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Academic literature on the topic 'Wall layer model'

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Published: 11 March 2023

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Journal articles on the topic "Wall layer model"

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Landahl, M. T. "Near-wall model for boundary layer turbulence." Applied Scientific Research 51, no. 1-2 (June 1993): 435–43. http://dx.doi.org/10.1007/bf01082573.

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Gerodimos, G., and R. M. C. So. "Near-Wall Modeling of Plane Turbulent Wall Jets." Journal of Fluids Engineering 119, no. 2 (June 1, 1997): 304–13. http://dx.doi.org/10.1115/1.2819135.

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In most two-dimensional simple turbulent flows, the location of zero shear usually coincides with that of vanishing mean velocity gradient. However, such is not the case for plane turbulent wall jets. This could be due to the fact that the driving potential is the jet exit momentum, which gives rise to an outer region that resembles a free jet and an inner layer that is similar to a boundary layer. The interaction of a free-jet like flow with a boundary-layer type flow distinguishes the plane wall jet from other simple flows. Consequently, in the past, two-equation turbulence models are seldom able to predict the jet spread correctly. The present study investigates the appropriateness of two-equation modeling; particularly the importance of near-wall modeling and the validity of the equilibrium turbulence assumption. An improved near-wall model and three others are analyzed and their predictions are compared with recent measurements of plane wall jets. The jet spread is calculated correctly by the improved model, which is able to replicate the mixing behavior between the outer jet-like and inner wall layer and is asymptotically consistent. Good agreement with other measured quantities is also obtained. However, other near-wall models tested are also capable of reproducing the Reynolds-number effects of plane wall jets, but their predictions of the jet spread are incorrect.
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3

Jai, John, George S. Springer, Laszlo P. Kollar, and Helmut Krawinkler. "Reinforcing Masonry Walls with Composite Materials-Model." Journal of Composite Materials 34, no. 18 (September 2000): 1548–81. http://dx.doi.org/10.1106/38xx-ggb5-nxc9-tjha.

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In this investigation, a procedure is developed for determining the effectiveness of composite materials in retrofitting masonry buildings to reduce seismic damage. The reinforcement considered is a thin layer of fiber-reinforced composite applied to the wall in a wallpaper-like fashion. Models were developed which predict the behavior of masonry walls reinforced in such a fashion and subjected to static, in-plane normal and shear loads. Solid walls, as well as walls with openings (such as windows and doors), were considered. The models estimate the load-deflection characteristic of the wall, the load set at which the wall fails, and the deflection of the wall at the instant of failure. Numerical results were also generated which indicate that composite reinforcement applied in a wallpaper-like fashion may increase substantially the load carrying capacities of masonry walls.
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Keirsbulck, L., L. Labraga, A. Mazouz, and C. Tournier. "Surface Roughness Effects on Turbulent Boundary Layer Structures." Journal of Fluids Engineering 124, no. 1 (October 15, 2001): 127–35. http://dx.doi.org/10.1115/1.1445141.

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A turbulent boundary layer structure which develop over a k-type rough wall displays several differences with those found on a smooth surface. The magnitude of the wake strength depends on the wall roughness. In the near-wall region, the contribution to the Reynolds shear stress fraction, corresponding to each event, strongly depends on the wall roughness. In the wall region, the diffusion factors are influenced by the wall roughness where the sweep events largely dominate the ejection events. This trend is reversed for the smooth-wall. Particle Image Velocimetry technique (PIV) is used to obtain the fluctuating flow field in the turbulent boundary layer in order to confirm this behavior. The energy budget analysis shows that the main difference between rough- and smooth-walls appears near the wall where the transport terms are larger for smooth-wall. Vertical and longitudinal turbulent flux of the shear stress on both smooth and rough surfaces is compared to those predicted by a turbulence model. The present results confirm that any turbulence model must take into account the effects of the surface roughness.
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Gre´goire, G., M. Favre-Marinet, and F. Julien Saint Amand. "Modeling of Turbulent Fluid Flow Over a Rough Wall With or Without Suction." Journal of Fluids Engineering 125, no. 4 (July 1, 2003): 636–42. http://dx.doi.org/10.1115/1.1593705.

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The turbulent flow close to a wall with two-dimensional roughness is computed with a two-layer zonal model. For an impermeable wall, the classical logarithmic law compares well with the numerical results if the location of the fictitious wall modeling the surface is considered at the top of the rough boundary. The model developed by Wilcox for smooth walls is modified to account for the surface roughness and gives satisfactory results, especially for the friction coefficient, for the case of boundary layer suction.
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Hamdhan, Indra Noer, and Fauziah Fitriani Iskandar. "Analisis Perkuatan Timbunan Di Atas Tanah Lunak Menggunakan Dinding Turap dengan Pendekatan Model Numerik." MEDIA KOMUNIKASI TEKNIK SIPIL 25, no. 1 (August 10, 2019): 48. http://dx.doi.org/10.14710/mkts.v25i1.18006.

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Embankment on soft clay may be affect settlement at subgrade, causing lateral deformation and vertical deformation around embankment. Therefore, reinforcement is needed to overcome the effects caused of the embankment. This research was conducted to find out the influence of sheet pile wall of embankment using PLAXIS 2D program based the finite element method. The analysis was done by varying of two condition, they are installation of sheet pile wall under the embankment and the sheet pile wall outside embankment. Sheet pile wall installation is carried out before embankment construction and length of sheet pile wall in this model is 15 m. The soil layers beneath the embankment consist of 10 m layer of soft clay layer and 5 m of sand layer. The height of embankment in this analysis is 8 m, where the constructing of the embankment was done in stages. The distance of sheet pile wall position under embankment from toe of embankment are -9 m, -6 m, -3 m, 0 m, 3 m dan 6 m. The results of analysis show the effective position for displacement are toe of embankment. The Installation of sheet pile walls below the embankment will reducing deformation up to 78% and the safety factor will increase up to 10%.
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Hultmark, Marcus, Marc Calaf, and Marc B. Parlange. "A New Wall Shear Stress Model for Atmospheric Boundary Layer Simulations." Journal of the Atmospheric Sciences 70, no. 11 (October 31, 2013): 3460–70. http://dx.doi.org/10.1175/jas-d-12-0257.1.

