for numerical simulation of a multicomponent charged particle beam from ion sources is presented. The library is aimed for simulation of high current, low energy multicomponent ion beam from ion source through beamline and realized under the Windows user interface for the IBM PC. It is used for simulation and optimization of beam dynamics and based on successive and consistent application of two methods: the momentum method of distribution function (RMS technique) and particle in cell method. The library has been used to simulate and optimize the transportation of tantalum ion beam from the laser ion source (CERN) and calcium ion beam from the ECR ion source (JINR, Dubna).
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
Interpretation of ponded infiltration data using numerical experiments
Directory of Open Access Journals (Sweden)
Dohnal Michal
2016-09-01
Full Text Available Ponded infiltration experiment is a simple test used for in-situ determination of soil hydraulic properties, particularly saturated hydraulic conductivity and sorptivity. It is known that infiltration process in natural soils is strongly affected by presence of macropores, soil layering, initial and experimental conditions etc. As a result, infiltration record encompasses a complex of mutually compensating effects that are difficult to separate from each other. Determination of sorptivity and saturated hydraulic conductivity from such infiltration data is complicated. In the present study we use numerical simulation to examine the impact of selected experimental conditions and soil profile properties on the ponded infiltration experiment results, specifically in terms of the hydraulic conductivity and sorptivity evaluation. The effect of following factors was considered: depth of ponding, ring insertion depth, initial soil water content, presence of preferential pathways, hydraulic conductivity anisotropy, soil layering, surface layer retention capacity and hydraulic conductivity, and presence of soil pipes or stones under the infiltration ring. Results were compared with a large database of infiltration curves measured at the experimental site Liz (Bohemian Forest, Czech Republic. Reasonably good agreement between simulated and observed infiltration curves was achieved by combining several of factors tested. Moreover, the ring insertion effect was recognized as one of the major causes of uncertainty in the determination of soil hydraulic parameters.
The power of simulating experiments
Meyer, K.M.; Mooij, W.M.; Vos, M.; Hol, W.H.G.; Putten, van der W.H.
2009-01-01
Addressing complex ecological research questions often requires complex empirical experiments. However, due to the logistic constraints of empirical studies there is a trade-off between the complexity of experimental designs and sample size. Here, we explore if the simulation of complex ecological
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.
Numerical simulations for investigating EMC problems in industrial life
Directory of Open Access Journals (Sweden)
Bernd Jaekel W.
2008-01-01
Full Text Available The complexity of current EMC problems and the necessity to solve them in an accurate, reliable and efficient way require various analysis techniques. Numerical simulations can be considered as one of the most powerful tools for performing EMC analysis. Computational electromagnetics is used within basic research for example at universities as well as during nearly all phases of a product or system development process occurring in industrial life. Especially here, several challenges result from the application of numerical simulations. The most important ones are described and discussed in this paper. An exemplary interference problem is presented demonstrating the relevance and impact of those challenges.
Numerical time-domain simulation of diffusive ultrasound in concrete.
Schubert, Frank; Koehler, Bernd
2004-04-01
Certain aspects of diffusive ultrasound fields in concrete are still unknown and thus, systematic parameter studies using numerical time-domain simulations of the ultrasonic propagation process could lead to further insights into theoretical and experimental questions. In the present paper, the elastodynamic finite integration technique (EFIT) is used to simulate a diffusive reverberation measurement at a concrete specimen taking aggregates, pores, and viscoelastic damping explicitly into account. The numerical results for dissipation and diffusivity are compared with theoretical models. Moreover, the influence of air-filled pores in the cement matrix is demonstrated.
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.
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...
Compressible Turbulent Flow Numerical Simulations of Tip Vortex Cavitation
Khatami, F.; van der Weide, Edwin Theodorus Antonius; Hoeijmakers, Hendrik Willem Marie
2015-01-01
For an elliptic Arndt’s hydrofoil numerical simulations of vortex cavitation are presented. An equilibrium cavitation model is employed. This single-fluid model assumes local thermodynamic and mechanical equilibrium in the mixture region of the flow, is employed. Furthermore, for characterizing the
A numerical technique to simulate display pixels based on electrowetting
Roghair, I.; Musterd, M.; van den Ende, Henricus T.M.; Kleijn, C.; Kleijn, C.; Kreutzer, M.T.; Mugele, Friedrich Gunther
2015-01-01
We present a numerical simulation technique to calculate the deformation of interfaces between a conductive and non-conductive fluid as well as the motion of liquid–liquid–solid three-phase contact lines under the influence of externally applied electric fields in electrowetting configuration. The
Numerical simulation of three phase asynchronous motor to ...
African Journals Online (AJOL)
Numerical simulation of three phase asynchronous motor to diagnose precisely the stator unbalanced voltage anomaly. ... First, the stator currents data pattern is used as a preliminary diagnosis. ... This similarity leads to uncertainty in the detection of the fault, which makes imperative the use of complementary technique.
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
Numerical simulation of linear friction welding of aeronautical alloys
Potet, Antoine; Mocellin, Katia; Fourment, Lionel
2017-10-01
Numerical simulation of linear friction welding (LFW) of Titanium alloys is considered with the Forge® software, using a JMatPro constitutive model with the aim of supporting process design for the welding of dissimilar materials, such as Titanium and Inconel. Relying on forces and temperature experimental measurements, friction and other unknown parameters of the model have to be calibrated.
Numerical simulation of species dependent interaction in a polluted ...
African Journals Online (AJOL)
In this study, we have utilized a sound numerical simulation technique to derive the conditions under which a legally-binding control related policy is necessary in order to mitigate the endemic Niger Delta polluted environmental issue. The implication of this present analysis if implemented will have several benefits for the ...
A Numerical Simulation of Temperature Distribution and Power Loss ...
African Journals Online (AJOL)
A Numerical Simulation of Temperature Distribution and Power Loss of Slider Bearings Lubricated With Fluids Having Constant Viscosity. ... The stream wise pressure gradient, shear stresses and flow rate obtained from post processing of the finite element solution of the Reynolds equation act as inputs when the energy ...
Numerical simulation of an intense precipitation event over ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Earth System Science; Volume 124; Issue 7. Numerical simulation of an intense precipitation event ... Incursion of moist air, in the lower levels, converges at the foothills of the mountains and rise along the orography to form the updraft zone of the storm. Such rapid unstable ascent leads to deep ...
Response maxima in modulated turbulence: II: Numerical simulations
von der Heydt, A.; Grossmann, Siegfried; Lohse, Detlef
2003-01-01
Numerical simulations of fully developed turbulence driven by a modulated energy input rate or driving force are performed within two dynamical cascade models, the Gkedzer-Ohkitani-Yamada shell model and a reduced wave vector set approximation of the Navier-Stokes equation. The frequency behavior of
Numerical Simulations of Shock-Induced Mixing and Combustion
Energy Technology Data Exchange (ETDEWEB)
Bell, J B; Day, M; Kuhl, A L
2003-04-22
In this paper we use numerical simulation to investigate shock-induced ignition and combustion of a hydrocarbon gas. The focus of this paper is on quantifying the effect of fidelity in the chemical kinetics on the overall solution. We model the system using the compressible Navier Stokes equations for a reacting mixture. These equations express conservation of species mass, momentum, total energy.
Numerical simulation of two-phase flow in offshore environments
Wemmenhove, Rik
2008-01-01
Numerical Simulation of Two-Phase Flow in Offshore Environments Rik Wemmenhove Weather conditions on full sea are often violent, leading to breaking waves and lots of spray and air bubbles. As high and steep waves may lead to severe damage on ships and offshore structures, there is a great need for
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 Sediment Transport in Horizontal Channel
Energy Technology Data Exchange (ETDEWEB)
Uhlmann, M.
2006-07-01
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.
A framework for multiscale and multiscience modeling and numerical simulations
Chopard, B.; Falcone, J.-L.; Hoekstra, A.G.; Borgdorff, J.
2011-01-01
The Complex Automata (CxA) methodology offers a new framework to develop multiscale and multiscience numerical simulations. The CxA approach assumes that a multiscale model can be formulated in terms of several coupled single-scale submodels. With concepts such as the scale separation map, the
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)
Numerical simulations of viscoelastic flows with free surfaces
DEFF Research Database (Denmark)
Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri
2013-01-01
We present a new methodology to simulate viscoelastic flows with free-surfaces. These simulations are motivated by the modelling of polymers manufacturing techniques, such as extrusion and injection moulding. One of the consequences of viscoelasticity is that polymeric materials have a “memory......” of their past deformations. This generates some numerical difficulties which are addressed with the log-conformation transformation. The main novelty of this work lies on the use of the volume-of-fluid method to track the free surfaces of the viscoelastic flows. We present some preliminary results of test case...... simulations where the different features of the model are tested independently....
Turbulent mix experiments and simulations
Energy Technology Data Exchange (ETDEWEB)
Dimonte, G.; Schneider, M.; Frerking, C.E.
1995-08-01
Hydrodynamic instabilities produce material mixing that can significantly degrade weapons performance. We investigate the Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities in the turbulent regime in two experimental venues. RM experiments are conducted on the Nova laser with strong radiatively driven shocks (Mach > 20) in planar, two fluid targets. Interfacial perturbations are imposed with single sinusoidal modes to test linear theory and with three dimensional (3D) random modes to produce turbulent mix. RT experiments are conducted on a new facility, the Linear Electric Motor (LEM), in which macroscopic fluids are accelerated with arbitrary temporal profiles. This allows detailed diagnosis of the turbulence over a wide range of conditions. The Nova experiments study the high compression regime whereas the LEM experiments are incompressible. The results are compared to hydrodynamic simulations with the arbitrary Lagrangian-Eulerian code (CALE). The goal is to develop and test engineering models of mix.
Surface nanobubbles: Theory, numerics and experiments
Weijs, Joost H.
2013-11-01
When a solid is brought into contact with water, surface nanobubbles can be formed at the solid-liquid interface. These nanobubbles are small; their height is of order 10nm and their lateral sizes vary from 10-100 nm. Initially, the only proof of the existence of surface nanobubbles was delivered by atomic force microscopy. Later, additional techniques such as infrared attenuated total reflectance have confirmed the existence of gaseous domains on the solid-liquid interface. Before this overwhelming evidence, the existence of surface nanobubbles was controversial because they possess some unusual properties. For example, nanobubbles are surprisingly robust against dissolution by diffusion and Laplace pressure: Instead of the expected lifetime of about a microsecond, nanobubbles are found to survive for several hours and in some cases even several days. Additionally, surface nanobubbles are flatter than predicted by Young's law and are able to resist strong tensile stresses (~-6 MPa), rather than serving as a nucleation site for a macroscopic bubble. A deep understanding of surface nanobubbles is crucial for practical applications (e.g. drag reduction in microfluidic devices) but nanobubbles also pose fundamental questions on the validity of continuum models at the nanoscale. In this talk, we will discuss these open questions in detail by considering theoretical efforts and molecular dynamics simulations. Theoretically, we study the consequences of a pinned contact line. We find that the pinned contact line can explain the long lifetimes and many other nanobubble properties. From molecular dynamics results, we clarify the influence of the gas species on the contact angle. Finally, we will discuss some very recent experimental and theoretical work on the effects of an acoustic field on nanobubbles. We provide experimental data combined with a theoretical analysis and find that the acoustic driving can cause the nanobubbles to grow by rectified diffusion.
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.
Visualization of a Numerical Simulation of GW 150914
Rosato, Nicole; Healy, James; Lousto, Carlos
2017-01-01
We present an analysis of a simulation displaying apparent horizon curvature and radiation emitted from a binary black hole system modeling GW-150914 during merger. The simulation follows the system from seven orbits prior to merger to the resultant Kerr black hole. Horizon curvature was calculated using a mean curvature flow algorithm. Radiation data was visualized via the Ψ4 component of the Weyl scalars, which were determined using a numerical quasi-Kinnersley method. We also present a comparative study of the differences in quasi-Kinnersley and PsiKadelia tetrads to construct Ψ4. The analysis is displayed on a movie generated from these numerical results, and was done using VisIt software from Lawrence Livermore National Laboratory. This simulation and analysis gives more insight into the merger of the system GW 150914.
Numerical simulation of a meteorological regime of Pontic region
Toropov, P.; Silvestrova, K.
2012-04-01
initial data in WRF model are used FNL the analysis, pumped up each six hours. The data is in the open access (http://nomad3.ncep.noaa.gov/pub/) in a grib format. Spatial step FNL of the FNL analysis is 1 degree. In the experiment 1-3 February 2011, was made the assimilation of station data located within the territory or identified during our expeditions. It is shown that the model WRF successfully reproduces the meteorological regime the Black Sea coast. The average error of simulation n without learning station data is as follows: for a temperature of 1.5 s for wind speed - 2 m / sec. The maximum error for the temperature is 5 C, and for wind speed 10 m / sec. To experiment with the assimilation of station data the error is reduced by an average of 20%. The spatial structure of temperature and wind fields close to the actually observed. Thus, it can be argued that the model WRF can be successfully applied to numerical forecast a dangerous phenomenon, such as «Novorossiysk nord-ost». The work is done in Natural Risk Assessment Laboratory under contract G.34.31.0007.
Numerical simulation of tip clearance impact on a pumpjet propulsor
Directory of Open Access Journals (Sweden)
Lin Lu
2016-05-01
Full Text Available Numerical simulation based on the Reynolds Averaged Navier–Stokes (RANS Computational Fluid Dynamics (CFD method had been carried out with the commercial code ANSYS CFX. The structured grid and SST k–ω turbulence model had been adopted. The impact of non-condensable gas (NCG on cavitation performance had been introduced into the Schnerr and Sauer cavitation model. The numerical investigation of cavitating flow of marine propeller E779A was carried out with different advance ratios and cavitation numbers to verify the numerical simulation method. Tip clearance effects on the performance of pumpjet propulsor had been investigated. Results showed that the structure and characteristics of the tip leakage vortex and the efficiency of the propulsor dropped more sharply with the increase of the tip clearance size. Furthermore, the numerical simulation of tip clearance cavitation of pumpjet propulsor had been presented with different rotational speed and tip clearance size. The mechanism of tip clearance cavitation causing a further loss of the efficiency had been studied. The influence of rotational speed and tip clearance size on tip clearance cavitation had been investigated.
Simulation of Wave Overtopping of Maritime Structures in a Numerical Wave Flume
Directory of Open Access Journals (Sweden)
Tiago C. A. Oliveira
2012-01-01
Full Text Available A numerical wave flume based on the particle finite element method (PFEM is applied to simulate wave overtopping for impermeable maritime structures. An assessment of the performance and robustness of the numerical wave flume is carried out for two different cases comparing numerical results with experimental data. In the first case, a well-defined benchmark test of a simple low-crested structure overtopped by regular nonbreaking waves is presented, tested in the lab, and simulated in the numerical wave flume. In the second case, state-of-the-art physical experiments of a trapezoidal structure placed on a sloping beach overtopped by regular breaking waves are simulated in the numerical wave flume. For both cases, main overtopping events are well detected by the numerical wave flume. However, nonlinear processes controlling the tests proposed, such as nonlinear wave generation, energy losses along the wave propagation track, wave reflection, and overtopping events, are reproduced with more accuracy in the first case. Results indicate that a numerical wave flume based on the PFEM can be applied as an efficient tool to supplement physical models, semiempirical formulations, and other numerical techniques to deal with overtopping of maritime structures.
Numerical simulations of synthetic jets in aerodynamic applications
Directory of Open Access Journals (Sweden)
Alexandru Catalin MACOVEI
2014-04-01
Full Text Available This paper presents numerical simulations of synthetic jets in aerodynamic applications. We’ve analyzed the formation of isolated synthetic jets, the influence of nozzle geometry and the interaction of synthetic jets with a uniform flow on a flat plate. Also we’ve studied the influence of the active control in interaction with a stalled airfoil and the controllability of dynamic stall phenomenon. The results are obtained using a dedicated CFD solver. Appropriate comparisons are made with results from scientific literature; as well the numerical results are compared with a set of experimental images.
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 PHYSICAL SYSTEMS IN AGRI-FOOD ENGINEERING
Directory of Open Access Journals (Sweden)
Angelo Fabbri
2012-06-01
Full Text Available In agri-food engineering many complex problems arise in plant and process design. Specifically the designer has to deal with fluid dynamics, thermal or mechanical problems, often characterized by physics coupling, non-linearity, irregular geometry, anisotropy and in definitive rather high complexity. In recent years, the ever growing availability of computational power at low cost, made these problems more often approached with numerical simulation techniques. Mainly in terms of finite elements and finite volumes. In this paper the fundamentals of numerical methods are briefly recalled and a discussion about their possibility of application in the food and agricultural engineering is developed.
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)
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.
Page 1 Numerical simulation of the Indian monsoon 161 points out ...
Indian Academy of Sciences (India)
Numerical simulation of the Indian monsoon 161 points out “the dynamics of the whole terrestrial climate cannot be separated from the heat Storage effects of the upper ocean". For monsoon studies, the Indian. 9°ºan is the only ocean which experiences a bi-annual reversal of the wind circu- lation. The generation of the ...
Numerical simulation of premixed Hydrogen/air combustion pressure in a spherical vessel
Guo Han-yu; Tao Gang; Zhang Li-jing
2016-01-01
In order to study the development process of hydrogen combustion in a closed vessel, an on-line chemical equilibrium calculator and a numerical simulation method would be used to analysis the combustion pressure and flame front of mixed gas, which based on 20L H2/air explosion experiments in spherical vessel (Crowl and Jo,2009). The results showed that, the turbulent model could reflect the process of combustion, and the error of combustion pressure by simulation is smaller than the Chemical ...
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.
Ladd, A J C
1993-01-01
A new and very general technique for simulating solid-fluid suspensions has been described in a previous paper (Part I); the most important feature of the new method is that the computational cost scales with the number of particles. In this paper (Part II), extensive numerical tests of the method are described; for creeping flows, both with and without Brownian motion, and at finite Reynolds numbers. Hydrodynamic interactions, transport coefficients, and the short-time dynamics of random dispersions of up to 1024 colloidal particles have been simulated.
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 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...
Modified Numerical Simulation Model of Blood Flow in Bend.
Liu, X; Zhou, X; Hao, X; Sang, X
2015-12-01
The numerical simulation model of blood flow in bend is studied in this paper. The curvature modification is conducted for the blood flow model in bend to obtain the modified blood flow model in bend. The modified model is verified by U tube. By comparing the simulation results with the experimental results obtained by measuring the flow data in U tube, it was found that the modified blood flow model in bend can effectively improve the prediction accuracy of blood flow data affected by the curvature effect.
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.
Direct Numerical Simulations of Reacting Fronts in Incompressible Flows
Vladimirova, N.; Cattaneo, F.; Malagoli, A.; Oberman, A.; Ruchayskiy, 0.; Rosner, R.
2000-11-01
We perform direct numerical simulations of an advected scalar field which diffuses and reacts according to a nonlinear reaction law. The goal of the simulations is to study flame stability with respect to initial conditions, and to determine how the bulk burning rate of the reaction front is affected by an imposed flow. We focus for simplicity on the cases of an imposed periodic shear or cellular flow. The interaction between the reaction front and the applied flow is determined by the following parameters: (a) the ratio between the laminar front thickness and the shear length scale, (b) the ratio between the laminar flame speed and the characteristic flow velocity, and (c) the ratio between heat conductivity and material diffusion (Lewis Number). We compare the numerical results with recent work of P. Constantin and collaborators, in particularly, their prediction for flame stability and analytical upper and lower bounds for the bulk burning rate.
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.
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.
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
Numerical simulation of 3D backward facing step flows at various Reynolds numbers
Directory of Open Access Journals (Sweden)
Louda Petr
2015-01-01
Full Text Available The work deals with the numerical simulation of 3D turbulent flow over backward facing step in a narrow channel. The mathematical model is based on the RANS equations with an explicit algebraic Reynolds stress model (EARSM. The numerical method uses implicit finite volume upwind discretization. While the eddy viscosity models fail in predicting complex 3D flows, the EARSM model is shown to provide results which agree well with experimental PIV data. The reference experimental data provide the 3D flow field. The simulations are compared with experiment for 3 values of Reynolds number.
Numerical Simulation of Polynomial-Speed Convergence Phenomenon
Li, Yao; Xu, Hui
2017-10-01
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 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.
Using a {sigma}-coordinate numerical ocean model for simulating the circulation at Ormen Lange
Energy Technology Data Exchange (ETDEWEB)
Eliassen, Inge K.; Berntsen, Jarle
2000-01-01
This report describes a numerical model for the simulation of circulation at the Ormen Lange oil field. The model uses a topography following vertical coordinate and time split integration procedure. The model is implemented for a 28 km x 46 km area at Ormen Lange. The equations are given in detail and numerical experiments are discussed. The numerical studies investigate how the flow specified at open boundaries surrounding the Ormen Lange area may be interpolated into the interior domain taking into account the conservation laws that are believed to determine the flow and the local topography.
Direct Numerical Simulation of Multiphase flow over Realistic Superhydrophobic Surfaces
Alame, Karim; Mahesh, Krishnan
2017-11-01
Direct numerical simulations are performed using the volume of fluid methodology, for turbulent channel flow of water over a realistic superhydrophobic surface, which traps air. The surface is obtained from scanned data of the real sprayed surface. Multiphase laminar Couette flow and turbulent channel cases are examined. Drag reduction for different interface heights are shown, and the effect of turbulence on multiphase flow over rough surfaces is discussed. This work is supported by the Office of Naval Research.
The Numerical Simulation Analysis of Hydro Forming of Hollow Crankshaft
Directory of Open Access Journals (Sweden)
Wang Shi Gang
2016-01-01
Full Text Available The hydro forming process of hollow crankshaft was numerically analyzed and simulated based on Dynaform. Then the influence to hydro forming process in different loading paths was studied and the match relations between optimum forming pressure and axial feeding were obtained. The forming result was ideal and the forming parts were qualified. Finally, to the same material, the change trend of pipe billet wall thickness under the same forming pressure and axial feeding was discussed.
Mobile phone as a platform for numerical simulation
Sala, Filip A.
2012-01-01
In this work numerical simulations performed on mobile devices equipped with ARM microprocessors are shown. Calculations include: light propagation in linear and nonlinear media based on one-dimensional Schrödinger equation and molecules reorientation in nematic liquid crystals. The purpose of this publication is to show advantages and disadvantages of using mobile devices as a platform for education and research. Discussion about software development is provided.
Numerical simulation of underexpanded air jet using OpenFOAM
Talukdar, Mohammad
2015-01-01
Master's thesis in Risk management It is of utmost importance for the awareness of safety issues involved in high pressure gas storage to perceive the adjacent field of high pressure gas jet release for the establishment of the decomposition laws in the far field. The numerical simulations of the first cell of an underexpanded gas jet can be performed executing finite volume solver which can be validated later by means of available literature source. The prominence of OpenFoam is irrefutab...
Deorbit efficiency assessment through numerical simulation of electromagnetic tether devices
Directory of Open Access Journals (Sweden)
Alexandru IONEL
2016-03-01
Full Text Available This paper examines the deorbit efficiency of an electromagnetic tether deorbit device when used to deorbit an upper stage at end of mission from low Earth orbit. This is done via a numerical simulation in Matlab R2013a, using ode45, taking into account perturbations on the upper stage’s trajectory. The perturbations taken into account are the atmospheric drag, the 3rd body (Sun and Moon, and Earth’s gravitational potential expanded into spherical harmonics.
Numerical simulation of flow in the wet scrubber for desulfurization
Directory of Open Access Journals (Sweden)
Novosád Jan
2015-01-01
Full Text Available This article deals with numerical simulation of flow and chemical reactions in absorber for desulfurization of flue-gas. The objective of the work is the investigation of effect of different nozzles types and their placement in spray layers. These nozzles distribute lime suspension into flue gas stream. The research includes two types of nozzles and four different arrangements of nozzles and spray layers. Conclusion describes the effect of nozzle types and their arrangements on the suspension concentration in absorber.
Numerical Simulation Method for Combustion in a Oxyhydrogen Rocket Motor
Taki, Shiro; Fujiwara, Toshitaka; 滝, 史郎; 藤原, 俊隆
1984-01-01
Numerical simulations of unsteady phenomena in the combustion chamber of an oxyhydrogen rocket motor were made in an attempt to develop a computer code for use in investigating such phenomena as vibrating combustion. The combustion in this system is controlled by diffusion, the effect of which works much slower than sound or pressure waves, so that diffusions are usually solved using the implicit finite difference method for unlimited time step size caused by stability criterion. However, the...
