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Добірка наукової літератури з теми "Turbulence Closures"

Автор: Grafiati

Опубліковано: 11 березня 2023

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Статті в журналах з теми "Turbulence Closures"

Pearson, Brodie C., Alan L. M. Grant, and Jeff A. Polton. "Pressure–strain terms in Langmuir turbulence." Journal of Fluid Mechanics 880 (October 7, 2019): 5–31. http://dx.doi.org/10.1017/jfm.2019.701.

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This study investigates the pressure–strain tensor ($\unicode[STIX]{x1D72B}$) in Langmuir turbulence. The pressure–strain tensor is determined from large-eddy simulations (LES), and is partitioned into components associated with the mean current shear (rapid), the Stokes shear and the turbulent–turbulent (slow) interactions. The rapid component can be parameterized using existing closure models, although the coefficients in the closure models are particular to Langmuir turbulence. A closure model for the Stokes component is proposed, and it is shown to agree with results from the LES. The slow component of $\unicode[STIX]{x1D72B}$ does not agree with existing ‘return-to-isotropy’ closure models for five of the six components of the Reynolds stress tensor, and a new closure model is proposed that accounts for these deviations which vary systematically with Langmuir number, $La_{t}$, and depth. The implications of these results for second- and first-order closures of Langmuir turbulence are discussed.

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Larsen, Bjarke Eltard, and David R. Fuhrman. "On the over-production of turbulence beneath surface waves in Reynolds-averaged Navier–Stokes models." Journal of Fluid Mechanics 853 (August 23, 2018): 419–60. http://dx.doi.org/10.1017/jfm.2018.577.

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In previous computational fluid dynamics studies of breaking waves, there has been a marked tendency to severely over-estimate turbulence levels, both pre- and post-breaking. This problem is most likely related to the previously described (though not sufficiently well recognized) conditional instability of widely used turbulence models when used to close Reynolds-averaged Navier–Stokes (RANS) equations in regions of nearly potential flow with finite strain, resulting in exponential growth of the turbulent kinetic energy and eddy viscosity. While this problem has been known for nearly 20 years, a suitable and fundamentally sound solution has yet to be developed. In this work it is demonstrated that virtually all commonly used two-equation turbulence closure models are unconditionally, rather than conditionally, unstable in such regions. A new formulation of the $k$–$\unicode[STIX]{x1D714}$ closure is developed which elegantly stabilizes the model in nearly potential flow regions, with modifications remaining passive in sheared flow regions, thus solving this long-standing problem. Computed results involving non-breaking waves demonstrate that the new stabilized closure enables nearly constant form wave propagation over long durations, avoiding the exponential growth of the eddy viscosity and inevitable wave decay exhibited by standard closures. Additional applications on breaking waves demonstrate that the new stabilized model avoids the unphysical generation of pre-breaking turbulence which widely plagues existing closures. The new model is demonstrated to be capable of predicting accurate pre- and post-breaking surface elevations, as well as turbulence and undertow velocity profiles, especially during transition from pre-breaking to the outer surf zone. Results in the inner surf zone are similar to standard closures. Similar methods for formally stabilizing other widely used closure models ($k$–$\unicode[STIX]{x1D714}$ and $k$–$\unicode[STIX]{x1D700}$ variants) are likewise developed, and it is recommended that these be utilized in future RANS simulations of surface waves. (In the above $k$ is the turbulent kinetic energy density, $\unicode[STIX]{x1D714}$ is the specific dissipation rate, and $\unicode[STIX]{x1D700}$ is the dissipation.)

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Gladskikh, Daria, Lev Ostrovsky, Yuliya Troitskaya, Irina Soustova, and Evgeny Mortikov. "Turbulent Transport in a Stratified Shear Flow." Journal of Marine Science and Engineering 11, no. 1 (January 6, 2023): 136. http://dx.doi.org/10.3390/jmse11010136.

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Within the framework of the theory of unsteady turbulent flows in a stratified fluid, a new parameterization of the turbulent Prandtl number is proposed. The parameterization is included in the k-ε-closure and used within the three-dimensional model of thermohydrodynamics of an enclosed water body where density distribution includes pycnocline. This allows us to describe turbulence in a stratified shear flow without the restrictions associated with the gradient Richardson number and justify the choice of closure constants. Numerical experiments, where the downward penetration of turbulence was considered, confirm the advantage of the developed approach in describing the effects neglected in the classical closures.

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Mauritsen, Thorsten, Gunilla Svensson, Sergej S. Zilitinkevich, Igor Esau, Leif Enger, and Branko Grisogono. "A Total Turbulent Energy Closure Model for Neutrally and Stably Stratified Atmospheric Boundary Layers." Journal of the Atmospheric Sciences 64, no. 11 (November 1, 2007): 4113–26. http://dx.doi.org/10.1175/2007jas2294.1.

