Relevant bibliographies by topics / Eddy flux Mathematical models

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

Academic literature on the topic 'Eddy flux Mathematical models'

Author: Grafiati
Published: 4 June 2021
Last updated: 13 February 2022

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Journal articles on the topic "Eddy flux Mathematical models"

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Tirabassi, Tiziano, Daniela Buske, Davidson M. Moreira, and Marco T. Vilhena. "A Two-Dimensional Solution of the Advection–Diffusion Equation with Dry Deposition to the Ground." Journal of Applied Meteorology and Climatology 47, no. 8 (August 1, 2008): 2096–104. http://dx.doi.org/10.1175/2008jamc1674.1.

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Abstract A mathematical scheme is developed to simulate the vertical turbulent dispersion of air pollution that is absorbed or deposited to the ground. The scheme is an exact analytical solution of the atmospheric diffusion equation, without any restriction to the vertical profile of wind speed and eddy diffusivities, and taking into account the dry deposition by a boundary condition of a nonzero flux to the ground. The performances of the solution, with a proper parameterization of the vertical profiles of the wind and eddy diffusivities, were evaluated against the dataset from the Hanford (Washington) diffusion experiment, in which two tracers (one depositing and one nondepositing) were released simultaneously. In addition, the solution derived in this work is compared with four different models, with deposition at the ground, found in the literature.
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Niemimäki, Ossi, and Stefan Kurz. "Quasi 3D modelling and simulation of axial flux machines." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 33, no. 4 (July 1, 2014): 1220–32. http://dx.doi.org/10.1108/compel-11-2012-0352.

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Purpose – The purpose of this paper is to investigate the theoretical foundation of the so-called quasi 3D modelling method of axial flux machines, and the means for the simulation of the resulting models. Design/methodology/approach – Starting from the first principles, a 3D magnetostatic problem is geometrically decomposed into a coupled system of 2D problems. Genuine 2D problems are derived by decoupling the system. The construction of the 2D simulation models is discussed, and their applicability is evaluated by comparing a finite element implementation to an existing industry-used model. Findings – The quasi 3D method relies on the assumption of vanishing radial magnetic flux. The validity of this assumption is reflected in a residual gained from the 3D coupled system. Moreover, under a modification of the metric of the 2D models, an axial flux machine can be presented as a family of radial flux machines. Research limitations/implications – The evaluation and interpretation of the residual has not been carried out. Furthermore, the inclusion of eddy currents has not been detailed in the present study. Originality/value – A summary of existing modelling and simulation methods of axial flux machines is provided. As a novel result, proper mathematical context for the quasi 3D method is given and the underlying assumptions are laid out. The implementation of the 2D models is approached from a general angle, strengthening the foundation for future research.
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Mukhartova, Iuliia, Alexander Krupenko, Polina Mangura, and Alexander Olchev. "Mathematical Modeling of Vegetation Heterogeneity and Complex Topography Effects on Turbulent Exchange of GHG within the Atmospheric Surface Layer." Proceedings 2, no. 20 (October 17, 2018): 1310. http://dx.doi.org/10.3390/proceedings2201310.

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The local-scale 2D and 3D models of greenhouse gases (GHG) exchange between a non-uniform land surface and the atmosphere were developed. They are based on solution of the system of averaged Navier-Stokes, continuity and diffusion-advection equations. For numerical solution of the differential equations the stable finite-difference schemes were suggested. The models were applied to derive effects of complex topography and vegetation heterogeneity on 2D-3D air flow patterns, as well as on CO2 exchange within the atmospheric surface layer. Several numerical experiments were also provided to describe the air-flow re-establishing after its interaction with some obstacle (e.g., forest edge). Quantitative criteria for selection of the experimental sites for continuous eddy covariance flux measurements characterized by minimum effects of horizontal advection on measured fluxes were suggested.
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Grinstein, F. F., and C. Fureby. "Recent Progress on MILES for High Reynolds Number Flows." Journal of Fluids Engineering 124, no. 4 (December 1, 2002): 848–61. http://dx.doi.org/10.1115/1.1516576.

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A promising large-eddy simulation (LES) approach is monotonically integrated LES (MILES) which involves solving the Navier-Stokes equations using high-resolution monotone algorithms. In MILES, the subgrid scale (SGS) flow physics is provided by intrinsic, nonlinear, high-frequency filters built into the discretization and implicit SGS models. Mathematical and physical aspects of implicit SGS modeling using nonlinear flux-limiters are addressed using a formalism based on the modified LES equations approach. Detailed properties of the implicit subgrid model are related to the flux limiter, which in turn depends on the specifics of the numerical scheme; we illustrate how the latter properties can directly affect their potential in the MILES framework. Major unresolved issues relevant to LES of complex practical turbulent flows are discussed in this context, including some aspects of boundary condition modeling and overall computational model validation.
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Saenz, Juan A., Qingshan Chen, and Todd Ringler. "Prognostic Residual Mean Flow in an Ocean General Circulation Model and its Relation to Prognostic Eulerian Mean Flow." Journal of Physical Oceanography 45, no. 9 (September 2015): 2247–60. http://dx.doi.org/10.1175/jpo-d-15-0024.1.