NUMERICAL SIMULATION OF DIGITAL VLSI TOTAL DOSE FUNCTIONAL FAILURES
Directory of Open Access Journals (Sweden)
O. A. Kalashnikov
2016-10-01
Full Text Available The technique for numerical simulation of digital VLSI total dose failures is presented, based on fuzzy logic sets theory. It assumes transfer from boolean logic model of a VLSI with values {0,1} to fuzzy model with continuous interval [0,1], and from boolean logic functions to continuous minimax functions. The technique is realized as a calculation system and allows effective estimating of digital VLSI radiation behavior without experimental investigation.
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.
Experiences with linear solvers for oil reservoir simulation problems
Energy Technology Data Exchange (ETDEWEB)
Joubert, W.; Janardhan, R. [Los Alamos National Lab., NM (United States); Biswas, D.; Carey, G.
1996-12-31
This talk will focus on practical experiences with iterative linear solver algorithms used in conjunction with Amoco Production Company`s Falcon oil reservoir simulation code. The goal of this study is to determine the best linear solver algorithms for these types of problems. The results of numerical experiments will be presented.
Numerical simulation of wave interactions during sudden stratospheric warming
Gavrilov, N. M.; Koval, A. V.; Pogoreltsev, A. I.; Savenkova, E. N.
2017-11-01
Parameterizations of normal atmospheric modes (NAMs) and orographic gravity waves (OGWs) are implemented into the mechanistic general circulation model of the middle and upper atmosphere (MUA). Numerical experiments of sudden stratospheric warming (SSW) events are performed for climatological conditions typical for January and February using meteorological reanalysis data from the UK MET Office in the MUA model averaged over the years 1992-2011 with the easterly phase of quasi-biennial oscillation (QBO). The simulation shows that an increase in the OGW amplitudes occurs at altitudes higher than 30 km in the Northern Hemisphere after SSW. The OGW amplitudes have maximums at altitudes of about 50 km over the North American and European mountain systems before and during SSW, as well as over the Himalayas after SSW. At high latitudes of the Northern Hemisphere, significant (up to 50-70%) variations in the amplitudes of stationary planetary waves (SPWs) are observed during and after the SSW. Westward travelling NAMs have local amplitude maximums not only in the Northern Hemisphere, but also in the Southern Hemisphere, where there are waveguides for the propagation of these modes. Calculated variations of SPW and NAM amplitudes correspond to changes in the mean temperature and wind fields, as well as the Eliassen-Palm flux and atmospheric refractive index for the planetary waves, during SSW. Including OGW thermal and dynamical effects leads to an increase in amplitude (by 30-70%) of almost all SPWs before and during SSW and to a decrease (up to 20-100%) after the SSW at middle and high latitudes of the Northern Hemisphere.
Numerical Homogenization of Jointed Rock Masses Using Wave Propagation Simulation
Gasmi, Hatem; Hamdi, Essaïeb; Bouden Romdhane, Nejla
2014-07-01
Homogenization in fractured rock analyses is essentially based on the calculation of equivalent elastic parameters. In this paper, a new numerical homogenization method that was programmed by means of a MATLAB code, called HLA-Dissim, is presented. The developed approach simulates a discontinuity network of real rock masses based on the International Society of Rock Mechanics (ISRM) scanline field mapping methodology. Then, it evaluates a series of classic joint parameters to characterize density (RQD, specific length of discontinuities). A pulse wave, characterized by its amplitude, central frequency, and duration, is propagated from a source point to a receiver point of the simulated jointed rock mass using a complex recursive method for evaluating the transmission and reflection coefficient for each simulated discontinuity. The seismic parameters, such as delay, velocity, and attenuation, are then calculated. Finally, the equivalent medium model parameters of the rock mass are computed numerically while taking into account the natural discontinuity distribution. This methodology was applied to 17 bench fronts from six aggregate quarries located in Tunisia, Spain, Austria, and Sweden. It allowed characterizing the rock mass discontinuity network, the resulting seismic performance, and the equivalent medium stiffness. The relationship between the equivalent Young's modulus and rock discontinuity parameters was also analyzed. For these different bench fronts, the proposed numerical approach was also compared to several empirical formulas, based on RQD and fracture density values, published in previous research studies, showing its usefulness and efficiency in estimating rapidly the Young's modulus of equivalent medium for wave propagation analysis.
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.
The numerical simulation based on CFD of hydraulic turbine pump
Duan, X. H.; Kong, F. Y.; Liu, Y. Y.; Zhao, R. J.; Hu, Q. L.
2016-05-01
As the functions of hydraulic turbine pump including self-adjusting and compensation with each other, it is far-reaching to analyze its internal flow by the numerical simulation based on CFD, mainly including the pressure field and the velocity field in hydraulic turbine and pump.The three-dimensional models of hydraulic turbine pump are made by Pro/Engineer software;the internal flow fields in hydraulic turbine and pump are simulated numerically by CFX ANSYS software. According to the results of the numerical simulation in design condition, the pressure field and the velocity field in hydraulic turbine and pump are analyzed respectively .The findings show that the static pressure decreases systematically and the pressure gradient is obvious in flow area of hydraulic turbine; the static pressure increases gradually in pump. The flow trace is regular in suction chamber and flume without spiral trace. However, there are irregular traces in the turbine runner channels which contrary to that in flow area of impeller. Most of traces in the flow area of draft tube are spiral.
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 heating in Particle-In-Cell simulations with Monte Carlo binary collisions
Alves, E. Paulo; Mori, Warren; Fiuza, Frederico
2017-10-01
The binary Monte Carlo collision (BMCC) algorithm is a robust and popular method to include Coulomb collision effects in Particle-in-Cell (PIC) simulations of plasmas. While a number of works have focused on extending the validity of the model to different physical regimes of temperature and density, little attention has been given to the fundamental coupling between PIC and BMCC algorithms. Here, we show that the coupling between PIC and BMCC algorithms can give rise to (nonphysical) numerical heating of the system, that can be far greater than that observed when these algorithms operate independently. This deleterious numerical heating effect can significantly impact the evolution of the simulated system particularly for long simulation times. In this work, we describe the source of this numerical heating, and derive scaling laws for the numerical heating rates based on the numerical parameters of PIC-BMCC simulations. We compare our theoretical scalings with PIC-BMCC numerical experiments, and discuss strategies to minimize this parasitic effect. This work is supported by DOE FES under FWP 100237 and 100182.
Solution of AntiSeepage for Mengxi River Based on Numerical Simulation of Unsaturated Seepage
Directory of Open Access Journals (Sweden)
Youjun Ji
2014-01-01
Full Text Available Lessening the leakage of surface water can reduce the waste of water resources and ground water pollution. To solve the problem that Mengxi River could not store water enduringly, geology investigation, theoretical analysis, experiment research, and numerical simulation analysis were carried out. Firstly, the seepage mathematical model was established based on unsaturated seepage theory; secondly, the experimental equipment for testing hydraulic conductivity of unsaturated soil was developed to obtain the curve of two-phase flow. The numerical simulation of leakage in natural conditions proves the previous inference and leakage mechanism of river. At last, the seepage control capacities of different impervious materials were compared by numerical simulations. According to the engineering actuality, the impervious material was selected. The impervious measure in this paper has been proved to be effectible by hydrogeological research today.
Numerical Simulations of Granular Physics in the Solar System
Ballouz, Ronald
2017-08-01
numerical results to laboratory experiments and observations by spacecraft we can begin to understand which microscopic properties (i.e., grain properties) control the macroscopic properties of the system. For example, we can compare the mechanical response of a spacecraft to landing or Cassini observations of Saturn's ring to understand how the penetration depth of a spacecraft or the complex optical depth structure of a ring system depends on the size and surface properties of the grains in those systems.
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.
Stress Analysis of Non-Ferrous Metals Welds by Numerical Simulation
Directory of Open Access Journals (Sweden)
Kravarikova Helena
2017-01-01
Full Text Available Thermal energy welded material unevenly heated and thus supports the creation of tension. During the fusing process welding transient tensions generated in the welded material. Generation of the transient tensions depends on the thermal expansion and fixed permanently welded parts. Tensions are the result of the interaction of material particles. For welded parts and constructions it is necessary to know the size and direction of application of tensions. The emerging tensions can cause local change or a total deformation of welded materials. Deformations and residual stresses impair the performance of a welded construction, reduces the stability of the parts. To reduce or eliminate of action or a screening direction stresses and strains it is necessary to know the mechanism of their emergence. It is now possible to examine the emergence of tensions numerical experiments on any model using numerical simulation using FEM. Results of numerical experiment is the analysis of stress and deformation course. In the plane the tension it divided into normal σ and τ tangential folders. Decomposition stress on components simplifies the stress analysis. The results obtained from numerical analysis are correct to predict the stress distribution and size. The paper presents the results of numerical experiments stress analysis solutions fillet welds using FEM numerical simulation of welding of non-ferrous metals.
Numerical experiment with modelled return echo of a satellite
Indian Academy of Sciences (India)
Abstract. We have simulated the return echo of a satellite altimeter from a rough ocean surface using an analytical formula and have studied its sensitivity with respect to various oceanic and altimeter parameters. Our numerical expcriment shows that for normally observed significant wave heights (SWFI) the effect of ...
Towards an Automated Full-Turbofan Engine Numerical Simulation
Reed, John A.; Turner, Mark G.; Norris, Andrew; Veres, Joseph P.
2003-01-01
The objective of this study was to demonstrate the high-fidelity numerical simulation of a modern high-bypass turbofan engine. The simulation utilizes the Numerical Propulsion System Simulation (NPSS) thermodynamic cycle modeling system coupled to a high-fidelity full-engine model represented by a set of coupled three-dimensional computational fluid dynamic (CFD) component models. Boundary conditions from the balanced, steady-state cycle model are used to define component boundary conditions in the full-engine model. Operating characteristics of the three-dimensional component models are integrated into the cycle model via partial performance maps generated automatically from the CFD flow solutions using one-dimensional meanline turbomachinery programs. This paper reports on the progress made towards the full-engine simulation of the GE90-94B engine, highlighting the generation of the high-pressure compressor partial performance map. The ongoing work will provide a system to evaluate the steady and unsteady aerodynamic and mechanical interactions between engine components at design and off-design operating conditions.
Vosegaard, T; 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 c...
Numerical Simulation of Delamination Growth in Composite Materials
Camanho, P. P.; Davila, C. G.; Ambur, D. R.
2001-01-01
The use of decohesion elements for the simulation of delamination in composite materials is reviewed. The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially. After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion elements is described. Problems related with decohesion element constitutive equations, mixed-mode crack growth, element numerical integration and solution procedures are discussed. Based on these investigations, it is concluded that the use of interfacial decohesion elements is a promising technique that avoids the need for a pre-existing crack and pre-defined crack paths, and that these elements can be used to simulate both delamination onset and growth.
Numerical simulation of hydrogen plasma in MPCVD reactor
Huang, Di
A numerical study was conducted to build a model able to estimate the plasma properties under different working conditions for pure hydrogen plasma in a MPCVD reactor. A plasma model based on standing wave assumption and a linear estimation of ne and coupled the EM simulation, heat transfer simulation and UDF calculations of plasma properties was built in COMSOL Muitiphysics and tested with six different working conditions. The reliability of COMSOL EM solver was tested through comparing the simulation results with a benchmark EM solver, ANSYS HFSS. The validities of two assumptions made about the electrical field, standing wave assumption and sinusoidal oscillation field assumption, were tested by a PDE solver in COMSOL for utilizing the drift-diffusion model of ne.
Numerical simulation of explosive welding using Smoothed Particle Hydrodynamics method
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J Feng
2017-09-01
Full Text Available In order to investigate the mechanism of explosive welding and the influences of explosive welding parameters on the welding quality, this paper presents numerical simulation of the explosive welding of Al-Mg plates using Smoothed Particle Hydrodynamics method. The multi-physical phenomena of explosive welding, including acceleration of the flyer plate driven by explosive detonation, oblique collision of the flyer and base plates, jetting phenomenon and the formation of wavy interface can be reproduced in the simulation. The characteristics of explosive welding are analyzed based on the simulation results. The mechanism of wavy interface formation is mainly due to oscillation of the collision point on the bonding surfaces. In addition, the impact velocity and collision angle increase with the increase of the welding parameters, such as explosive thickness and standoff distance, resulting in enlargement of the interfacial waves.
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 and experimental study of explosive projectile devices
Selivanov, V. V.; Gryaznov, E. F.; Goldenko, N. A.; Sudomoev, A. D.; Feldstein, V. A.
2017-06-01
A study of explosive-throwing device (ETD) was undertaken to simulate the hypervelocity impact of space debris fragments (SDF) and meteoroids with spacecrafts. The principle of operation of an ETD is based on the cumulative effect in combination with the cut-off head of the cumulative jet, which enables one to simulate a compact particle, such as a meteoroid or a fragment of space debris. Different design schemes of ETD with different composition explosive charge initiation schemes with notably low speeds of the jet cut-off are explored, and a method to control the particle velocity is proposed. Numerical simulation of device modes and basic technical characteristics of experimental testing are investigated.
Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova
Energy Technology Data Exchange (ETDEWEB)
James Glimm
2009-06-04
The three year plan for this project was to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (Direct Numerical Simulation (DNS), Large Eddy Simulations (LES), full two fluid simulations and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We model 2D and 3D perturbations of planar or circular interfaces. We compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. Multiple layers and reshock are considered here.
On Improving Analytical Models of Cosmic Reionization for Matching Numerical Simulations
Energy Technology Data Exchange (ETDEWEB)
Kaurov, Alexander A. [Univ. of Chicago, IL (United States)
2016-01-01
The methods for studying the epoch of cosmic reionization vary from full radiative transfer simulations to purely analytical models. While numerical approaches are computationally expensive and are not suitable for generating many mock catalogs, analytical methods are based on assumptions and approximations. We explore the interconnection between both methods. First, we ask how the analytical framework of excursion set formalism can be used for statistical analysis of numerical simulations and visual representation of the morphology of ionization fronts. Second, we explore the methods of training the analytical model on a given numerical simulation. We present a new code which emerged from this study. Its main application is to match the analytical model with a numerical simulation. Then, it allows one to generate mock reionization catalogs with volumes exceeding the original simulation quickly and computationally inexpensively, meanwhile reproducing large scale statistical properties. These mock catalogs are particularly useful for CMB polarization and 21cm experiments, where large volumes are required to simulate the observed signal.
Stochastic algorithms for the analysis of numerical flame simulations
Energy Technology Data Exchange (ETDEWEB)
Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.
2001-12-14
Recent progress in simulation methodologies and new, high-performance parallel architectures have made it is possible to perform detailed simulations of multidimensional combustion phenomena using comprehensive kinetics mechanisms. However, as simulation complexity increases, it becomes increasingly difficult to extract detailed quantitative information about the flame from the numerical solution, particularly regarding the details of chemical processes. In this paper we present a new diagnostic tool for analysis of numerical simulations of combustion phenomena. Our approach is based on recasting an Eulerian flow solution in a Lagrangian frame. Unlike a conventional Lagrangian viewpoint in which we follow the evolution of a volume of the fluid, we instead follow specific chemical elements, e.g., carbon, nitrogen, etc., as they move through the system. From this perspective an ''atom'' is part of some molecule that is transported through the domain by advection and diffusion. Reactions ca use the atom to shift from one species to another with the subsequent transport given by the movement of the new species. We represent these processes using a stochastic particle formulation that treats advection deterministically and models diffusion as a suitable random-walk process. Within this probabilistic framework, reactions can be viewed as a Markov process transforming molecule to molecule with given probabilities. In this paper, we discuss the numerical issues in more detail and demonstrate that an ensemble of stochastic trajectories can accurately capture key features of the continuum solution. We also illustrate how the method can be applied to studying the role of cyanochemistry on NOx production in a diffusion flame.
Stochastic algorithms for the analysis of numerical flame simulations
Energy Technology Data Exchange (ETDEWEB)
Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.
2004-04-26
Recent progress in simulation methodologies and high-performance parallel computers have made it is possible to perform detailed simulations of multidimensional reacting flow phenomena using comprehensive kinetics mechanisms. As simulations become larger and more complex, it becomes increasingly difficult to extract useful information from the numerical solution, particularly regarding the interactions of the chemical reaction and diffusion processes. In this paper we present a new diagnostic tool for analysis of numerical simulations of reacting flow. Our approach is based on recasting an Eulerian flow solution in a Lagrangian frame. Unlike a conventional Lagrangian view point that follows the evolution of a volume of the fluid, we instead follow specific chemical elements, e.g., carbon, nitrogen, etc., as they move through the system . From this perspective an ''atom'' is part of some molecule of a species that is transported through the domain by advection and diffusion. Reactions cause the atom to shift from one chemical host species to another and the subsequent transport of the atom is given by the movement of the new species. We represent these processes using a stochastic particle formulation that treats advection deterministically and models diffusion and chemistry as stochastic processes. In this paper, we discuss the numerical issues in detail and demonstrate that an ensemble of stochastic trajectories can accurately capture key features of the continuum solution. The capabilities of this diagnostic are then demonstrated by applications to study the modulation of carbon chemistry during a vortex-flame interaction, and the role of cyano chemistry in rm NO{sub x} production for a steady diffusion flame.
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
The Three-Dimensional Numerical Simulation and Experimental Research on Screw Compressor
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He Xueming
2015-01-01
Full Text Available This paper presents the mathematical model of screw compressors’ working process, in which the internal flow domains are divided into three kinds of fluids—the inlet fluid, the primitive volume fluid, and outlet fluid. Grid interface method and dynamic mesh technique of Computational Fluid Dynamics (CFD theory were utilized to simulate the suction, compression, and discharge process in order to model the dynamic characteristics of the flow domains in a screw compressor. To verify that the model is numerically accurate and the simulation method is effective, experiments on the pressure-volume changes in screw compressor were carried out. The result has shown that the simulation data is in good agreement with the experimental data. Therefore, the numerical calculation model and the simulation method can be very useful for the screw compressor design and research.
Numerical Simulation of Thin Film Breakup on Nonwettable Surfaces
Suzzi, N.; Croce, G.
2017-01-01
When a continuous film flows on a nonwettable substrate surface, it may break up, with the consequent formation of a dry-patch. The actual shape of the resulting water layer is of great interest in several engineering applications, from in-flight icing simulation to finned dehumidifier behavior modeling. Here, a 2D numerical solver for the prediction of film flow behavior is presented. The effect of the contact line is introduced via the disjoining pressure terms, and both gravity and shear are included in the formulation. The code is validated with literature experimental data for the case of a stationary dry-patch on an inclined plane. Detailed numerical results are compared with literature simplified model prediction. Numerical simulation are then performed in order to predict the threshold value of the film thickness allowing for film breakup and to analyze the dependence of the dynamic contact angle on film velocity and position along the contact line. Those informations will be useful in order to efficiently predict more complex configuration involving multiple breakups on arbitrarily curved substrate surfaces (as those involved in in-flight icing phenomena on aircraft).
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 the sucker-rod pumping system
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Oldrich Joel Romero
2014-11-01
Full Text Available The sucker rod pump is an artificial lift method frequently applied in onshore petroleum wells. This system can be described using a numerical simulation based on the behavior of a rod string. In the past, the elastic behavior of the rod string made it difficult to model the system. However, since the 1960s and with the advent of digital computers, it has been modeled numerically. The rod string be-haves like a slender bar, and thus, the propagation of elastic waves along the bar can be represented by a one-dimensional equation. Gibbs (1963 presented a mathematical model based on the wave equation, which is described on the basis of the analysis of forces on the rod string and is incorporated into a boundary value problem involving partial differential equations. The use of the finite differ-ence method allows for a numerical solution by the discretization of the wave equation developed in the mathematical formulation with appropriate boundary and initial conditions. This work presents a methodology for implementing an academic computer code that allows simulation of the upstroke and downstroke motion of the rod string described by the wave equation under ideal operating conditions, assuming a harmonic motion of the rod at one end and downhole pump at the other end. The goal of this study is to generate the downhole dynamometer card, an important and consolidated tool that controls the pump system by diagnosing oper-ational conditions of the downhole pump.
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.
Numerical Simulation of Water Jet Flow Using Diffusion Flux Mixture Model
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Zhi Shang
2014-01-01
Full Text Available A multidimensional diffusion flux mixture model was developed to simulate water jet two-phase flows. Through the modification of the gravity using the gradients of the mixture velocity, the centrifugal force on the water droplets was able to be considered. The slip velocities between the continuous phase (gas and the dispersed phase (water droplets were able to be calculated through multidimensional diffusion flux velocities based on the modified multidimensional drift flux model. Through the numerical simulations, comparing with the experiments and the simulations of traditional algebraic slip mixture model on the water mist spray, the model was validated.
An Object Model for a Rocket Engine Numerical Simulator
Mitra, D.; Bhalla, P. N.; Pratap, V.; Reddy, P.
1998-01-01
Rocket Engine Numerical Simulator (RENS) is a packet of software which numerically simulates the behavior of a rocket engine. Different parameters of the components of an engine is the input to these programs. Depending on these given parameters the programs output the behaviors of those components. These behavioral values are then used to guide the design of or to diagnose a model of a rocket engine "built" by a composition of these programs simulating different components of the engine system. In order to use this software package effectively one needs to have a flexible model of a rocket engine. These programs simulating different components then should be plugged into this modular representation. Our project is to develop an object based model of such an engine system. We are following an iterative and incremental approach in developing the model, as is the standard practice in the area of object oriented design and analysis of softwares. This process involves three stages: object modeling to represent the components and sub-components of a rocket engine, dynamic modeling to capture the temporal and behavioral aspects of the system, and functional modeling to represent the transformational aspects. This article reports on the first phase of our activity under a grant (RENS) from the NASA Lewis Research center. We have utilized Rambaugh's object modeling technique and the tool UML for this purpose. The classes of a rocket engine propulsion system are developed and some of them are presented in this report. The next step, developing a dynamic model for RENS, is also touched upon here. In this paper we will also discuss the advantages of using object-based modeling for developing this type of an integrated simulator over other tools like an expert systems shell or a procedural language, e.g., FORTRAN. Attempts have been made in the past to use such techniques.
NUMERICAL SIMULATION OF AN AGRICULTURAL SOIL SHEAR STRESS TEST
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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.
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.
Direct numerical simulation of microcavitation processes in different bio environments
Ly, Kevin; Wen, Sy-Bor; Schmidt, Morgan S.; Thomas, Robert J.
2017-02-01
Laser-induced microcavitation refers to the rapid formation and expansion of a vapor bubble inside the bio-tissue when it is exposed to intense, pulsed laser energy. With the associated microscale dissection occurring within the tissue, laserinduced microcavitation is a common approach for high precision bio-surgeries. For example, laser-induced microcavitation is used for laser in-situ keratomileusis (LASIK) to precisely reshape the midstromal corneal tissue through excimer laser beam. Multiple efforts over the last several years have observed unique characteristics of microcavitions in biotissues. For example, it was found that the threshold energy for microcavitation can be significantly reduced when the size of the biostructure is increased. Also, it was found that the dynamics of microcavitation are significantly affected by the elastic modules of the bio-tissue. However, these efforts have not focused on the early events during microcavitation development. In this study, a direct numerical simulation of the microcavitation process based on equation of state of the biotissue was established. With the direct numerical simulation, we were able to reproduce the dynamics of microcavitation in water-rich bio tissues. Additionally, an experimental setup in deionized water and 10% PAA gel was made to verify the results of the simulation for early micro-cavitation formation for 10% Polyacrylamide (PAA) gel in deionized water.
NUMERICAL SIMULATION OF A PREMIXED TURBULENT V-SHAPED FLAME
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M I El Khazen
2011-01-01
Full Text Available In this paper we simulate a turbulent premixed V-shape flame stabilized on a hot wire. The device used is composed of a vertical combustion chamber where the methane-air mixture is convected upwards with a mean velocity of 4ms-1. The flow was simulated running Fluent 6.3, which numerically solved the stationary Favre-averaged mass balance; Navier-Stokes equations; combustion progress variable, and k-ε equations on a two-dimensional numerical mesh. We model gaseous mixture, ignoring Soret and Dufour effects and radiation heat transfer. The progress variable balance equation was closed using Eddy Break Up model. The results of our simulations allow us to analyze the influence of equivalence ratio and the turbulent intensity on the properties of the flame (velocity, fluctuation, progress variable and Thickness of flame.This work gives us an idea on the part which turbulence can play to decrease the risks of extinction and instabilities caused by the lean premixed combustion.
Assessing numerical methods for molecular and particle simulation.