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Abstract A new wall shear stress model to be used as a wall boundary condition for large-eddy simulations of the atmospheric boundary layer is proposed. The new model computes the wall shear stress and the vertical derivatives of the streamwise velocity component by means of a modified, instantaneous, and local law-of-the-wall formulation. By formulating a correction for the modeled shear stress, using experimental findings of a logarithmic region in the streamwise turbulent fluctuations, the need for a filter is eliminated. This allows one to model the wall shear stress locally, and at the same time accurately recover the correct average value. The proposed model has been applied to both unique high Reynolds number experimental data and a suite of large-eddy simulations, and compared to previous models. It is shown that the proposed model performs equally well or better than the previous filtered models. A nonfiltered model, such as the one proposed, is an essential first step in developing a universal wall shear stress model that can be used for flow over heterogeneous surfaces, studies of diurnal cycles, or analyses of flow over complex terrain.
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Badano, Nicolás D., and Angel N. Menéndez. "Accuracy of boundary layer treatments at different Reynolds scales." Open Engineering 10, no. 1 (April 8, 2020): 295–310. http://dx.doi.org/10.1515/eng-2020-0033.

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AbstractResistive forces associated to boundary layers (‘friction’) are usually out of scale in physical models of hydraulic structures, especially in the case of hydraulically smooth walls, generating distortions in the model results known as scale effects, that can be problematic in some relevant engineering problems. These scale effects can be quantified and corrected using suitable numerical models. In this paper the accuracy of using numerical simulation through the Reynolds Averaged Navier-Stokes (RANS) approximation in order to represent the head losses introduced by friction in hydraulically smooth walls is evaluated for a wide range of Reynolds scales. This is performed by comparing the numerical results for fully developed flow on circular pipes and between parallel plates against experimental results, using the most popular wall treatments. The associated numerical errors, mesh requirements and ranges of application are established for each treatment. It is shown that, when properly applied, RANS models are able to simulate the head losses produced by smooth wall friction accurately enough as to quantify the scale effects present in physical models. A methodology for upscaling physical model results to prototype scale, free of scale effects, is proposed.
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Basu B., Mallik, and Garain D.N. "Mathematical Model of Blood Flow through Capillaries to Study Transport of Nanoparticles Using Power Law Fluid Model." International Journal of Zoological Investigations 08, special issue (2022): 275–84. http://dx.doi.org/10.33745/ijzi.2022.v08i0s.034.

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A model of blood capillary flow that is axially symmetric with a peripheral layer and wall slip is provided mathematically in this study. Power law fluid was employed in the core area of suspension of all erythrocytes whereas Newtonian fluid was used in the periphery plasma layer to analyse longitudinal transport of nanoparticles within blood vessels. The capillary walls are impenetrable to nanoparticles in our study, and they are not absorbent. The formulas for the velocity profile, flow rate, mean velocity, and solute concentration were produced, and the findings were discussed using graphs.
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Tang, Yang Yang, Zhi Qiang Li, Yong Wang, Ya Chao Di, Huan Xu, and Qing Yang. "Numerical Investigation of the Compressible Flat-Plate Turbulent Boundary Layer with Extended GAO-YONG Turbulence Model." Applied Mechanics and Materials 444-445 (October 2013): 416–22. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.416.

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The extended GAO-YONG turbulence model is used to simulate the flow and heat transfer of flat-plate turbulent boundary layer, and the results indicate that GAO-YONG turbulence model may well describe boundary layer flow and heat transfer from near-wall region to far outer area, without using any empirical coefficients and near-wall treatments, such as wall-function or modified low Reynolds number model, which are used widely in all RANS turbulence models.
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Dissertations / Theses on the topic "Wall layer model"

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Dilip, Deepu. "Wall Modeled Large Eddy Simulation of Flow over a Wall Mounted Hump." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64356.

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Large Eddy Simulation (LES) is a relatively more accurate and reliable alternative to solution of Reynolds Averaged Navier Stokes (RANS) equations in simulating complex turbulent flows at a lesser computational cost than a direct numerical simulation (DNS). However, LES of wall-bounded flows still requires a very high grid resolution in the inner wall layer making its widespread use difficult. Different attempts have been made in the past time to overcome this problem by modeling the near wall turbulence instead of resolving it. One such approach is a two-layer wall model that solves for a reduced one-dimensional equation in the inner wall layer, while solving for the filtered Navier-Stokes equations in the outer layer. The use of such a model allows for a coarser grid resolution than a wall resolved LES. This work validates the performance of a two-layer wall model developed for an arbitrary body fitted non-orthogonal grid in the flow over a wall mounted hump at Reynolds number 9.36x105. The wall modeled large eddy simulation (WMLES) relaxes the grid requirement compared to a wall resolved LES (WRLES) by allowing the first off-wall grid point to be placed at a y+ of approximately 20-40. It is found that the WMLES results are general good agreement with WRLES and experiments. Surface pressure coefficient, skin friction, mean velocity profiles, and the reattachment location compare very well with experiment. The WMLES and WRLES exhibit some under prediction of the peak values in the turbulent quantities close to the reattachment location, with better agreement with the experiment in the separated region. In contrast, a simulation that did not employ the wall model on the grid used for WMLES failed to predict flow separation and showed large discrepancies with the experimental data. In addition to the relaxation of the grid requirement in the wall normal direction, it was also observed that the wall model allowed a reduction in the number of computational cells in the span-wise direction by half. However an LES calculation on a grid with reduced number of cells in span-wise direction turned unstable almost immediately, thereby highlighting the effectiveness of the wall model. Besides reducing the number of grid points in the spatial domain, the relaxed grid resolution for the WMLES also permitted the use of a larger time step. This resulted in an order of magnitude reduction in the total CPU time relative to WRLES.
Master of Science
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Fakhari, Ahmad. "Wall-Layer Modelling of massive separation in Large Eddy Simulation of coastal flows." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11104.

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2012/2013
The subject of modelling flow near wall is still open in turbulent wall bounded flows, since there is no wall layer model which works perfectly. Most of the present models work well in attached flows, specially for very simple geometries like plane channel flows. Weakness of the models appears in complex geometries, and many of them do not capture flow separation accurately in detached flows, specially when the slope of wall changes gradually. In many engineering applications, we deal with complex geometries. A possible way to simulate flows influenced by complex geometry using a structured grid, is to consider the geometry as immersed boundary for the simulation. Current wall layer models for the immersed boundaries are more complex and less accurate than the body-fitted cases (cases without immersed boundaries). In this project the accuracy of wall layer model in high Reynolds number flows is targeted, using LES for attached flows as well as detached flows (flows with separation). In addition to the body fitted cases, wall layer model in the presence of immersed boundaries which is treated totally different also regarded. A single solver LES-COAST (IE-Fluids, University of Trieste) is used for the flow simulations, and the aim is to improve wall layer model in the cases with uniform coarse grid. This is in fact novelty of the thesis to introduce a wall layer model applied on the first off-wall computational node of a uniform coarse grid, and merely use LES on the whole domain. This work for the immersed boundaries is in continuation of the methodology proposed by Roman et al. (2009) in which velocities at the cells next to immersed boundaries are reconstructed analytically from law of the wall. In body-fitted cases, since smaller Smagorinsky constant is required close to the walls than the other points, wall layer model in dynamic Smagorinsky sub-grid scale model using dynamic k (instead of Von Karman constant) is applied to optimize wall function in separated flows. In the presence of immersed boundaries, the present wall layer model is calibrated, and then improved in attached and also detached flows with two different approaches. The results are also compared to experiment and resolved LES. Consequently the optimized wall layer models show an acceptable accuracy, and are more reliable. In the last part of this thesis, LES is applied to model the wave and wind driven sea water circulation in Kaneohe bay, which is a bay with a massive coral reef. This is the first time that LES-COAST is applied on a reef-lagoon system which is very challenging since the bathymetry changes very steeply. For example the water depth differs from less than 1 meter over the reef to more than 10 meters in vicinity of the reef, in lagoon. Since a static grid is implemented, the effect of wave is imposed as the velocity of current over the reef, which is used on the boundary of our computational domain. Two eddies Smagorinsky SGS model is used for this simulation.
XXVI Ciclo
1983
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Zhang, Yufang. "Coupled convective heat transfer and radiative energy transfer in turbulent boundary layers." Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00969159.

