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Добірка наукової літератури з теми "Physical boundary conditions"

Автор: Grafiati

Опубліковано: 24 липня 2022

Оновлено: 8 серпня 2022

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Статті в журналах з теми "Physical boundary conditions"

Kausel, E. "Physical interpretation and stability of paraxial boundary conditions." Bulletin of the Seismological Society of America 82, no. 2 (April 1, 1992): 898–913. http://dx.doi.org/10.1785/bssa0820020898.

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Abstract We derive in this paper the dynamic impedance matrices associated with some paraxial boundary conditions for wave motions in unbounded homogenous elastic media and use them to establish the existence of directions of propagation of waves for which the boundaries supply rather than dissipate energy. Also, we explore the existence of solutions of exponential growth and discuss conditions under which they can arise. These considerations may be used to provide a physical interpretation to the paraxial boundaries and to understand possible sources of instability that can develop in time-domain implementations of these schemes with finite differences.

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Juffer, A. H., and H. J. C. Berendsen. "Dynamic surface boundary conditions." Molecular Physics 79, no. 3 (June 20, 1993): 623–44. http://dx.doi.org/10.1080/00268979300101501.

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Becker, Theodor S., Nele Börsing, Dirk-Jan van Manen, Thomas Haag, Christoph Bärlocher, and Johan O. Robertsson. "Physical implementation of immersive boundary conditions in acoustic waveguides." Journal of the Acoustical Society of America 144, no. 3 (September 2018): 1759. http://dx.doi.org/10.1121/1.5067788.

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Marquis‐Favre, Cathy, and Julien Faure. "Physical and perceptual assessment of glass plate boundary conditions." Journal of the Acoustical Society of America 112, no. 5 (November 2002): 2412. http://dx.doi.org/10.1121/1.4779857.

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Becker, Theodor S., Dirk-Jan van Manen, Carly Donahue, and Johan O. Robertsson. "Physical implementation of immersive boundary conditions in one dimension." Journal of the Acoustical Society of America 141, no. 5 (May 2017): 3833. http://dx.doi.org/10.1121/1.4988519.

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Michelén Ströfer, Carlos A., Xin-Lei Zhang, Heng Xiao, and Olivier Coutier-Delgosha. "Enforcing boundary conditions on physical fields in Bayesian inversion." Computer Methods in Applied Mechanics and Engineering 367 (August 2020): 113097. http://dx.doi.org/10.1016/j.cma.2020.113097.

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Roberts, A. J. "Boundary conditions for approximate differential equations." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 34, no. 1 (July 1992): 54–80. http://dx.doi.org/10.1017/s0334270000007384.

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AbstractA large number of mathematical models are expressed as differential equations. Such models are often derived through a slowly-varying approximation under the assumption that the domain of interest is arbitrarily large; however, typical solutions and the physical problem of interest possess finite domains. The issue is: what are the correct boundary conditions to be used at the edge of the domain for such model equations? Centre manifold theory [24] and its generalisations may be used to derive these sorts of approximations, and higher-order refinements, in an appealing and systematic fashion. Furthermore, the centre manifold approach permits the derivation of appropriate initial conditions and forcing for the models [25, 7]. Here I show how to derive asymptotically-correct boundary conditions for models which are based on the slowly-varying approximation. The dominant terms in the boundary conditions typically agree with those obtained through physical arguments. However, refined models of higher order require subtle corrections to the previously-deduced boundary conditions, and also require the provision of additional boundary conditions to form a complete model.

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Tian, Qianzhu. "Existence of nonlinear boundary layer solution to the Boltzmann equation with physical boundary conditions." Journal of Mathematical Analysis and Applications 356, no. 1 (August 2009): 42–59. http://dx.doi.org/10.1016/j.jmaa.2009.02.028.

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Kim, Jae Wook, and Duck Joo Lee. "Implementation of Boundary Conditions for Optimized High-Order Compact Schemes." Journal of Computational Acoustics 05, no. 02 (June 1997): 177–91. http://dx.doi.org/10.1142/s0218396x97000113.

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The optimized high-order compact (OHOC) finite difference schemes, proposed as central schemes are used for aeroacoustic computations on interior nodes. On near-boundary nodes, accurate non-central or one-sided compact schemes are formulated and developed in this paper for general computations in domains with non-periodic boundaries. The near-boundary non-central compact schemes are optimized in the wavenumber domain by using Fourier error analysis. Analytic optimization methods are devised to minimize the dispersion and dissipation errors, and to obtain maximum resolution characteristics of the near-boundary compact schemes. With the accurate near-boundary schemes, the feasibility of implementing physical boundary conditions for the OHOC schemes are investigated to provide high-quality wave solutions. Characteristics-based boundary conditions and the free-field impedance conditions are used as the physical boundary conditions for direct computations of linear and nonlinear wave propagation and radiation. It is shown that the OHOC schemes present accurate wave solutions by using the optimized near-boundary compact schemes and the physical boundary conditions.

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Evans, Lawrence Christopher, and Robert Gastler. "Some results for the primitive equations with physical boundary conditions." Zeitschrift für angewandte Mathematik und Physik 64, no. 6 (March 20, 2013): 1729–44. http://dx.doi.org/10.1007/s00033-013-0320-6.