Shang, Xiaocheng; Kröger, Martin; Leimkuhler, Benedict
2017-11-22
We discuss the design of state-of-the-art numerical methods for molecular dynamics, focusing on the demands of soft matter simulation, where the purposes include sampling and dynamics calculations both in and out of equilibrium. We discuss the characteristics of different algorithms, including their essential conservation properties, the convergence of averages, and the accuracy of numerical discretizations. Formulations of the equations of motion which are suited to both equilibrium and nonequilibrium simulation include Langevin dynamics, dissipative particle dynamics (DPD), and the more recently proposed "pairwise adaptive Langevin" (PAdL) method, which, like DPD but unlike Langevin dynamics, conserves momentum and better matches the relaxation rate of orientational degrees of freedom. PAdL is easy to code and suitable for a variety of problems in nonequilibrium soft matter modeling; our simulations of polymer melts indicate that this method can also provide dramatic improvements in computational efficiency. Moreover we show that PAdL gives excellent control of the relaxation rate to equilibrium. In the nonequilibrium setting, we further demonstrate that while PAdL allows the recovery of accurate shear viscosities at higher shear rates than are possible using the DPD method at identical timestep, it also outperforms Langevin dynamics in terms of stability and accuracy at higher shear rates.
Wind Tunnel to Flight: Numerical Simulations of Hypersonic Propulsion Systems
Iaccarino, Gianluca
2009-11-01
Uncertainties in the flight conditions and limitations of ground based facilities create inherent difficulties in assessing the performance of hypersonic propulsion systems. We use numerical simulations to investigate the correlation of wind-tunnel measurements (Steelant et al., 2006) and flight data (Hass et al., 2005) for the HyShot vehicle; the objective is to identify potential engine unstart events occurring under different combustion regimes. As a first step we perform simulations corresponding to both reacting and non-reacting conditions in the ground-based facility to validate the numerical tools. Next, we focus on reproducing the flight conditions; a fundamental difficulty is the lack of precise information about the vehicle trajectory. A Bayesian inversion strategy is used to infer the altitude, angle of attack and Mach number from the noisy pressure measurements collected during the flight. The estimated conditions, together with the scatter due to the measurement uncertainty, are then used to study the flow and thermal fields in the combustor. The details of the methods used to characterize the uncertainty in the flow simulations and to perform the Bayesian inversion will also be discussed.
Numeric Simulation of Heat Transfer from a Single Round Tube Shielded with Wire Mesh
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Dymo B.V.
2015-08-01
Full Text Available This paper presents the results of development and investigation of heat transfer at transverse flow of round tube with wire screen using the software ANSYS Fluent 3D-model. Selection of optimal parameters of the finite element model, in particular, transition shear stress transport model as well and boundary conditions are realized. Instructed and combined net is used at numerical calculations. This net is built with the help of generators grid-torus ANSYS CFX Mesh 14.0. The problem of verification of conformity of the numerical model of the heat transfer of a single screen-covered round tubes according to physical experiment for the same tubes in the range of Reynolds numbers Re = (5000...35000 was studied. We established that discrepancy between physical experiments and numerical simulation results not exceeds 5% with respect to the data of physical experiment.
Numerical simulations of fluidization dynamics in a hot model of a CLC process
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Żyłka Anna
2017-01-01
The paper presents numerical simulations of the dynamic fluidized bed for Chemical Looping Combustion using CeSFaMB software. The model was validated on the basis of the results obtained from experiments, which were carried out on the Fluidized-Bed Chemical-Looping-Combustion of Solid-Fuels (FB-CLC-SF unit. The studies were conducted in air atmosphere at temperature of 850°C. The validation of the 1.5D model showed that the maximum relative error between experiment and simulations results does not exceed 12%.
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.
Numerical simulations of drop impact on superhydrophobic structured surfaces
Guzzetti, Davide; Larentis, Stefano; Pugno, Nicola
2011-11-01
During the last decade drop impact dynamics on superhydrophobic surfaces has been intensively investigated because of the incredible properties of water repellency exhibited by this kind of surfaces, mostly inspired by biological examples such as Lotus leave. Thanks to the recent progress in micro-fabrication technology is possible to tailor surfaces wettability defining specific pillar-like structured surfaces. In this work, the behavior of impinging drops on these pillar-like surfaces is simulated, characterizing temporal evolution of droplets contact radius and drop maximal deformation dependence on Weber number. Numerical simulations results are compared with theoretical and experimental results guaranteeing simulation reliability. Fingering patterns obtained from drop impact has been studied obtaining a correlation between number of fingers and Weber number. Drop fragmentation pattern obtained from simulations supports the proposed correlation. Different drop impact outcomes (e.g. rebound, fragmentation) on structured superhydrophobic surfaces are simulated, focusing on the influence of micro-structured surface geometrical pattern. This investigation is relevant in order to define design rules for possible reliable non wettable surfaces. Financial support by Alta Scuola Politecnica.
Numerical integration of detector response functions via Monte Carlo simulations
Kelly, K. J.; O'Donnell, J. M.; Gomez, J. A.; Taddeucci, T. N.; Devlin, M.; Haight, R. C.; White, M. C.; Mosby, S. M.; Neudecker, D.; Buckner, M. Q.; Wu, C. Y.; Lee, H. Y.
2017-09-01
Calculations of detector response functions are complicated because they include the intricacies of signal creation from the detector itself as well as a complex interplay between the detector, the particle-emitting target, and the entire experimental environment. As such, these functions are typically only accessible through time-consuming Monte Carlo simulations. Furthermore, the output of thousands of Monte Carlo simulations can be necessary in order to extract a physics result from a single experiment. Here we describe a method to obtain a full description of the detector response function using Monte Carlo simulations. We also show that a response function calculated in this way can be used to create Monte Carlo simulation output spectra a factor of ∼ 1000 × faster than running a new Monte Carlo simulation. A detailed discussion of the proper treatment of uncertainties when using this and other similar methods is provided as well. This method is demonstrated and tested using simulated data from the Chi-Nu experiment, which measures prompt fission neutron spectra at the Los Alamos Neutron Science Center.
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 simulations of seepage flow in rough single rock fractures
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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.
Direct numerical simulation of coalescing droplets in turbulence
Li Sing How, Melanie; Collins, Lance
2017-11-01
There is a rich body of numerical, experimental and theoretical work looking at the role of turbulence in particle collisions, with a particular emphasis on how it might accelerate the evolution of clouds in the atmosphere. This study is a continuation of that lineage. We perform direct numerical simulations of isotropic turbulence with embedded droplets that, upon collision, coalesce to produce a daughter droplet that conserves the mass and momentum of the parent droplets. As a consequence of coalescence, the droplet size distribution evolves over time from its monodisperse initial condition. The work is an extension of Reade and Collins (J. Fluid Mech. 415:45-64, 2000), which considered the same problem at a much lower Reynolds number. We observe important effects of intermittency at Reynolds numbers that are several-fold higher. The collisions do not yet take into account the effect of the lubricating gas layer, which will be the topic of future work. NSF Award CBET-1605195.
Experimental Validation of Numerical Simulations for an Acoustic Liner in Grazing Flow
Tam, Christopher K. W.; Pastouchenko, Nikolai N.; Jones, Michael G.; Watson, Willie R.
2013-01-01
A coordinated experimental and numerical simulation effort is carried out to improve our understanding of the physics of acoustic liners in a grazing flow as well our computational aeroacoustics (CAA) method prediction capability. A numerical simulation code based on advanced CAA methods is developed. In a parallel effort, experiments are performed using the Grazing Flow Impedance Tube at the NASA Langley Research Center. In the experiment, a liner is installed in the upper wall of a rectangular flow duct with a 2 inch by 2.5 inch cross section. Spatial distribution of sound pressure levels and relative phases are measured on the wall opposite the liner in the presence of a Mach 0.3 grazing flow. The computer code is validated by comparing computed results with experimental measurements. Good agreements are found. The numerical simulation code is then used to investigate the physical properties of the acoustic liner. It is shown that an acoustic liner can produce self-noise in the presence of a grazing flow and that a feedback acoustic resonance mechanism is responsible for the generation of this liner self-noise. In addition, the same mechanism also creates additional liner drag. An estimate, based on numerical simulation data, indicates that for a resonant liner with a 10% open area ratio, the drag increase would be about 4% of the turbulent boundary layer drag over a flat wall.
The numerical and experimental simulation of hypervelocity flow around the HYFLEX vehicle forebody
Johnston, I. A.; Tuttle, S. L.; Jacobs, P. A.; Shimoda, T.
Numerical and experimental techniques are used to model the flow and pressure distribution around the forebody of the HYFLEX hypersonic flight vehicle. We compare numerical simulation results with modified Newtonian theory and flight data to determine the accuracy of the computational fluid dynamics (CFD) technique used. The numerical simulations closely match the trends in flight data, and show that real gas effects have a small but significant influence on the nose pressure distribution. We also present pressure results from a scale-model tested in a shock tunnel, and compare them with simulation results. For the shock tunnel experiment, the model was placed such that part of the upper surface was in a region of the test flow where nonuniformities were significant, and it was shown that the numerical simulation could adequately capture these experimental flow features. The binary scaling parameter (describing the similarity in species dissociation between flight and model) was used to design the scale-model tests in the shock tunnel, and its effectiveness is discussed. We find that matching the flight Mach number in the shock tunnel experiment is not critical for reproducing flight pressure data, so long as flight velocity is matched, and binary scaling is maintained.
Numerical Simulations Of Hydrodynamic Open-Water Characteristics Of A Ship Propeller
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Felicjancik Judyta
2016-12-01
Full Text Available The paper presents the results of numerical simulations of ship propeller operation bearing the name of Propeller Open Water (POW Tests. The object of tests was a sample ship propeller (PPTC1, the geometrical and kinematic data of which are available, along with the results of model tests, on the official page of the research centre involved in the measurements. The research aimed at verifying the correctness of results of numerical simulations performed in the model and real scale. The results of numerical analyses performed in the model scale were confronted with those measured in the experiment. Then, making use of dimensionless coefficients which characterise propeller’s operation, the recorded model data were extrapolated to real conditions and compared with corresponding results of simulations. Both the numerical simulations and the experimental research were performed for the same propeller load states. The reported research is in line with other activities which aim at developing advanced numerical methods to support the process of ship propeller designing.
Computer-based numerical simulations of adsorption in nanostructures
Khashimova, Diana
2014-08-01
Zeolites are crystalline oxides with uniform, molecular-pore diameters of 3-14Å. Significant developments since 1950 made production of synthetic zeolites with high purity and controlled chemical composition possible. In powder-form, zeolites are major role-players in high-tech, industrial catalysis, adsorption, and ion exchange applications. Understanding properties of thin-film zeolites has been a focus of recent research. The ability to fine-tune desired macroscopic properties by controlled alteration at the molecular level is paramount. The relationships between macroscopic and molecular-level properties are established by experimental research. Because generating macroscopic, experimental data in a controlled laboratory can be prohibitively costly and time-consuming, reliable numerical simulations, which remove such difficulties, are an attractive alternative. Using a Configurational Biased Monte Carlo (CBMC) approach in grand canonical ensemble, numerical models for pure component and multicomponent adsorption processes were developed. Theoretical models such as ideal (IAST) and real adsorbed solution theory (RAST) to predict mixture adsorption in nanopores were used for comparison. Activity coefficients used in RAST calculations were determined from the Wilson, spreading pressure and COSMO-RS models. Investigative testing of the method on known materials, represented by all-silica zeolites such as MFI (channel type) and DDR (cage type), proved successful in replicating experimental data on adsorption of light hydrocarbons - alkanes, such as methane, ethane, propane and butane. Additionally, adsorption of binary and ternary mixtures was simulated. The given numerical approach developed can be a powerful, cost and time saving tool to predict process characteristics for different molecular-structure configurations. The approach used here for simulating adsorption properties of nanopore materials including process characteristics, may have great potential for
Direct Numerical Simulation of an Airfoil with Sand Grain Roughness on the Leading Edge
Ribeiro, Andre F. P.; Casalino, Damiano; Fares, Ehab; Choudhari, Meelan
2016-01-01
As part of a computational study of acoustic radiation due to the passage of turbulent boundary layer eddies over the trailing edge of an airfoil, the Lattice-Boltzmann method is used to perform direct numerical simulations of compressible, low Mach number flow past an NACA 0012 airfoil at zero degrees angle of attack. The chord Reynolds number of approximately 0.657 million models one of the test conditions from a previous experiment by Brooks, Pope, and Marcolini at NASA Langley Research Center. A unique feature of these simulations involves direct modeling of the sand grain roughness on the leading edge, which was used in the abovementioned experiment to trip the boundary layer to fully turbulent flow. This report documents the findings of preliminary, proof-of-concept simulations based on a narrow spanwise domain and a limited time interval. The inclusion of fully-resolved leading edge roughness in this simulation leads to significantly earlier transition than that in the absence of any roughness. The simulation data is used in conjunction with both the Ffowcs Williams-Hawkings acoustic analogy and a semi-analytical model by Roger and Moreau to predict the farfield noise. The encouraging agreement between the computed noise spectrum and that measured in the experiment indicates the potential payoff from a full-fledged numerical investigation based on the current approach. Analysis of the computed data is used to identify the required improvements to the preliminary simulations described herein.
Numerical simulation of singularly perturbed differential equation with small shift
Arora, Geeta; Kaur, Mandeep
2017-07-01
In the present paper, perturbed singular differential equations of second order with small shift are treated for their numerical simulation. These equations arise in the mathematical models for the study of neuronal behavior and their basic activities. Collocation method is used to solve these boundary value problems using modified B-spline basis functions. To partition the domain the piecewise uniform mesh-shiskhin mesh is generated that generate more partitions near the boundary region. The study targets on the impact of small parameters on the solution. To confirm the coherence of the method test problems are presented and conduct of solution of the problem with the time lag parameter is shown.
NUMERICAL SIMULATIONS OF MAP IOP2B WITH AROME
Seity, Y.
2005-01-01
Abstract: The goal of this study is to use the large amount of measurements collected during the MAP IOP2B, to validate a new Numerical Weather Prediction system : AROME. We also evaluate AROME by comparison with ALADIN and Meso-NH simulations of this IOP. The AROME 2.5 km results are sensitive to the choice of the coupling model. AROME 2.5 km coupled with AROME 10 km is able in pseudo-operational conditions (long time step and coupled with forecasts) to reproduce the main features of the ...
Numerical simulations of thermal convection at high Prandtl numbers
Silano, Gabriella
2009-01-01
2007/2008 In this thesis we present the results of an extensive campaign of direct numerical simulations of Rayleigh-B\\'enard convection at high Prandtl numbers ($10^{-1}\\leq Pr \\leq 10^4$) and moderate Rayleigh numbers ($10^{5}\\leq Pr \\leq 10^9$). The computational domain is a cylindrical cell of aspect-ratio (diameter over cell height) $\\Gamma=1/2$, with the no-slip condition imposed to the boundaries. By scaling the results, we find a $1/\\sqrt{Pr}$ correction to apply to the free-...
Numerical Simulation of Transient Moisture Transfer into an Electronic Enclosure
DEFF Research Database (Denmark)
Shojaee Nasirabadi, Parizad; Jabbaribehnam, Mirmasoud; Hattel, Jesper Henri
2016-01-01
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 theCPU-time and make a way for subsequent factorial design analysis, a simplifying modification is applied in which...... the real3D geometry is approximated by a 2D axial symmetry one. The results for 2D and 3D models were compared in order tocalibrate the 2D representation. Furthermore, simulation results were compared with experimental data and good agreementwas found....
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.
Accurate numerical methods for micromagnetics simulations with general geometries
García-Cervera, C J
2003-01-01
In current FFT-based algorithms for micromagnetics simulations, the boundary is typically replaced by a staircase approximation along the grid lines, either eliminating the incomplete cells or replacing them by complete cells. Sometimes the magnetizations at the boundary cells are weighted by the volume of the sample in the corresponding cell. We show that this leads to large errors in the computed exchange and stray fields. One consequence of this is that the predicted switching mechanism depends sensitively on the orientation of the numerical grid. We present a boundary-corrected algorithm to efficiently and accurately handle the incomplete cells at the boundary. We show that this boundary-corrected algorithm greatly improves the accuracy in micromagnetics simulations. We demonstrate by using A. Arrott's example of a hexagonal element that the switching mechanism is predicted independently of the grid orientation.
Numerical simulations of heat transfer in plane channel flow
Gharbi, Najla El; Benzaoui, Ahmed
2010-01-01
Reynolds-averaged Navier-Stokes (RANS) turbulence models (such as k-{\\epsilon} models) are still widely used for engineering applications because of their relatively simplicity and robustness. In fully developed plane channel flow (i.e. the flow between two infinitely large plates), even if available models and near-wall treatments provide adequate mean flow velocities, they fail to predict suitable turbulent kinetic energy "TKE" profiles near walls. TKE is involved in determination of eddy viscosity/diffusivity and could therefore provide inaccurate concentrations and temperatures. In order to improve TKE a User Define Function "UDF" based on an analytical profile for TKE was developed and implemented in Fluent. Mean streamwise velocity and turbulent kinetic energy "TKE" profiles were compared to DNS data for friction Reynolds number $Re_{\\tau}$ = 150. Simulation results for TKE show accurate profiles. Simulation results for horizontal heated channel flows obtained with Fluent are presented. Numerical result...
Numerical simulation of low pressure die-casting aluminum wheel
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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 oil spills in a generalized domain
Energy Technology Data Exchange (ETDEWEB)
Cuesta, I.; Grau, F.X.; Giralt, F. (Barcelona Univ., Tarragona (Spain). Dept. d' Enginyeria Quimica i Bioqumica)
1990-01-01
A numerical model has been developed to simulate the time-space evolution of oil spills in marine environments of arbitrary and complex geometry. The model is applicable to gravity-viscosity regimes, i.e. up to 1 week for large spills, and takes into account dispersion caused by wind, tides and currents, spreading and evaporation, as well as accumulation and dispersion along the shorelines. The computer model is tested against data reported from the Amoco Cadiz accident, with satisfactory agreement on the extent and location of the slick. The model is also used to simulate and estimate the consequences of a hypothetical accidental spill occurring in the vicinity of the Tarragona harbour during transportation or unloading operations of crude oil. This is of importance because the Mediterranean coast of Tarragona, and in particular the Costa Daurada region, is one of the leading European tourist resorts. (author).
Numerical Simulation of Combustion Chamber for Button Turbojet Engine
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Ma Hongpeng
2016-01-01
Full Text Available To provide reference data for ultra-micro combustor, a new type button turbojet engine was designed and simulated the combustion’s steady-state process. The boundary condition of inlet was calculated using isentropic numerical calculation, taken into turbulent chemical reaction, heat radiation, and so on, getting the combustion chamber’s steady-state of the velocity, temperature and component concentration distribution, analysis the fuel/air flow and backflow, combustion efficiency and total pressure recovery coefficient, and compared with the experimental data. The calculation results can accurately reflect the actual combustion. The results show that combustion chamber exit velocity is about 65m/s, outlet temperature is around 1000K, the simulation and experimental data are similar, combustion chamber structure design is reasonable, and this paper will provide a basis for the future improvement of the millimeter scale turbojet engine.
[Numerical flow simulation : A new method for assessing nasal breathing].
Hildebrandt, T; Osman, J; Goubergrits, L
2016-08-01
The current options for objective assessment of nasal breathing are limited. The maximum they can determine is the total nasal resistance. Possibilities to analyze the endonasal airstream are lacking. In contrast, numerical flow simulation is able to provide detailed information of the flow field within the nasal cavity. Thus, it has the potential to analyze the nasal airstream of an individual patient in a comprehensive manner and only a computed tomography (CT) scan of the paranasal sinuses is required. The clinical application is still limited due to the necessary technical and personnel resources. In particular, a statistically based referential characterization of normal nasal breathing does not yet exist in order to be able to compare and classify the simulation results.
Numerical simulation of flow fields and particle trajectories
DEFF Research Database (Denmark)
Mayer, Stefan
2000-01-01
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...... contact between particle and cilia. A local capture efficiency is defined and its value computed for various values of beat frequencies and other parameters. The results indicate that the simulated particle capture process is most effective when the flow field oscillates within timescales comparable......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...
Numerical simulation of study and unsteady sheet cavitation
Energy Technology Data Exchange (ETDEWEB)
Schnerr, G.H.; Spengler, C. (Karlsruhe Univ. (T.H.) (Germany). Abt. Stroemungsmaschinen)
1998-01-01
The aim of the work is to provide an efficient code to simulate developed sheet cavitation including the unsteady behavior at the end of the sheet. The vapor region is calculated directly by using a 'compressible system' of equations. To simulate the liquid phase an 'incompressible system' of equations is used. The numerical method is based on an extended method of artificial compressibility which allows the simultaneous calculation of compressible and incompressible flows. To verify the code a first cavitating result of the inviscid flow around a NACA0012 hydrofoil at a Mach number M=0.1, an angle of attack [alpha]=4 , and a cavitation number [sigma]=1.0 is presented. (orig.)
Numerical simulation of study and unsteady sheet cavitation
Energy Technology Data Exchange (ETDEWEB)
Schnerr, G.H.; Spengler, C. [Karlsruhe Univ. (T.H.) (Germany). Abt. Stroemungsmaschinen
1998-12-31
The aim of the work is to provide an efficient code to simulate developed sheet cavitation including the unsteady behavior at the end of the sheet. The vapor region is calculated directly by using a `compressible system` of equations. To simulate the liquid phase an `incompressible system` of equations is used. The numerical method is based on an extended method of artificial compressibility which allows the simultaneous calculation of compressible and incompressible flows. To verify the code a first cavitating result of the inviscid flow around a NACA0012 hydrofoil at a Mach number M=0.1, an angle of attack {alpha}=4 , and a cavitation number {sigma}=1.0 is presented. (orig.)
Material flow data for numerical simulation of powder injection molding
Duretek, I.; Holzer, C.
2017-01-01
The powder injection molding (PIM) process is a cost efficient and important net-shape manufacturing process that is not completely understood. For the application of simulation programs for the powder injection molding process, apart from suitable physical models, exact material data and in particular knowledge of the flow behavior are essential in order to get precise numerical results. The flow processes of highly filled polymers are complex. Occurring effects are very hard to separate, like shear flow with yield stress, wall slip, elastic effects, etc. Furthermore, the occurrence of phase separation due to the multi-phase composition of compounds is quite probable. In this work, the flow behavior of a 316L stainless steel feedstock for powder injection molding was investigated. Additionally, the influence of pre-shearing on the flow behavior of PIM-feedstocks under practical conditions was examined and evaluated by a special PIM injection molding machine rheometer. In order to have a better understanding of key factors of PIM during the injection step, 3D non-isothermal numerical simulations were conducted with a commercial injection molding simulation software using experimental feedstock properties. The simulation results were compared with the experimental results. The mold filling studies amply illustrate the effect of mold temperature on the filling behavior during the mold filling stage. Moreover, the rheological measurements showed that at low shear rates no zero shear viscosity was observed, but instead the viscosity further increased strongly. This flow behavior could be described with the Cross-WLF approach with Herschel-Bulkley extension very well.
Numerical experiments with rubble piles : equilibrium shapes and spins
Richardson, Derek C.; Elankumaran, Pradeep; Sanderson, Robyn E.
2005-01-01
We present numerical experiments investigating the shape and spin limits of self-gravitating "perfect" rubble piles that consist of identical, smooth, rigid, spherical particles with configurable normal coefficient of restitution and no sliding friction. Such constructs are currently employed in a
Numerical simulation of spark ignition engine using OpenFOAM®
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B.T. Kannan
2016-09-01
Full Text Available The present work is the numerical investigation of Spark Ignition (SI engines using an open source Computational Fluid Dynamics (CFD tool. Investigations on the usage of OpenFOAM® CFD tool has been carried out for the simulation of SI engines using engineFoam solver. Four-valve pent roof type engine is chosen for the present simulations. The standard k–ɛ turbulence model is used along with the Reynolds Averaged Navier Stokes (RANS equations for simulating the flow field. Energy equation and transport equation for regress variable is solved along with the momentum equations. Xi model is used for the transport and Gulder's correlation is used for laminar flame speed. Unstrained model is used for calculating the laminar flame speed velocity. Two simulations are carried out one with cold flow and the other with combustion. For combustion analysis, Iso-octane fuel is used. Average cylinder pressure is tracked for different Crank Angles (CA from −180 to 60. The temperature contours are plotted on a vertical plane inside the cylinder to indicate the rise in temperature due to combustion. The results indicate that the open source CFD code can be an ideal choice for engine designers.