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AbstractRecent work has shown that taking the thickness-weighted average (TWA) of the Boussinesq equations in buoyancy coordinates results in exact equations governing the prognostic residual mean flow where eddy–mean flow interactions appear in the horizontal momentum equations as the divergence of the Eliassen–Palm flux tensor (EPFT). It has been proposed that, given the mathematical tractability of the TWA equations, the physical interpretation of the EPFT, and its relation to potential vorticity fluxes, the TWA is an appropriate framework for modeling ocean circulation with parameterized eddies. The authors test the feasibility of this proposition and investigate the connections between the TWA framework and the conventional framework used in models, where Eulerian mean flow prognostic variables are solved for. Using the TWA framework as a starting point, this study explores the well-known connections between vertical transfer of horizontal momentum by eddy form drag and eddy overturning by the bolus velocity, used by Greatbatch and Lamb and Gent and McWilliams to parameterize eddies. After implementing the TWA framework in an ocean general circulation model, the analysis is verified by comparing the flows in an idealized Southern Ocean configuration simulated using the TWA and conventional frameworks with the same mesoscale eddy parameterization.
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Arshad, Salman, Bo Kong, Alan Kerstein, and Michael Oevermann. "A strategy for large-scale scalar advection in large eddy simulations that use the linear eddy sub-grid mixing model." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 10 (October 1, 2018): 2463–79. http://dx.doi.org/10.1108/hff-09-2017-0387.

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PurposeThe purpose of this numerical work is to present and test a new approach for large-scale scalar advection (splicing) in large eddy simulations (LES) that use the linear eddy sub-grid mixing model (LEM) called the LES-LEM.Design/methodology/approachThe new splicing strategy is based on an ordered flux of spliced LEM segments. The principle is that low-flux segments have less momentum than high-flux segments and, therefore, are displaced less than high-flux segments. This strategy affects the order of both inflowing and outflowing LEM segments of an LES cell. The new splicing approach is implemented in a pressure-based fluid solver and tested by simulation of passive scalar transport in a co-flowing turbulent rectangular jet, instead of combustion simulation, to perform an isolated investigation of splicing. Comparison of the new splicing with a previous splicing approach is also done.FindingsThe simulation results show that the velocity statistics and passive scalar mixing are correctly predicted using the new splicing approach for the LES-LEM. It is argued that modeling of large-scale advection in the LES-LEM via splicing is reasonable, and the new splicing approach potentially captures the physics better than the old approach. The standard LES sub-grid mixing models do not represent turbulent mixing in a proper way because they do not adequately represent molecular diffusion processes and counter gradient effects. Scalar mixing in turbulent flow consists of two different processes, i.e. turbulent mixing that increases the interface between unmixed species and molecular diffusion. It is crucial to model these two processes individually at their respective time scales. The LEM explicitly includes both of these processes and has been used successfully as a sub-grid scalar mixing model (McMurtry et al., 1992; Sone and Menon, 2003). Here, the turbulent mixing capabilities of the LES-LEM with a modified splicing treatment are examined.Originality/valueThe splicing strategy proposed for the LES-LEM is original and has not been investigated before. Also, it is the first LES-LEM implementation using unstructured grids.
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Majda, Andrew J. "New Multiscale Models and Self-Similarity in Tropical Convection." Journal of the Atmospheric Sciences 64, no. 4 (April 1, 2007): 1393–404. http://dx.doi.org/10.1175/jas3880.1.

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Abstract One of the unexplained striking features of tropical convection is the observed statistical self-similarity in clusters, superclusters, and intraseasonal oscillations through complex multiscale processes ranging from the mesoscales to the equatorial synoptic scales to the intraseasonal/planetary scales. Here new multispatial-scale, multitime-scale, simplified asymptotic models are derived systematically from the equatorial primitive equations on the range of scales from mesoscale to equatorial synoptic to planetary/intraseasonal, which provide a useful analytic framework for addressing these issues. New mesoscale equatorial synoptic dynamical (MESD) models and balanced MESD (BMESD) models are developed for the multitime, multispace interaction from mesoscales to equatorial synoptic scales; new multitime versions of the intraseasonal planetary equatorial synoptic dynamics (IPESD) models are developed for multiple spatiotemporal interactions on equatorial synoptic scales and planetary scales. The mathematical character derived below for all these simplified models explicitly demonstrates that the main nonlinear interactions across scales are quasi-linear where eddy flux divergences of momentum and temperature from nonlinear advection from the smaller-scale spatiotemporal flows as well as mean source effects accumulate in time and drive the waves on the successively larger spatiotemporal scales. Furthermore, these processes that transfer energy to the next larger, longer, spatiotemporal scales are self-similar in a suitable sense established here. On the other hand, the larger scales set the environment for this transport through processes such as mean advection of the smaller scales.
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van Heerwaarden, Chiel C., and Juan Pedro Mellado. "Growth and Decay of a Convective Boundary Layer over a Surface with a Constant Temperature." Journal of the Atmospheric Sciences 73, no. 5 (May 1, 2016): 2165–77. http://dx.doi.org/10.1175/jas-d-15-0315.1.