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If radiation plays an important role in many engineering applications, especially in those including combustion systems, influence of radiation on turbulent flows, particularly on the turbulent boundary layers, is still not well known. The objective is here to perform a detailed study of radiation effect on turbulent flows. An optimized emission-based reciprocal (OERM) approach of the Monte-Carlo method is proposed for radiation simulation using the CK model for radiative gas properties. OERM allows the uncertainty of results to be locally controlled while it overcomes the drawback of the original emission-based reciprocity approach by introducing a new frequency distribution function that is based on the maximum temperature of the domain. Direct Numerical Simulation (DNS) has been performed for turbulent channel flows under different pressure, wall temperatures and wall emissivity conditions. Flow field DNS simulations are fully coupled with radiation simulation using the OERM approach. The role of radiation on the mean temperature field and fluctuation field are analyzed in details. Modification of the mean temperature profile leads to changes in wall conductive heat fluxes and new wall laws for temperature when radiation is accounted for. The influence on temperature fluctuations and the turbulent heat flux is investigated through their respective transport equations whose balance is modified by radiation. A new wall-scaling based on the energy balance is proposed to improve collapsing of wall-normal turbulent flux profiles among different channel flows with/without considering radiation transfer. This scaling enables a new turbulent Prandtl number model to be introduced to take into account the effects of radiation. In order to consider the influence of radiation in the near-wall region and predict the modified wall law, a one-dimensional wall model for Large Eddy Simulation (LES) is proposed. The 1D turbulent equilibrium boundary layer equations are solved on an embedded grid in the inner layer. The obtained wall friction stress and wall conductive flux are then fed back to the LES solver. The radiative power term in the energy equation of the 1D wall model is computed from an analytical model. The proposed wall model is validated by a comparison with the former DNS/Monte-Carlo results. Finally, two criteria are proposed and validated. The first one is aimed to predict the importance of wall radiative heat flux while the other one predicts whether a wall model accounting for radiation in the near wall region is necessary. A parametric study is then performed where a k-ǫ model and a turbulent Prandtl number model are applied to simulate the velocity and temperature field of different channel flows under various flow conditions. The obtained criteria values are analyzed and compared.
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Stocca, Valentina. "Development of a predictive LES model for the study of the pollutant dispersion in urban areas." Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3512.

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2008/2009
In this thesis, a new large-eddy simulation solver, LES-AIR, has been developed, tested and applied to a practical situation of flow and pollutant dispersion in urban environments. The novelty of the present research resides in the application of a high resolution, accurate, CFD technique to the simulation of real-life flows. The code uses a body fitted curvilinear grid to account for the macro geometry such as terrain slopes, and is thus able to reproduce in detail the complex conditions typical of urban areas; by utilizing the technique of immersed boundaries, the code is also able to mimic the presence the micro complexities such as anthropic structures (i.e. buildings). The first part of the thesis presents a detailed description of the mathematical and numerical model on which the code is based. An extensive set of validation tests was performed in flow configurations having an increasing degree of complexity in terms of forcing and geometry. The numerical model thus validated is applied for obtaining flow and pollutant dispersion in the Servola-Valmaura suburban area of the city of Trieste in Italy. The pollutant was introduced into the domain from a line source near the ground, mimicking the emission from vehicular traffic. In spite of the idealizations inherent to the model, LES-AIR is able to predict the flow and dispersion patterns well, and has proven to be a reliable tool for adaptation in urban pollution studies.
Nella presente tesi è stato sviluppato, testato ed applicato ad un caso studio applicativo un nuovo solutore numerico, chiamato codice LES-AIR, capace di predire i campi di vento e la dispersione di nquinanti in ambienti urbani. La maggiore novità di questo lavoro risiede nell’utilizzo di una tecnica fluidodinamica molto accurata e ad alta risoluzione per la simulazione di flussi reali. Il codice LES-AIR è capace di riprodurre con grande dettaglio le geometrie complesse tipiche delle aree urbane tramite l’utilizzo congiunto di una griglia curvilinea, che si adatta all’ orografia del terreno, e della tecnica dei corpi immersi, con la quale vengono riprodotti gli ostacoli antropici, quali gli edifici. Nella prima parte della tesi viene fornita una descrizione dettagliata del modello matematico e numerico su cui si basa il codice. Il modello è stato validato per mezzo di un esteso set di casi test, aventi un grado crescente di complessit à in termini di forzanti e di configurazione geometriche. Il modello così validato è stato applicato alla riproduzione di un caso applicativo nel quale i campi di vento e la dispersione di un inquinante nella zona di Servola-Valmaura, situata nella periferia di Trieste, sono stati simulati. L’ inquinante è stato introdotto da una sorgente lineare posta in prosimità del terreno e rappresentante l’emissione derivante dal traffico cittadino. Nonostante le condizioni idealizzate di vento considerate, il codice LES-AIR si è dimostrato molto efficace nella predizione del flusso e della dispersione dell’inquinante e quindi si è attestato essere un valido strumento negli studi d’ inquinamento urbani.
XXII Ciclo
1981
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Catchirayer, Mathieu. "Modélisation de paroi en simulation des grandes échelles dans une turbomachine." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0110.