Numerical Simulation of Solitary Waves Using Smoothed Particle Hydrodynamics Method
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Swapnadip De Chowdhury
2012-09-01
Full Text Available Understanding shallow water wave propagation is of major concern in any coastal mitigation effort. Many times, a solitary wave replicates a shallow water wave in its extreme sense which includes a tsunami wave. It is mainly due to known physical characteristics of such waves. Therefore, the study of propagation of solitary waves in the near shore waters is of equal importance in the context of non linear water waves. Owing to the significant growth in computational technologies in the last few decades, a significant number of numerical methods have emerged and applied to simulate nonlinear solitary wave propagation. In this study, one such method, the Smoothed Particle Hydrodynamics (SPH method has been described to simulate the solitary waves. The split-up of a single solitary wave while it crosses a continental kind of shelf has been simulated by the present model. Then SPH model is coupled with the Boussinesq model to predict the time interval between two successive solitary waves on landfall. It has also been shown to be equally efficient in simulating the wave breaking while a solitary wave propagates over a mild slope.
Numerical simulations of GAE stabilization in NSTX-U
Belova, Elena; Fredrickson, Eric; Crocker, Neal; NSTX-U Team
2017-10-01
Beam-driven Global Alfven Eigenmodes (GAEs) were frequently observed on NSTX and NSTX-U and have been linked with a flattening of the electron temperature profile in the plasma core. New experimental results from NSTX-U have demonstrated that neutral beam injection from the new beam sources with large tangency radii deposit beam ions with large pitch, which can very effectively stabilize all unstable GAEs. Numerical simulations using the HYM code have been performed to study the excitation and stabilization of GAEs in the NSTX-U right before and shortly after the additional off-axis beam injection. HYM simulations reproduce experimental finding, namely it is shown that off-axis neutral beam injection reliably and strongly suppresses all unstable GAEs. Before additional beam injection, the simulations show unstable counter-rotating GAEs with toroidal mode numbers n =7-12, and frequencies that match the experimentally observed unstable GAEs. Additional of-axis beam injection has been modeled by adding beam ions with large pitch, and about 1/3 of the total beam ion inventory. The simulations in this case show a complete stabilization of all unstable GAEs (n =7-12), even for the cases when the HYM calculated GAE growth rates were relatively large. Work supported by U.S. DOE Contract DE'AC02'09CH11466.
A numerical experiment on light pollution from distant sources
Kocifaj, M.
2011-08-01
To predict the light pollution of the night-time sky realistically over any location or measuring point on the ground presents quite a difficult calculation task. Light pollution of the local atmosphere is caused by stray light, light loss or reflection of artificially illuminated ground objects or surfaces such as streets, advertisement boards or building interiors. Thus it depends on the size, shape, spatial distribution, radiative pattern and spectral characteristics of many neighbouring light sources. The actual state of the atmospheric environment and the orography of the surrounding terrain are also relevant. All of these factors together influence the spectral sky radiance/luminance in a complex manner. Knowledge of the directional behaviour of light pollution is especially important for the correct interpretation of astronomical observations. From a mathematical point of view, the light noise or veil luminance of a specific sky element is given by a superposition of scattered light beams. Theoretical models that simulate light pollution typically take into account all ground-based light sources, thus imposing great requirements on CPU and MEM. As shown in this paper, a contribution of distant sources to the light pollution might be essential under specific conditions of low turbidity and/or Garstang-like radiative patterns. To evaluate the convergence of the theoretical model, numerical experiments are made for different light sources, spectral bands and atmospheric conditions. It is shown that in the worst case the integration limit is approximately 100 km, but it can be significantly shortened for light sources with cosine-like radiative patterns.
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.
Proudman and Chrystal resonances simulated with three numerical models
Bubalo, Maja; Janeković, Ivica; Orlić, Mirko
2017-04-01
The aim of this work was to validate and compare how Proudman and Chrystal resonances are reproduced with different, nowadays widely used, numerical models. The test case was based on simple air pressure disturbances of two commonly used shapes (a boxcar and a sinusoidal), having various wave lengths, and propagating at different speeds. Our test domain was a rectangular basin, 300 km long with a uniform depth of 50 m. For each simulation, we saved water level anomalies and computed the integral of the energy density spectrum for a number of points distributed along the basin. The 341 simulations were performed using three different numerical models: ADCIRC, ROMS and SCHISM. A comparison of the results shows that the models represent the resonant phenomena in different ways. For the Proudman resonance, the most consistent results, closest to the analytical solution, were obtained with ROMS model, which reproduced the mean resonant speed equal to 21.99 m/s - i.e., close to the theoretical value of 22.14 m/s. ADCIRC model showed small deviations from that value, with the mean speed being slightly lower - 21.79 m/s. SCHISM differed the most from the analytical solution, with the mean speed equalling 21.04 m/s. For the Chrystal resonance, all the models showed similar behaviour, with ADCIRC model providing slightly lower values of the mean resonant period than the other two models.
Constitutive Modeling and Numerical Simulation of Frp Confined Concrete Specimens
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Smitha Gopinath
2014-09-01
Full Text Available Fiber-reinforced polymer (FRP composites are generally used for the seismic retrofit of concrete members to enhance their strength and ductility. In the present work, the confining effect of Carbon Fiber-Reinforced Polymer (CFRP composite layers has been investigated by numerical simulation. The numerical simulation has been carried out using nonlinear finite element analysis (FEA to predict the response behaviour of CFRP-wrapped concrete cylinders. The nonlinear behaviour of concrete in compression and the linear elastic behaviour of CFRP has been modeled using an appropriate constitutive relationship. A cohesive model has been developed for modeling the interface between the concrete and CFRP. The interaction and damage failure criteria between the concrete to the cohesive element and the cohesive element to the CFRP has also been accounted for in the modeling. The response behaviour of the wrapped concrete specimen has been compared with the proposed interface model and with a perfectly bonded condition. The results obtained from the present study showed good agreement with the experimental load-displacement response and the failure pattern in the literature. Further, a sensitivity analysis has been carried out to study the effect of the number of layers of CFRP on the concrete specimens. It has been observed that wrapping with two layers was found to be the optimum, beyond which the response becomes flexible but with a higher load-carrying capacity
Constitutive Modeling and Numerical Simulation of Frp Confined Concrete Specimens
Smitha, Gopinath; Ramachandramurthy, Avadhanam; Nagesh, Ranganatha Iyer; Shahulhameed, Eduvammal Kunhimoideen
2014-09-01
Fiber-reinforced polymer (FRP) composites are generally used for the seismic retrofit of concrete members to enhance their strength and ductility. In the present work, the confining effect of Carbon Fiber-Reinforced Polymer (CFRP) composite layers has been investigated by numerical simulation. The numerical simulation has been carried out using nonlinear finite element analysis (FEA) to predict the response behaviour of CFRP-wrapped concrete cylinders. The nonlinear behaviour of concrete in compression and the linear elastic behaviour of CFRP has been modeled using an appropriate constitutive relationship. A cohesive model has been developed for modeling the interface between the concrete and CFRP. The interaction and damage failure criteria between the concrete to the cohesive element and the cohesive element to the CFRP has also been accounted for in the modeling. The response behaviour of the wrapped concrete specimen has been compared with the proposed interface model and with a perfectly bonded condition. The results obtained from the present study showed good agreement with the experimental load-displacement response and the failure pattern in the literature. Further, a sensitivity analysis has been carried out to study the effect of the number of layers of CFRP on the concrete specimens. It has been observed that wrapping with two layers was found to be the optimum, beyond which the response becomes flexible but with a higher load-carrying capacity
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.
Direct Numerical Simulation of Disperse Multiphase High-Speed Flows
Energy Technology Data Exchange (ETDEWEB)
Nourgaliev, R R; Dinh, T N; Theofanous, T G; Koning, J M; Greenman, R M; Nakafuji, G T
2004-02-17
A recently introduced Level-Set-based Cartesian Grid (LSCG) Characteristics-Based Matching (CBM) method is applied for direct numerical simulation of shock-induced dispersal of solid material. The method incorporates the latest advancements in the level set technology and characteristics-based numerical methods for solution of hyperbolic conservation laws and boundary treatment. The LSCG/CBM provides unique capabilities to simulate complex fluid-solid (particulate) multiphase flows under high-speed flow conditions and taking into account particle-particle elastic and viscoelastic collisions. The particular emphasis of the present study is placed on importance of appropriate modeling of particle-particle collisions, which are demonstrated to crucially influence the global behavior of high-speed multiphase particulate flows. The results of computations reveal the richness and complexity of flow structures in compressible disperse systems, due to dynamic formation of shocks and contact discontinuities, which provide an additional long-range interaction mechanism in dispersed high-speed multiphase flows.
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 of Spray Atomization in Supersonic Flows
Wang, Jiangfeng; Liu, Chen; Wu, Yizhao
With the rapid development of the air-breathing hypersonic vehicle design, an accurate description of the combustion properties becomes more and more important, where one of the key techniques is the procedure of the liquid fuel mixing, atomizing and burning coupled with the supersonic crossflow in the combustion chamber. The movement and distribution of the liquid fuel droplets in the combustion chamber will influence greatly the combustion properties, as well as the propulsion performance of the ramjet/scramjet engine. In this paper, numerical simulation methods on unstructured hybrid meshes were carried out for liquid spray atomization in supersonic crossflows. The Kelvin-Helmholtz/Rayleigh-Taylor hybrid model was used to simulate the breakup process of the liquid spray in a supersonic crossflow with Mach number 1.94. Various spray properties, including spray penetration height, droplet size distribution, were quantitatively compared with experimental results. In addition, numerical results of the complex shock wave structure induced by the presence of liquid spray were illustrated and discussed.
Numerical Simulation of Rocket Exhaust Interaction with Lunar Soil
Liever, Peter; Tosh, Abhijit; Curtis, Jennifer
2012-01-01
This technology development originated from the need to assess the debris threat resulting from soil material erosion induced by landing spacecraft rocket plume impingement on extraterrestrial planetary surfaces. The impact of soil debris was observed to be highly detrimental during NASA s Apollo lunar missions and will pose a threat for any future landings on the Moon, Mars, and other exploration targets. The innovation developed under this program provides a simulation tool that combines modeling of the diverse disciplines of rocket plume impingement gas dynamics, granular soil material liberation, and soil debris particle kinetics into one unified simulation system. The Unified Flow Solver (UFS) developed by CFDRC enabled the efficient, seamless simulation of mixed continuum and rarefied rocket plume flow utilizing a novel direct numerical simulation technique of the Boltzmann gas dynamics equation. The characteristics of the soil granular material response and modeling of the erosion and liberation processes were enabled through novel first principle-based granular mechanics models developed by the University of Florida specifically for the highly irregularly shaped and cohesive lunar regolith material. These tools were integrated into a unique simulation system that accounts for all relevant physics aspects: (1) Modeling of spacecraft rocket plume impingement flow under lunar vacuum environment resulting in a mixed continuum and rarefied flow; (2) Modeling of lunar soil characteristics to capture soil-specific effects of particle size and shape composition, soil layer cohesion and granular flow physics; and (3) Accurate tracking of soil-borne debris particles beginning with aerodynamically driven motion inside the plume to purely ballistic motion in lunar far field conditions. In the earlier project phase of this innovation, the capabilities of the UFS for mixed continuum and rarefied flow situations were validated and demonstrated for lunar lander rocket
Numerical simulation of wave interacting with a free rolling body
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Jae Hwan Jung
2013-09-01
Full Text Available The present study numerically models the interaction between a regular wave and the roll motion of a rectangular floating structure. In order to simulate two-dimensional incompressible viscous two-phase flow in a numerical wave tank with the rectangular floating structure, the present study used the volume of fluid method based on the finite volume method. The sliding mesh technique is adopted to handle the motion of the rectangular floating structure induced by fluid-structure interaction. The effect of the wave period on the flow, roll motion and forces acting on the structure is examined by considering three different wave periods. The time variations of the wave height and the roll motion of the rectangular structure are in good agreement with experimental results for all wave periods. The present response amplitude operator is in good agreement with experimental results with the linear potential theory. The present numerical results effectively represent the entire process of vortex generation and evolution described by the experimental results. The longer wave period showed a different mechanism of the vortex evolution near each bottom corner of the structure compared to cases of shorter wave periods. In addition, the x-directional and z-directional forces acting on the structure are analyzed.
Direct numerical simulation of heat transfer over riblets
Energy Technology Data Exchange (ETDEWEB)
Stalio, E.; Nobile, E
2003-06-01
Riblets are well-known as a passive mean for drag reduction in turbulent flow conditions, but their effectiveness for heat transfer is quite controversial. In this paper we present the numerical results for fully developed laminar and turbulent flow and heat transfer in a channel with triangular riblets. The turbulent study is performed by means of direct numerical simulation at a Reynolds number Re{sub {tau}}=180 based on the wall-shear velocity, for a fluid with a Prandtl number Pr=0.71. Four different ribbed channels are considered, under a constant heat flux boundary condition, and correspond to ridge angle {alpha}=45 deg. and 60 deg., and riblet spacing s{sup +}=20 and s{sup +}=40. The results obtained, for the flow and turbulent quantities, are in good agreement with past experimental and numerical studies, and correctly reproduce drag reduction over the smaller s{sup +}=20 riblets and drag increase over the larger s{sup +}=40 riblets. The predicted heat transfer efficiency of riblets do not agree with some experimental results, and is below that of a flat plate for all the configurations. The conditions for heat transfer enhancement are discussed.
Mathematical modelling and numerical simulation of oil pollution problems
2015-01-01
Written by outstanding experts in the fields of marine engineering, atmospheric physics and chemistry, fluid dynamics and applied mathematics, the contributions in this book cover a wide range of subjects, from pure mathematics to real-world applications in the oil spill engineering business. Offering a truly interdisciplinary approach, the authors present both mathematical models and state-of-the-art numerical methods for adequately solving the partial differential equations involved, as well as highly practical experiments involving actual cases of ocean oil pollution. It is indispensable that different disciplines of mathematics, like analysis and numerics, together with physics, biology, fluid dynamics, environmental engineering and marine science, join forces to solve today’s oil pollution problems. The book will be of great interest to researchers and graduate students in the environmental sciences, mathematics and physics, showing the broad range of techniques needed in order to solve these poll...
Energy Technology Data Exchange (ETDEWEB)
Nielsen, Bjoern Fredrik
1997-12-31
The main purpose of this thesis has been to analyse self-adjoint second order elliptic partial differential equations arising in reservoir simulation. It studies several mathematical and numerical problems for the pressure equation arising in models of fluid flow in porous media. The theoretical results obtained have been illustrated by a series of numerical experiments. The influence of large variations in the mobility tensor upon the solution of the pressure equation is analysed. The performance of numerical methods applied to such problems have been studied. A new upscaling technique for one-phase flow in heterogeneous reservoirs is developed. The stability of the solution of the pressure equation with respect to small perturbations of the mobility tensor is studied. The results are used to develop a new numerical method for a model of fully nonlinear water waves. 158 refs, 39 figs., 12 tabs.
Numerical simulation of fire spread in terminal 2 of Belgrade airport
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Stevanović Žarko
2007-01-01
Full Text Available This paper concern the results of software fire spread process prototype in terminal 2 of Belgrade airport using computational fluid dynamics. Numerical simulation of fire for the most critical fire scenario has been performed, primarily obtaining the space and time distribution of: velocity, pressure, temperature, and smoke concentration, assuming that HVAC systems have been switched off and all doors on the evacuation ways have been opened, just as the fire started. Also, two simulations have been compared of the smoke ventilation and not ventilation for the same scenario. Within the framework of the results presentation, isosurfaces of constant temperature (100 ºC and smoke concentration (4000 ppm are presented, based on the numerical simulation. Progression of these surfaces along the terminal 2 coincides to the experimental and experience evidence, forming the plume zone just above the fireplace, and spreading in the zone of underground ceiling and stairwell openings. .
Yang, Zongzhen; Zhang, Xiaofeng; Bao, Xinjie; Chen, Shuyang
2017-05-01
A Weather Research and Forecasting Model (WRF) and random walk model have been used to numerical simulate and analysis the characteristics of meso-micro scale wind field and atmospheric diffusion in coastal area of a sit. The results indicated that the atmospheric dispersion in this area is determined both by synoptic scale system and land-sea breeze circulation. Spatial variation of wind field is not obvious in synoptic scale system situation, which leads to the straight dispersion plume. Temporal variation of wind field, particularly the wind direction transition caused by transient of land-sea breezes is obvious. The method of random walk simulation better reflects the characteristics of the air pollutants transportation and diffusion. The atmospheric diffusion parameters obtained with numerical simulation experiment may reflect well the characteristics of the air diffusion in local area.
Numerical Simulation of the Aircraft Wake Vortex Flowfield
Ahmad, Nashat N.; Proctor, Fred H.; Perry, R. Brad
2013-01-01
The near wake vortex flowfield from a NACA0012 half-wing was simulated using a fully unstructured Navier-Stokes flow solver in three dimensions at a chord Reynolds number of 4.6 million and a Mach number of approximately 0.15. Several simulations were performed to examine the effect of boundary conditions, mesh resolution and turbulence scheme on the formation of wingtip vortex and its downstream propagation. The standard Spalart-Allmaras turbulence model was compared with the Dacles-Mariani and Spalart-Shur corrections for rotation and curvature effects. The simulation results were evaluated using the data from experiment performed at NASA Ames' 32in x 48in low speed wind tunnel.
Direct numerical simulation of free falling sphere in creeping flow
Reddy, Rupesh K.; Jin, Shi; Nandakumar, K.; Minev, Peter D.; Joshi, Jyeshtharaj B.
2010-03-01
In the present study, direct numerical simulations (DNS) are performed on single and a swarm of particles settling under the action of gravity. The simulations have been carried out in the creeping flow range of Reynolds number from 0.01 to 1 for understanding the hindrance effect, of the other particles, on the settling velocity and drag coefficient. The DNS code is a non-Lagrange multiplier-based fictitious-domain method, which has been developed and validated by Jin et al. (2008; A parallel algorithm for the direct numerical simulation of 3D inertial particle sedimentation. In: Conference proceedings of the 16th annual conference of the CFD Society of Canada). It has been observed that the time averaged settling velocity of the particle in the presence of other particles, decreases with an increase in the number of particles surrounding it (from 9 particles to 245 particles). The effect of the particle volume fraction on the drag coefficient has also been studied and it has been observed that the computed values of drag coefficients are in good agreement with the correlations proposed by Richardson and Zaki (1954; Sedimentation and fluidization: part I. Transactions of the Institution of Chemical Engineers, 32, 35-53) and Pandit and Joshi (1998; Pressure drop in packed, expanded and fluidised beds, packed columns and static mixers - a unified approach. Reviews in Chemical Engineering, 14, 321-371). The suspension viscosity-based model of Frankel and Acrivos (1967; On the viscosity of a concentrated suspension of solid spheres. Chemical Engineering Science, 22, 847-853) shows good agreement with the DNS results.
Hu, Ping; Liu, Li-zhong; Zhu, Yi-guo
2013-01-01
Over the last 15 years, the application of innovative steel concepts in the automotive industry has increased steadily. Numerical simulation technology of hot forming of high-strength steel allows engineers to modify the formability of hot forming steel metals and to optimize die design schemes. Theories, Methods and Numerical Technology of Sheet Metal Cold and Hot Forming focuses on hot and cold forming theories, numerical methods, relative simulation and experiment techniques for high-strength steel forming and die design in the automobile industry. Theories, Methods and Numerical Technology of Sheet Metal Cold and Hot Forming introduces the general theories of cold forming, then expands upon advanced hot forming theories and simulation methods, including: • the forming process, • constitutive equations, • hot boundary constraint treatment, and • hot forming equipment and experiments. Various calculation methods of cold and hot forming, based on the authors’ experience in commercial CAE software f...
NUMERICAL SIMULATION OF POLLUTION DISPERSION IN URBAN STREET
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M. M. Biliaiev
2017-08-01
Full Text Available Purpose. The scientific paper solves the question of 2D numerical model development, which allows quick computation of air pollution in streets from vehicles. The aim of the work is numerical model development that would enable to predict the level of air pollution by using protective barriers along the road. Methodology. The developed model is based on the equation of inviscid flow and equation of pollutant transfer. Potential equation is used to compute velocity field of air flow near road in the case of protection barriers application. To solve equation for potential flow implicit difference scheme of «conditional approximation« is used. The implicit change – triangle difference scheme is used to solve equation of convective – diffusive dispersion. Numerical integration is carried out using the rectangular difference grid. Method of porosity technique («markers method» is used to create the form of comprehensive computational region. Emission of toxic gases from vehicle is modeled using Delta function for point source.Findings. Authors developed 2D numerical model. It takes into account the main physical factors affecting the process of dispersion of pollutants in the atmosphere when emissions of vehicle including protection barriers near the road. On the basis of the developed numerical models a computational experiment was performed to estimate the level of air pollution in the street. Originality. A numerical model has been created. It makes it possible to calculate 2D aerodynamics of the wind flow in the presence of noises and the process of mass transfer of toxic gas emissions from the motorway. The model allows taking into account the presence of the car on the road, the form of a protective barrier, the presence of a curb. Calculations have been performed to determine the contamination zone formed at the protective barrier that is located at the motorway. Practical value. An effective numerical model that can be applied in the
A numerical study of rays in random media. [Monte Carlo method simulation
Youakim, M. Y.; Liu, C. H.; Yeh, K. C.
1973-01-01
Statistics of electromagnetic rays in a random medium are studied numerically by the Monte Carlo method. Two dimensional random surfaces with prescribed correlation functions are used to simulate the random media. Rays are then traced in these sample media. Statistics of the ray properties such as the ray positions and directions are computed. Histograms showing the distributions of the ray positions and directions at different points along the ray path as well as at given points in space are given. The numerical experiment is repeated for different cases corresponding to weakly and strongly random media with isotropic and anisotropic irregularities. Results are compared with those derived from theoretical investigations whenever possible.
Numerical Simulation of Three-Dimensional Dendritic Growth
Energy Technology Data Exchange (ETDEWEB)
Karma, A.; Rappel, W. [Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115 (United States)
1996-11-01
Dendritic crystal growth in a pure undercooled melt is simulated quantitatively in three dimensions using a phase-field approach. The classic parameter {sigma}{sup *} that characterizes the dynamically selected operating state of the dendrite tip as well as the full nonaxisymmetric tip morphology are determined as a function of anisotropy for a crystal with a cubic symmetry. Results are compared to experiment and used to critically test solvability theory. {copyright} {ital 1996 The American Physical Society.}
Plasma temperature measurements in disruption simulated experiment
Energy Technology Data Exchange (ETDEWEB)
Arkhipov, N.I. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation); Bakhtin, V.P. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation); Safronov, V.M. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation); Toporkov, D.A. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation); Vasenin, S.G. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation); Wurz, H. [Kernforschungszentrum Karlsruhe, INR (Germany); Zhitlukhin, A.M. [Troitsk Inst. for Innovation and Fusion Research (Russian Federation)
1995-12-31
Results are reported of experiments to measure the temporal and spatial distributions of a temperature and radiation of a near surface plasma cloud appearing in the disruption simulated experiments. These measurements are needed to verificate the different numerical models of vapor shielding layer which appears to arise near the divertor plates surface and prevents them from the bulk of the incoming energy. Experiments with graphite and tungsten samples were carried out at the 2MK-200 plasma facility. Long CUSP trap was used as a source of high temperature deuterium plasma with a power density W = 10 MW/cm{sup 2} and time duration t = 20 mcs. Laser scattering, space and time resolved soft x-ray spectroscopy was employed to measure the plasma cloud temperature and radiation. The different behaviour of shielding layer parameters was shown for a graphite and tungsten samples. For a tungsten the sharp boundary existed between the incoming deuterium plasma and the thin layer of ablated material plasma and the strong gradient of electron temperature took place in this zone. For a graphite this boundary was broadened at the distance and the main part of the screening layer consisted of the mixture of the incoming deuterium and ablated carbon plasma. (orig.).
Directory of Open Access Journals (Sweden)
V. Salajka
2017-01-01
Full Text Available This article deals with an analysis of the behaviour of brick ceramic walls. The behaviour of the walls was analysed experimentally in order to obtain their bearing capacity under static loading and their seismic resistance. Simultaneously, numerical simulations of the experiments were carried out in order to obtain additional information on the behaviour of masonry walls made of ceramic blocks. The results of the geometrically and materially nonlinear computations were compared to the results of the performed tests.
Direct numerical simulation of turbulent flow over a backward-facing step
Le, Hung; Moin, Parviz
1993-01-01
The objectives of this study are as follows: (1) to conduct a direct numerical simulation of turbulent backward facing step flow using inflow and outflow conditions; and (2) to provide data in the form of Reynolds stress budgets for Reynolds averaged modeling. The report presents the basic statistical data and comparisons with the concurrent experiments of Jovic and Driver and budgets of turbulent kinetic energy.