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Abstract This paper presents a turbulence closure for neutral and stratified atmospheric conditions. The closure is based on the concept of the total turbulent energy. The total turbulent energy is the sum of the turbulent kinetic energy and turbulent potential energy, which is proportional to the potential temperature variance. The closure uses recent observational findings to take into account the mean flow stability. These observations indicate that turbulent transfer of heat and momentum behaves differently under very stable stratification. Whereas the turbulent heat flux tends toward zero beyond a certain stability limit, the turbulent stress stays finite. The suggested scheme avoids the problem of self-correlation. The latter is an improvement over the widely used Monin–Obukhov-based closures. Numerous large-eddy simulations, including a wide range of neutral and stably stratified cases, are used to estimate likely values of two free constants. In a benchmark case the new turbulence closure performs indistinguishably from independent large-eddy simulations.

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Harcourt, Ramsey R. "An Improved Second-Moment Closure Model of Langmuir Turbulence." Journal of Physical Oceanography 45, no. 1 (January 2015): 84–103. http://dx.doi.org/10.1175/jpo-d-14-0046.1.

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AbstractA prior second-moment closure (SMC) model of Langmuir turbulence in the upper ocean is modified by introduction of inhomogeneous pressure–strain rate and pressure–scalar gradient closures that are similar to the high Reynolds number, near-wall treatments for solid wall boundaries. This repairs several near-surface defects in the algebraic Reynolds stress model (ARSM) of the prior SMC by redirecting Craik–Leibovich (CL) vortex force production of turbulent kinetic energy out of the surface-normal vertical component and into a horizontal one, with an associated reduction in near-surface CL production of vertical momentum flux. A surface-proximity function introduces a new closure parameter that is tuned to previous results from large-eddy simulations (LES), and a numerical SMC model based on stability functions from the new ARSM produces improved comparisons with mean profiles of momentum and TKE components from steady-state LES results forced by aligned wind and waves. An examination of higher-order quasi-homogeneous closures and a numerical simulation of Langmuir turbulence away from the boundaries both show the near-surface inhomogeneous closure to be both necessary for consistency and preferable for simplicity.

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Mortikov, E. V., A. V. Glazunov, A. V. Debolskiy, V. N. Lykosov, and S. S. Zilitinkevich. "On the modelling of the dissipation rate of turbulent kinetic energy." Доклады Академии наук 489, no. 4 (December 10, 2019): 414–18. http://dx.doi.org/10.31857/s0869-56524894414-418.

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We consider a relaxation equation for turbulence wavenumber for use in semi-empirical turbulence closures. It is shown that the well-known phenomenological equation for the dissipation rate of turbulent kinetic energy can be related to this relaxation equation as a close approximation of the latter for stably stratified quasi-stationary flows. The proposed approach allows for more physically found definition of the empirical constants and improvement of atmospheric and oceanic boundary layer turbulence closures by using direct numerical and large eddy simulation data to define equilibrium states and relaxation mechanisms.

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GODEFERD, F. S., C. CAMBON, and J. F. SCOTT. "Two-point closures and their applications: report on a workshop." Journal of Fluid Mechanics 436 (June 10, 2001): 393–407. http://dx.doi.org/10.1017/s0022112001004359.

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This international scientific workshop was organized in Lyon, France, from 10 to 12 May 2000. Its focus was ‘Two-point closures and their applications’, with the understanding that the analysis and design of such models requires expert knowledge coming from a wide range of areas in turbulence research, e.g. experiments, numerical simulations, asymptotic models, etc.In the global challenge of turbulence modelling, two-point closures prove useful in many ways. Two-point correlations and spectra are useful measures of the distortion of the eddy structure of turbulence by stratification, large-scale strains, rotation, etc. In some cases, e.g. near boundaries, spectra can be drastically changed. In addition to the accurate characterization of turbulence, the explicit computation of two-point correlations or spectra shows how the internal dynamics of the various scales of motion are affected by such distortion, especially the cascade process on which the production/dissipation relationship depends. Distortion can be the cause of large departures from isotropic homogeneous turbulence, pulling turbulent flows far away from the local equilibrium that is often assumed. A rather weak departure can allow the use of linearized theories such as rapid distortion theory, for the applicability of which rational bounds may be estimated by comparisons with weakly nonlinear calculations. A different approach is necessary when dealing with larger departures, for instance due to growth of instabilities. In that case new physical or similarity arguments have to be employed to obtain a satisfactory description of the modification to the cascade process, which can even undergo reversal in the limit when three-dimensional turbulence becomes two-dimensional. Of course, significant changes in spectra have direct implications for one-point measures of turbulence – which can be explicitly derived by integration of two-point correlations – used in most industrial closure schemes. Such one-point models consequently need to be adapted when turbulence is strongly affected by distortion.

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Yang, S. L., B. D. Peschke, and K. Hanjalic. "Second-Moment Closure Model for IC Engine Flow Simulation Using Kiva Code1." Journal of Engineering for Gas Turbines and Power 122, no. 2 (August 31, 1999): 355–63. http://dx.doi.org/10.1115/1.483213.