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Abstract The growth and decay of a convective boundary layer (CBL) over a surface with a constant surface temperature that develops into a linear stratification is studied, and a mathematical model for this system is derived. The study is based on direct numerical simulations with four different Reynolds numbers; the two simulations with the largest Reynolds numbers display Reynolds number similarity, suggesting that the results can be extrapolated to the atmosphere. Because of the interplay of the growing CBL and the gradually decreasing surface buoyancy flux, the system has a complex time evolution in which integrated kinetic energy, buoyancy flux, and dissipation peak and subsequently decay. The derived model provides characteristic scales for bulk properties of the CBL. Even though the system is unsteady, self-similar vertical profiles of buoyancy, buoyancy flux, and velocity variances are recovered. There are two important implications for atmospheric modeling. First, the magnitude of the surface buoyancy flux sets the time scale of the system; thus, over a rough surface the roughness length is a key variable. Therefore, the performance of the surface model is crucial in large-eddy simulations of convection over water surfaces. Second, during the phase in which kinetic energy decays, the integrated kinetic energy never follows a power law, because the buoyancy flux and dissipation balance until the kinetic energy has almost vanished. Therefore, the applicability of power-law decay models to the afternoon transition in the atmospheric boundary layer is questionable; the presented model provides a physically sound alternative.
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Karthaus, Jan, Benedikt Groschup, Robin Krüger, and Kay Hameyer. "Mechanical stress distribution and the utilisation of the magneto-elastic effect in electrical machines." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 4 (July 1, 2019): 1085–97. http://dx.doi.org/10.1108/compel-10-2018-0387.

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Purpose Due to the increasing amount of high power density high-speed electrical machines, a detailed understanding of the consequences for the machine’s operational behaviour and efficiency is necessary. Magnetic materials are prone to mechanical stress. Therefore, this paper aims to study the relation between the local mechanical stress distribution and magnetic properties such as magnetic flux density and iron losses. Design/methodology/approach In this paper, different approaches for equivalent mechanical stress criteria are analysed with focus on their applicability in electrical machines. Resulting machine characteristics such as magnetic flux density distribution or iron are compared. Findings The study shows a strong influence on the magnetic flux density distribution when considering the magneto-elastic effect for all analysed models. The influence on the iron loss is smaller due to a high amount of stress-independent eddy current loss component. Originality/value The understanding of the influence of mechanical stress on dimensions of electrical machines is important to obtain an accurate machine design. In this paper, the discussion on different equivalent stress approaches allows a new perspective for considering the magneto-elastic effect.
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Wu, Zheng, and Thomas Reichler. "Surface Control of the Frequency of Stratospheric Sudden Warming Events." Journal of Climate 32, no. 15 (July 3, 2019): 4753–66. http://dx.doi.org/10.1175/jcli-d-18-0801.1.

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AbstractThe frequency of stratospheric sudden warming events (SSWs) is an important characteristic of the coupled stratosphere–troposphere system. However, many modern climate models are unable to reproduce the observed SSW frequency. A previous study suggested that one of the reasons could be the momentum damping at the surface. The goal of the present study is to understand what determines the climatological SSW frequency and how the surface damping comes into play. To this end, we conduct a parameter sweep with an idealized model, using a wide range of values for the surface damping. It is found that the SSW frequency is a strong and nonlinear function of the surface damping. Various tropospheric and stratospheric factors are identified to link the surface damping to the SSW frequency. The factors include the magnitude of the surface winds, the meridional and vertical wind shear, the synoptic eddy activity in the troposphere, the transient wave activity flux at the lower stratosphere, and the strength of the stratospheric polar vortex. Mathematical–statistical modeling, informed by the parameter sweep, is used to quantify how the different factors relate to each other. This successfully reproduces the complex variations of the SSW frequency with the surface damping seen in the parameter sweep. The results may help in explaining some of the difficulties that climate models have in simulating the observed SSW frequency.
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Dissertations / Theses on the topic "Eddy flux Mathematical models"

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Porumbel, Ionut. "Large Eddy Simulation of premixed and partially premixed combustion." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14050.