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Дисертації з теми "Physical boundary conditions"

Helanow, Christian. "Basal boundary conditions, stability and verification in glaciological numerical models." Doctoral thesis, Stockholms universitet, Institutionen för naturgeografi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141641.

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To increase our understanding of how ice sheets and glaciers interact with the climate system, numerical models have become an indispensable tool. However, the complexity of these systems and the natural limitation in computational power is reflected in the simplifications of the represented processes and the spatial and temporal resolution of the models. Whether the effect of these limitations is acceptable or not, can be assessed by theoretical considerations and by validating the output of the models against real world data. Equally important is to verify if the numerical implementation and computational method accurately represent the mathematical description of the processes intended to be simulated. This thesis concerns a set of numerical models used in the field of glaciology, how these are applied and how they relate to other study areas in the same field. The dynamical flow of glaciers, which can be described by a set of non-linear partial differential equations called the Full Stokes equations, is simulated using the finite element method. To reduce the computational cost of the method significantly, it is common to lower the order of the used elements. This results in a loss of stability of the method, but can be remedied by the use of stabilization methods. By numerically studying different stabilization methods and evaluating their suitability, this work contributes to constraining the values of stabilization parameters to be used in ice sheet simulations. Erroneous choices of parameters can lead to oscillations of surface velocities, which affects the long term behavior of the free-surface ice and as a result can have a negative impact on the accuracy of the simulated mass balance of ice sheets. The amount of basal sliding is an important component that affects the overall dynamics of the ice. A part of this thesis considers different implementations of the basal impenetrability condition that accompanies basal sliding, and shows that methods used in literature can lead to a difference in velocity of 1% to 5% between the considered methods. The subglacial hydrological system directly influences the glacier's ability to slide and therefore affects the velocity distribution of the ice. The topology and dominant mode of the hydrological system on the ice sheet scale is, however, ill constrained. A third contribution of this thesis is, using the theory of R-channels to implement a simple numerical model of subglacial water flow, to show the sensitivity of subglacial channels to transient processes and that this limits their possible extent. This insight adds to a cross-disciplinary discussion between the different sub-fields of theoretical, field and paleo-glaciology regarding the characteristics of ice sheet subglacial hydrological systems. In the study, we conclude by emphasizing areas of importance where the sub-fields have yet to unify: the spatial extent of channelized subglacial drainage, to what degree specific processes are connected to geomorphic activity and the differences in spatial and temporal scales. As a whole, the thesis emphasizes the importance of verification of numerical models but also acknowledges the natural limitations of these to represent complex systems. Focusing on keeping numerical ice sheet and glacier models as transparent as possible will benefit end users and facilitate accurate interpretations of the numerical output so it confidently can be used for scientific purposes.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Greenland Analogue Project

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Williams, Hannah Elizabeth. "Uncertainty in the prediction of overtopping parameters in numerical and physical models due to offshore spectral boundary conditions." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30339/.

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The accurate prediction of wave overtopping is one of the most important aspects in the design of coastal defence structures. This can be achieved by using three different approaches: by physical modelling using laboratory tests, by empirical formulae available in literature derived from physical modelling and field tests, or by numerical simulation of the hydraulic response of the structure. All of these prediction methods are subject to a certain level of uncertainty. One source of this is the requirement of a defined free surface elevation and velocity time series seaward boundary condition in any model. Often, these are not available but the modeller is instead provided with an incident energy density spectrum. A time series will then be reconstructed from this spectrum to be used as boundary conditions. Since the energy density spectrum provides only information on the amplitude of the components, it is usually assumed that the phases of these components are randomly distributed. To create the randomly generated phases, an initial seed value is required to generate a population of uniformly distributed random phases. By varying this value for each simulation a different time series will be produced. The overall objective of this research is to quantify the uncertainty in the prediction of overtopping due to this process. This research involved carrying out two sets of laboratory experiments. Firstly, those carried out in the 2D wave flume at HR Wallingford, which provided a reference case for the validation of a numerical model, as well as a measured incident wave spectra for the generation of the population of reconstructed offshore boundary time series. The second set of experiments was carried out in the smaller 2D flume at the University of Nottingham to investigate the effect of random seeding to generate the time series at the wave paddle on the resulting overtopping parameters. This was also carried out to allow a comparison in the variability between the physical and numerical results. It was found in the work, that when a measured free surface elevation is used as the input, good agreement between the numerical solver prediction and the overtopping measurements was observed. Subsequently, when a Monte Carlo approach was used to generate the population of reconstructed offshore boundary time series from the measured incident spectra the statistical analysis of the results showed that the variability was higher for the small numbers of overtopping waves and decreases as overtopping becomes more frequent. To allow for more generalised conclusions on the uncertainty, further numerical tests were then carried out with synthetic spectra allowing different hydraulic and structural parameters to be considered. These showed good agreement with the findings of the initial statistical analysis. Finally, the results from the physical model tests carried out at the University of Nottingham were analysed. The influence of laboratory effects were studied and analysis was carried out to establish the magnitude and sources of variability in these results. As with the numerical results, the characteristics of the distribution of the predicted overtopping parameters were also studied.

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Stoor, Daniel. "Solution of the Stefan problem with general time-dependent boundary conditions using a random walk method." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-385147.