Color Gradients Within Globular Clusters: Restricted Numerical Simulation
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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 Density Current Evolution in a Diverging Channel
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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 backward erosion piping in heterogeneous fields
Liang, Yue; Yeh, Tian-Chyi Jim; Wang, Yu-Li; Liu, Mingwei; Wang, Junjie; Hao, Yonghong
2017-04-01
Backward erosion piping (BEP) is one of the major causes of seepage failures in levees. Seepage fields dictate the BEP behaviors and are influenced by the heterogeneity of soil properties. To investigate the effects of the heterogeneity on the seepage failures, we develop a numerical algorithm and conduct simulations to study BEP progressions in geologic media with spatially stochastic parameters. Specifically, the void ratio e, the hydraulic conductivity k, and the ratio of the particle contents r of the media are represented as the stochastic variables. They are characterized by means and variances, the spatial correlation structures, and the cross correlation between variables. Results of the simulations reveal that the heterogeneity accelerates the development of preferential flow paths, which profoundly increase the likelihood of seepage failures. To account for unknown heterogeneity, we define the probability of the seepage instability (PI) to evaluate the failure potential of a given site. Using Monte-Carlo simulation (MCS), we demonstrate that the PI value is significantly influenced by the mean and the variance of ln k and its spatial correlation scales. But the other parameters, such as means and variances of e and r, and their cross correlation, have minor impacts. Based on PI analyses, we introduce a risk rating system to classify the field into different regions according to risk levels. This rating system is useful for seepage failures prevention and assists decision making when BEP occurs.
Scaling of turbulence and turbulent mixing using Terascale numerical simulations
Donzis, Diego A.
Fundamental aspects of turbulence and turbulent mixing are investigated using direct numerical simulations (DNS) of stationary isotropic turbulence, with Taylor-scale Reynolds numbers (Rlambda) ranging from 8 to 650 and Schmidt numbers (Sc) from 1/8 to 1024. The primary emphasis is on important scaling issues that arise in the study of intermittency, mixing and turbulence under solid-body rotation. Simulations up to 20483 in size have been performed using large resource allocations on Terascale computers at leading supercomputing centers. Substantial efforts in algorithmic development have also been undertaken and resulted in a new code based on a two-dimensional domain decomposition which allows the use of very large number of processors. Benchmark tests indicate very good parallel performance for resolutions up to 40963 on up to 32768 processors, which is highly promising for future simulations at higher resolutions and processor counts eventually to approach Petascale levels. Investigation of intermittency through the statistics of dissipation and enstrophy in a series of simulations at the same Reynolds number but different resolution indicate that accurate results in high-order moments require a higher degree of fine-scale resolution than commonly practiced. However, statistics up to fourth order are satisfactory if the grid spacing is not larger than Komogorov scale, without the requirement of a clear analytic range for corresponding structure functions as suggested by recent theories. Results from highly resolved simulations provide support for a modified resolution criterion derived in this work for structure functions of different orders and as a function of Rlambda. At the highest Reynolds number in our simulations (400 and 650) dissipation and enstrophy exhibit extreme fluctuations of O(1000) the mean which have not been studied in the literature before. The far tails of the probability density functions of dissipation and enstrophy appear to coincide
Numerical simulation study on rolling-chemical milling process of aluminum-lithium alloy skin panel
Huang, Z. B.; Sun, Z. G.; Sun, X. F.; Li, X. Q.
2017-09-01
Single curvature parts such as aircraft fuselage skin panels are usually manufactured by rolling-chemical milling process, which is usually faced with the problem of geometric accuracy caused by springback. In most cases, the methods of manual adjustment and multiple roll bending are used to control or eliminate the springback. However, these methods can cause the increase of product cost and cycle, and lead to material performance degradation. Therefore, it is of significance to precisely control the springback of rolling-chemical milling process. In this paper, using the method of experiment and numerical simulation on rolling-chemical milling process, the simulation model for rolling-chemical milling process of 2060-T8 aluminum-lithium alloy skin was established and testified by the comparison between numerical simulation and experiment results for the validity. Then, based on the numerical simulation model, the relative technological parameters which influence on the curvature of the skin panel were analyzed. Finally, the prediction of springback and the compensation can be realized by controlling the process parameters.
Numerical simulation of porous burners and hole plate surface burners
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Nemoda Stevan
2004-01-01
Full Text Available In comparison to the free flame burners the porous medium burners, especially those with flame stabilization within the porous material, are characterized by a reduction of the combustion zone temperatures and high combustion efficiency, so that emissions of pollutants are minimized. In the paper the finite-volume numerical tool for calculations of the non-isothermal laminar steady-state flow, with chemical reactions in laminar gas flow as well as within porous media is presented. For the porous regions the momentum and energy equations have appropriate corrections. In the momentum equations for the porous region an additional pressure drop has to be considered, which depends on the properties of the porous medium. For the heat transfer within the porous matrix description a heterogeneous model is considered. It treats the solid and gas phase separately, but the phases are coupled via a convective heat exchange term. For the modeling of the reaction of the methane laminar combustion the chemical reaction scheme with 164 reactions and 20 chemical species was used. The proposed numerical tool is applied for the analyses of the combustion and heat transfer processes which take place in porous and surface burners. The numerical experiments are accomplished for different powers of the porous and surface burners, as well as for different heat conductivity character is tics of the porous regions.
Numerical simulation and structural optimization of the inclined oil/water separator.
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Liqiong Chen
Full Text Available Improving the separation efficiency of the inclined oil/water separator, a new type of gravity separation equipment, is of great importance. In order to obtain a comprehensive understanding of the internal flow field of the separation process of oil and water within this separator, a numerical simulation based on Euler multiphase flow analysis and the realizable k-ε two equation turbulence model was executed using Fluent software. The optimal value ranges of the separator's various structural parameters used in the numerical simulation were selected through orthogonal array experiments. A field experiment on the separator was conducted with optimized structural parameters in order to validate the reliability of the numerical simulation results. The research results indicated that the horizontal position of the dispenser, the hole number, and the diameter had significant effects on the oil/water separation efficiency, and that the longitudinal position of the dispenser and the position of the weir plate had insignificant effects on the oil/water separation efficiency. The optimal structural parameters obtained through the orthogonal array experiments resulted in an oil/water separation efficiency of up to 95%, which was 4.996% greater than that realized by the original structural parameters.
Numerical Simulations of Asperity Crushing—Application to cold rolling
Carretta, Y.; Legrand, N.; Laugier, M.; Ponthot, J.-P.
2011-05-01
Asperity flattening has a huge influence on friction and wear in metal forming processes. Nevertheless, phenomena that occur at the microscopic scale are still not well understood. Since no experiments can be easily performed in real forming conditions, numerical models are essential to achieve a better knowledge of what happens in these contact regions. In this paper, two finite elements models are presented. The first one represents the flattening of a serrated asperity field in plane strain conditions. The results are compared to the experiments conducted by Sutcliffe [1]. The second one is a tri-dimensional asperity model flattened by a rigid plane. The boundary conditions applied to this model correspond to the ones encountered in a real cold rolling case. The results are compared to the relative contact area computed by a strip rolling model using the analytical laws proposed by Wilson & Sheu [2] and Marsault [3].
Energy Technology Data Exchange (ETDEWEB)
Chung, Chulhun, E-mail: chchung5@dankook.ac.kr [Department of Civil and Environmental Engineering, Dankook University, 126 Jukjeon-dong, Yongin-si 448-701 (Korea, Republic of); Lee, Jungwhee, E-mail: jwhee2@dankook.ac.kr [Department of Civil and Environmental Engineering, Dankook University, 126 Jukjeon-dong, Yongin-si 448-701 (Korea, Republic of); Jung, Raeyoung, E-mail: k701jry@kins.re.kr [Korea Institute of Nuclear Safety, 62 Gwahak-ro, Yuseong-gu, Daejeon 305-600 (Korea, Republic of)
2015-12-15
Highlights: • The procedures and results performed during the IRIS-2010/2012 projects are described. • Numerical impact simulations were performed and the initial FE model was updated. • Loading function with a fictitious loading plate approach was suggested. • Three concrete models were used and the results were compared. - Abstract: This paper describes the procedures and results of the works done by the Korea Institute of Nuclear Safety (KINS) as a participant of the IRIS-2010 and 2012 benchmark projects, which have been organized by OECD/NEA IAGE working group. Within the scope of the IRIS-2012 project, uniaxial and tri-axial concrete tests were performed and the results were supplied. With these material test data, impact simulations of IRIS-2010 experiments (Punching P1 and Bending B1) were re-performed to improve the accuracy of the simulation results and to reduce the computation time. Numerical impact simulations were performed using an explicit dynamic code, LS-DYNA, and the initial FE model was updated through numerous parametric studies. Considering the symmetry of the structure, an updated model was constructed for ¼ of the structure, and the stiffness and mass of the supporting structure was considered. Loading function with a fictitious loading plate was applied instead of modeling projectiles to reduce the computation time. Three concrete models, Concrete damage rel. 3 (*MAT-072R3), Winfrith concrete (*MAT-084-085), and CSCM concrete (*MAT-159), were used for the impact simulations and the results were compared.
Frenod, Emmanuel
2013-01-01
In this note, a classification of Homogenization-Based Numerical Methods and (in particular) of Numerical Methods that are based on the Two-Scale Convergence is done. In this classification stand: Direct Homogenization-Based Numerical Methods; H-Measure-Based Numerical Methods; Two-Scale Numerical Methods and TSAPS: Two-Scale Asymptotic Preserving Schemes.
Advances in Integrated Vehicle Thermal Management and Numerical Simulation
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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 the passive gas mixture flow
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Kyncl Martin
2016-01-01
Full Text Available The aim of this paper is the numerical solution of the equations describing the non-stationary compressible turbulent multicomponent flow in gravitational field. The mixture of perfect inert gases is assumed. We work with the RANS equations equipped with the k-omega and the EARSM turbulence models. For the simulation of the wall roughness we use the modification of the specific turbulent dissipation. The finite volume method is used, with thermodynamic constants being functions in time and space. In order to compute the fluxes through the boundary faces we use the modification of the Riemann solver, which is the original result. We present the computational results, computed with the own-developed code (C, FORTRAN, multiprocessor, unstructured meshes in general.
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 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.
Parallelization of a numerical simulation code for isotropic turbulence
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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).
Direct numerical simulation of three-dimensional liquid jet breakup
Constante, Ricardo; Kahouadji, Lyes; Nicolle, Andre; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Matar, Omar K.
2017-11-01
We carry out direct numerical simulations of liquid jet dynamics and breakup using a high-performance code, Blue, which uses a hybrid technique based on the front-tracking and the level-set method; it defines the interface position through a marker function and a local triangular Lagrangian mesh. Liquid jet breakup is an example of interfacial complexity associated with multiphase flows because of the formation of ligaments and their pinch off to give rise to droplet formation. We consider the atomisation of a liquid jet released into a stagnant gas phase where the velocity is stimulated sinusoidally to promote the growth of Kelvin-Helmholtz instabilities, thus forming a flow system characterized by complex interfaces. The spread of cylindrical liquid jet into a coflowing external stream is also considered (essentially, a replication of the Marmottant and Villermaux experimental work). Funding from BP gratefully acknowledged.
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.
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.
Direct Numerical Simulation and Visualization of Biswirling Jets
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Jie Yan
2014-07-01
Full Text Available Two parallel swirling/rotating jets with a distance between them are termed biswirling jets here, which have important and complicated vortex structures different from the single swirling jet due to the negligible vortex-vortex interactions. The visualization of vortex-vortex interaction between the biswirling jets is accomplished by using direct numerical simulation. The evolution of vortex structures of the biswirling jets is found rather complicated. The turbulent kinetic energy and turbulence dissipation in the central convergence region are augmented locally and rather strongly. The modulation of turbulent kinetic energy by jet-jet interaction upon different scales of vortices is dominated by the swirling levels and the distance between the jets. The turbulent kinetic energy upon intermediate and small scale vortices in bijets with not very high swirling level and at a very close distance is smaller than that in single swirling jets, whereas the opposite is true under a far distance, and so forth.
Numerical simulation of high Reynolds number bubble motion
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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.
Direct numerical simulation of pattern formation in subaqueous sediment
Kidanemariam, Aman G
2014-01-01
We present results of direct numerical simulation of incompressible fluid flow over a thick bed of mobile, spherically-shaped particles. The algorithm is based upon the immersed boundary technique for fluid-solid coupling and uses a soft-sphere model for the solid-solid contact. Two parameter points in the laminar flow regime are chosen, leading to the emergence of sediment patterns classified as `small dunes', while one case under turbulent flow conditions leads to `vortex dunes' with significant flow separation on the lee side. Wavelength, amplitude and propagation speed of the patterns extracted from the spanwise-averaged fluid-bed interface are found to be consistent with available experimental data. The particle transport rates are well represented by available empirical models for flow over a plane sediment bed in both the laminar and the turbulent regimes.
The steady state of epidermis: mathematical modeling and numerical simulations.
Gandolfi, Alberto; Iannelli, Mimmo; Marinoschi, Gabriela
2016-12-01
We consider a model with age and space structure for the epidermis evolution. The model, previously presented and analyzed with respect to the suprabasal epidermis, includes different types of cells (proliferating cells, differentiated cells, corneous cells, and apoptotic cells) moving with the same velocity, under the constraint that the local volume fraction occupied by the cells is constant in space and time. Here, we complete the model proposing a mechanism regulating the cell production in the basal layer and we focus on the stationary case of the problem, i.e. on the case corresponding to the normal status of the skin. A numerical scheme to compute the solution of the model is proposed and its convergence is studied. Simulations are provided for realistic values of the parameters, showing the possibility of reproducing the structure of both "thin" and "thick" epidermis.
Numerical simulation of pool boiling of a Lennard-Jones liquid
Inaoka, Hajime
2013-09-01
We performed a numerical simulation of pool boiling by a molecular dynamics model. In the simulation, a liquid composed of Lennard-Jones particles in a uniform gravitational field is heated by a heat source at the bottom of the system. The model successfully reproduces the change in regimes of boiling from nucleate boiling to film boiling with the increase of the heat source temperature. We present the pool boiling curve by the model, whose general behavior is consistent with those observed in experiments of pool boiling. © 2013 Elsevier B.V. All rights reserved.
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Honisch, M.; Klotz, D. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany). Inst. fuer Hydrologie
1999-02-01
A small-scale lysimeter plant on the premises of GSF has been dedicated to the study of water movement in sediments of Quaternary and Tertiary origin. The purpose of the present study was to describe water transport and non-reactive transport in the lysimeters under transient conditions and test the suitability of the numerical simulation programme Hydrus-2D for the unsaturated zone. The hydraulic characteristics and dispersiveness parameters were derived from earlier studies. The validity of these values was determined on the basis of a tracer experiment using the ideal tracer tritium water. [Deutsch] Zur Charakterisierung der Wasserbewegung in Sedimenten quartaeren und tertiaeren Ursprungs wird auf dem Gelaende der GSF eine Kleinlysimeteranlage betrieben. Ziel der vorliegenden Untersuchung war es, den Wasserfluss und nicht-reaktiven Transport in den Saeulen unter transienten Bedingungen zu beschreiben und hierbei die Eignung des numerischen Simulationsprogramms Hydrus-2D fuer die ungesaettigte Zone zu ueberpruefen. Die hydraulischen Kenngroessen und Dispersivitaetsparameter waren aus frueheren Untersuchungen abzuleiten. Die offene Frage hinsichtlich der Validitaet dieser Werte sollte auf der Grundlage eines Tracerexperiments mit tritiiertem Wasser als idealem Tracer ueberprueft werden. (orig.)
Time delay systems theory, numerics, applications, and experiments
Ersal, Tulga; Orosz, Gábor
2017-01-01
This volume collects contributions related to selected presentations from the 12th IFAC Workshop on Time Delay Systems, Ann Arbor, June 28-30, 2015. The included papers present novel techniques and new results of delayed dynamical systems. The topical spectrum covers control theory, numerical analysis, engineering and biological applications as well as experiments and case studies. The target audience primarily comprises research experts in the field of time delay systems, but the book may also be beneficial for graduate students alike. .
Numerical experiments for Gromov's stochastic particle flow filters
Daum, Fred; Noushin, Arjang; Huang, Jim
2017-05-01
We show the results of numerical experiments for a new algorithm for stochastic particle flow filters designed using Gromov's method. We derive a simple exact formula for Q in certain special cases. The purpose of using stochastic particle flow is two fold: improve estimation accuracy of the state vector and improve the accuracy of uncertainty quantification. Q is the covariance matrix of the diffusion for particle flow corresponding to Bayes' rule.
Numerical simulation of turbulent flow in corrugated pipes
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Azevedo, Henrique S. de; Morales, Rigoberto E.M.; Franco, Admilson T.; Junqueira, Silvio L.M.; Erthal, Raul H. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil). Dept. Academico de Mecanica (DAMEC)]. E-mails: rique.stel@gmail.com; rmorales@utfpr.edu.br; admilson@utfpr.edu.br; silvio@utfpr.edu.br; rherthal@utfpr.edu.br; Goncalves, Marcelo de Albuquerque Lima [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)]. E-mail: marcelog@petrobras.com.br
2008-07-01
Corrugated pipes are used in various engineering applications such heat exchangers and oil transport. In most cases these pipes consist of periodically distributed grooves at the duct inner wall. Numerical and experimental works reported the influence of grooves height and length in the turbulent flow by inspection of several turbulent properties such as velocity fluctuations and Reynolds stress. The present article aims to investigate the influence of grooves height and length in the global friction factor of turbulent flow through periodically corrugated pipes. Mass and momentum conservation equations are revised and specific boundary conditions are set to characterize a periodic fully developed regime in a single axisymmetric bidimensional module which represents the periodically corrugated duct geometry. The set of algebraic equations is discretized through the Finite Volume Method, with the Hybrid interpolation scheme applied to the convective terms, and solved using the commercial software PHOENICS CFD. The simulation of turbulent, incompressible, isothermal and single-phase flow is considered. The algebraic turbulence model LVEL is used. Four geometric configurations are assumed, including grooves height and length variations, in order to compare their influence on the friction factor. The obtained numerical friction factors show good agreement with previous experimental results, specially for Reynolds numbers over 20000. Numerical results for corrugated pipes compared to the Blasius smooth pipe correlation shows that the friction factor increases compared to smooth pipes, and such increase is more significant for higher Reynolds numbers and for larger grooves as well. These trends appear to be related to an enhancement of the momentum transport over the corrugated wall due to the recirculating pattern inside the grooves, in accordance with previous experimental works (author)
Numerical Simulation of Real Debris-Flow Events
Fraccarollo, L.; Papa, M.
2000-09-01
A one-dimensional model is presented to predict debris-flow runouts. The model is based on shallow water type assumptions. The fluid is assumed to be homogeneous and the original bed of the flow domain to be unerodible. The fluid is characterized by a rheology of Bingham type. A numerical tool able to cope with the nature of debris flows has been worked out. It represents an extension of a second order accurate and conservative method of Godunov type. Special care has been devoted to the influence of the source terms and of the geometrical representation of the natural cross sections, which play a fundamental role. The application concerns a monitored event in the Dolomites in Italy, where field analyses allowed a characterization of the behavior of solid-liquid mixture as a yield stress material. The comparison between numerical simulations and field observations highlights the impossibility of representing all phases of the flow with constant values of the rheological parameters. Nevertheless the results show that it is possible to separately represent the phase of the flow in the upstream reach and the phase of the deposition in the alluvial fan, with a good agreement with field observations.
Numerical simulation of electro-fishing in seawater
Directory of Open Access Journals (Sweden)
Edo D'Agaro
2010-01-01
Full Text Available We evaluated the feasibility of an electro-fishing system using numerical simulations for laboratory tanks and the open sea. A non-homogeneous bi-dimensional electric-field model for water and fish based on discrete formulation of electro-magnetic field equations was developed using GAME (geometric approach for Maxwell equations software. Current densities (μA/cm2 and voltage differences (V/m were calculated for a fixed shape and spatial geometry of electrodes (one circular anode central to two symmetric linear cathodes 10 m distant from each other. Voltage gradients inside the fish and close to the body (head–tail potential difference and mean, maximum and minimum field modules were determined. Tank and open sea environments were numerically described for single fish 10 cm or 30 cm long and for groups of 30 fish 10 cm long. In the open sea, a tension of 90 V at the electrodes and a water conductibility of 5 S/m resulted in an area of fish attraction (voltage gradient >10 V/m of about 30 m2. Fish in the open sea and in groups had greater internal voltage differences than did fish in tanks and single fish.
Numerical Simulations on Origin of Galilean Moons' Magnetic Anomalies
Jiao, LiQuo; Kuang, WeiJia; Ma, ShiZhuang
2011-01-01
Galileo mission detected the magnetic anomalies originated from Galilean moons. These anomalies are likely generated in the moons interiors, under the influence of a strong ambient Jovian field. Among various possible generation mechanisms of the anomalies, we focus on magneto-convection and dynamos in the interiors via numerical simulation. To mimic the electromagnetic environment of the moons, we introduce in our numerical model an external uniform magnetic field B(sub 0) with a fixed orientation but varying field strength. Our results show that a finite B(sub 0) can substantially alter the dynamo processes inside the core. When the ambient field strength B(sub 0) increases to approximately 40% of the field generated by the pure dynamo action, the convective state in the core changes significantly: the convective flow decreases by 80% in magnitude, but the differential rotation becomes stronger in much of the fluid layer, leading to a stronger field generated in the core. The field morphologies inside the core tend to align with the ambient field, while the flow patterns show the symmetry-breaking effect under the influence of B(sub 0). Furthermore, the generated field tends to be temporally more stable.
Quantifying paleosecular variation: Insights from numerical dynamo simulations
Lhuillier, F.; Gilder, S. A.
2013-12-01
Numerical dynamo simulations can be used to investigate paleosecular variation of Earth-like magnetic fields over several million-year timescales. Using a set of five numerical models integrated over the equivalent of 40-50 Myr, we generated synthetic data analogous to paleomagnetic data. We show that paleosecular variation among the five models is best discriminated by the relative variability in paleointensity (ɛ_F) and the precision parameter (k) of directions or poles. Whether the geodynamo operated in different regimes in its past can be best tested with these parameters in combination. Roughly one million years of time with 200 time-independent samples is required to achieve convergence of ɛ_F and k. The quantities ɛ_F and k correlate well with the average chron duration (μ_chr), which suggests that excursions and reversals are an integral part of palaeosecular variation. If applicable to the geodynamo, the linear dependence of k on μ_chr could help to predict μ_chr for the Earth during geologic times with no available reversal frequency data; it also predicts much higher average k for directions during superchrons (k ≈ 2500 for the Cretaceous normal superchron) than during actively reversing times (k ≈ 35 for the last 80 Myr). As such high k values are not observed, either this family of dynamo models is not applicable to the geodynamo, or the geodynamo regime acting during superchrons lies statistically within the same energy state as at present.
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 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.
3D Numerical Simulation on the Rockslide Generated Tsunamis
Chuang, M.; Wu, T.; Wang, C.; Chu, C.