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Les défis énergétiques rencontrés par les motoristes aéronautiques requiert une compréhension plus fine des écoulements régissant leurs turbomachines. La simulation aux grandes échelles (LES) peut combler ce besoin. Cependant, dans le cas de couches limites à des nombres de Reynolds typiques de ceux rencontrés en aéronautique, son coût de calcul devient prohibitif. Une manière d'éviter cet écueil est de recourir à une approche WMLES (Wall-Modeled LES) : la turbulence en proche paroi est modélisée par un modèle de paroi. Toutefois, l'utilisation d'une WMLES sur des géométries industrielles reste une question ouverte. Ainsi, un modèle de paroi adapté aux écoulements de turbomachines est ici développé : l'iWMLES (integral WMLES). Les profils de vitesse et de température sont paramétrisés et les paramètres inconnus sont déterminés pour respecter des conditions aux limites issues des équations de couche limite intégrales. L'iWMLES peut alors prendre en compte les effets de compressibilité, de gradients de température et de pression à un faible coût de calcul. Sa validation est réalisée sur des écoulements académiques : des cas de canal plan isothermes et adiabatiques à différents nombres de Reynolds et de Mach sont considérés, ainsi qu'une couche limite soumise à un gradient de pression adverse. À chaque fois, les moments statistiques jusqu'à l'ordre un sont en accord avec les données de référence. Ces différentes simulations montrent que l'iWMLES a un domaine de validité plus étendu que les modèles de paroi classiques. Enfin, l'iWMLES est appliqué sur un étage de compresseur axial, démontrant sa robustesse, et les résultats sont comparés avec ceux d'une LES résolue en paroi
Due to the energetic challenges faced by aeronautical engine manufacturers, a better understanding of the flows governing their gas turbines is required. Numerical simulations through Large-Eddy Simulation (LES) approach is well suited to this quest for innovation. However, its computational cost is prohibitive in the case of boundary layers at Reynolds numbers encountered in aeronautics. One way to tackle this limitation is to use a WMLES (Wall-Modeled LES) approach: near-wall turbulence is modeled thanks to a wall-model. Nonetheless, this approach is still an open issue for industrials flows. Therefore, a new suited wall-model is developed in this study: the iWMLES (integral WMLES). The velocity and temperature profiles are parameterized, and unknown coefficients are determined by matching boundary conditions obeying the integral boundary layer equations. It allows compressibility, temperature and pressure gradients effects to be taken into account at a low computational cost. The proposed wall-model is then assessed on academic flows. First, adiabatic and isothermal plane channel flows at several friction Reynolds and Mach numbers are simulated. In all cases, mean profiles, wall fluxes, and turbulent fluctuations are in agreement with direct numerical simulation data. Especially, the supersonic flow cases show that the iWMLES has a wider domain of validity than standard wall-models. Second, an experimental boundary layer under adverse pressure gradient is considered. The iWMLES is shown to predict correctly the one-point turbulence statistics. Finally, the iWMLES is applied to an axial compressor stage, proving its robustness, and results are compared with LES data
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Kubwimana, Thierry. "Simulation de l'écoulement atmosphérique au voisinage d'une tête de tunnel." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEC023.

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La conception d’un système de ventilation mécanique dans un tunnel nécessite de recenser tous les phénomènes physiques mis en jeu dans le mouvement de l’air dans le tunnel. Et ceci afin d’établir les capacités de ventilation nécessaires au regard d’objectifs règlementaires. On peut compter parmi ces phénomènes les effets atmosphériques, et notamment l’effet du vent, susceptible de générer des surpressions ou dépressions à proximité des ouvertures d’un tunnel et par conséquent d’induire ou de modifier un courant d’air établi à l’intérieur de celui-ci. Le présent travail entend contribuer à une meilleure compréhension ainsi qu’à une meilleure prise en compte de l’écoulement atmosphérique extérieur dans les études de ventilation de tunnel.Modélisations expérimentale et numérique ont été mises en œuvre pour cela. Des essais en soufflerie ont été menés dans la soufflerie atmosphérique de l’École Centrale de Lyon et ont fait appel à différentes techniques (PIV, anémométrie à fils chauds, micromanomètre) pour mesurer les caractéristiques moyennes et turbulentes de l’écoulement atmosphérique au voisinage d’un tunnel. Et nous avons également employé les approches numériques moyenne (RANS) et filtrée (LES) pour simuler l’écoulement atmosphérique autour d’un tunnel.La représentation de l’écoulement atmosphérique, instationnaire et turbulent, en entrée d’un domaine de calcul LES pose des difficultés. Nous avons, au cours de ce travail, implémenté un générateur synthétique de conditions amont dans le code de calcul FLUENT et, à l’appui des résultats expérimentaux, établi le paramétrage optimal d’une simulation LES de couche limite atmosphérique pleinement rugueuse.Deux configurations de tunnel ont ensuite été étudiées par voies numérique et expérimentale. Dans une première série d’essais, le champ de pression sur la tête d’un tunnel assimilée à la section frontale d’une cavité parallélépipédique a été étudié. Les comparaisons entre les différentes approches ont mis en évidence l’influence de la géométrie du tunnel et du bâti environnant, ainsi que la meilleure performance de l’approche LES dans la caractérisation de l’écoulement turbulent. Et dans une deuxième série d’essais, nous nous sommes rapprochés d’une configuration réelle et avons instrumenté une maquette de tête de tunnel ouverte dans lequel nous pouvions créer un courant d’air dirigé vers l’intérieur ou l’extérieur de l’ouvrage. Les résultats ont montré une interaction importante entre la couche limite atmosphérique et le jet pariétal tridimensionnel issu du tunnel
The design of a mechanical ventilation system in a tunnel requires to identify all the physical phenomena involved in the movement of the air in the tunnel. That is in order to establish the necessary ventilation capacities with regard to regulatory objectives. Atmospheric effects feature among the mechanisms likely to generate overpressures or depressions near the openings of a tunnel and consequently to induce or to modify the airflow established inside. This research work intends to contribute to a better understanding as well as a better consideration of the external atmospheric effects in tunnel ventilation studies.Experimental and numerical modeling have been completed. Wind tunnel tests were carried out in the atmospheric wind tunnel of the École Centrale de Lyon and used different techniques (PIV, hot wire anemometry, micromanometer) to measure the mean and turbulent statistics of the atmospheric flow in the vicinity of a tunnel. Time averaged (RANS) and filtered (LES) turbulence models were also used to simulate the atmospheric flow around a tunnel.The suitable representation of the unsteady turbulent atmospheric flow at the inlet of an LES computational domain remains an issue. During this work, we implemented a synthetic turbulence generator in the CFD code Fluent and, through comparison with experimental data, derived the optimal setup for the simulation of a fully rough atmospheric boundary layer.Thereafter, two tunnel configurations were studied by numerical and experimental means. In a first series of tests, the pressure field at the front section of a rectangular cavity was studied. The comparisons between the different approaches highlighted the influence of the geometry of the tunnel and the arrangement of the surrounding urban-like environment, as well as a better performance of the LES model in the description the turbulent flow. And in a second series of tests, we got closer to a realistic configuration and instrumented an open tunnel in which we could create an airflow directed towards the outside or the inside of the structure. The results showed a significant interaction between the atmospheric boundary layer and the three-dimensional wall jet from the tunnel
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7

Caillé, Jean. "New integral and differential computational procedures for incompressible wall-bounded turbulent flows." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/37425.