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This work deals with the one-dimensional Stefan problem with a general time- dependent boundary condition at the fixed boundary. The solution will be obtained using a discrete random walk method and the results will be compared qualitatively with analytical- and finite difference method solutions. A critical part has been to model the moving boundary with the random walk method. The results show that the random walk method is competitive in relation to the finite difference method and has its advantages in generality and low effort to implement. The finite difference method has, on the other hand, higher accuracy for the same computational time with the here chosen step lengths. For the random walk method to increase the accuracy, longer execution times are required, but since the method is generally easily adapted for parallel computing, it is possible to speed up. Regarding applications for the Stefan problem, there are a large range of examples such as climate models, the diffusion of lithium-ions in lithium-ion batteries and modelling steam chambers for oil extraction using steam assisted gravity drainage.

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Albert, Francisca [Verfasser]. "Identification of kinematic boundary conditions triggering removal of material in tectonically erosive margins : Insight from scaled physical experiments / Francisca Albert." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1068191414/34.

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Zhao, Lin. "Aggregate Modeling of Large-Scale Cyber-Physical Systems." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512111263124549.

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Albert, Francisca [Verfasser]. "Identification of kinematic boundary conditions triggering removal of material in tectonically erosive margins : insight from scaled physical experiments / Francisca Albert. Deutsches GeoForschungsZentrum GFZ." Potsdam : Deutsches GeoForschungsZentrum GFZ, 2013. http://d-nb.info/1041525230/34.

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Råsmark, Per Johan. "On the Structure and Dynamics of Polyelectrolyte Gel Systems and Gel-surfactant Complexes." Doctoral thesis, Uppsala universitet, Fysikalisk-kemiska institutionen, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4652.

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This thesis describes the results of experimental work on polyelectrolyte gels and their interaction with oppositely charged surfactants, and presents two new algorithms applicable to the simulation of colloid and polymer systems. The model systems investigated were crosslinked poly(acrylate) (PA) and poly(styrene sulphonate) (PSS), and the surfactant was dodecyl trimethylammonium bromide (DoTAB). Pure gel materials were studied using dynamic light scattering. It was shown that the diffusion coefficient (D) increases with increasing degree of swelling and the concentration dependence is larger than predicted by scaling arguments. For gels at swelling equilibrium D increases with increasing degree of crosslinking. In subsequent studies on gel particles in DoTAB solution, Raman spectra were recorded at different positions in the gel. For both types of gels two distinct regions could be observed. For PA the surfactant is localised in the outer phase without any surfactant in the core, while for PSS the surfactant was distributed such that it had the same concentration relative to the polymer throughout the gel. In a second experiment, the kinetics for the deswelling of microscopic PSS particles in DoTAB solution was studied. It was found that the final volume varied linearly with the DoTAB concentration, and the rate of volume decrease could be fitted to a single exponential indicating stagnant layer diffusion to be the rate limiting process for the deswelling of the PSS particles. In the second part, I first describe an algorithm showing an efficient way to detect percolation in simulations, with periodic boundary conditions, using recursion. Spherical boundary conditions is an alternative to periodic boundary conditions for systems with long-range interactions. In the last part, the possibility to use the surface of a hypersphere in four dimensions for simulations of polymer systems is investigated, and algorithms for Monte Carlo and Brownian dynamics simulations are described.

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Kadri, Harouna Souleymane. "Ondelettes pour la prise en compte de conditions aux limites en turbulence incompressible." Grenoble, 2010. http://www.theses.fr/2010GRENM050.

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Ce travail de thèse concerne les méthodes numériques à base d'ondelettes pour la simulation de la turbulence incompressible. L'objectif principal est la prise en compte de conditions aux limites physiques dans la résolution des équations de Navier-Stokes. Contrairement aux travaux précédents où la vorticité était décomposée sur base d'ondelettes classiques, le point de vue qui est adopté ici vise à calculer le champ de vitesse de l'écoulement sous la forme d'une série d'ondelettes à divergence nulle. On est alors dans le cadre des équations de Navier-Stokes incompressibles en formulation vitesse-pression, pour lesquelles les conditions aux limites sur la vitesse s'écrivent explicitement, ce qui diffère de la formulation vitesse-tourbillon. Le principe de la méthode développée dans cette thèse consiste à injecter directement les conditions aux limites sur la base d'ondelettes. Ce travail prolonge la thèse de E. Deriaz réalisée dans le cas périodique. La première partie de ce travail a donc été la définition et la mise en œuvre de nouvelles bases d'ondelettes à divergence nulle ou à rotationnel nul sur [0,1]n, permettant la prise en compte de conditions aux limites, à partir des travaux originaux de P. G. Lemarié-Rieusset, K. Urban, E. Deriaz et V. Perrier. Dans une deuxième partie, des méthodes numériques efficaces utilisant ces nouvelles ondelettes sont proposées pour résoudre différents problèmes classiques : équation de la chaleur, problème de Stokes et calcul de la décomposition de Helmholtz-Hodge en non périodique. L'existence d'algorithmes rapides associés rend les méthodes compétitives. La dernière partie est consacrée à la définition de deux nouveaux schémas de résolution des équations de Navier-Stokes incompressibles par ondelettes, qui utilisent les ingrédients précédents. Des expériences numériques menées pour la simulation d'écoulement en cavité entraînée en dimension deux ou le problème de la reconnection de tubes de vortex en dimension trois montrent le fort potentiel des algorithmes développés
This work concerns wavelet numerical methods for the simulation of incompressible turbulent flow. The main objective of this work is to take into account physical boundary conditions in the resolution of Navier-Stokes equations on wavelet basis. Unlike previous work where the vorticity field was decomposed in term of classical wavelet bases, the point of view adopted here is to compute the velocity field of the flow in its divergence-free wavelet series. We are then in the context of velocity-pressure formulation of the incompressible Navier-Stokes equations, for which the boundary conditions are written explicitly on the velocity field, which differs from the velocity-vorticity formulation. The principle of the method implemented is to incorporate directly the boundary conditions on the wavelet basis. This work extends the work of the thesis of E. Deriaz realized in the periodic case. The first part of this work highlights the definition and the construction of new divergence-free and curl-free wavelet bases on [0,1]n, which can take into account boundary conditions, from original works of P. G. Lemarie-Rieusset, K. Urban, E. Deriaz and V. Perrier. In the second part, efficient numerical methods using these new wavelets are proposed to solve various classical problem: heat equation, Stokes problem and Helmholtz-Hodge decomposition in the non-periodic case. The existence of fast algorithms makes the associated methods more competitive. The last part is devoted to the definition of two new numerical schemes for the resolution of the incompressible Navier-Stokes equations into wavelets, using the above ingredients. Numerical experiments conducted for the simulation of driven cavity flow in two dimensions or the issue of reconnection of vortex tubes in three dimensions show the strong potential of the developed algorithms