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Large Eddy Simulation (LES) of bluff body stabilized premixed and partially premixed combustion close to the flammability limit is carried out in this thesis. The LES algorithm has no ad-hoc adjustable model parameters and is able to respond automatically to variations in the inflow conditions. Algorithm validation is achieved by comparison with reactive and non-reactive experimental data. In the reactive flow, two scalar closure models, Eddy Break-Up (EBULES) and Linear Eddy Mixing (LEMLES), are used and compared. Over important regions, the flame lies in the Broken Reaction Zone regime. Here, the EBU model assumptions fail. The flame thickness predicted by LEMLES is smaller and the flame is faster to respond to turbulent fluctuations, resulting in a more significant wrinkling of the flame surface. As a result, LEMLES captures better the subtle effects of the flame-turbulence interaction. Three premixed (equivalence ratio = 0.6, 0.65, and 0.75) cases are simulated. For the leaner case, the flame temperature is lower, the heat release is reduced and vorticity is stronger. As a result, the flame in this case is found to be unstable. In the rich case, the flame temperature is higher, and the spreading rate of the wake is increased due to the higher amount of heat release Partially premixed combustion is simulated for cases where the transverse profile of the inflow equivalence ratio is variable. The simulations show that for mixtures leaner in the core the vortical pattern tends towards anti-symmetry and the heat release decreases, resulting also in instability of the flame. For mixtures richer in the core, the flame displays sinusoidal flapping resulting in larger wake spreading. More accurate predictions of flame stability will require the use of detailed chemistry, raising the computational cost of the simulation. To address this issue, a novel algorithm for training Artificial Neural Networks (ANN) for prediction of the chemical source terms has been implemented and tested. Compared to earlier methods, the main advantages of the ANN method are in CPU time and disk space and memory reduction.
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Comer, Neil Thomas. "Validation and heterogeneity investigation of the Canadian Land Surface Scheme (CLASS) for wetland landscapes." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38173.

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This thesis examines the development and validation of Canadian Land Surface Scheme (CLASS) for various wetland landscapes individually, along with an evaluation of modelled results over a heterogeneous surface with airborne observations. A further statistical analysis of the effects of land surface classification procedures over the study area and their influence on modelled results is performed. CLASS is tested over individual wetland types: bog, fen and marsh in a stand-alone (non-GCM coupled) mode. Atmospheric conditions are provided for the eight site locations from tower measured data, while each surface is parameterized within the model from site specific measurements. Resulting model turbulent and radiative flux output is then statistically evaluated against observed tower data. Findings show that while CLASS models vascular dominated wetland areas (fen and marsh) quite well, non-vascular wetlands (bogs) are poorly represented, even with improved soil descriptions. At times when the water table is close to the surface, evaporation is greatly overestimated, whereas lowered water tables generate a vastly underestimated latent heat flux. Because CLASS does not include a moisture transfer scheme applicable for non-vascular vegetation, the description of this vegetation type as either a vascular plant or bare soil appears inappropriate.
CLASS was then tuned for a specific bog location found in the Hudson Bay Lowland (HBL) during the Northern Wetlands Study (NOWES). With bog surfaces better described within the model, testing of CLASS over a highly heterogeneous 169 km2 HBL region is then undertaken. The model is first modified for lake and pond surfaces and then separate runs for bog, fen, lake and tree/shrub categories is undertaken. Using a GIS, the test region under which airborne flux measurements are available is divided into 104 grid cells and proportions of each surface type are calculated within each cell. Findings indicate that although the modelled grid average radiation and flux values are reasonably well reproduced (4% error for net radiation, 10% for latent heat flux and 30% for sensible heat flux), spatial agreement between modelled and observed grid cells is disappointing. (Abstract shortened by UMI.)
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Calhoon, William Henry Jr. "On subgrid combustion modeling for large-eddy simulations." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12336.

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Kim, Won-Wook. "A new dynamic subgrid-scale model for large-eddy simulation of turbulent flows." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12143.

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Wong, Ching-chi, and 黃精治. "Flow and pollutant dispersion over idealized urban street canyons using large-eddy simulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/206698.

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Flows and pollutant dispersion over flat rural terrain have been investigated for decades. However, our understanding of their behaviours over urban areas is rather limited. Most cases have either focused on street level or in the roughness sub-layer (RSL) of urban boundary layer (UBL). Whereas, only a handful of studies have looked into the coupling between street-level and UBL-core dynamics, and their effects on pollutant dispersion. In this thesis, computational fluid dynamics (CFD) is employed to examine the flows and pollutant transport in and over urban roughness. Idealised two-dimensional (2D) street canyons are used as the basic units fabricating hypothetical urban surfaces. A ground-level passive and chemically inert pollutant source is applied to simulate the flows and pollutant dispersion over rough surfaces in isothermal condition. Large-eddy simulation (LES) with the one-equation subgrid-scale model is used to solve explicitly the broad range of scales in turbulent flows. Arrays of idealized street canyons of both uniform and non-uniform building height are used to formulate a unified theory for the flows and pollutant dispersion over urban areas of different morphology. The geometry of roughness elements is controlled by the building-height-to-street-width (aspect) ratio (0.083 ≤ AR ≤ 2) and/or the building height variability (BHV = 0.2, 0.4 and 0.6), in which the characteristic regimes of skimming flow, wake-interference and isolated roughness are covered. A detailed analysis on the roof-level turbulence structure reveals parcels of low-speed air masses in the streamwise flows and narrow high-speed down-drafts in the urban canopy layer, signifying the momentum entrainment into the street canyons. The decelerating streamwise flows in turn initiate up-drafts carrying pollutants away from the street canyons, illustrating the basic pollutant removal mechanism in 2D street canyons. Turbulent transport processes, in the form of ejection and sweep, are the key events governing the exchanges of air and pollutant of street canyon. Air exchange rate (ACH) along the roof level is dominated by turbulent transport, in particular over narrow street canyons. The LES results show that both the turbulence level and ACH increase with increasing aerodynamic resistance defined in term of the Fanning friction factor. At the same AR, BHV greatly increases the friction factor and the ACH in dense built areas (AR ≤ 0.25). The turbulence intensity is peaked on the windward side of street canyons that does not overlap with the maximum velocity gradient near the leeward building corners, suggesting the importance of background turbulence in street-level ventilation. Over the building roughness, pollutant plume dispersion after the ground-level area source in cross flows resumes the self-similar Gaussian shape in the vertical direction in which the vertical plume coverage is proportional to the square root of downwind distance in the streamwise direction. Moreover, the vertical dispersion coefficient is proportional to the one-fourth power of friction factor over idealised street canyons. Conclusively, friction factor can be used to parametrise ventilation and pollutant dispersion over urban areas.
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Mechanical Engineering
Doctoral
Doctor of Philosophy
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Sreedhar, Madhu K. "Large eddy simulation of turbulent vortices and mixing layers." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-163324/.