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Three new computational procedures are presented for the simulation of incompressible wall-bounded turbulent flows. First, an integral method based on the strip integral method has been developed for the solution of three-dimensional turbulent boundary-layer flows. The integral equations written in a general form using non-orthogonal streamline coordinates include the turbulent shear stress at the upper limit of an inner strip inside the boundary-layer. The shear stress components are modeled using the Boussinesq assumption, and the eddy viscosity is defined explicitly as in differential methods. The turbulence modeling is not hidden in opaque empirical correlations as in conventional integral methods. A practical four-parameter velocity profile has been established based on the Johnston Law of the Wall using a triangular model for the crosswise velocity. Two strips are used to solve for the four unknowns: skin friction coefficient, wall crossflow angle, boundary-layer thickness, and location of maximum crosswise velocity. The location of maximum crosswise velocity proves to be a natural and adequate parameter in the formulation, but it is numerically sensitive and has a strong influence on the wall crossflow angle. Good results were obtained when compared to predictions of other integral or differential methods. Secondly, two computational procedures solving the Reynolds Averaged Navier-Stokes equations for 20 and 3D flows respectively have also been developed using a new treatment of the near-wall region. The flow is solved down to the wall with a slip velocity based on Clauser's idea of a pseudolaminar velocity profile. The present idea is different from the wall-function methods and does not require a multi-layer eddy viscosity model. The solution of the equations of motion is obtained by the Finite Element Method using the wall shear stress as a boundary condition along solid surfaces, and using the Clauser outer region model for the eddy viscosity. The wall shear stress distribution is updated by solving integral equations obtained from the enforcement of conservation of mass and momentum over an inner strip in the near-wall region. The Navier-Stokes solution provides the necessary information to the inner strip integral formulation in order to evaluate the skin friction coefficient for 2D flows, or the skin friction coefficient and the wall crossflow angle for 3D flows. The procedures converge to the numerically "exact" solution in a few iterations depending on the accuracy of the initial guess for the wall shear stress. A small number of nodes is required in the boundary-layer to represent adequately the physics of the flow, which proves especially useful for 3D calculations. Excellent results were obtained for the 2D simulations with a simple eddy viscosity model. 3D calculations gave good results for the turbulent boundary-layer flows considered here. The present methods were validated using well-known experiments chosen for the STANFORD conferences and EUROVISC workshop. The 2D numerical predictions are compared with the experimental measurements obtained by Wieghardt-Tillmann, Samuel-Joubert, and Schubauer-Klebanoff. For the 3D analyses, the numerical predictions obtained by the strip-integral method and the Finite Element Navier-Stokes Integral Equation procedure are validated using the Van den Berg-Elsenaar and Müller-Krause experiments.
Ph. D.
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8

SACCO, FRANCESCO. "Mathematical models and analysis of turbulent, wall-bounded, complex flows." Doctoral thesis, Gran Sasso Science Institute, 2020. http://hdl.handle.net/20.500.12571/15321.

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In the classical wall bounded turbulent flow a fundamental statement is the existence of a layer, called overlap layer, in which every flow behaves the same and the mean streamwise velocity of each system can be described with only the wall normal coordinate with a logarithmic profile, characterized by the von Kármán constant. This law has been at first derived on data on parallel flows and boundary layer, that are model flows for wall turbulence, but indeed have a much simpler flow than complex shape geometries. The formulation of Millikan has much more general requirement on the flow and it is based on the asymptotic expansion of the velocity field; this theory of the logarithmic behavior of the overlap layer is an asymptotic approximation, and so holds for very high Reynolds numbers, Re_τ → ∞. For this reason much of the research effort has been directed at increasing the Reynolds number. However, due to the limits in resources, and so in the possibility of reaching the highest possible value, every similarity theory is still incomplete; but like all asymptotic approximations, it can be improved with the addition of higher-order terms. We develop a correction of the classical von Kármán logarithmic law for a turbulent Taylor-Couette (TC) flow, the fluid flow developing between two coaxial, independently rotating cylinders, when the curvature of the system is small, i.e. with an inner to outer radius ratio η = r_i /r_o ≥ 0.9, when both the cylinder rotates with the same magnitude but in opposite directions. While in straight geometries like channel or pipe, the deviation from the law can be ascribed to the effect of pressure gradient, in small gap TC flow this effect can be accounted to the conserved transverse current of azimuthal motion. We show that, when the correction is applied, the logarithmic law is restored even when varying the curvature, and that the parameters founded here for TC flow converge to the ones founded in [P. Luchini. European Journal of Mechanics B Fluids, 71, 2018.] for plane Couette flow, in the limit of vanishing curvature η → 1.
In many shear- and pressure-driven wall-bounded turbulent flows secondary motions spontaneously develop and their interaction with the main flow alters the overall large-scale features and transfer properties. Taylor–Couette flow, the fluid motion developing in the gap between two concentric cylinders rotating at different angular velocities, is not an exception, and toroidal Taylor rolls have been observed from the early development of the flow up to the fully turbulent regime. In this manuscript we show that under the generic name of ‘Taylor rolls’ there is a wide variety of structures that differ in the vorticity distribution within the cores, the way they are driven and their effects on the mean flow. We relate the rolls at high Reynolds numbers not to centrifugal instabilities, but to a combination of shear and anti-cyclonic rotation, showing that they are preserved in the limit of vanishing curvature and can be better understood as a pinned cycle which shows similar characteristics as the self-sustained process of shear flows. By analysing the effect of the computational domain size, we show that this pinning is not a product of numerics, and that the position of the rolls is governed by a random process with the space and time variations depending on domain size.
We use experiments and direct numerical simulations to probe the phase space of low-curvature Taylor–Couette flow in the vicinity of the ultimate regime. The cylinder radius ratio is fixed at η = r_i /r_o = 0.91, where r_i (r_o ) is the inner (outer) cylinder radius. Non-dimensional shear drivings (Taylor numbers Ta) in the range 10^7 ≤ Ta ≤ 10^11 are explored for both co- and counter-rotating configurations. In the Ta range 10^8 ≤ Ta ≤ 10^10 , we observe two local maxima of the angular momentum transport as a function of the cylinder rotation ratio, which can be described as either ‘co-’ or ‘counter-rotating’ due to their location or as ‘broad’ or ‘narrow’ due to their shape. We confirm that the broad peak is accompanied by the strengthening of the large-scale structures, and that the narrow peak appears once the driving (Ta) is strong enough. As first evidenced in numerical simulations by Brauckmann et al. (J. Fluid Mech., vol. 790, 2016, pp. 419–452), the broad peak is produced by centrifugal instabilities and that the narrow peak is a consequence of shear instabilities. We describe how the peaks change with Ta as the flow becomes more turbulent. Close to the transition to the ultimate regime when the boundary layers (BLs) become turbulent, the usual structure of counter-rotating Taylor vortex pairs breaks down and stable unpaired rolls appear locally. We attribute this state to changes in the underlying roll characteristics during the transition to the ultimate regime. Further changes in the flow structure around Ta ≈ 10^10 cause the broad peak to disappear completely and the narrow peak to move. This second transition is caused when the regions inside the BLs which are locally smooth regions disappear and the whole boundary layer becomes active.
Large scale structures have been observed in many turbulent wall bounded flows, such as pipe, Couette or square duct flows. Many efforts have been made in order to capture such structures to understand and model them. However, commonly used methods have their limitations, such as arbitrariness in parameter choice or specificity to certain setups. In this manuscript we attempt to overcome these limitations by using two variants of Dynamic Mode Decomposition (DMD). We apply these methods to (rotating) Plane Couette flow, and verify that DMD-based methods are adequate to detect the coherent structures and to extract the distinct properties arising from different control parameters. In particular, these DMD variants are able to capture the influence of rotation on large-scale structures by coupling velocity components. We also show how high-order DMD methods are able to capture some complex temporal dynamics of the large-scale structures. These results show that DMD-based methods are a promising way of filtering and analysing wall bounded flows.
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9