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Kamerlin, Natasha. "Computer Simulations of Polymer Gels : Structure, Dynamics, and Deformation." Doctoral thesis, Uppsala universitet, Fysikalisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332575.

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This thesis presents the results of computer simulation studies of the structure, dynamics, and deformation of cross-linked polymer gels. Obtaining a fundamental understanding of the interrelation between the detailed structure and the properties of polymer gels is a challenge and a key issue towards designing materials for specific purposes. A new off-lattice method for constructing a closed network is presented that is free from defects, such as looping chains and dangling ends. Using these model networks in Brownian dynamics simulations, I show results for the structure and dynamics of bulk gels and describe a novel approach using spherical boundary conditions as an alternative to the periodic boundary conditions commonly used in simulations. This algorithm was also applied for simulating the diffusion of tracer particles within a static and dynamic network, to illustrate the quantitative difference and importance of including network mobility for large particles, as dynamic chains facilitate the escape of particles that become entrapped. I further investigate two technologically relevant properties of polymer gels: their stimuli-responsive behaviour and their mechanical properties. The collapse of core-shell nanogels was studied for a range of parameters, including the cross-linking degree and shell thickness. Two distinct regimes of gel collapse could be observed, with a rapid formation of small clusters followed by a coarsening stage. It is shown that in some cases, a collapsing shell may lead to an inversion of the core-shell particle which exposes the core polymer chains to the environment. This thesis also explores the deformation of bimodal gels consisting of both short and long chains, subject to uniaxial elongation, with the aim to understand the role of both network composition as well as structural heterogeneity on the mechanical response and the reinforcement mechanism of these materials. It is shown that a bimodal molecular weight distribution alone is sufficient to strongly alter the mechanical properties of networks compared to the corresponding unimodal networks with the same number-average chain length. Furthermore, it is shown that heterogeneities in the form of high-density short-chain clusters affect the mechanical properties relative to a homogeneous network, primarily by providing extensibility.

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Parham, Jonathan Brent. "Physically consistent boundary conditions for free-molecular satellite aerodynamics." Thesis, Boston University, 2014. https://hdl.handle.net/2144/21230.

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Thesis (M.Sc.Eng.)
To determine satellite trajectories in low earth orbit, engineers need to adequately estimate aerodynamic forces. But to this day, such a task su↵ers from inexact values of drag forces acting on complicated shapes that form modern spacecraft. While some of the complications arise from the uncertainty in the upper atmosphere, this work focuses on the problems in modeling the flow interaction with the satellite geometry. The only numerical approach that accurately captures e↵ects in this flow regime—like self-shadowing and multiple molecular reflections—is known as Test Particle Monte Carlo. This method executes a ray-tracing algorithm to follow particles that pass through a control volume containing the spacecraft and accumulates the momentum transfer to the body surfaces. Statistical fluctuations inherent in the approach demand particle numbers on the order of millions, often making this scheme too costly to be practical. This work presents a parallel Test Particle Monte Carlo method that takes advantage of both graphics processing units and multi-core central processing units. The speed at which this model can run with millions of particles enabled the exploration of regimes where a flaw was revealed in the model’s initial particle seeding. A new model introduces an analytical fix to this flaw—consisting of initial position distributions at the boundary of a spherical control volume and an integral for the correct number flux—which is used to seed the calculation. This thesis includes validation of the proposed model using analytical solutions for several simple geometries and demonstrates uses of the method for the aero-stabilization of the Phobos-Grunt Martian probe and pose-estimation for the ICESat mission.
2031-01-01

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Книги з теми "Physical boundary conditions"

Syed, Hasnain H. Electromagnetic scattering by coated convex surfaces and wedges simulated by approximate boundary conditions. Ann Arbor, Mich: University of Michigan, Radiation Laboratory, Dept. of Electrical Engineering and Computer Science, 1992.