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Goldin, Graham Mark. "A linear eddy model for steady-state turbulent combustion." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12547.

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Li, Xianxiang, and 李顯祥. "Large-eddy simulation of wind flow and air pollutant transport inside urban street canyons of different aspect ratios." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40687326.

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Chung, Nga-hang, and 鍾雅行. "Large-eddy simulation of transport of inert and chemically reactive pollutants over 2D idealized street canyons." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47849903.

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In view of the worsening air quality in the world, more concerns are focused on the environment. This thesis uses the technique of CFD and develops the computer model to investigate the wind and pollutant transport, as well as the chemistry of reactive pollutants in idealized two-dimensional (2D) street canyons. Three scientific questions are raised in this thesis. The first task is to find out the po- sition with the most favorable pollutant removal along the ground level over 2D idealized street canyon of different building-height-to-street-width (aspect) ratios (ARs). The di- mensionless parameter, C, represents the pollutant removal performance. In the isolated roughness regime, the two local maximum C locate at the reattachment point and the windward corner. In the wake interference regime, C is peaked on the windward side. The number of vertically aligned recirculations depends on the street depth in the skimming flow regime. The sizes of the secondary recirculation upstream and downstream deter- mine how the maximum C shifts from the street centre. After identifying the position of peaked pollutant removal rate at the ground level, the emission source should be placed with the highest constant C in order to remove the pollutants upward more quickly to safeguard the street-level air quality. After understanding the best pollutant removal in the street canyon of different ARs, the second task is to find out what AR is the most favorable for the ventilation and pollutant removal across the roof level. The three parameters, namely friction factor, air exchange rate (ACH) and pollutant exchange rate (PCH), are introduced to quantify the pressure difference to sustain the mean flow, the ventilation and pollutant removal, respectively. The turbulence contributes more than 70% to the total ACH and PCH in all the three flow regimes. By increasing the atmospheric turbulence in building geometry as well as the surface roughness, the ventilation and pollutant removal performance can be improved. The linear relation between the friction factor and ACH demonstrates the larger resistance that in turn promotes the air exchange over the roof level. The physical dispersion is studied; however atmospheric pollutants are seldom in- ert but chemically reactive instead. The last task is to include the three common air pollutants, NO, NO2 and O3, in the simple NOx ?O3 mechanism in terms of the photo- stationary state and reaction rates. The Damkohler numbers of NO and O3, DaNO and DaO3, are parameterized by the concentrations of the sources NO and O3. The normalized mean and fluctuation NO, NO2 and O3 are separately considered. The integrated pho- tostationary state (PSS) in the first canyon increases with DaO3 under the same DaNO. The integrated PSS of the second to the twelveth street canyons are compared with each case, the monotonic increase in the PSS from the second to twelveth canyon is perceived in DaNO/DaO3 1, 0.03, 0.02, 0.001 and 0.000333. Further decreases the DaNO/DaO3 to 0.000143, 0.000125, 0.000118, 0.000111 and 0.0001, the PSS is found to be non-linear and the trough appears in the fourth and fifth canyons.
published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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So, Shuk-pan Ellen, and 蘇淑彬. "Large eddy simulations of wind flow and pollution dispersion in an urban street canyon." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29332710.

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Books on the topic "Eddy flux Mathematical models"

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Mofjeld, Harold O. Formulas for velocity, sediment concentration and suspended sediment flux for steady uni-directional pressure-driven flow. Seattle, Wash: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Pacific Marine Environmental Laboratory, 1988.

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Gille, Sarah Tragler. Dynamics of the Antarctic circumpolar current: Evidence for topographic effects from altimeter data and numerical model output. [Woods Hole, Mass: Massachusetts Institute of Technology, Woods Hole Oceanographic Institution, Joint Program in Oceanography/Applied Ocean Science and Engineering, 1995.