Hinsberg, Nils Paul van. "Investigation of drop and spray impingement on a thin liquid layer accounting for the wall film topology." Aachen Shaker, 2009. http://d-nb.info/1000840115/04.

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Furbo, Eric. "Evaluation of RANS turbulence models for flow problems with signigicant impact of boundary layers." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-138757.

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This master’s thesis was provided by the Swedish Defence Research Agency, FOI. The task is to test several RANS (Reynolds-averaged Navier-Stokes) models on two different case geometries and compare the results with LES and experimental data. The first is two dimensional, constructed for flow separation at a sharp edge. The second is three dimensional and flow separation occurs at a smooth surface. The models tested are implemented in the open source CFD (Computational Fluid Dynamics) program, OpenFOAM. OpenFOAM uses the finite volume method and the SIMPLE algorithm as solution procedure. The main flow features evaluated is the shape, position and size of the flow separation. Most of the models tested have problems describing the complex dynamics of flow separation in these particular cases. In addition to the simulations, the RANS k-epsilon turbulence model is presented and the RANS equations and the equation for the turbulent kinetic energy are derived from the Navier-Stokes equations. The theory behind wall functions is described and these equations together with the equations in the k-epsilon model are compared with the equations implemented in OpenFOAM.
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Books on the topic "Wall layer model"

1

Sommer, T. P. A near-wall four-equation turbulence model for compressible boundary layers. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Program, 1992.

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Sommer, T. P. A near-wall four-equation turbulence model for compressible boundary layers. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Program, 1992.

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Sommer, T. P. A near-wall four-equation turbulence model for compressible boundary layers. Hampton, Va: Langley Research Center, 1992.

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1940-, Shih Tsan-Hsing, and United States. National Aeronautics and Space Administration., eds. A new time scale based [kappa-epsilon] model for near wall turbulence. [Washington, DC: National Aeronautics and Space Administration, 1992.

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Ridha, Abid, Speziale C. G. 1948-, and Langley Research Center, eds. Application of a new K-[tau] model to near wall turbulent flows. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1991.

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Ridha, Abid, Speziale C. G. 1948-, and Langley Research Center, eds. Application of a new K-[tau] model to near wall turbulent flows. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1991.

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Rodi, Wolfgang. Experience with two-layer models combining the K-E model with a one-equation model near the wall. Washington, D. C: American Institute of Aeronautics and Astronautics, 1991.

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J, Shamroth S., Langley Research Center, and Scientific Research Associates, eds. On the application of a hairpin vortex model of wall turbulence to trailing edge noise prediction. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1985.

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L, Guo K., and United States. National Aeronautics and Space Administration., eds. Application of a two-layer near wall model to fully developed and rotating channel turbulent flows. [Washington, DC: National Aeronautics and Space Administration, 1991.

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L, Guo K., and United States. National Aeronautics and Space Administration., eds. Application of a two-layer near wall model to fully developed and rotating channel turbulent flows. [Washington, DC: National Aeronautics and Space Administration, 1991.

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Book chapters on the topic "Wall layer model"

1

Landahl, M. T. "Near-Wall Model for Boundary Layer Turbulence." In Advances in Turbulence IV, 435–43. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1689-3_69.

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Stocca, V., V. Armenio, and K. R. Sreenivasan. "Improved wall-layer model for forced-convection environmental LES." In ERCOFTAC Series, 137–42. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-2482-2_23.

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Podvin, Bérengère. "A POD-Based Model for the Turbulent Wall Layer." In ERCOFTAC Series, 309–16. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-90-481-9603-6_32.

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MacGillivray, Ian, Alex Skvortsov, and Paul Dylejko. "A Viscoelastic Model of Rough-Wall Boundary-Layer Noise." In Flinovia—Flow Induced Noise and Vibration Issues and Aspects-III, 279–93. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-64807-7_13.

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Arad, Eran, and Micha Wolfshtein. "Two-Scale Double-Layer Model in Wall Bounded Turbulent Flow." In Turbulent Shear Flows 9, 7–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78823-9_2.

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Xiong, Yuqing, Ni Ren, Jizhou Wang, and Maojin Dong. "Model for Atomic Layer Deposition of Aluminumon Inner Wall of Rectangular Pipes Withlarge Length Aspect Ratio." In PRICM, 1967–73. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118792148.ch244.

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Xiong, Yuqing, Ni Ren, Jizhou Wang, and Maojin Dong. "Model for Atomic Layer Deposition of Aluminum on Inner Wall of Rectangular Pipes with Large Length Aspect Ratio." In Proceedings of the 8th Pacific Rim International Congress on Advanced Materials and Processing, 1967–73. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-48764-9_244.

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Chen, ZhenLi, Antoine Devesa, Stefan Hickel, Christian Stemmer, and Nikolaus A. Adams. "A Wall Model Based on Simplified Thin Boundary Layer Equations for Implicit Large Eddy Simulation of Turbulent Channel Flow." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 59–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14243-7_8.

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Spector, Aaron D. "Light-Shining-Through-Walls Experiments." In The Search for Ultralight Bosonic Dark Matter, 255–79. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-95852-7_9.