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The scaling limit of the correlation of holes on the triangular lattice with periodic boundary conditions. Providence, R.I: American Mathematical Society, 2009.

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Peter, Schloerb F., University of Massachusetts at Amherst. Dept. of Physics and Astronomy., and United States. National Aeronautics and Space Administration., eds. Boundary conditions for the paleoenvironment: Chemical and physical processes in the pre-solar nebula. [Amherst, Mass.]: Dept. of Physics and Astronomy, University of Massachusetts, 1985.

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Peter, Schloerb F., and United States. National Aeronautics and Space Administration., eds. Boundary conditions for the paleoenvironment: Chemical and physical processes in the pre-solar nebula : semi-annual status report no. 21, February 16, 1993 - August 15, 1993. Amherst, MA: Five College Radio Astronomy and Observatory, University of Massachusetts, 1993.

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Peter, Schoerb F., and United States. National Aeronautics and Space Administration, eds. Boundary conditions for the paleoenvironment: Chemical and physical processes in the pre-solar nebula : semi-annual status report no. 7, February 16, 1986 - August 15, 1986. [Amherst, Mass.]: Dept. of Physics and Astronomy, University of Massachusetts, 1986.

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Dervishi, Sokol. Sky Radiance and Luminance Models: The Boundary Conditions. Nova Science Publishers, Incorporated, 2019.

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Chemin, Jean-Yves, Benoit Desjardins, Isabelle Gallagher, and Emmanuel Grenier. Mathematical Geophysics. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198571339.001.0001.

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Aimed at graduate students, researchers and academics in mathematics, engineering, oceanography, meteorology, and mechanics, this text provides a detailed introduction to the physical theory of rotating fluids, a significant part of geophysical fluid dynamics. The text is divided into four parts, with the first part providing the physical background of the geophysical models to be analyzed. Part two is devoted to a self contained proof of the existence of weak (or strong) solutions to the imcompressible Navier-Stokes equations. Part three deals with the rapidly rotating Navier-Stokes equations, first in the whole space, where dispersion effects are considered. The case where the domain has periodic boundary conditions is then analyzed, and finally rotating Navier-Stokes equations between two plates are studied, both in the case of periodic horizontal coordinated and those in R2. In Part IV, the stability of Ekman boundary layers and boundary layer effects in magnetohydrodynamics and quasigeostrophic equations are discussed. The boundary layers which appear near vertical walls are presented and formally linked with the classical Prandlt equations. Finally spherical layers are introduced, whose study is completely open.

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J, Luebbers Raymond, Kunz Karl S, and United States. National Aeronautics and Space Administration., eds. Wideband finite difference time domain implementation of surface impedance boundary conditions for good conductors. [Washington, DC: National Aeronautics and Space Administration, 1991.

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Whence the boundary conditions in modern continuum physics?: Convegno internazionale, (Roma, 14-16 ottobre 2002). Roma: Accademia Nazionale dei Lincei, 2004.

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Guenther, B. D. Modern Optics Simplified. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198842859.001.0001.

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This textbook is designed for use in a standard physics course on optics at the sophomore level. The book is an attempt to reduce the complexity of coverage found in Modem Optics to allow a student with only elementary calculus to learn the principles of optics and the modern Fourier theory of diffraction and imaging. Examples based on real optics engineering problems are contained in each chapter. Topics covered include aberrations with experimental examples, correction of chromatic aberration, explanation of coherence and the use of interference theory to design an antireflection coating, Fourier transform optics and its application to diffraction and imaging, use of gaussian wave theory, and fiber optics will make the text of interest as a textbook in Electrical and bioengineering as well as Physics. Students who take this course should have completed an introductory physics course and math courses through calculus Need for experience with differential equations is avoided and extensive use of vector theory is avoided by using a one dimensional theory of optics as often as possible. Maxwell’s equations are introduced to determine the properties of a light wave and the boundary conditions are introduced to characterize reflection and refraction. Most discussion is limited to reflection. The book provides an introduction to Fourier transforms. Many pictures, figures, diagrams are used to provide readers a good physical insight of Optics. There are some more difficult topics that could be skipped and they are indicated by boundaries in the text.

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Частини книг з теми "Physical boundary conditions"

Gudehus, Gerd. "Boundary conditions." In Physical Soil Mechanics, 397–435. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-540-36354-5_10.

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Røed, L. P., and C. K. Cooper. "Open Boundary Conditions in Numerical Ocean Models." In Advanced Physical Oceanographic Numerical Modelling, 411–36. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-017-0627-8_23.

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Hahn, Hermann H. "Chemical Dosing Control — Physical and Chemical Boundary Conditions." In Chemical Water and Wastewater Treatment II, 153–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77827-8_10.

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Diettrich, Olaf. "The biological boundary conditions for our classical physical world view." In Evolutionary Epistemology, Language and Culture, 67–93. Dordrecht: Springer Netherlands, 2006. http://dx.doi.org/10.1007/1-4020-3395-8_4.

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Jaiani, George. "On Physical and Mathematical Moments and the Setting of Boundary Conditions for Cusped Prismatic Shells and Beams." In IUTAM Symposium on Relations of Shell Plate Beam and 3D Models, 133–46. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-8774-5_12.