2013-12-01
The rockslide generated tsunami is one of the most devastating nature hazards. However, the involvement of the moving obstacle and dynamic free-surface movement makes the numerical simulation a difficult task. To describe both the fluid motion and solid movement at the same time, we newly developed a two-way fully-coupled moving solid algorithm with 3D LES turbulent model. The free-surface movement is tracked by volume of fluid (VOF) method. The two-step projection method is adopted to solve the Navier-Stokes type government equations. In the new moving solid algorithm, a fictitious body force is implicitly prescribed in MAC correction step to make the cell-center velocity satisfied with the obstacle velocity. We called this method the implicit velocity method (IVM). Because no extra terms are added to the pressure Poission correction, the pressure field of the fluid part is stable, which is the key of the two-way fluid-solid coupling. Because no real solid material is presented in the IVM, the time marching step is not restricted to the smallest effective grid size. Also, because the fictitious force is implicitly added to the correction step, the resulting velocity is accurate and fully coupled with the resulting pressure field. We validated the IVM by simulating a floating box moving up and down on the free-surface. We presented the time-history obstacle trajectory and compared it with the experimental data. Very accurate result can be seen in terms of the oscillating amplitude and the period (Fig. 1). We also presented the free-surface comparison with the high-speed snapshots. At the end, the IVM was used to study the rock-slide generated tsunamis (Liu et al., 2005). Good validations on the slide trajectory and the free-surface movement will be presented in the full paper. From the simulation results (Fig. 2), we observed that the rockslide generated waves are manly caused by the rebounding waves from two sides of the sliding rock after the water is dragging
Numerical simulation of two-phase flow behavior in Venturi scrubber by interface tracking method
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Horiguchi, Naoki, E-mail: s1430215@u.tsukuba.ac.jp [Japan Atomic Energy Agency, 2-4, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8577 (Japan); Yoshida, Hiroyuki [Japan Atomic Energy Agency, 2-4, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Abe, Yutaka [University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8577 (Japan)
2016-12-15
Highlights: • Self-priming occur because of pressure balance between inside and outside of throat is confirmed. • VS has similar flow with a Venturi tube except of disturbance and burble flow is considered. • Some of atomization simulated are validated qualitatively by comparison with previous studies. - Abstract: From the viewpoint of protecting a containment vessel of light water reactor and suppressing the diffusion of radioactive materials from a light water reactor, it is important to develop the device which allows a filtered venting of contaminated high pressure gas. In the filtered venting system that used in European reactors, so called Multi Venturi scrubbers System is used to realize filtered venting without any power supply. This system is able to define to be composed of Venturi scrubbers (VS) and a bubble column. In the VS, scrubbing of contaminated gas is promoted by both gas releases through the submerged VS and gas-liquid contact with splay flow formed by liquid suctioned through a hole provided by the pressure difference between inner and outer regions of a throat part of the VS. However, the scrubbing mechanism of the self-priming VS including effects of gas mass flow rate and shape of the VS are understood insufficiently in the previous studies. Therefore, we started numerical and experimental study to understand the detailed two-phase flow behavior in the VS. In this paper, to understand the VS operation characteristics for the filtered venting, we performed numerical simulations of two-phase flow behavior in the VS. In the first step of this study, we perform numerical simulations of supersonic flow by the TPFIT to validate the applicability of the TPFIT for high velocity flow like flow in the VS. In the second step, numerical simulation of two-phase flow behavior in the VS including self-priming phenomena. As the results, dispersed flow in the VS was reproduced in the numerical simulation, as same as the visualization experiments.
Numerical simulations of topological and correlated quantum matter
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Assaad, Fakher F. [Wuerzburg Univ. (Germany). Inst. fuer Theoretische Physik und Astrophysik
2016-11-01
The complexity of the solid state does not allow us to carry out simulations of correlated materials without adopting approximation schemes. In this project we are tackling this daunting task with complementary techniques. On one hand one can start with density functional theory in the local density approximation and then add dynamical local interactions using the so called dynamical mean-field approximation. This approach has the merit of being material dependent in the sense that it is possible to include the specific chemical constituents of the material under investigation. Progress in this domain is described below. Another venue is to concentrate on phenomena occurring in a class of materials. Here, the strategy is to define models which one can simulate in polynomial time on supercomputing architectures, and which reproduce the phenomena under investigation. This route has been remarkably successful, and we are now in a position to provide controlled model calculations which can cope with antiferromagnetic fluctuations in metals, or nematic instabilities of fermi liquids. Both phenomena are crucial for our understanding of high temperature superconductivity in the cuprates and the pnictides. Access to the LRZ supercomputing center was imperative during the current grant period to do the relevant simulations on a wide range of topics on correlated electrons. In all cases access to supercomputing facilities allows to carry out simulations on larger and larger system sizes so as to be able to extrapolate to the thermodynamic limit relevant for the understanding of experiments and collective phenomena.
Direct Numerical Simulation of Turbulent Condensation in Clouds
Shariff, K.; Paoli, R.
2004-01-01
In this brief, we investigate the turbulent condensation of a population of droplets by means of a direct numerical simulation. To that end, a coupled Navier-Stokes/Lagrangian solver is used where each particle is tracked and its growth by water vapor condensation is monitored exactly. The main goals of the study are to find out whether turbulence broadens the droplet size distribution, as observed in in situ measurements. The second issue is to understand if and for how long a correlation between the droplet radius and the local supersaturation exists for the purpose of modeling sub-grid scale microphysics in cloud-resolving codes. This brief is organized as follows. In Section 2 the governing equations are presented, including the droplet condensation model. The implementation of the forcing procedure is described in Section 3. The simulation results are presented in Section 4 together with a sketch of a simple stochastic model for turbulent condensation. Conclusions and the main outcomes of the study are given in Section 5.
COMPARATIVE NUMERICAL SIMULATION OF THE TOHOKU 2011 TSUNAMI
Directory of Open Access Journals (Sweden)
Baranova N.A.
2015-10-01
Full Text Available The comparative numerical simulation of generation and propagation of tsunami waves generated by the source of the catastrophic 2011 Tohoku earthquake in Japan was performed based on the Okada model and the dynamic keyboard block model. The initial model is connected with the choice of orientation of longitudinal and transverse ruptures within the source region and the values of displacements along the main fault. A subsequent model is based on the premise that the initial stress distribution along the fault zone affects essentially the character of movements around the earthquake source and takes into account the stress-strain state of keyboard blocks. In the first case of the present study, the earthquake source was designated and constructed based on the parameters of the ten largest aftershocks within a finite time interval, while in the second case the source used included all aftershocks on the first day following the main event. Based on such comparative source simulations and far-field tsunami wave measurements, the results with both models were determined to have close similarities. However, in the near-field zone, the agreement with observable data was not as good. That can be attributed to inaccuracies in the placement of virtual tide gauges relative to real ones, as well as to features of bottom relief near the coast.
Numerical Simulation of Barite Sag in Pipe and Annular Flow
Directory of Open Access Journals (Sweden)
Patrick Kabanda
2017-01-01
Full Text Available With the ever increasing global energy demand and diminishing petroleum reserves, current advances in drilling technology have resulted in numerous directional wells being drilled as operators strive to offset the ever-rising operating costs. In as much as deviated-well drilling allows drillers to exploit reservoir potential by penetrating the pay zone in a horizontal, rather than vertical, fashion, it also presents conditions under which the weighting agents can settle out of suspension. The present work is categorized into two parts. In the first part, governing equations were built inside a two-dimensional horizontal pipe geometry and the finite element method utilized to solve the equation-sets. In the second part, governing equations were built inside a three-dimensional horizontal annular geometry and the finite volume method utilized to solve the equation-sets. The results of the first part of the simulation are the solid concentration, mixture viscosity, and a prediction of the barite bed characteristics. For the second part, simulation results show that the highest occurrence of barite sag is at low annular velocities, nonrotating drill pipe, and eccentric drill pipe. The CFD approach in this study can be utilized as a research study tool in understanding and managing the barite sag problem.
Numerical Simulations of Canted Nozzle and Scarfed Nozzle Flow Fields
Javed, Afroz; Chakraborty, Debasis
2017-10-01
Computational fluid dynamics (CFD) techniques are used for the analysis of issues concerning non-conventional (canted and scarfed) nozzle flow fields. Numerical simulations are carried out for the quality of flow in terms of axisymmetric nature at the inlet of canted nozzles of a rocket motor. Two different nozzle geometries are examined. The analysis of these simulation results shows that the flow field at the entry of the nozzles is non axisymmetric at the start of the motor. With time this asymmetry diminishes, also the flow becomes symmetric before the nozzle throat, indicating no misalignment of thrust vector with the nozzle axis. The qualitative flow fields at the inlet of the nozzles are used in selecting the geometry with lesser flow asymmetry. Further CFD methodology is used to analyse flow field of a scarfed nozzle for the evaluation of thrust developed and its direction. This work demonstrates the capability of the CFD based methods for the nozzle analysis problems which were earlier solved only approximately by making simplifying assumptions and semi empirical methods.
Numerical simulations of groundwater flow at New Jersey Shallow Shelf
Fehr, Annick; Patterson, Fabian; Lofi, Johanna; Reiche, Sönke
2016-04-01
During IODP Expedition 313, three boreholes were drilled in the so-called New Jersey transect. Hydrochemical studies revealed the groundwater situation as more complex than expected, characterized by several sharp boundaries between fresh and saline groundwater. Two conflicting hypotheses regarding the nature of these freshwater reservoirs are currently debated. One hypothesis is that these reservoirs are connected with onshore aquifers and continuously recharged by seaward-flowing groundwater. The second hypothesis is that fresh groundwater was emplaced during the last glacial period. In addition to the petrophysical properties measured during IODP 313 expedition, Nuclear Magnetic Resonance (NMR) measurements were performed on samples from boreholes M0027, M0028 and M0029 in order to deduce porosities and permeabilities. These results are compared with data from alternative laboratory measurements and with petrophysical properties inferred from downhole logging data. We incorporate these results into a 2D numerical model that reflects the shelf architecture as known from drillings and seismic data to perform submarine groundwater flow simulations. In order to account for uncertainties related to the spatial distribution of physical properties, such as porosity and permeability, systematic variation of input parameters was performed during simulation runs. The target is to test the two conflicting hypotheses of fresh groundwater emplacements offshore New Jersey and to improve the understanding of fluid flow processes at marine passive margins.
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 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
Authoring Systems for Laboratory Experiment Simulators.
Shacham, Mordechai; Cutlip, Michael B.
1988-01-01
Discussion of laboratory experiment simulation in science and engineering education focuses on the need for authoring systems that can be used to create simulations. An editor for a simulator model containing variables and mathematical equations is presented, and screen displays and data analysis are discussed. (LRW)
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
Numerical Simulation of Fluid Dynamics in a Monolithic Column
Directory of Open Access Journals (Sweden)
Kazuhiro Yamamoto
2017-01-01
Full Text Available As for the measurement of polycyclic aromatic hydrocarbons (PAHs, ultra-performance liquid chromatography (UPLC is used for PAH identification and densitometry. However, when a solvent containing a substance to be identified passes through a column of UPLC, a dedicated high-pressure-proof device is required. Recently, a liquid chromatography instrument using a monolithic column technology has been proposed to reduce the pressure of UPLC. The present study tested five types of monolithic columns produced in experiments. To simulate the flow field, the lattice Boltzmann method (LBM was used. The velocity profile was discussed to decrease the pressure drop in the ultra-performance liquid chromatography (UPLC system.
A Numerical Simulation of Hodgkin-Huxley Model : An Approach to an Understanding of a Brain
平田, 隆幸; 黒岩, 丈介; 浅井, 竜哉
2004-01-01
A numerical simulation of Hodgkin-Huxley model was carried out by using a Runge-Kutta method. In the numerical simulation, the functions of Numerical Recipes in C were used for solving the Hodgkin-Huxley equation. The accuracy of numerical solutions was discussed for both simple Runge-Kutta method and adaptive stepsize control Runge-Kutta method. The difference between simulation performed by using float type variables and one by using double type variables was also discussed. A large neural ...
Numerical simulation and analysis of confined turbulent buoyant jet with variable source
El-Amin, Mohamed
2016-01-23
In this work, experimental and numerical investigations are undertaken for confined buoyant turbulent jet with varying inlet temperatures. Results of the experimental work and numerical simulations for the problem under consideration are presented. Four cases of different variable inlet temperatures and different flow rates are considered. The realizable k-ɛ turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The average deviation of the simulated temperature by realizable k-ɛ turbulent model and the measured temperature is within 2%. The results indicate that temperatures along the vertical axis vary, generally, in nonlinear fashion as opposed to the approximately linear variation that was observed for the constant inlet temperature that was done in a previous work. Furthermore, thermal stratification exits, particularly closer to the entrance region. Further away from the entrance region the variation in temperatures becomes relatively smaller. The stratification is observed since the start of the experiment and continues during the whole course. Numerical experiments for constant, monotone increasing and monotone decreasing of inlet temperature are done to show its effect on the buoyancy force in terms of Richardson number.
Directory of Open Access Journals (Sweden)
José Eduardo Alamy Filho
2012-12-01
Full Text Available The Immerse Boundary Method (IBM was used to evaluate the sediment transport over deformable beds. Large Eddy Simulation (LES procedures were used for the mathematical treatment of turbulence, and the advection-diffusion equation was used to calculate sediment concentration. The Finite Differences Method with staggered grid was applied for the numerical solution of the governing equations (filtered Navier-Stokes, Continuity and advection-diffusion equations. Spatial derivatives were discretized using second order centered differences. A second order explicit Adams-Bashforth scheme was used for the time evolution in the advection-diffusion equation, while a fourth order Adams-Bashforth scheme was used for the filtered Navier-Stokes equations. The numerical simulation reproduced flow structures like large eddies after the dune crests and counter-rotative vortices, which are important in sediment transport. Resuspension fluxes and sedimentation (dependent on particle concentration were calculated using equations proposed in this study. The deformations of the bed caused by erosion and deposition may be well followed through the present procedures, showing that this methodology is adequate to evaluate bed modifications and sediment transport in alluvial flows.Se utilizó el método de fronteras inmersas para evaluar el transporte de sedimentos en lechos deformables. Los procedimientos de la simulación de gran escala fueron utilizados para el tratamiento matemático de la turbulencia, y se utilizó la ecuación de advección-difusión para calcular la concentración de sedimentos. Se aplicó el método de diferencias finitas con malla desplazada para la solución numérica de las ecuaciones básicas (Navier-Stokes filtrado, continuidad y las ecuaciones de advección-difusión. Las derivadas espaciales fueron discretizadas mediante diferencias de segundo orden centrado. Se utilizó un esquema explícito de Adams-Bashforth de segundo orden para la
Simulation strategies for the LHC ATLAS experiment
Buckley, A; The ATLAS collaboration
2010-01-01
The ATLAS experiment, operational at the new LHC collider, is fully simulated using the Geant4 tool. The simulation program has been built within the ATLAS common framework Athena. The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. The latest developments went into the direction to better represent the reality of the detector in all the possible details. The latest developments provide increased functionality and robustness. The full process is constantly monitored and profiled. Increased performance guarantee the best use of available resources without any degradation in the quality and accuracy of the simulation itself. In the presentation emphasis is...
Numerical simulation of the sea breeze, ideal and realistic: Baja California, Mexico case
Colorado, G.; Mateos, E.; Ayala, R.
2016-12-01
In studies, with data from weather stations in Bahia de Todos Santos, Baja California, Mexico, was found that the sea-land breeze is an important component of the wind circulation. Therefore, its behaviour was simulated numerically with the WRF model to identify not only the surface field, but the vertical component of this phenomenon, in addition to quantifying the number of events during the year 2010. The model was forced with NARR data, and triple nested meshes were defined, whose smallest nest has a horizontal resolution of 2 km. In parallel to realistic simulation, an idealized numerical experiment was done with the WRF-idealize sea breeze example to verify whether the WRF model can reproduce the sea breeze. In order to do this, three variables were analyzed: temperature, relative humidity and the U component of the wind.
Numerical simulation and experimental research of the integrated high-power LED radiator
Xiang, J. H.; Zhang, C. L.; Gan, Z. J.; Zhou, C.; Chen, C. G.; Chen, S.
2017-01-01
The thermal management has become an urgent problem to be solved with the increasing power and the improving integration of the LED (light emitting diode) chip. In order to eliminate the contact resistance of the radiator, this paper presented an integrated high-power LED radiator based on phase-change heat transfer, which realized the seamless connection between the vapor chamber and the cooling fins. The radiator was optimized by combining the numerical simulation and the experimental research. The effects of the chamber diameter and the parameters of fin on the heat dissipation performance were analyzed. The numerical simulation results were compared with the measured values by experiment. The results showed that the fin thickness, the fin number, the fin height and the chamber diameter were the factors which affected the performance of radiator from primary to secondary.
Bumblebees meet fully developed turbulence: high resolution numerical simulations
Engels, Thomas; Kolomenskiy, Dmitry; Schneider, Kai; Sesterhenn, Joern; Lehmann, Fritz-Olaf
2015-11-01
Numerical experiments of a tethered bumblebee in a wind tunnel with turbulent inflow of different intensity are performed at realistic Reynolds numbers on massively parallel computers. Ensemble averaging of different flow realizations shows that the mean forces (lift and drag, or horizontal and vertical), the moments (roll, pitch and yaw), and power, are robust and are not modified significantly by the turbulent inflow. Phase averaging of the vorticity field illustrates that in all cases the leading edge vortex is indeed persistent (in the average sense) as it is the case for laminar inflow, which explains the above findings. However, as expected, the corresponding standard deviations do increase with the turbulence intensity. In particular the roll moment shows the strongest increase of standard deviation. Considering that the moment of inertia of the bumblebee is the smallest around this axis yields a possible explanation for the experimentally observed flight instability around the roll axis under turbulent flow conditions.
Numerical simulation of crystalline ion beams in storage ring
Meshkov, I N; Katayama, T; Sidorin, A; Smirnov, A Yu; Syresin, E M; Trubnikov, G; Tsutsui, H
2004-01-01
The use of crystalline ion beams can increase luminosity in the collider and in experiments with targets for investigation of rare radioactive isotopes. The ordered state of circulating ion beams was observed at several storage rings: NAP-M (Proceedings of the Fourth All Union Conference on Charged Particle Accelerators, Vol. 2, Nauka, Moscow, 1975 (in Russian); Part. Accel. 7 (1976) 197; At. Energy 40 (1976) 49; Preprint CERN/PS/AA 79-41, Geneva, 1979) (Novosibirsk), ESR (Phys. Rev. Lett. 77 (1996) 3803) and SIS (Proceedings of EPAC'2000, 2000) (Darmstadt), CRYRING (Proceedings of PAC'2001, 2001) (Stockholm) and PALLAS (Proceedings of the Conference on Applications of Accelerators in Research and Industry, AIP Conference Proceedings, p. 576, in preparation) (Munchen). New criteria of the beam orderliness are derived and verified with a new program code. Molecular dynamics technique is inserted in BETACOOL program (Proceedings of Beam Cooling and Related Topics, Bad Honnef, Germany, 2001) and used for numeric...
Development of numerical models for Monte Carlo simulations of Th-Pb fuel assembly
Directory of Open Access Journals (Sweden)
Oettingen Mikołaj
2017-01-01
Full Text Available The thorium-uranium fuel cycle is a promising alternative against uranium-plutonium fuel cycle, but it demands many advanced research before starting its industrial application in commercial nuclear reactors. The paper presents the development of the thorium-lead (Th-Pb fuel assembly numerical models for the integral irradiation experiments. The Th-Pb assembly consists of a hexagonal array of ThO2 fuel rods and metallic Pb rods. The design of the assembly allows different combinations of rods for various types of irradiations and experimental measurements. The numerical model of the Th-Pb assembly was designed for the numerical simulations with the continuous energy Monte Carlo Burnup code (MCB implemented on the supercomputer Prometheus of the Academic Computer Centre Cyfronet AGH.
Direct numerical simulation of rotating fluid flow in a closed cylinder
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær; Christensen, Erik Adler
1995-01-01
Present numerical simulations of the transition scenario of a rotating fluid flow in a closed cylinder are presented, where the motion is created by a rotating lid. The numerical algorithm, which is based on a finite-difference discretization of the axisymmetric Navier-Stokes equations......, is validated against experimental visualizations of both transient and stable periodic flows. The complexity of the flow problem is illuminated numerically by injecting flow tracers into the flow domain and following their evolution in time. The vortex dynamics appears as stretching, folding and squeezing...... of flow structures which wave along the contour of a central vortex core. The main purpose of the study is to clarify the mechanisms of the transition scenario and relate these to experiences known from other dynamical systems and bifurcation theory. The dynamical system was observed to exhibit up...
Labotratory Simulation Experiments of Cometary Plasma
MINAMI, S.; Baum, P. J.; Kamin, G.; White, R. S.; 南, 繁行
1986-01-01
Laboratory simulation experiment to study the interaction between a cometary plasma and the solar wind has been performed using the UCR-T 1 space simulation facility at the Institute of Geophysics and Planetary Physics, the University of California, Riverside. Light emitting plasma composed of Sr, Ba and/or C simulating cometary coma plasma is produced by a plasma emitter which interacts with intense plasma flow produced by a co-axial plasma gun simulating the solar wind. The purpose of this ...
Numerical simulation of damage detection using laser-generated ultrasound.
Liu, Peipei; Nazirah, Ab Wahab; Sohn, Hoon
2016-07-01
Laser ultrasonic techniques have been widely investigated due to its high spatial resolution and capacity for remote and noncontact measurement. In this study, the laser induced ultrasonic wave on an aluminum plate is simulated, and a nonlinear feature is used to detect a micro crack introduced in the plate model. A multi-physics simulation is conducted and optimized considering the effect of thermal diffusion. A nonlinear feature, called Bhattacharyya Distance (BD), is calculated to show the crack-induced geometric difference among the state space attractors obtained from closely spaced measurement points near the crack. First, a 3D model is built, and its simulation result is compared with an experiment performed using a noncontact laser ultrasonic measurement system. Then, by creating a micro crack in the model, BD is extracted and the crack is successfully detected and visualized. Finally, the effects of BD parameters, such as embedding dimension and frequency band, on damage visualization are investigated. Copyright © 2016 Elsevier B.V. All rights reserved.
Analysis of the Osteogenic Effects of Biomaterials Using Numerical Simulation.
Wang, Lan; Zhang, Jie; Zhang, Wen; Yang, Hui-Lin; Luo, Zong-Ping
2017-01-01
We describe the development of an optimization algorithm for determining the effects of different properties of implanted biomaterials on bone growth, based on the finite element method and bone self-optimization theory. The rate of osteogenesis and the bone density distribution of the implanted biomaterials were quantitatively analyzed. Using the proposed algorithm, a femur with implanted biodegradable biomaterials was simulated, and the osteogenic effects of different materials were measured. Simulation experiments mainly considered variations in the elastic modulus (20-3000 MPa) and degradation period (10, 20, and 30 days) for the implanted biodegradable biomaterials. Based on our algorithm, the osteogenic effects of the materials were optimal when the elastic modulus was 1000 MPa and the degradation period was 20 days. The simulation results for the metaphyseal bone of the left femur were compared with micro-CT images from rats with defective femurs, which demonstrated the effectiveness of the algorithm. The proposed method was effective for optimization of the bone structure and is expected to have applications in matching appropriate bones and biomaterials. These results provide important insights into the development of implanted biomaterials for both clinical medicine and materials science.
Directory of Open Access Journals (Sweden)
M Shibuta
2016-09-01
Full Text Available In recent years, the food self-support rate of Japan is 40%, and this value is the lowest level of major advanced country. The stable supply of food is a big subject that Japan has. Therefore, rice powder attracts attention for improvement of the food self-support rate in Japan. Previously, the rice powder is produced by two methods. One is dry type, and the other is wet type. However, these systems have a fault of the heat damage of the starch and the consumption of a large quantity of water. In our laboratory, as solution of those problems, production of the rice powder by using the underwater shock wave is considered. Shock wave is the pressure wave which is over velocity of sound by discharging high energy in short time. Propagating shock wave in water is the underwater shock wave. This food processing using an underwater shock wave has little influence of heat and its processing time is very short, preventing the loss of nutrients. In this research optical observation experiment and the numerical simulation were performed using trial vessel, in order to understand the behavior of the underwater shock wave in the development of the rice powder production vessel using an underwater shock wave at the factory. In addition, in order to understand the rice powder production and to develop it, the numerical simulation about pulverization of rice is performed. By this method, the pressure which takes for rice at the time of pulverization, and its pulverization phenomenon are solved. Analysis soft LS-DYNA was used for these numerical simulations. The comparative study of the experiment and the numerical simulation was investigated. The behavior of the shock wave in the device and transformation of rice were able to be clarified.
Numerical simulation of X90 UOE pipe forming process
Zou, Tianxia; Ren, Qiang; Peng, Yinghong; Li, Dayong; Tang, Ding; Han, Jianzeng; Li, Xinwen; Wang, Xiaoxiu
2013-12-01
The UOE process is an important technique to manufacture large-diameter welding pipes which are increasingly applied in oil pipelines and offshore platforms. The forming process of UOE mainly consists of five successive operations: crimping, U-forming, O-forming, welding and mechanical expansion, through which a blank is formed into a pipe in a UOE pipe mill. The blank with an appropriate edge bevel is bent into a cylindrical shape by crimping (C-forming), U-forming and O-forming successively. After the O-forming, there is an open-seam between two ends of the plate. Then, the blank is welded by automatic four-electrode submerged arc welding technique. Subsequently, the welded pipe is expanded with a mechanical expander to get a high precision circular shape. The multiple operations in the UOE mill make it difficult to control the quality of the formed pipe. Therefore, process design mainly relies on experience in practical production. In this study, the UOE forming of an API X90 pipe is studied by using finite element simulation. The mechanical properties tests are performed on the API X90 pipeline steel blank. A two-dimensional finite element model under the hypothesis of plane strain condition is developed to simulate the UOE process according to data coming from the workshop. A kinematic hardening model is used in the simulation to take the Bauschinger effect into account. The deformation characteristics of the blank during the forming processes are analyzed. The simulation results show a significant coherence in the geometric configurations comparing with the practical manufacturing.