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AbstractThe light-shining-through-walls (LSW) method of searching for ultralight bosonic dark matter (UBDM) uses lasers and strong dipole magnets to probe the coupling between photons and UBDM in the presence of a magnetic field. Since these experiments take place entirely in the laboratory, they offer a unique opportunity to perform a model independent measurement of this interaction. This involves shining a high-power laser through a magnetic field toward a wall which blocks the light. The interaction between the laser and the magnetic field generates a beam of UBDM that passes through the wall. Beyond the wall is another region of strong magnetic field that reconverts the UBDM back to photons that can then be measured by a single photon detection system. The sensitivity of these kinds of experiments can be improved further by implementing optical cavities before and after the wall to amplify the power of the light propagating through the magnetic fields. This chapter gives an introduction to LSW experiments and discusses a number of interesting challenges associated with the technique.
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Aubry, N., P. Holmes, J. L. Lumley, and E. Stone. "Models for Coherent Structures in the Wall Layer." In Advances in Turbulence, 346–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83045-7_39.

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Conference papers on the topic "Wall layer model"

1

Bond, Ryan, Frederick Blottner, and Thomas Smith. "Validation of a Wall-Layer Model for a Shock-Wave/Boundary-Layer Interaction." In 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-115.

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SMITH, BRIAN. "The k-kl turbulence model and wall layer model for compressible flows." In 21st Fluid Dynamics, Plasma Dynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-1483.

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EVERSMAN, WALTER, and WILLI MOEHRING. "A model of the wall boundary layer for ducted propellers." In 11th Aeroacoustics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1987. http://dx.doi.org/10.2514/6.1987-2742.

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Gao, Jun, Jia-Ning Zhao, Fu-Sheng Gao, Jing Liu, and Zhao-Jun Wang. "Study on a Multi-Layer Analytical Model of Natural Ventilation in Large Single-Cell Buildings." In ASME 2005 International Solar Energy Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/isec2005-76139.

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In large single-cell buildings, a multi-layer analytical model of natural ventilation is presented in this paper. The fluid mechanics of a plume developing in multi-layer environment is investigated based on the plume theory. Using the basic equations for a thermal plume, a mathematical model demonstrating this mechanics is established. Multi-layer thermal stratification of air density or temperature is considered driven by heat flux along wall surfaces. Airflow along vertical walls is modeled with two separate methods, one considering separate wall plumes for each layer and another modeling continuous airflow along the whole wall surface. A multi-layer model is established through balance equations for mass flow rate and heat in each layer. Two separate multi-layer models are presented and then are used to predict the ventilation flow rate and vertical temperature profiles. CFD simulation is also carried out using the RNG κ-ε model, together with an enhanced wall boundary treatment. Results of both present models are compared with those of CFD simulation. Comparisons of the results show that one model using turbulent boundary layer to calculate continuous airflow along vertical walls gives more reasonable and reliable predictions than the other one.
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Satou, Manabu. "Mechanical Fatigue of Wall Surface Caused by Liquid Droplet Impingement." In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25436.

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Pipe wall thinning caused by water or steam flow was observed associated with oxide layer inside of the pipe. Interaction between oxide formation and corrosion or erosion due to the water or steam flow may be an essential phenomenon of the wall thinning. Thinning rate of the wall therefore depends on the formation of the oxide. In the case of wall thinning caused by liquid droplet impingement (LDI) erosion models, mechanical fatigue of the layers is of interest from estimation of the wall thinning rate. In this paper, from a fundamental point of view, to examine parameters related to adhesion strength of the interface in the model equation of material removal from the wall by multiple droplet impingements, evaluation of adhesion strength between piping material and surface oxide layer was carried out using a laser shock method. Several model oxide layers were prepared at elevated temperatures in oxidizing environments on a carbon steel. Results from the measurements of the adhesive strength of the oxide layer formed on the carbon steel at elevated temperatures, the interface had a comparative strength or less of the yield stress of the carbon steel. It was found that reputation of the loading by laser shots up to 104 times did not affect the adhesive strength so far. A kinetic modeling of the wall thinning caused by the LDI was suggested higher cycle mechanical fatigue.
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Johnson, Mark W., and Ali H. Ercan. "A Boundary Layer Transition Model." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-444.

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A new boundary layer transition model is presented which relates the velocity fluctuations near the wall to the formation of turbulent spots. A relationship for the near wall velocity frequency spectra is also established, which indicates an increasing bias towards low frequencies as the skin friction coefficient for the boundary layer decreases. This result suggests that the dependence of transition on the turbulent length scale is greatest at low freestream turbulence levels. This transition model is incorporated in a conventional boundary layer integral technique and is used to predict eight of the ERCOFTAC test cases. Three of these test cases are for nominally zero pressure gradient and the remaining five are for a pressure distribution typical of an aft loaded turbine blade. The model is demonstrated to predict the development of the boundary layer through transition reasonably accurately for all the test cases. The sensitivity of start of transition to the turbulent length scale at low freestream turbulence levels is also demonstrated.
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Stripf, M., A. Schulz, H. J. Bauer, and S. Wittig. "Extended Models for Transitional Rough Wall Boundary Layers With Heat Transfer: Part I—Model Formulations." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50494.

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Two extended models for the calculation of rough wall transitional boundary layers with heat transfer are presented. Both models comprise a new transition onset correlation, which accounts for the effects of roughness height and density, turbulence intensity and wall curvature. In the transition region, an intermittency equation suitable for rough wall boundary layers is used to blend between the laminar and fully turbulent state. Finally, two different submodels for the fully turbulent boundary layer complete the two models. In the first model, termed KS-TLK-T in this paper, a sand roughness approach from Durbin et al., which builds upon a two-layer k-ε-turbulence model, is used for this purpose. The second model, the so-called DEM-TLV-T model, makes use of the discrete-element roughness approach, which was recently combined with a two-layer k-ε-turbulence model by the present authors. The discrete element model will be formulated in a new way suitable for randomly rough topographies. Part I of the paper will provide detailed model formulations as well as a description of the database used for developing the new transition onset correlation. Part II contains a comprehensive validation of the two models, using a variety of test cases with transitional and fully turbulent boundary layers. The validation focuses on heat transfer calculations on both, the suction and the pressure side of modern turbine airfoils. Test cases include extensive experimental investigations on a high-pressure turbine vane with varying surface roughness and turbulence intensity, recently published by the current authors as well as new experimental data from a low-pressure turbine vane. In the majority of cases, the predictions from both models are in good agreement with the experimental data.
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8

SMITH, BRIAN. "A wall layer model for use in Reynolds stress closure turbulence modeling." In 1st National Fluid Dynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1988. http://dx.doi.org/10.2514/6.1988-3579.

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Astrakova, Anna S., Dmitry Yu Kushnir, Nikolay N. Velker, and Gleb V. Dyatlov. "2D electromagnetic inversion using ANN solver for three–layer model with wall." In Недропользование. Горное дело. Направления и технологии поиска, разведки и разработки месторождений полезных ископаемых. Экономика. Геоэкология. Федеральное государственное бюджетное учреждение науки Институт нефтегазовой геологии и геофизики им. А.А. Трофимука Сибирского отделения Российской академии наук, 2020. http://dx.doi.org/10.18303/b978-5-4262-0102-6-2020-031.