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Millitzer, Jonathan, Jan Hansmann, Giovanni Lapiccirella, Christoph Tamm, and Sven Herold. "Tuning and Emulation of Mechanical Characteristics – Tunable Mounts and a Mechanical Hardware-in-the-Loop Approach for More Efficient Research and Testing." In Lecture Notes in Mechanical Engineering, 129–44. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77256-7_12.

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AbstractNumerical simulations offer a wide range of benefits, therefore they are widely used in research and development. One of the biggest benefits is the possibility of automated parameter variation. This allow testing different scenarios in a very short period of time. Nevertheless, physical experiments in the laboratory or on a test rig are still necessary and will still be necessary in the future. The physical experiments offer benefits e.g. for very complex and/or nonlinear systems and are needed for the validation of numerical models.Fraunhofer LBF has developed hardware solutions to bring the benefit of rapid and automated parameter variation to experimental environments. These solutions allow the tuning and emulation of the mechanical properties, like stiffness, damping and eigenfrequencies of structures.The work presents two approaches: First a stiffness tunable mount, which has been used in laboratory tests in the field of semi-active load path redistribution. It allowed the researcher to test the semi-active system under different mechanical boundary conditions in a short period of time. Second, a mechanical Hardware-in-the-loop (mHIL) approach for the NVH development of vehicles components is presented. Here a mHIL-system is used to emulate the mechanical characteristics of a vehicle’s body in white in a wide frequency range. This allows the experimental NVH optimization of vehicle components under realistic boundary conditions, without actually needing a (prototype) body in white.

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Younis, O., J. Pallares, and F. X. Grau. "Effect of the thermal boundary conditions and physical properties variation on transient natural convection of high Prandtl number fluids." In Computational Fluid Dynamics 2006, 813–18. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-92779-2_128.

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Adomian, George. "Integral Boundary Conditions." In Solving Frontier Problems of Physics: The Decomposition Method, 196–210. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-015-8289-6_8.

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Olmeda, R., P. Breda, C. Stemmer, and M. Pfitzner. "Large-Eddy Simulations for the Wall Heat Flux Prediction of a Film-Cooled Single-Element Combustion Chamber." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 223–34. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_14.

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Abstract In order for modern launcher engines to work at their optimum, film cooling can be used to preserve the structural integrity of the combustion chamber. The analysis of this cooling system by means of CFD is complex due to the extreme physical conditions and effects like turbulent fluctuations damping and recombination processes in the boundary layer which locally change the transport properties of the fluid. The combustion phenomena are modeled by means of Flamelet tables taking into account the enthalpy loss in the proximity of the chamber walls. In this work, Large-Eddy Simulations of a single-element combustion chamber experimentally investigated at the Technical University of Munich are carried out at cooled and non-cooled conditions. Compared with the experiment, the LES shows improved results with respect to RANS simulations published. The influence of wall roughness on the wall heat flux is also studied, as it plays an important role for the lifespan of a rocket engine combustors.

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Adomian, George. "Boundary Conditions at Infinity." In Solving Frontier Problems of Physics: The Decomposition Method, 211–23. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-015-8289-6_9.

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Тези доповідей конференцій з теми "Physical boundary conditions"

Nikolić, B., and B. Sazdović. "From Neuman to Dirichlet boundary conditions." In SIXTH INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION. AIP, 2007. http://dx.doi.org/10.1063/1.2733081.

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Dulikravich, George S., and Youhao Jing. "Boundary Conditions for Electro-Magneto-Hydrodynamics." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0478.

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Abstract A general mathematical model of characteristic and non-reflecting boundary conditions for a system of partial differential equations governing unified Electro-Magneto-Hydrodynamic (EMHD) flows is developed. The novelty of this work is that it includes effects of linear polarization and magnetization of the media. A formulation using characteristic wave relations at the boundaries is derived for the extended Maxwell’s equations and the extended Navier-Stokes equations so that it can be used to specify inflow and outflow free boundary conditions. The emphasis is on using recent theoretical results on well-posedness of boundary conditions for standard Navier-Stokes and Maxwell’s equations to construct a systematic method for specifying the physical and numerical boundary conditions for electro-magneto-hydrodynamics. The formulation is fully three-dimensional and suitable for direct numerical implementation. The results show strong influence of electric and magnetic fields on fluid flow characteristics.

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Shimmell, Dennis, and Paul Hollenbeck. "Incorporation of Boundary Conditions into Finite Element Analysis and the Physical Verification." In Noise & Vibration Conference & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1999. http://dx.doi.org/10.4271/1999-01-1755.

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Chaquet, Jose M., and Roque Corral. "Incompatible Boundary Conditions in Heat Equation Coupled With Air System Models." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14011.

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Abstract Heat transfer problem is one of the main challenges in the design process of turbomachinery components for aeronautic applications. Good prediction capabilities are required to estimate metal temperatures, specially in those regions where the working fluid reaches temperatures near to the material melting point. In this context, it is common to perform multi-physics simulations involving different solvers. Special care must be taken at the interfaces between the several domains to avoid non-physical solutions. Concretely speaking, the coupling process between a thermal code (discretized heat diffusion equation solver) and a fluid network (low fidelity models representing air flows) is studied. Several non-physical boundary conditions examples are provided. The models are solved using an in-house thermal code called Saturn. The effects both in the results and in the convergence process are described. Non-physical boundary conditions provoke instabilities in the flow direction at some parts of the fluid network. A method to analyze the compatibility and convergence of the coupled problem is described and used in the examples. Also, some heuristics to achieve converge in the ill-posed models are commented.