Experimentation and numerical simulation of steel fibre reinforced concrete pipes
Directory of Open Access Journals (Sweden)
de la Fuente, Albert
2011-06-01
Full Text Available 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/m^{3} 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.
En este artículo se presentan los resultados principales de un estudio experimental y numérico del comportamiento de tubos hormigón reforzado con fibras de acero (THFA. Se fabricaron y ensayaron 18 tubos de 600 mm de diámetro con cuantías de 10, 20 y 40 kg/m^{3} de fibras, concluyéndose varios aspectos tecnológicos relacionados con la fabricación y el ensayo así como del comportamiento resistente. Por otra parte, se ha desarrollado el modelo numérico MAP que permite la simulación del comportamiento resistente de THFA sometidos al ensayo de aplastamiento. Los resultados han sido satisfactorios para cualquier régimen de carga, permitiendo concluir que el modelo es una herramienta útil para el diseño óptimo de este tipo de tubos. Se concluye que el uso del modelo conduce a una reducción del coste del armado y da un impulso al uso de fibras como elemento de refuerzo en esta tipología estructural.
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.
Direct numerical simulation of a laminar vortex ring
James, S.; Madnia, C. K.
1996-09-01
Results are presented of direct numerical simulations (DNS) of a viscous, laminar ring. The effects of different generator configurations and velocity programs on the formation and post-formation characteristics of the ring are studied. It is shown that during the formation phase of the ring, total circulation and impulse in the flowfield are approximately the same for the ``nozzle'' and ``orifice'' generators. It is also found that throughout this period the slug flow model under-predicts the total circulation in the flow. During the formation phase, the simulation results for the time evolution of total circulation and location of the vortex spiral center are in agreement with the experimental findings of Didden [J. Appl. Mech. Phys. (ZAMP) 30, 101 (1979)]. The results of the flow visualization studies show that during the post-formation phase a vortex bubble is formed. As the bubble propels itself forward a wake is formed in the rear of the bubble. The impulse and vorticity from the bubble are continuously shed into this wake. It is found that the total value of the circulation in the flow varies as (t1*)-0.33 which is consistent with Maxworthy's [J. Fluid Mech. 81, 465 (1977)] prediction of the decay of circulation for a vortex ring. The transport of a passive Shvab-Zeldovich scalar variable is used to study the mixing and to obtain the maximum product formation in a chemical reaction of the type A+B→Products in a vortex ring. It is found that as the bubble containing the fuel propels itself forward, the outside oxidizer flow is entrained into it and reacts to form a product. Some of this product then is de-entrained into the wake of the bubble.
Numerical Simulation Study of the Sanchiao Fault Earthquake Scenarios
Wang, Yi-Min; Lee, Shiann-Jong
2015-04-01
Sanchiao fault is a western boundary fault of the Taipei basin located in northern Taiwan, close to the densely populated Taipei metropolitan area. Recent study indicated that there is about 40 km of the fault trace extended to the marine area offshore northern Taiwan. Combining the marine and terrestrial parts, the total fault length of Sanchiao fault could be nearly 70 kilometers which implies that this fault has potential to produce a big earthquake. In this study, we analyze several Sanchiao fault earthquake scenarios based on the recipe for predicting strong ground motion. The characterized source parameters include fault length, rupture area, seismic moment, asperity, and slip pattern on the fault plane. According to the assumption of the characterized source model, Sanchiao fault has been inferred to have the potential to produce an earthquake with moment magnitude (Mw) larger than 7.0. Three-dimensional seismic simulation results based upon spectral-element method (SEM) indicate that peak ground acceleration (PGA) is significantly stronger along the fault trace. The basin effect also plays an important role when wave propagates in the Taipei basin which cause seismic wave amplified and prolong the shaking for a very long time. Among all rupture scenarios, the rupture propagated from north to south is the most serious one. Owing to the rupture directivity as well as the basin effects, large PGA (>1g) was observed in the Taipei basin, especially in the northwest side. The results of these scenario earthquake simulations will provide important physically-based numerical data for earthquake mitigation and seismic hazard assessment.
Numerical simulations of concrete flow: A benchmark comparison
DEFF Research Database (Denmark)
Roussel, Nicolas; Gram, Annika; Cremonesi, Massimiliano
2016-01-01
First, we define in this paper two benchmark flows readily usable by anyone calibrating a numerical tool for concrete flow prediction. Such benchmark flows shall allow anyone to check the validity of their computational tools no matter the numerical methods and parameters they choose. Second, we...... compare numerical predictions of the concrete sample final shape for these two benchmark flows obtained by various research teams around the world using various numerical techniques. Our results show that all numerical techniques compared here give very similar results suggesting that numerical...
Riedler, M.; Michelic, S.; Bernhard, C.
2016-07-01
The phase transformations in solidification of steel are accompanied by shrinkage and sudden changes in the solubility of alloying elements, resulting in negative side effects as micro- and macrosegregation and the formation of gas and shrinkage porosities. This paper deals with the numerical and experimental simulation of the formation of shrinkage porosity during the solidification of steel. First the physical basics for the mechanism of shrinkage pore formation will be discussed. The main reason for this type of porosity is the restraint of fluid flow in the mushy zone which leads to a pressure drop. The pressure decreases from the dendrite tip to the root. When the pressure falls below a critical value, a pore can form. The second part of the paper deals with different approaches for the prediction of the formation of shrinkage porosity. The most common one according to these models is the usage of a simple criterion function, like the Niyama criterion. For the computation of the porosity criterion the thermal gradient, cooling rate and solidification rate must be known, easily to determine from numerical simulation. More complex simulation tools like ProCAST include higher sophisticated models, which allow further calculations of the shrinkage cavity. Finally, the different approaches will be applied to a benchmark laboratory experiment. The presented results deal with an ingot casting experiment under variation of taper. The dominant influence of mould taper on the formation of shrinkage porosities can both be demonstrated by the lab experiment as well as numerical simulations. These results serve for the optimization of all ingot layouts for lab castings at the Chair of Ferrous Metallurgy.
Goodrich, John W.
2017-01-01
This paper presents results from numerical experiments for controlling the error caused by a damping layer boundary treatment when simulating the propagation of an acoustic signal from a continuous pressure source. The computations are with the 2D Linearized Euler Equations (LEE) for both a uniform mean flow and a steady parallel jet. The numerical experiments are with algorithms that are third, fifth, seventh and ninth order accurate in space and time. The numerical domain is enclosed in a damping layer boundary treatment. The damping is implemented in a time accurate manner, with simple polynomial damping profiles of second, fourth, sixth and eighth power. At the outer boundaries of the damping layer the propagating solution is uniformly set to zero. The complete boundary treatment is remarkably simple and intrinsically independant from the dimension of the spatial domain. The reported results show the relative effect on the error from the boundary treatment by varying the damping layer width, damping profile power, damping amplitude, propagtion time, grid resolution and algorithm order. The issue that is being addressed is not the accuracy of the numerical solution when compared to a mathematical solution, but the effect of the complete boundary treatment on the numerical solution, and to what degree the error in the numerical solution from the complete boundary treatment can be controlled. We report maximum relative absolute errors from just the boundary treatment that range from O[10-2] to O[10-7].
ANUGA SOFTWARE FOR NUMERICAL SIMULATIONS OF SHALLOW WATER FLOWS
Directory of Open Access Journals (Sweden)
Sudi Mungkasi
2012-07-01
Full Text Available Shallow water flows are governed by the shallow water wave equations, also known as the Saint-Venant system. This paper presents a finite volume method used to solve the two-dimensional shallow water wave equations and how the finite volume method is implemented in ANUGA software. This finite volume method is the numerical method underlying the software. ANUGA is open source software developed by Australian National University (ANU and Geoscience Australia (GA. This software uses the finite volume method with triangular domain discretisation for the computation. Four test cases are considered in order to evaluate the performance of the software. Overall, ANUGA is a robust software to simulate two-dimensional shallow water flows. Arus air dangkal diatur dalam persamaan gelombang air dangkal, dikenal sebagai sistem Saint-Venant. Penelitian ini menyajikan metode finite volumeyang digunakan untuk menyelesaikan persamaan gelombang air dangkal dua dimensi dan bagaimana metode finite volumediimplementasikan dalam perangkat lunak ANUGA. Metode finite volumeadalah metode numerik yang mendasari perangkat lunakANUGA. ANUGA sendiri adalah perangkat lunak open source yang dikembangkan oleh Australian National University(ANU dan Geoscience Australia (GA. Perangkat lunak ini menggunakan metode finite volumedengan diskritisasi domain segitiga dalam proseskomputasi. Empat uji kasus digunakan untuk mengevaluasi kinerja perangkat lunak. Secara keseluruhan, ANUGA adalah perangkat lunak yang robust untuk mensimulasikan dua dimensi aliran arus air dangkal.
Numerical simulation of bionic foils in tandem arrangement
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Kai Zhou
2016-05-01
Full Text Available Based on the backgrounds of underwater propulsors with high hydrodynamic performance, the article focuses on the flapping foils in tandem arrangement and tries to formulate the physical mode and mathematical model of flapping propulsion. Using the commercial software Fluent, the governing equations are discretized by the finite volume method, and dynamic mesh method is adopted to solve the moving boundaries. In order to verify validity and feasibility of the method, hydrodynamic performance of single flapping foil is analyzed. The present results of single flapping foil compare well with those in experimental researches. After that, numerical simulations of flapping foils in tandem arrangement are conducted to reveal the energy absorption mechanisms. By extracting performance parameters and characteristics of the flow field, the interaction between upstream foil and downstream foil is analyzed. The results indicate that the vortices shedding from upstream foil have a significant effect on the hydrodynamic performance of downstream foil, and the downstream foil can use energy from the flow field to improve the hydrodynamic performance. Therefore, the hydrodynamic performance of the system can be improved by adjusting the locations of foils and motion parameters.
Mathematical approaches to bone reformation phenomena and numerical simulations
Matsuura, Yoshinori; Oharu, Shinnosuke; Takata, Takashi; Tamura, Akio
2003-09-01
Bone remodeling is metabolism of the bone through repetition of the resorption by osteoclasts and formation by osteoblasts. Osteoblasts produce inorganic calcium phosphate, which is converted to hydroxyapatite, and organic matrix consisting mainly of type I collagen, and then they deposit new bone to the part of the bone resorbed by osteoclasts. Osteoclasts dissociate calcium by secreting acid and degrade organic components by releasing lysosomal enzymes. Moreover, osteocytes in the bone play an important role in sensing various physical loads and conveying signals to activate osteoblasts. These three kinds of cells are linked to each other and perform the bone remodeling. Appropriate parameters representing the states of the bone and marrow are introduced and a mathematical model describing the bone remodeling phenomena is presented. The model involves an interface equation which determines the surface of the bone. The associated discrete model is formulated and its stable solvability is verified. Results of numerical simulations on a computer aided design system are visualized and then compared to clinical bone data. This work may be applied to medical science and in particular to dentistry.
Oil strategies benefits over different driving cycles using numerical simulation
Sara, Hanna; Chalet, David; Cormerais, Mickaël; Hetet, Jean-François
2017-08-01
95 g/km is the allowed quantity of CO2 emission normalized to NEDC to be set in 2020. In addition, NEDC will be replaced by more severe driving cycles and will be united worldwide. To respond to those criteria, automotive industries are working on every possible field. Thermal management has been proved to be effective in reducing fuel consumption. Cold start is a primordial reason of overconsumption, as the engine highest efficiency is at its optimal temperature. At cold start, the engine's oil is at its lowest temperature and thus its higher viscosity level. A high viscosity oil generates more friction, which is one of the most important heat losses in the engine. In this paper, hot oil storage is studied. Numerical simulations on GT-suite model were done. The model consists of a 4-cylinder turbocharged Diesel engine using a storage volume of 1 liter of hot oil. Ambient temperature variation were taken into consideration as well as different driving cycles. Furthermore, different configurations of the thermal strategy (multifunction oil sump) were proposed and evaluated. Lubricant temperature and viscosity profiles are presented in the article as well as fuel consumption savings for different configurations, driving cycles and ambient temperatures.
Numerical Simulations of Instabilities in Single-Hole Office Elements
Ahuja, Vineet; Hosangadi, Ashvin; Hitt, Matthew A.; Lineberry, David M.
2013-01-01
An orifice element is commonly used in liquid rocket engine test facilities either as a flow metering device, a damper for acoustic resonance or to provide a large reduction in pressure over a very small distance in the piping system. While the orifice as a device is largely effective in stepping down pressure, it is also susceptible to a wake-vortex type instability that generates pressure fluctuations that propagate downstream and interact with other elements of the test facility resulting in structural vibrations. Furthermore in piping systems an unstable feedback loop can exist between the vortex shedding and acoustic perturbations from upstream components resulting in an amplification of the modes convecting downstream. Such was the case in several tests conducted at NASA as well as in the Ariane 5 strap-on P230 engine in a static firing test where pressure oscillations of 0.5% resulted in 5% thrust oscillations. Exacerbating the situation in cryogenic test facilities, is the possibility of the formation of vapor clouds when the pressure in the wake falls below the vapor pressure leading to a cavitation instability that has a lower frequency than the primary wake-vortex instability. The cavitation instability has the potential for high amplitude fluctuations that can cause catastrophic damage in the facility. In this paper high-fidelity multi-phase numerical simulations of an orifice element are used to characterize the different instabilities, understand the dominant instability mechanisms and identify the tonal content of the instabilities.
Numerical Simulation of Particle Distribution in Capillary Membrane during Backwash
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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.
Fulfilling Magnetostatic Conditions in Numerical Simulations of Expanding Flux Tubes
Utz, D.; Van Doorsselaere, T.; Kühner, O.; Magyar, N.; Calvo Santamaria, I.; Campos Rozo, J. I.
A long-lasting problem of solar physics is the topic of the heating of the outer atmospheric layers of the Sun. Among the possible heating scenarios are wave driven heating processes. In this scenario disturbances and turbulence in the photosphere of the Sun causes the creation of waves which propagate upwards into the higher atmosphere where these waves are at least partially damped and absorbed, causing heating of the atmosphere. Nowadays it is thought that especially MHD waves play an important role in such heating scenarios. The created MHD waves are guided especially well along strong vertical magnetic field configurations, so-called flux-tubes, into the higher atmosphere. To obtain deeper insights into this fascinating topic, numerical simulations are a useful tool at hand. However, up to now it is still quite common to assume simple non stratified flux tubes which feature in addition weak magnetic field strengths. While this makes the modeling of the solar atmosphere and the magnetic field configuration much easier, the results might be changed drastically by these simplifications. In the current contribution we wish to outline a method of how to construct self-consistent, magneto-static flux tube atmospheres.
Numerical simulation of nonlinear dynamics of 1D pulsating detonations
Borisov, S. P.; Kudryavtsev, A. N.
2017-10-01
The development of 1D instability of a detonation wave is numerically simulated for a two-stage chemical model. The shock-fitting approach is employed to track the leading detonation front. In order to determine its motion, the equation for the acceleration of the shock wave derived from the Rankine-Hugoniot conditions and the characteristic relations is integrated along with the reactive Euler equations. The fifth-order WENO scheme is used, time stepping is performed with the four-stage Runge-Kutta-Gill method. It is shown that in a certain range of parameters of the problem (the degree of overdrive f, the dissociation energy Ed and the activation energy Ea ), the Zeldovich-Neumann-Döring stationary solution is unstable with respect to 1D disturbances. The evolution of disturbances at later nonlinear stages is studied. Nonlinear saturation of the growth of disturbances leads to the formation of a stable limit cycle. When changing the parameters of the problem, the period doubling bifurcation can occur leading to the appearance of pulsations with two different maxima of the amplitude.
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 Tower Rotor Interaction for Downwind Wind Turbine
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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.
Temperature considerations in numerical simulations of collapsing bubbles
Johnsen, Eric; Alahyari Beig, Shahaboddin
2014-11-01
In naval and biomedical engineering applications, the inertial collapse of cavitation bubbles is known to damage its surroundings. While significant attention has been dedicated to investigating the pressures produced by this process, less is known about heating of the surrounding medium, which may be important when collapse occurs near objects whose properties strongly depend on temperature (e.g., polymers). Euler simulations are capable of predicting the high pressures thereby generated. However, numerical errors can occur when solving the Navier-Stokes equations for compressible interface problems. Using a newly developed computational approach that prevents such errors, we investigate the dynamics of shock-induced and Rayleigh collapse of individual and collections of gas bubbles, in a free field and near rigid surfaces. We characterize the temperature rises based on the relevant non-dimensional parameters entering the problem. In particular, we show that the temperature of a neighboring object rises due to two mechanisms: the shock produced at collapse and heat diffusion from the hot bubble as it moves toward the object. This work was supported by ONR Grant N00014-12-1-0751.
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 and Scaling Analysis of Cell Printing
Qiao, Rui; He, Ping
2011-11-01
Cell printing, i.e., printing three dimensional (3D) structures of cells held in a tissue matrix, is gaining significant attention in the biomedical community. The key idea is to use inkjet printer or similar devices to print cells into 3D patterns with a resolution comparable to the size of mammalian cells. Achieving such a resolution in vitro can lead to breakthroughs in areas such as organ transplantation. Although the feasibility of cell printing has been demonstrated recently, the printing resolution and cell viability remain to be improved. Here we investigate a unit operation in cell printing, namely, the impact of a cell-laden droplet into a pool of highly viscous liquids. The droplet and cell dynamics are quantified using both direct numerical simulation and scaling analysis. These studies indicate that although cell experienced significant stress during droplet impact, the duration of such stress is very short, which helps explain why many cells can survive the cell printing process. These studies also revealed that cell membrane can be temporarily ruptured during cell printing, which is supported by indirect experimental evidence.
Numerical Simulations of Driven Supersonic Relativistic MHD Turbulence
Zrake, Jonathan; MacFadyen, Andrew
2011-08-01
Models for GRB outflows invoke turbulence in relativistically hot magnetized fluids. In order to investigate these conditions we have performed high-resolution three-dimensional numerical simulations of relativistic magneto-hydrodynamical (RMHD) turbulence. We find that magnetic energy is amplified to several percent of the total energy density by turbulent twisting and folding of magnetic field lines. Values of ɛB>~0.01 are thus naturally expected. We study the dependence of saturated magnetic field energy fraction as a function of Mach number and relativistic temperature. We then present power spectra of the turbulent kinetic and magnetic energies. We also present solenoidal (curl-like) and dilatational (divergence-like) power spectra of kinetic energy. We propose that relativistic effects introduce novel couplings between these spectral components. The case we explore in most detail is for equal amounts of thermal and rest mass energy, corresponding to conditions after collisions of shells with relative Lorentz factors of several. These conditions are relevant in models for internal shocks, for the late afterglow phase, for cocoon material along the edge of a relativistic jet as it propagates through a star, as well neutron stars merging with each other and with black hole companions. We find that relativistic turbulence decays extremely quickly, on a sound crossing time of an eddy. Models invoking sustained relativistic turbulence to explain variability in GRB prompt emission are thus strongly disfavored unless a persistant driving of the turbulence is maintained for the duration of the prompt emission.
Energy Technology Data Exchange (ETDEWEB)
Chapyak, E.J.; Godwin, R.P. [Los Alamos National Lab., NM (United States); Vogel, A. [Medizinisches Laserzentrum Luebeck GmbH (Germany)
1997-04-01
In numerical calculations of idealized bubble dynamics test problems, Los Alamos computational tools perform well. A realistic equation of state must be used and geometrical features must be carefully modeled to simulate experiments accurately. In this work, we compare numerical simulations taking these features into account with experiments performed at the Medizinisches Laserzentrum Lubeck. We compare the measured and calculated positions of the shock front and of the bubble wall as a function of time in the laser optical breakdown of water produced by 30-ps 1-mJ Nd:YAG laser pulses.
The Numerical Analysis and Experiment of Shock Processing for Bouef
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Y Yamashita
2016-09-01
Full Text Available When the shock wave processing is applied to food, it is understood to obtain the change in various physical properties. For instance, when hard beef is processed by the underwater shock wave, the tenderization of meat can be expected. In the future, it is a goal that the shock wave processor is spread in general as a home electrical appliance. In the design for the suitable pressure vessels for food processing, the phenomenon in pressure vessel are very complex in multi-physics manners. Therefore, in numerical calculation, a lot of parameter for the numerical analysis is need for pressure vessel material and various foods. In this study, we chose a beef as a sample of the food processing. First, we obtained an unknown parameter of the beef by measuring the front and the shock wave speed of the sample. Then, we will show some numerical results for shock loading of beef by using LS-DYNA3D. The experiments were carried out using the high-speed image converter camera, high-speed video camera and the explosive experimental facilities.
Numerical Simulation of Natural Gas Flow in Anisotropic Shale Reservoirs
Negara, Ardiansyah
2015-11-09
Shale gas resources have received great attention in the last decade due to the decline of the conventional gas resources. Unlike conventional gas reservoirs, the gas flow in shale formations involves complex processes with many mechanisms such as Knudsen diffusion, slip flow (Klinkenberg effect), gas adsorption and desorption, strong rock-fluid interaction, etc. Shale formations are characterized by the tiny porosity and extremely low-permeability such that the Darcy equation may no longer be valid. Therefore, the Darcy equation needs to be revised through the permeability factor by introducing the apparent permeability. With respect to the rock formations, several studies have shown the existence of anisotropy in shale reservoirs, which is an essential feature that has been established as a consequence of the different geological processes over long period of time. Anisotropy of hydraulic properties of subsurface rock formations plays a significant role in dictating the direction of fluid flow. The direction of fluid flow is not only dependent on the direction of pressure gradient, but it also depends on the principal directions of anisotropy. Therefore, it is very important to take into consideration anisotropy when modeling gas flow in shale reservoirs. In this work, the gas flow mechanisms as mentioned earlier together with anisotropy are incorporated into the dual-porosity dual-permeability model through the full-tensor apparent permeability. We employ the multipoint flux approximation (MPFA) method to handle the full-tensor apparent permeability. We combine MPFA method with the experimenting pressure field approach, i.e., a newly developed technique that enables us to solve the global problem by breaking it into a multitude of local problems. This approach generates a set of predefined pressure fields in the solution domain in such a way that the undetermined coefficients are calculated from these pressure fields. In other words, the matrix of coefficients
Mukhadiyev, Nurzhan
2017-05-01
Combustion at extreme conditions, such as a turbulent flame at high Karlovitz and Reynolds numbers, is still a vast and an uncertain field for researchers. Direct numerical simulation of a turbulent flame is a superior tool to unravel detailed information that is not accessible to most sophisticated state-of-the-art experiments. However, the computational cost of such simulations remains a challenge even for modern supercomputers, as the physical size, the level of turbulence intensity, and chemical complexities of the problems continue to increase. As a result, there is a strong demand for computational cost reduction methods as well as in acceleration of existing methods. The main scope of this work was the development of computational and numerical tools for high-fidelity direct numerical simulations of premixed planar flames interacting with turbulence. The first part of this work was KAUST Adaptive Reacting Flow Solver (KARFS) development. KARFS is a high order compressible reacting flow solver using detailed chemical kinetics mechanism; it is capable to run on various types of heterogeneous computational architectures. In this work, it was shown that KARFS is capable of running efficiently on both CPU and GPU. The second part of this work was numerical tools for direct numerical simulations of planar premixed flames: such as linear turbulence forcing and dynamic inlet control. DNS of premixed turbulent flames conducted previously injected velocity fluctuations at an inlet. Turbulence injected at the inlet decayed significantly while reaching the flame, which created a necessity to inject higher than needed fluctuations. A solution for this issue was to maintain turbulence strength on the way to the flame using turbulence forcing. Therefore, a linear turbulence forcing was implemented into KARFS to enhance turbulence intensity. Linear turbulence forcing developed previously by other groups was corrected with net added momentum removal mechanism to prevent mean
"Physically-based" numerical experiment to determine the dominant hillslope processes during floods?