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Solovev, Mikhail A. Assessment of mesoscale eddy parameterizations for coarse resolution ocean models. Cambridge, Mass: Massachusetts Institute of Technology, 1999.

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United States. National Environmental Satellite, Data, and Information Service. Atlas of surface marine data 1994. Washington, D.C: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Environmental Satellite, Data, and Information Service, 1994.

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Bui, Trong T. A parallel, finite-volume algorithm for large-eddy simulation of turbulent flows. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Center, 1999.

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Touzani, Rachid, and Jacques Rappaz. Mathematical Models for Eddy Currents and Magnetostatics. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-0202-8.

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Sediment flux modeling. New York: Wiley-Interscience, 2001.

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Elements of direct and large-eddy simulation. Philadelphia, PA: R.T. Edwards, 2003.

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Large eddy simulation for incompressible flows: An introduction. 2nd ed. Berlin: Springer, 2002.

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ERCOFTAC Workshop on Direct and Large-Eddy Simulation (1st 1994 University of Surrey). Direct and large-eddy simulation I: Selected papers from the First ERCOFTAC Workshop on Direct and Large-Eddy Simulation. Dordrecht [Netherlands]: Kluwer Academic, 1994.

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Book chapters on the topic "Eddy flux Mathematical models"

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Berselli, Luigi C., and Franco Flandoli. "On a Stochastic Approach to Eddy Viscosity Models for Turbulent Flows." In Advances in Mathematical Fluid Mechanics, 55–81. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-04068-9_5.

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Chacón Rebollo, Tomás, and Roger Lewandowski. "Steady Navier–Stokes Equations with Wall Laws and Fixed Eddy Viscosities." In Mathematical and Numerical Foundations of Turbulence Models and Applications, 155–201. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-0455-6_6.

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Rabinovich, Boris I., Valeryi G. Lebedev, and Alexander I. Mytarev. "Mathematical Models of High Electrical Conductivity Ferromagnetic Elements with Eddy Currents." In Vortex Processes and Solid Body Dynamics, 3–35. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1038-9_2.

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Rabinovich, Boris I., Valeryi G. Lebedev, and Alexander I. Mytarev. "Experimental Verification of Mathematical Models for Eddy Currents and Vortex Motions of Liquid." In Vortex Processes and Solid Body Dynamics, 123–55. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1038-9_5.

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Mayergoyz, I. D. "Eddy Current Hysteresis. Core Losses." In Mathematical Models of Hysteresis and Their Applications, 377–468. Elsevier, 2003. http://dx.doi.org/10.1016/b978-012480873-7/50007-4.

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Berner, Robert A. "Atmospheric Carbon Dioxide over Phanerozoic Time." In The Phanerozoic Carbon Cycle. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195173338.003.0007.

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In this chapter the methods and results of modeling the long-term carbon cycle are presented in terms of predictions of past levels of atmospheric CO2. The modeling results are then compared with independent determinations of paleo-CO2 by means of a variety of different methods. Results indicate that there is reasonable agreement between methods as to the general trend of CO2 over Phanerozoic time. Values of fluxes in the long-term carbon cycle can be calculated from the fundamental equations for total carbon and 13C mass balance that are stated in the introduction and are repeated here: . . . dMc/dt = Fwc + Fwg + Fmc + Fmg – Fbc – Fbg (1.10) . . . . . . d(δcMc)/dt = δwcFwc + δwgFwg + δmcFmc + δmgFmg – δbcFbc – δbgFbg (1.11) . . . where Mc = mass of carbon in the surficial system consisting of the atmosphere, oceans, biosphere, and soils Fwc = flux from weathering of Ca and Mg carbonates Fwg = flux from weathering of sedimentary organic matter Fmc = degassing flux for carbonates from volcanism, metamorphism, and diagenesis Fmg = degassing flux for organic matter from volcanism, metamorphism, and diagenesis Fbc = burial flux of carbonates in sediments Fbg = burial flux of organic matter in sediments δ = [(13C/12C)/(13C/12C)stnd – 1]1000. Variants of equations (1.10) and (1.11) have been treated in terms of non–steady-state modeling (e.g., Berner et al., 1983; Wallmann, 2001; Hansen and Wallmann, 2003; Mackenzie et al., 2003; Bergman et al., 2003), where the evolution of both oceanic and atmospheric composition, including Ca, Mg, and other elements in seawater, is tracked over time. However, since the purpose of this book is to discuss the carbon cycle with respect to CO2 and O2, and so as not to overburden the reader with too many mathematical expressions, I discuss only those aspects of the non–steady-state models that directly impact carbon. These are combined with results from steady-state strictly carbon-cycle modeling (Garrels and Lerman, 1984; Berner, 1991, 1994; Kump and Arthur, 1997; Francois and Godderis, 1998; Tajika, 1998; Berner and Kothavala, 2001; Kashiwagi and Shikazono, 2002).
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Conference papers on the topic "Eddy flux Mathematical models"

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Yang, Xiang I. A., Vishal Jariwala, Haosen H. A. Xu, and Louis Larosiliere. "Aerodynamic Functional Diagnostics Based on Angular Momentum Transport Lines." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59595.