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Link, Michael, and Zheng Qian. "Updating Substructure Models With Dynamic Boundary Conditions." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0701.

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Abstract In recent years procedures for updating analytical model parameters have been developed by minimizing differences between analytical and preferably experimental modal analysis results. Provided that the initial analysis model contains parameters capable of describing possible damage these techniques could also be used for damage detection. In this case the parameters are updated using test data before and after the damage. Looking at complex structures with hundreds of parameters one generally has to measure the modal data at many locations and try to reduce the number of unknown parameters by some kind of localization technique because the measurement information is generally not sufficient to identify all the parameters equally distributed all over the structure. Another way of reducing the number of parameters shall be presented here. This method is based on the idea of measuring only a part of the structure and replacing the residual structure by dynamic boundary conditions which describe the dynamic stiffness at the interfaces between the measured main structure and the remaining unmeasured residual structure. This approach has some advantage since testing could be concentrated on critical areas where structural modifications are expected either due to damage or due to intended design changes. The dynamic boundary conditions are expressed in Craig-Bampton (CB) format by transforming the mass and stiffness matrices of the unmeasured residual structure to the interface degrees of freedom (DOF) and to the modal DOFs of the residual structure fixed at the interface. The dynamic boundary stiffness concentrates all physical parameters of the residual structure in only a few parameters which are open for updating. In this approach damage or modelling errors within the unmeasured residual structure are taken into account only in a global sense whereas the measured main structure is parametrized locally as usual by factoring mass and stiffness submatrices defining the type and the location of the physical parameters to be identified. The procedure was applied to identify the design parameters of a beam type frame structure with bolted joints using experimental modal data.

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Fraga Filho, Carlos Alberto Dutra. "Physical Reflective Boundary Conditions in Particle Methods: a Collision Detection and Response Algorithm." In XXXVIII Iberian-Latin American Congress on Computational Methods in Engineering. Florianopolis, Brazil: ABMEC Brazilian Association of Computational Methods in Engineering, 2017. http://dx.doi.org/10.20906/cps/cilamce2017-0202.

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CHARLES, R., J. BROUWER, and G. SAMUELSEN. "The sensitivity of swirl-stabilized distributed reactions to inlet flow and physical boundary conditions." In 25th AIAA Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1987. http://dx.doi.org/10.2514/6.1987-304.

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Harris, Zachary, Joshua Bittle, and Ajay Agrawal. "Role of Inlet Boundary Conditions on Fuel-Air Mixing at Supercritical Conditions." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-3004.

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Abstract Advanced engine design and alternative fuels present the possibility of fuel injection at purely supercritical conditions in diesel engines and gas turbines. The complex interactions that govern this phenomenon still need significant research for reliable modeling efforts. Boundary conditions for fuel injection are critical to accurate simulation. However, the flow inside the injector itself is often omitted to reduce the computational efforts, and thus, velocity, mass flux, or total pressure is specified at the injector exit (or domain inlet), often with an assumed top hat profile and assumed turbulence levels. Past studies have shown that such simplified inlet boundary treatment has minimal effects on the results for fuel injection in the compressed liquid phase. However, the validity of this approach at supercritical fuel injection conditions has not been assessed so far. In this study, comprehensive real-gas and binary fluid mixing models have been implemented for computational fluid dynamic (CFD) analysis of fuel-air mixing at supercritical conditions. The model is verified using prior CFD results from the literature. Next, the model is used to investigate the effects of the shape of axial velocity and mass fraction profiles at the inlet boundary with the goal to improve the comparison of predictions to experimental data. Results show that the boundary conditions have a significant effect on the predictions, and none of the cases match precisely with experimental data. The study reveals that the physical location of the inlet boundary might be difficult to infer correctly from the experiments and highlights the need for high-quality, repeatable measurements at supercritical conditions to support the development of relevant high-fidelity models for fuel-air mixing.

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Tomii, Masaaki, Thomas Blum, Daniel Hoying, Taku Izubuchi, Luchang Jin, Chulwoo Jung, and Amarjit Soni. "$K \to \pi\pi$ decay matrix elements at the physical point with periodic boundary conditions." In The 38th International Symposium on Lattice Field Theory. Trieste, Italy: Sissa Medialab, 2022. http://dx.doi.org/10.22323/1.396.0394.

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Liu, H. F., X. Y. Luo, and Z. X. Cai. "Stability and Pressure Boundary Conditions in the Collapsible Channel Flows." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77767.

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In this study, we investigate dynamic behaviour and the linear stability of collapsible channel flows under various physical parameters and boundary conditions. Two approaches are adopted in the study: one is a fully coupled numerical solver for solving fluid-structure governing equations; the other is an eigenvalue solver which is used for linear stability analysis. We focus on the situation where the inlet pressure drop (relative to the outlet) is prescribed. Static divergence and mode-1 instabilities are found in addition to higher modes, which can co-exist in a structure which is quite different from the cascade structure identified with the flow rate inlet boundary condition. Mode transfer from lower to higher modes is also discovered as the stiffness of the elastic wall is reduced. Finally, our results are compared with the asymptotic prediction for high Reynolds number and tension region.