Gaume, Eric; Esclaffer, Thomas; Dangla, Patrick; Payrastre, Olivier
2016-04-01
To study the dynamics of hillslope responses during flood event, a fully coupled "physically-based" model for the combined numerical simulation of surface runoff and underground flows has been developed. A particular attention has been given to the selection of appropriate numerical schemes for the modelling of both processes and of their coupling. Surprisingly, the most difficult question to solve, from a numerical point of view, was not related to the coupling of two processes with contrasted kinetics such as surface and underground flows, but to the high gradient infiltration fronts appearing in soils, source of numerical diffusion, instabilities and sometimes divergence. The model being elaborated, it has been successfully tested against results of high quality experiments conducted on a laboratory sandy slope in the early eighties, which is still considered as a reference hillslope experimental setting (Abdul & Guilham). The model appeared able to accurately simulate the pore pressure distributions observed in this 1.5 meter deep and wide laboratory hillslope, as well as its outflow hydrograph shapes and the measured respective contributions of direct runoff and groundwater to these outflow hydrographs. Based on this great success, the same model has been used to simulate the response of a theoretical 100-meter wide and 10% sloped hillslope, with a 2 meter deep pervious soil and impervious bedrock. Three rain events have been tested: a 100 millimeter rainfall event over 10 days, over 1 day or over one hour. The simulated responses are hydrologically not realistic and especially the fast component of the response, that is generally observed in the real-world and explains flood events, is almost absent of the simulated response. Thinking a little about the whole problem, the simulation results appears totally logical according to the proposed model. The simulated response, in fact a recession hydrograph, corresponds to a piston flow of a relatively uniformly
Numerical simulations of energy transfer in two collisionless interpenetrating plasmas
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Davis S.
2013-11-01
Full Text Available Ion stream instabilities are essential for collisionless shock formation as seen in astrophysics. Weakly relativistic shocks are considered as candidates for sources of high energy cosmic rays. Laboratory experiments may provide a better understanding of this phenomenon. High intensity short pulse laser systems are opening possibilities for efficient ion acceleration to high energies. Their collision with a secondary target could be used for collisionless shock formation. In this paper, using particle-in-cell simulations we are studying interaction of a sub-relativistic, laser created proton beam with a secondary gas target. We show that the ion bunch initiates strong electron heating accompanied by the Weibel-like filamentation and ion energy losses. The energy repartition between ions, electrons and magnetic fields are investigated. This yields insight on the processes occurring in the interstellar medium (ISM and gamma-ray burst afterglows.
Numerical simulation of flow and compression of green sand
DEFF Research Database (Denmark)
Hovad, Emil
with the ﬂow of the sand particles and the deposition of sand dur-ing the production of sand molds using the sand shot in the DISAMATIC process. The deposition of the green sand in the chamber was investigated with a special cavity design where air vents were placed inside the cavities. The air vents are used...... to transport the green sand with an airﬂow during the sand shot. By changing the air vents settings in the chamber and in the cavities it was possible to improve the ﬁlling in the narrow passages in the cavity design, thereby improving the ﬁnal sand mold as well. The sand shot with the cavity design...... was simulated by the discrete element method (DEM) modelling the ﬂow of the green sand combined with classical computational ﬂuid dynamics (CFD) for modelling the airﬂow in the chamber and the airﬂow through the air vents. These experiments and simulations gave beneﬁcial insights to the DISAMATIC process...
Damyanova, M.; Sabchevski, S.; Zhelyazkov, I.; Vasileva, E.; Balabanova, E.; Dankov, P.; Malinov, P.
2016-10-01
As the most powerful CW sources of coherent radiation in the sub-terahertz to terahertz frequency range the gyrotrons have demonstrated a remarkable potential for numerous novel and prospective applications in the fundamental physical research and the technologies. Among them are powerful gyrotrons for electron cyclotron resonance heating (ECRH) and current drive (ECCD) of magnetically confined plasma in various reactors for controlled thermonuclear fusion (e.g., tokamaks and most notably ITER), high-frequency gyrotrons for sub-terahertz spectroscopy (for example NMR-DNP, XDMR, study of the hyperfine structure of positronium, etc.), gyrotrons for thermal processing and so on. Modelling and simulation are indispensable tools for numerical studies, computer-aided design (CAD) and optimization of such sophisticated vacuum tubes (fast-wave devices) operating on a physical principle known as electron cyclotron resonance maser (ECRM) instability. During the recent years, our research team has been involved in the development of physical models and problem-oriented software packages for numerical analysis and CAD of different gyrotrons in the framework of a broad international collaboration. In this paper we present the current status of our simulation tools (GYROSIM and GYREOSS packages) and illustrate their functionality by results of numerical experiments carried out recently. Finally, we provide an outlook on the envisaged further development of the computer codes and the computational modules belonging to these packages and specialized to different subsystems of the gyrotrons.
Simulator experiments: effects of NPP operator experience on performance
Energy Technology Data Exchange (ETDEWEB)
Beare, A.N.; Gray, L.H.
1984-01-01
During the FY83 research, a simulator experiment was conducted at the control room simulator for a GE Boiling Water Reactor (BWR) NPP. The research subjects were licensed operators undergoing requalification training and shift technical advisors (STAs). This experiment was designed to investigate the effects of senior reactor operator (SRO) experience, operating crew augmentation with an STA and practice, as a crew, upon crew and individual operator performance, in response to anticipated plant transients. Sixteen two-man crews of licensed operators were employed in a 2 x 2 factorial design. The SROs leading the crews were split into high and low experience groups on the basis of their years of experience as an SRO. One half of the high- and low-SRO experience groups were assisted by an STA. The crews responded to four simulated plant casualties. A five-variable set of content-referenced performance measures was derived from task analyses of the procedurally correct responses to the four casualties. System parameters and control manipulations were recorded by the computer controlling the simulator. Data on communications and procedure use were obtained from analysis of videotapes of the exercises. Questionnaires were used to collect subject biographical information and data on subjective workload during each simulated casualty. For four of the five performance measures, no significant differences were found between groups led by high (25 to 114 months) and low (1 to 17 months as an SRO) experience SROs. However, crews led by low experience SROs tended to have significantly shorter task performance times than crews led by high experience SROs. The presence of the STA had no significant effect on overall team performance in responding to the four simulated casualties. The FY84 experiments are a partial replication and extension of the FY83 experiment, but with PWR operators and simulator.
Numerical Experiments for Storm Surge Inundation in Korean Coastal Area
Yoon, J.; Shim, J.; Jun, K.
2012-12-01
Sea-level rising due to climate change following the global warming and the increased intensity of typhoon are magnifying inundation hazards up to the unpredictable level, resulting from the typhoon surge in Korea and other coastal states around the world. Typhoon is the most serious natural disaster in Korean coastal area. Many people died by storm surge inundation every year. And typhoon caused a lot of damage to property. Climate changes due to global warming are producing a stronger natural disaster. Coastal zones have been damaged by typhoons and accompanying storm surge. Especially, the most serious loss of life and terrible property damage caused by typhoon Maemi in 2003. The typhoon Maemi invaded Korean Peninsula leaving property loss of $ 4 Billion and killing 131 people. After then, there has been an increased interest in these coastal zone problems. If storm surges coincide with high tides, the loss of life and property damage due to high waters arc even worse. Therefore it is desirable to accurately forecast the amount water level increase. In this study, using a numerical model FVCOM(finite volume coastal circulation model, Chen et al.,2004), storm surge was simulated to examine its fluctuation characteristics for the coastal area behind Masan, Yeosu and Busan city in Korea. In the numerical model, a moving boundary condition(wet-dry treatment) was incorporated to explain wave inundation. To simulate the inundation scenario, the model grids were extended up to the area inside the lowland in application of the digital elevation data(DEM) made by precisely combining the aero-LiDAR survey data and bathymetry data for the 3 demonstration regions of Busan, Masan and Yeosu. Minimum grid of 300 m unstructured triangular mesh applied to calculate the storm surge was adopted as a grid system. And the minimum grid size of 30 m was built near Busan, Masan and Yeosu area which are the fine coastal regions and where the inundation is simulated. Numerically
Numerical simulation of the porous filter properties for the internal arc mollifying effects
Energy Technology Data Exchange (ETDEWEB)
Rochette, D.; Bussiere, W. [Laboratoire Arc Electrique et Plasmas thermiques, CNRS FRE 3120, Universite, Blaise Pascal, IUT de Montlucon, Avenue Aristide Briand, BP 2235, 03101, Montlucon Cedex (France); Clain, S. [Institut de Mathematiques, CNRS UMR 5219, Universite Paul Sabatier Toulouse, 3, 118 route de Narbonne, F-31062 Toulouse Cedex 4 (France); Gentils, F.; Wild, J. [Schneider Electric - Science and Technology Division - Research Center A2, 38050, Grenoble Cedex 9 (France)
2011-01-15
A mathematical model and numerical experiments of pressure wave impacts with a porous medium are presented to simulate the valve burst out of a medium voltage switchgear and to evaluate the protection filter efficiency. A simplified one-dimensional gas flow model in porous medium with variable porosity is used. To solve numerically the governing equations, we employed the numerical method presented in Rochette et al. (2005) to take into account the non-conservative term P({partial_derivative}{phi}/{partial_derivative}x). Three sets of test are performed to study several filter prototypes. The objective is to provide a filter which does not produce a high reflected wave and cools enough the ejected hot gas. We first consider filters with variable porosity and simulate the interaction with an incident pressure wave, then we consider two types of granular material to characterize their incidence on the flow and finally, we simulate two different fluid flows (air and SF6) going through the porous medium. (author)
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Frantisek KAVICKA
2010-12-01
Full Text Available The thermophysical properties of steels have significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The determination of these 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, cylinder or slab (generally a concasting. The influence of individual properties should be neither under- nor over-estimated. Therefore, an analysis/parametric study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation and optimization were also determined. Individual properties, which, in some cases, were obtained from tables, and in others experimentally, were substituted by an approximation using orthogonal polynomials. The accuracy of each polynomial is dependent on the precision of individual values. The order of significance of individual 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 and universal 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.
Numerical Simulations of Subscale Wind Turbine Rotor Inboard Airfoils at Low Reynolds Number
Energy Technology Data Exchange (ETDEWEB)
Blaylock, Myra L. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Thermal/ Fluid Sciences & Engineering Dept.; Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.; Resor, Brian R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.
2015-04-01
New blade designs are planned to support future research campaigns at the SWiFT facility in Lubbock, Texas. The sub-scale blades will reproduce specific aerodynamic characteristics of utility-scale rotors. Reynolds numbers for megawatt-, utility-scale rotors are generally above 2-8 million. The thickness of inboard airfoils for these large rotors are typically as high as 35-40%. The thickness and the proximity to three-dimensional flow of these airfoils present design and analysis challenges, even at the full scale. However, more than a decade of experience with the airfoils in numerical simulation, in the wind tunnel, and in the field has generated confidence in their performance. Reynolds number regimes for the sub-scale rotor are significantly lower for the inboard blade, ranging from 0.7 to 1 million. Performance of the thick airfoils in this regime is uncertain because of the lack of wind tunnel data and the inherent challenge associated with numerical simulations. This report documents efforts to determine the most capable analysis tools to support these simulations in an effort to improve understanding of the aerodynamic properties of thick airfoils in this Reynolds number regime. Numerical results from various codes of four airfoils are verified against previously published wind tunnel results where data at those Reynolds numbers are available. Results are then computed for other Reynolds numbers of interest.
Numerical optimization of a plasma wakefield acceleration experiment
Directory of Open Access Journals (Sweden)
K. V. Lotov
2007-05-01
Full Text Available One possible way to demonstrate both the efficiency and beam quality in a plasma wakefield accelerator is to prepare matched drive and accelerated beams by removing a central slice from a single high-quality electron bunch (parent beam. For parameters of the parent beam given, the question arises how to maximize the number and energy of accelerated particles and minimize their energy spread and emittance. This question is addressed by numerical simulations. The optimum shape of the beams, required plasma length, achievable energy gain, and energy spread are found as functions of the plasma density and parent beam characteristics. The required control accuracy of adjustable beam and plasma parameters is determined.
Simulation of white light generation and near light bullets using a novel numerical technique
Zia, Haider
2018-01-01
An accurate and efficient simulation has been devised, employing a new numerical technique to simulate the derivative generalised non-linear Schrödinger equation in all three spatial dimensions and time. The simulation models all pertinent effects such as self-steepening and plasma for the non-linear propagation of ultrafast optical radiation in bulk material. Simulation results are compared to published experimental spectral data of an example ytterbium aluminum garnet system at 3.1 μm radiation and fits to within a factor of 5. The simulation shows that there is a stability point near the end of the 2 mm crystal where a quasi-light bullet (spatial temporal soliton) is present. Within this region, the pulse is collimated at a reduced diameter (factor of ∼2) and there exists a near temporal soliton at the spatial center. The temporal intensity within this stable region is compressed by a factor of ∼4 compared to the input. This study shows that the simulation highlights new physical phenomena based on the interplay of various linear, non-linear and plasma effects that go beyond the experiment and is thus integral to achieving accurate designs of white light generation systems for optical applications. An adaptive error reduction algorithm tailor made for this simulation will also be presented in appendix.
Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations
Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.
2010-12-01
We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian
Mukherjee, A.; Shankar, D.; Chatterjee, Abhisek; Vinayachandran, P. N.
2017-08-01
We simulate the East India Coastal Current (EICC) using two numerical models (resolution 0.1° × 0.1°), an oceanic general circulation model (OGCM) called Modular Ocean Model and a simpler, linear, continuously stratified (LCS) model, and compare the simulated current with observations from moorings equipped with acoustic Doppler current profilers deployed on the continental slope in the western Bay of Bengal (BoB). We also carry out numerical experiments to analyse the processes. Both models simulate well the annual cycle of the EICC, but the performance degrades for the intra-annual and intraseasonal components. In a model-resolution experiment, both models (run at a coarser resolution of 0.25° × 0.25° ) simulate well the currents in the equatorial Indian Ocean (EIO), but the performance of the high-resolution LCS model as well as the coarse-resolution OGCM, which is good in the EICC regime, degrades in the eastern and northern BoB. An experiment on forcing mechanisms shows that the annual EICC is largely forced by the local alongshore winds in the western BoB and remote forcing due to Ekman pumping over the BoB, but forcing from the EIO has a strong impact on the intra-annual EICC. At intraseasonal periods, local (equatorial) forcing dominates in the south (north) because the Kelvin wave propagates equatorward in the western BoB. A stratification experiment with the LCS model shows that changing the background stratification from EIO to BoB leads to a stronger surface EICC owing to strong coupling of higher order vertical modes with wind forcing for the BoB profiles. These high-order modes, which lead to energy propagating down into the ocean in the form of beams, are important only for the current and do not contribute significantly to the sea level.
Numerical Simulation of Ion Rings and Ion Beam Propagation.
Mankofsky, Alan
This thesis presents the development of numerical simulation techniques for studying the physics of ion beams and rings in a background plasma as applicable to certain problems in magnetic and inertial confinement fusion. Two codes have been developed for these purposes: RINGA and CIDER. The 2 and 1/2-dimensional (r,z,v(,r),v(,(theta)),v(,z); (PAR-DIFF)/(PAR-DIFF)(theta) = 0) particle code RINGA follows the trajectories of ions in their self-consistent magnetic field. The code assumes strict charge neutrality and admits currents only in the azimuthal direction, i.e., (PHI) = J(,r) = J(,z) = 0. The injection and resistive trapping of ion rings has been studied with RINGA. The number of particles trapped as a fraction of the total number injected N is found to be strongly dependent upon (1) N (in the range 2.85 x 10('16) - 3.99 x 10('17)) and (2) mirror ratios in the system (1.05 -1.14), and more weakly dependent upon (3) wall resistance per unit length (0.72 (OMEGA)/cm - 1.80 (OMEGA)/cm) and (4) beam divergence (0(DEGREES)-6(DEGREES)). Fractions of trapped particles in excess of 0.9 have been observed. Modifications to RINGA to include finite pressure of confined plasma and beam ion-electron slowing down collisions are discussed. Finite plasma pressure leads to a diamagnetic current which increases the field reversal factor in ion ring equilibria, while causing the closed flux surfaces to expand outward. The ideal magnetohydrodynamic stability of the plasma is analyzed in the high toroidal mode number limit, where the beam ions are noninteracting. The existence of stable high-(beta) equilibria is demonstrated. One such equilibrium, stable to both ideal interchange and ballooning modes, has (TBOND) 8(pi) / (DBLTURN) 55%. In the CIDER hybrid code, ions are represented by particles and electrons by an inertialess thermal fluid which obeys a generalized Ohm's law. Fields are solved in the quasineutral Darwin approximation. Several collisional and atomic processes are
Numerical simulation of floating bodies in extreme free surface waves
Directory of Open Access Journals (Sweden)
Z. Z. Hu
2011-02-01
Full Text Available In this paper, we use the in-house Computational Fluid Dynamics (CFD flow code AMAZON-SC as a numerical wave tank (NWT to study wave loading on a wave energy converter (WEC device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water. The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
Numerical Simulations of X-Ray Free Electron Lasers (XFEL)
Antonelli, Paolo
2014-11-04
We study a nonlinear Schrödinger equation which arises as an effective single particle model in X-ray free electron lasers (XFEL). This equation appears as a first principles model for the beam-matter interactions that would take place in an XFEL molecular imaging experiment in [A. Fratalocchi and G. Ruocco, Phys. Rev. Lett., 106 (2011), 105504]. Since XFEL are more powerful by several orders of magnitude than more conventional lasers, the systematic investigation of many of the standard assumptions and approximations has attracted increased attention. In this model the electrons move under a rapidly oscillating electromagnetic field, and the convergence of the problem to an effective time-averaged one is examined. We use an operator splitting pseudospectral method to investigate numerically the behavior of the model versus that of its time-averaged version in complex situations, namely the energy subcritical/mass supercritical case and in the presence of a periodic lattice. We find the time-averaged model to be an effective approximation, even close to blowup, for fast enough oscillations of the external field. This work extends previous analytical results for simpler cases [P. Antonelli, A. Athanassoulis, H. Hajaiej, and P. Markowich, Arch. Ration. Mech. Anal., 211 (2014), pp. 711--732].
Multifactor estimation of ecological risks using numerical simulation
Voskoboynikova, G.; Shalamov, K.; Khairetdinov, M.; Kovalevsky, V.
2017-10-01
In this paper, the problem of interaction of acoustic waves falling at a given angle on a snow layer on the ground and seismic waves arising both in this layer and in the ground is considered. A system of differential equations with boundary conditions describing the propagation of incident and reflected acoustic waves in the air refracted and reflected from the boundary of seismic waves in elastic media (snow and ground) is constructed and solved for a three-layer air-snow layer-ground model. The coefficients of reflection and refraction are calculated in the case of an acoustic wave falling onto both the ground and snow on the ground. The ratio of the energy of the refracted waves to the energy of the falling acoustic wave is obtained. It is noted that snow has a strong influence on the energy transfer into the ground, which can decrease by more than an order of magnitude. The numerical results obtained are consistent with the results of field experiments with a vibrational source performed by the Siberian Branch of the Russian Academy of Sciences.
Numerical simulation of floating bodies in extreme free surface waves
Hu, Z. Z.; Causon, D. M.; Mingham, C. G.; Qian, L.
2011-02-01
In this paper, we use the in-house Computational Fluid Dynamics (CFD) flow code AMAZON-SC as a numerical wave tank (NWT) to study wave loading on a wave energy converter (WEC) device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water). The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
Reed, John A.; Afjeh, Abdollah A.
1995-01-01
A major difficulty in designing aeropropulsion systems is that of identifying and understanding the interactions between the separate engine components and disciplines (e.g., fluid mechanics, structural mechanics, heat transfer, material properties, etc.). The traditional analysis approach is to decompose the system into separate components with the interaction between components being evaluated by the application of each of the single disciplines in a sequential manner. Here, one discipline uses information from the calculation of another discipline to determine the effects of component coupling. This approach, however, may not properly identify the consequences of these effects during the design phase, leaving the interactions to be discovered and evaluated during engine testing. This contributes to the time and cost of developing new propulsion systems as, typically, several design-build-test cycles are needed to fully identify multidisciplinary effects and reach the desired system performance. The alternative to sequential isolated component analysis is to use multidisciplinary coupling at a more fundamental level. This approach has been made more plausible due to recent advancements in computation simulation along with application of concurrent engineering concepts. Computer simulation systems designed to provide an environment which is capable of integrating the various disciplines into a single simulation system have been proposed and are currently being developed. One such system is being developed by the Numerical Propulsion System Simulation (NPSS) project. The NPSS project, being developed at the Interdisciplinary Technology Office at the NASA Lewis Research Center is a 'numerical test cell' designed to provide for comprehensive computational design and analysis of aerospace propulsion systems. It will provide multi-disciplinary analyses on a variety of computational platforms, and a user-interface consisting of expert systems, data base management and
A Numerical Simulator for a Crop-Producing Greenhouse
DEFF Research Database (Denmark)
Ursem, Rasmus Kjær; Krink, Thiemo; Filipic, Bogdan
2002-01-01
This report describes a greenhouse simulator. The described simulator is translated from a German description (Pohlheim and Heißner, 1996), and some minor modifications are introduced. The simulator is reimplemented in Java and is based on the original MatLab version. The purpose of the simulator...
Kozic Mirko S.; Ristic Slavica S.; Puharic Mirjana A.; Katavic Boris T.
2011-01-01
This paper presents the results of numerical flow simulation in ventilation mill of Kostolac B power plant, where louvers and centrifugal separator with adjustable blade angle are used. Numerical simulations of multiphase flow were performed using the Euler-Euler and Euler-Lagrange approach of ANSYS FLUENT software package. The results of numerical simulations are compared with measurements in the mill for both types of separators. Due to very complex geometry and large number of the gr...
High performance Python for direct numerical simulations of turbulent flows
Mortensen, Mikael; Langtangen, Hans Petter
2016-06-01
Direct Numerical Simulations (DNS) of the Navier Stokes equations is an invaluable research tool in fluid dynamics. Still, there are few publicly available research codes and, due to the heavy number crunching implied, available codes are usually written in low-level languages such as C/C++ or Fortran. In this paper we describe a pure scientific Python pseudo-spectral DNS code that nearly matches the performance of C++ for thousands of processors and billions of unknowns. We also describe a version optimized through Cython, that is found to match the speed of C++. The solvers are written from scratch in Python, both the mesh, the MPI domain decomposition, and the temporal integrators. The solvers have been verified and benchmarked on the Shaheen supercomputer at the KAUST supercomputing laboratory, and we are able to show very good scaling up to several thousand cores. A very important part of the implementation is the mesh decomposition (we implement both slab and pencil decompositions) and 3D parallel Fast Fourier Transforms (FFT). The mesh decomposition and FFT routines have been implemented in Python using serial FFT routines (either NumPy, pyFFTW or any other serial FFT module), NumPy array manipulations and with MPI communications handled by MPI for Python (mpi4py). We show how we are able to execute a 3D parallel FFT in Python for a slab mesh decomposition using 4 lines of compact Python code, for which the parallel performance on Shaheen is found to be slightly better than similar routines provided through the FFTW library. For a pencil mesh decomposition 7 lines of code is required to execute a transform.
Analytical approximation and numerical simulations for periodic travelling water waves
Kalimeris, Konstantinos
2017-12-01
We present recent analytical and numerical results for two-dimensional periodic travelling water waves with constant vorticity. The analytical approach is based on novel asymptotic expansions. We obtain numerical results in two different ways: the first is based on the solution of a constrained optimization problem, and the second is realized as a numerical continuation algorithm. Both methods are applied on some examples of non-constant vorticity. This article is part of the theme issue 'Nonlinear water waves'.
A New Numerical Simulation technology of Multistage Fracturing in Horizontal Well
Cheng, Ning; Kang, Kaifeng; Li, Jianming; Liu, Tao; Ding, Kun
2017-11-01
Horizontal multi-stage fracturing is recognized the effective development technology of unconventional oil resources. Geological mechanics in the numerical simulation of hydraulic fracturing technology occupies very important position, compared with the conventional numerical simulation technology, because of considering the influence of geological mechanics. New numerical simulation of hydraulic fracturing can more effectively optimize the design of fracturing and evaluate the production after fracturing. This paper studies is based on the three-dimensional stress and rock physics parameters model, using the latest fluid-solid coupling numerical simulation technology to engrave the extension process of fracture and describes the change of stress field in fracturing process, finally predict the production situation.
Directory of Open Access Journals (Sweden)
Yuan-Lin Guan
2015-07-01
Full Text Available A flexible caudal fin made of the macro fiber composites and the carbon fiber orthotropic composite was investigated by the numerical simulations and the experiments. First, a three-dimensional numerical simulation procedure was adopted to research the torsion propulsion mode of the caudal fin and the impact of the water for the structural torsion frequency of the caudal fin. Then, a two-dimensional unsteady fluid computational method was used to analyze the hydrodynamic performance with the periodic swing of the caudal fin on the torsion mode. Based on the simulation results, the flow field was demonstrated and discussed. The interaction between the caudal fin and the water was explained. Finally, the laser vibrometer system was built to verify the torsion propulsion mode. Meanwhile, the application of the caudal fin was realized on the torsion propulsion, and the measured system was established to demonstrate the performance of the caudal fin. The established simulation procedures and experimental methods in this study may provide guidance to the fins made of the composite materials during the structural design and the investigation of the flow field characteristics with the movement of the fins.