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Abstract In analogy with the classical concept of mass-flux-based streamlines, we define Angular Momentum Transport (AMT) lines as an aerodynamic functional diagnostic tool. The AMT lines are the ones whose tangents are given by the average angular momentum flux. The mathematical and physical properties of these AMT lines are exploited to study the generation, removal, and transport of angular momentum in turbomachinery components. We illustrate the concept by visualizing AMT lines in two relatively simple flows, namely, vaneless incompressible diffuser and von Karman flow (a model of centrifugal compressors). Next, we apply the proposed diagnostic tool to flow in a return channel. A return channel is a part of a multistage centrifugal compressor stage. Its principal function is to remove angular momentum. In this work, we apply the diagnostic tool of AMT lines to a Reynolds averaged Navier Stokes simulation (RANS) and a wall-modeled large eddy simulation (LES) of flow in the return channel. We show that AMT lines give us insights into the angular momentum transport process that are otherwise not available with conventional visualization tools.
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Huai, Y., A. Sadiki, S. Pfadler, M. Loffler, Frank Beyrau, Alfred Leipertz, and Friedrich Dinkelacker. "Experimental Assessment of Scalar Flux Models for Large Eddy Simulations of Non-Reacting Flows." In Turbulence, Heat and Mass Transfer 5. Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer. New York: Begellhouse, 2006. http://dx.doi.org/10.1615/ichmt.2006.turbulheatmasstransf.470.

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Stolz, Steffen. "High-Pass Filtered Eddy-Viscosity Models for Large-Eddy Simulations of Compressible Wall-Bounded Flows." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56540.

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Eddy-viscosity models such as the Smagorinsky model [1] are the most often employed subgrid-scale (SGS) models for large-eddy simulations (LES). However, for a correct prediction of the viscous sublayer of wall-bounded turbulent flows van-Driest wall damping functions or a dynamic determination of the constant [2] have to be employed. Alternatively, high-pass filtered (HPF) quantities can be used instead of the full velocity field for the computation of the subgrid-scale model terms. This approach has been independently proposed by Vreman [3] and Stolz et al. [4]. In this contribution we consider LES of a spatially developing supersonic turbulent boundary layer at a Mach number of 2.5 and momentum-thickness Reynolds numbers at inflow of approximately 4500, using the HPF Smagorinsky model. The model is supplemented by a HPF eddy-diffusivity ansatz for the SGS heat flux in the energy equation. Turbulent inflow conditions are generated by a rescaling and recycling technique proposed by [5] where the mean and fluctuating part of the turbulent boundary layer at some distance downstream of inflow is rescaled and reintroduced at inflow.
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Chumakov, Sergei, and Christopher J. Rutland. "Dynamic Structure SGS Models for Large Eddy Simulations." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56459.

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Large Eddy Simulation (LES) is based on separation of variable of interest into two parts — resolved and unresolved, where resolved parts are obtained numerically using transport equations, and the effect of unresolved parts on resolved is modeled using subgrid-scale (SGS) models. This technique has been successfully applied to variety of problems including simulation of internal combustion engines. In this paper we present and discuss three new LES sub-grid scale (SGS) models for: • SGS scalar flux; • SGS scalar dissipation; • SGS energy dissipation. The proposed models belong to a new family of SGS models — Dynamic Structure (DS) models. The DS models take the structure of the model term from the corresponding Leonard-type term, and a particular form of a scaling factor is then used. The models are evaluated a priori using available DNS data for a non-reacting mixing layer and decaying isotropic turbulence. The evaluation results compare well with viscosity and similarity models. During the a priori tests, the DS models were found do be robust and perform better than dynamic viscosity and similarity models under variety of conditions including different test-to-base filter size ratios and non-symmetric filters. To evaluate the models a posteriori, they are implemented into a high-order finite-difference code and two LES simulations are conducted: an LES of decaying isotropic turbulence and an LES non-reacting incompressible mixing layer. The results from both runs are compared with data available from the literature and DNS simulations.
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Hradisky, Michal, and Thomas Hauser. "Evaluating LES Subgrid-Scale Models for High Heat Flux Flows." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32504.

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This work is concerned with the modeling of a strongly heated, low Mach number, gas flowing upward within a vertical tube with constant heat flux boundary conditions. Four large eddy subgrid models are compared in their ability to predict the temperature distribution in the heated pipe. All LES models predict the mean velocity profile reasonably well. The RMS values of the Smagorinsky-Lilly model and the WALE model show the same shape but different magnitude while the standard Smagorinsky model shows the maximum at a different location. The mean temperature profiles along the wall in the section with the prescribed heat flux are underpredicted by all LES models.
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Zhang, Ye, Bing-Chen Wang, Ilias Kotsireas, Roderick Melnik, and Brian West. "Large-Eddy Simulation of Streamwise Rotating Turbulent Thermal Flows Based on Advanced Subgrid-Scale Models." In ADVANCES IN MATHEMATICAL AND COMPUTATIONAL METHODS: ADDRESSING MODERN CHALLENGES OF SCIENCE, TECHNOLOGY, AND SOCIETY. AIP, 2011. http://dx.doi.org/10.1063/1.3663468.