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Звіти організацій з теми "Physical boundary conditions"

Shani, Uri, Lynn Dudley, Alon Ben-Gal, Menachem Moshelion, and Yajun Wu. Root Conductance, Root-soil Interface Water Potential, Water and Ion Channel Function, and Tissue Expression Profile as Affected by Environmental Conditions. United States Department of Agriculture, October 2007. http://dx.doi.org/10.32747/2007.7592119.bard.

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Constraints on water resources and the environment necessitate more efficient use of water. The key to efficient management is an understanding of the physical and physiological processes occurring in the soil-root hydraulic continuum.While both soil and plant leaf water potentials are well understood, modeled and measured, the root-soil interface where actual uptake processes occur has not been sufficiently studied. The water potential at the root-soil interface (yᵣₒₒₜ), determined by environmental conditions and by soil and plant hydraulic properties, serves as a boundary value in soil and plant uptake equations. In this work, we propose to 1) refine and implement a method for measuring yᵣₒₒₜ; 2) measure yᵣₒₒₜ, water uptake and root hydraulic conductivity for wild type tomato and Arabidopsis under varied q, K⁺, Na⁺ and Cl⁻ levels in the root zone; 3) verify the role of MIPs and ion channels response to q, K⁺ and Na⁺ levels in Arabidopsis and tomato; 4) study the relationships between yᵣₒₒₜ and root hydraulic conductivity for various crops representing important botanical and agricultural species, under conditions of varying soil types, water contents and salinity; and 5) integrate the above to water uptake term(s) to be implemented in models. We have made significant progress toward establishing the efficacy of the emittensiometer and on the molecular biology studies. We have added an additional method for measuring ψᵣₒₒₜ. High-frequency water application through the water source while the plant emerges and becomes established encourages roots to develop towards and into the water source itself. The yᵣₒₒₜ and yₛₒᵢₗ values reflected wetting and drying processes in the rhizosphere and in the bulk soil. Thus, yᵣₒₒₜ can be manipulated by changing irrigation level and frequency. An important and surprising finding resulting from the current research is the obtained yᵣₒₒₜ value. The yᵣₒₒₜ measured using the three different methods: emittensiometer, micro-tensiometer and MRI imaging in both sunflower, tomato and corn plants fell in the same range and were higher by one to three orders of magnitude from the values of -600 to -15,000 cm suggested in the literature. We have added additional information on the regulation of aquaporins and transporters at the transcript and protein levels, particularly under stress. Our preliminary results show that overexpression of one aquaporin gene in tomato dramatically increases its transpiration level (unpublished results). Based on this information, we started screening mutants for other aquaporin genes. During the feasibility testing year, we identified homozygous mutants for eight aquaporin genes, including six mutants for five of the PIP2 genes. Including the homozygous mutants directly available at the ABRC seed stock center, we now have mutants for 11 of the 19 aquaporin genes of interest. Currently, we are screening mutants for other aquaporin genes and ion transporter genes. Understanding plant water uptake under stress is essential for the further advancement of molecular plant stress tolerance work as well as for efficient use of water in agriculture. Virtually all of Israel’s agriculture and about 40% of US agriculture is made possible by irrigation. Both countries face increasing risk of water shortages as urban requirements grow. Both countries will have to find methods of protecting the soil resource while conserving water resources—goals that appear to be in direct conflict. The climate-plant-soil-water system is nonlinear with many feedback mechanisms. Conceptual plant uptake and growth models and mechanism-based computer-simulation models will be valuable tools in developing irrigation regimes and methods that maximize the efficiency of agricultural water. This proposal will contribute to the development of these models by providing critical information on water extraction by the plant that will result in improved predictions of both water requirements and crop yields. Plant water use and plant response to environmental conditions cannot possibly be understood by using the tools and language of a single scientific discipline. This proposal links the disciplines of soil physics and soil physical chemistry with plant physiology and molecular biology in order to correctly treat and understand the soil-plant interface in terms of integrated comprehension. Results from the project will contribute to a mechanistic understanding of the SPAC and will inspire continued multidisciplinary research.

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Pettit, Chris, and D. Wilson. A physics-informed neural network for sound propagation in the atmospheric boundary layer. Engineer Research and Development Center (U.S.), June 2021. http://dx.doi.org/10.21079/11681/41034.

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We describe what we believe is the first effort to develop a physics-informed neural network (PINN) to predict sound propagation through the atmospheric boundary layer. PINN is a recent innovation in the application of deep learning to simulate physics. The motivation is to combine the strengths of data-driven models and physics models, thereby producing a regularized surrogate model using less data than a purely data-driven model. In a PINN, the data-driven loss function is augmented with penalty terms for deviations from the underlying physics, e.g., a governing equation or a boundary condition. Training data are obtained from Crank-Nicholson solutions of the parabolic equation with homogeneous ground impedance and Monin-Obukhov similarity theory for the effective sound speed in the moving atmosphere. Training data are random samples from an ensemble of solutions for combinations of parameters governing the impedance and the effective sound speed. PINN output is processed to produce realizations of transmission loss that look much like the Crank-Nicholson solutions. We describe the framework for implementing PINN for outdoor sound, and we outline practical matters related to network architecture, the size of the training set, the physics-informed loss function, and challenge of managing the spatial complexity of the complex pressure.

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