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We propose an approach to inversion of induction LWD measurements based on calculation of the synthetic signals by artificial neural networks (ANN) specially trained on some database. The database for ANN training is generated by means of the proprietary 2D solver Pie2d. Validation of the proposed approach and estimation of computation time is performed for the problem of reconstruction of the three–layer model with a wall. Also, we make uncertainty analysis for the reconstructed model parameters for two tool configurations.
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Stripf, M., A. Schulz, H. J. Bauer, and S. Wittig. "Extended Models for Transitional Rough Wall Boundary Layers With Heat Transfer: Part II—Model Validation and Benchmarking." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50495.

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Two extended models for the calculation of rough wall transitional boundary layers with heat transfer are presented. Both models comprise a new transition onset correlation, which accounts for the effects of roughness height and density, turbulence intensity and wall curvature. In the transition region, an intermittency equation suitable for rough wall boundary layers is used to blend between the laminar and fully turbulent state. Finally, two different submodels for the fully turbulent boundary layer complete the two models. In the first model, termed KS-TLK-T in this paper, a sand roughness approach from Durbin et al., which builds upon a two-layer k-ε-turbulence model, is used for this purpose. The second model, the so-called DEM-TLV-T model, makes use of the discrete-element roughness approach, which was recently combined with a two-layer k-ε-turbulence model by the present authors. The discrete element model will be formulated in a new way suitable for randomly rough topographies. Part I of the paper will provide detailed model formulations as well as a description of the database used for developing the new transition onset correlation. Part II contains a comprehensive validation of the two models, using a variety of test cases with transitional and fully turbulent boundary layers. The validation focuses on heat transfer calculations on both, the suction and the pressure side of modern turbine airfoils. Test cases include extensive experimental investigations on a high-pressure turbine vane with varying surface roughness and turbulence intensity, recently published by the current authors as well as new experimental data from a low-pressure turbine vane. In the majority of cases, the predictions from both models are in good agreement with the experimental data.
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Reports on the topic "Wall layer model"

1

Peloquin, Mark S. Direct Measurement of the Mode O Turbulent Boundary Layer Wall Pressure and Wall Shear Stress Spectra Using Air-Backed and Oil-Filled Multichannel Wavenumber Filters. Fort Belvoir, VA: Defense Technical Information Center, May 1999. http://dx.doi.org/10.21236/ada371294.

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Stephen, Sharon O., and Vipin Michael. Effects of Passive Porous Walls on the First Mode of Hypersonic Boundary Layers Over a Sharp Cone. Fort Belvoir, VA: Defense Technical Information Center, January 2013. http://dx.doi.org/10.21236/ada581526.

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Brenan, J. M., K. Woods, J. E. Mungall, and R. Weston. Origin of chromitites in the Esker Intrusive Complex, Ring of Fire Intrusive Suite, as revealed by chromite trace element chemistry and simple crystallization models. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328981.

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To better constrain the origin of the chromitites associated with the Esker Intrusive Complex (EIC) of the Ring of Fire Intrusive Suite (RoFIS), a total of 50 chromite-bearing samples from the Black Thor, Big Daddy, Blackbird, and Black Label chromite deposits have been analysed for major and trace elements. The samples represent three textural groups, as defined by the relative abundance of cumulate silicate phases and chromite. To provide deposit-specific partition coefficients for modeling, we also report on the results of laboratory experiments to measure olivine- and chromite-melt partitioning of V and Ga, which are two elements readily detectable in the chromites analysed. Comparison of the Cr/Cr+Al and Fe/Fe+Mg of the EIC chromites and compositions from previous experimental studies indicates overlap in Cr/Cr+Al between the natural samples and experiments done at >1400oC, but significant offset of the natural samples to higher Fe/Fe+Mg. This is interpreted to be the result of subsolidus Fe-Mg exchange between chromite and the silicate matrix. However, little change in Cr/Cr+Al from magmatic values, owing to the lack of an exchangeable reservoir for these elements. A comparison of the composition of the EIC chromites and a subset of samples from other tectonic settings reveals a strong similarity to chromites from the similarly-aged Munro Township komatiites. Partition coefficients for V and Ga are consistent with past results in that both elements are compatible in chromite (DV = 2-4; DGa ~ 3), and incompatible in olivine (DV = 0.01-0.14; DGa ~ 0.02), with values for V increasing with decreasing fO2. Simple fractional crystallization models that use these partition coefficients are developed that monitor the change in element behaviour based on the relative proportions of olivine to chromite in the crystallizing assemblage; from 'normal' cotectic proportions involving predominantly olivine, to chromite-only crystallization. Comparison of models to the natural chromite V-Ga array suggests that the overall positive correlation between these two elements is consistent with chromite formed from a Munro Township-like komatiitic magma crystallizing olivine and chromite in 'normal' cotectic proportions, with no evidence of the strong depletion in these elements expected for chromite-only crystallization. The V-Ga array can be explained if the initial magma responsible for chromite formation is slightly reduced with respect to the FMQ oxygen buffer (~FMQ- 0.5), and has assimilated up to ~20% of wall-rock banded iron formation or granodiorite. Despite the evidence for contamination, results indicate that the EIC chromitites crystallized from 'normal' cotectic proportions of olivine to chromite, and therefore no specific causative link is made between contamination and chromitite formation. Instead, the development of near- monomineralic chromite layers likely involves the preferential removal of olivine relative to chromite by physical segregation during magma flow. As suggested for some other chromitite-forming systems, the specific fluid dynamic regime during magma emplacement may therefore be responsible for crystal sorting and chromite accumulation.
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4

NUMERICAL SIMULATION ANALYSIS OF TEMPERATURE FIELD OF BOX-TYPE COMPOSITE WALL. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.321.

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The spatial and temporal characteristics of the internal temperature field of the box-type composite wall have great significance to high temperature mechanical response and fire resistance performance of composite wall subjected to fire. A series of assumptions for the simplified model were made after determining the influence of various thermal parameters, the boundary conditions of surface and the contact conditions. And the finite element software(ABAQUS) was used to establish the temperature field analysis model to conduct nonlinear transient temperature response analysis, then the validity of the model was verified by relevant test results. On this basis, the distribution of temperature field during the whole process and its key measuring points under fire are analyzed, and the parameters of each component are researched. The results show that the thickness of rock wool, the type, the thickness and number of layers of cladding plates have obvious influence on the temperature field distribution inside the composite wall, and other factors have little effect. According to the analysis results, the fire-resistant design idea of the composite wall and the temperature prediction formulas of the key temperature-control point are proposed, which provide the basis for the application of the boxtype steel structure system.
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