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Horyachko, Vsevolod, Orest Hamola, and Taras Ryzhyi. "Calculation of Windings Differential Inductances of Electrical Devices in Mathematical Models with a Total Magnetic Flux." In 2020 IEEE 21st International Conference on Computational Problems of Electrical Engineering (CPEE). IEEE, 2020. http://dx.doi.org/10.1109/cpee50798.2020.9238713.

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Ling, Julia, Kevin J. Ryan, Julien Bodart, and John K. Eaton. "Analysis of Turbulent Scalar Flux Models for a Discrete Hole Film Cooling Flow." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42092.

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Algebraic closures for the turbulent scalar fluxes were evaluated for a discrete hole film cooling geometry using the results from the high-fidelity Large Eddy Simulation (LES) of Bodart et al. [1]. Several models for the turbulent scalar fluxes exist, including the widely used Gradient Diffusion Hypothesis, the Generalized Gradient Diffusion Hypothesis [2], and the Higher Order Generalized Gradient Diffusion Hypothesis [3]. By analyzing the results from the LES, it was possible to isolate the error due to these turbulent mixing models. Distributions of the turbulent diffusivity, turbulent viscosity, and turbulent Prandtl number were extracted from the LES results. It was shown that the turbulent Prandtl number varies significantly spatially, undermining the applicability of the Reynolds analogy for this flow. The LES velocity field and Reynolds stresses were fed into a RANS solver to calculate the fluid temperature distribution. This analysis revealed in which regions of the flow various modeling assumptions were invalid and what effect those assumptions had on the predicted temperature distribution.
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Sandberg, R. D., R. Tan, J. Weatheritt, A. Ooi, A. Haghiri, V. Michelassi, and G. Laskowski. "Applying Machine Learnt Explicit Algebraic Stress and Scalar Flux Models to a Fundamental Trailing Edge Slot." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75444.

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A form of supervised machine learning was applied to highly resolved large-eddy simulation (LES) data to develop non linear turbulence stress and heat flux closures with increased prediction accuracy for trailing-edge cooling slot cases. The LES data were generated for a thick and a thin trailing-edge slot and shown to agree well with experimental data, thus providing suitable training data for model development. A Gene Expression Programming (GEP) based algorithm was used to symbolically regress novel nonlinear Explicit Algebraic Stress Models (EASM) and heat-flux closures based on either the gradient diffusion or the generalized gradient diffusion approaches. Following a-priori assessment, the new models were used for steady RANS calculations of both thin and thick trailing-edge slot geometries, testing their performance and robustness. Overall, the best agreement with LES data was found when training the RANS model in the near wall region where high levels of anisotropy exist and using the mean squared error of the anisotropy tensor as cost function. In the case of the thin lip geometry, combining an improved EASM model with the standard eddy-diffusivity model predicted the adiabatic wall effectiveness in good agreement with the LES and experimental data. Crucially, the obtained model was also applied to different blowing ratios of the thin lip geometry and a significant improvement in the predictive accuracy of adiabatic wall effectiveness was observed for those cases not previously seen in the training process. For the thick lip case the match with reference values deteriorated due to the presence of large-scale, relative to the slot height, vortex shedding. The machine-learning algorithm was therefore also used to ‘learn’ an appropriate closure for the turbulent heat flux vector. The constructed scalar flux model, in conjunction with a trained RANS model, was found to have the capability to further improve the prediction of the adiabatic wall effectiveness.
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Fang, L., L. Shao, J. P. Bertoglio, L. P. Lu, and Z. S. Zhang. "Rapid and Slow Decomposition in Large Eddy Simulation of Scalar Turbulence." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30654.

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In large eddy simulation of turbulent flow, because of the spatial filter, inhomogeneity and anisotropy affect the subgrid stress via the mean flow gradient. A method of evaluating the mean effects is to split the subgrid stress tensor into “rapid” and “slow” parts. This decomposition was introduced by Shao et al. (1999) and applied to A Priori tests of existing subgrid models in the case of a turbulent mixing layer. In the present work, the decomposition is extended to the case of a passive scalar in inhomogeneous turbulence. The contributions of rapid and slow subgrid scalar flux, both in the equations of scalar variance and scalar flux, are analyzed. A Priori numerical tests are performed in a turbulent Couette flow with a mean scalar gradient. Results are then used to evaluate the performances of different popular subgrid scalar models. It is shown that existing models can not well simulate the slow part and need to be improved. In order to improve the modeling, an extension of the model proposed by Cui et al. (2004) is introduced for the slow part, whereas the Scale-Similarity model is used reproduce the rapid part. Combining both models, A Priori tests lead to a better performance. However, the remaining problem is that none eddy-diffusion model can correctly represent the strong scalar dissipation near the wall. This problem will be addressed in future work.
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