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The flow and turbulence in an IC engine cylinder were studied using the SSG variant of the Reynolds stress turbulence closure model. In-cylinder turbulence is characterized by strong turbulence anisotropy and flow rotation, which aid in air-fuel mixing. It is argued that solving the differential transport equations for each turbulent stress tensor component, as implied by second-moment closures, can better reproduce stress anisotropy and effects of rotation, than with eddy-viscosity models. Therefore, a Reynolds stress model that can meet the demands of in-cylinder flows was incorporated into an engine flow solver. The solver and SSG turbulence model were first successfully tested with two different validation cases. Finally, simulations were applied to IC-engine like geometries. The results showed that the Reynolds stress model predicted additional flow structures and yielded less diffusive profiles than those predicted by an eddy-viscosity model. [S0742-4795(00)00101-0]

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Pacciani, Roberto, Michele Marconcini, Francesco Bertini, Simone Rosa Taddei, Ennio Spano, Yaomin Zhao, Harshal D. Akolekar, Richard D. Sandberg, and Andrea Arnone. "Assessment of Machine-Learned Turbulence Models Trained for Improved Wake-Mixing in Low-Pressure Turbine Flows." Energies 14, no. 24 (December 10, 2021): 8327. http://dx.doi.org/10.3390/en14248327.

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This paper presents an assessment of machine-learned turbulence closures, trained for improving wake-mixing prediction, in the context of LPT flows. To this end, a three-dimensional cascade of industrial relevance, representative of modern LPT bladings, was analyzed, using a state-of-the-art RANS approach, over a wide range of Reynolds numbers. To ensure that the wake originates from correctly reproduced blade boundary-layers, preliminary analyses were carried out to check for the impact of transition closures, and the best-performing numerical setup was identified. Two different machine-learned closures were considered. They were applied in a prescribed region downstream of the blade trailing edge, excluding the endwall boundary layers. A sensitivity analysis to the distance from the trailing edge at which they are activated is presented in order to assess their applicability to the whole wake affected portion of the computational domain and outside the training region. It is shown how the best-performing closure can provide results in very good agreement with the experimental data in terms of wake loss profiles, with substantial improvements relative to traditional turbulence models. The discussed analysis also provides guidelines for defining an automated zonal application of turbulence closures trained for wake-mixing predictions.

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Frederiksen, Jorgen S., and Terence J. O’Kane. "Statistical Dynamics of Mean Flows Interacting with Rossby Waves, Turbulence, and Topography." Fluids 7, no. 6 (June 9, 2022): 200. http://dx.doi.org/10.3390/fluids7060200.

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Abridged statistical dynamical closures, for the interaction of two-dimensional inhomogeneous turbulent flows with topography and Rossby waves on a beta–plane, are formulated from the Quasi-diagonal Direct Interaction Approximation (QDIA) theory, at various levels of simplification. An abridged QDIA is obtained by replacing the mean field trajectory, from initial-time to current-time, in the time history integrals of the non-Markovian closure by the current-time mean field. Three variants of Markovian Inhomogeneous Closures (MICs) are formulated from the abridged QDIA by using the current-time, prior-time, and correlation fluctuation dissipation theorems. The abridged MICs have auxiliary prognostic equations for relaxation functions that approximate the information in the time history integrals of the QDIA. The abridged MICs are more efficient than the QDIA for long integrations with just two relaxation functions required. The efficacy of the closures is studied in 10-day simulations with an easterly large-scale flow impinging on a conical mountain to generate rapidly growing Rossby waves in a turbulent environment. The abridged closures closely agree with the statistics of large ensembles of direct numerical simulations for the mean and transients. An Eddy Damped Markovian Inhomogeneous Closure (EDMIC), with analytical relaxation functions, which generalizes the Eddy Dampened Quasi Normal Markovian (EDQNM) to inhomogeneous flows, is formulated and shown to be realizable under the same circumstances as the homogeneous EDQNM.

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Дисертації з теми "Turbulence Closures"

Weatheritt, Jack. "The development of data driven approaches to further turbulence closures." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/388092/.

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The closure of turbulence models at all levels of fidelity is addressed, using unconventional methods that rely on data. The purpose of the thesis is not to present new models of turbulence per se, but rather the main focus is to develop the methodologies that created them. The main tool, Gene Expression Programming, is a versatile evolutionary algorithm. Implementations of the algorithm allow for symbolic regression of scalar and tensor fields and the clustering of data sets. The last two applications are novel algorithms. Scalar field regression is used to construct length scale damping functions for Hybrid RANS/LES. Direct Numerical Simulation snapshots are filtered to mimic Hybrid RANS/LES flow fields and from this new damping functions are created. Two closures are constructed, one from data in a turbulent pipe and another from slices along the classic backward facing step geometry. The new closures are tested for a range of separated flow applications. Tests alongside existing closures of the same class show that both new methods adapt to the local mesh resolution and turbulence level at least as well as other hybrid closures. Tensor field regression is used to construct non-linear stress-strain relationships in a Reynolds-Averaged Navier-Stokes framework. A common two-equation model is modified by including a further term that accounts for extra anisotropy with respect to the Boussinesq approximation. This model term, regressed from time averaged Direct Numerical Simulation data, turns the linear closure into an Explicit Algebraic Stress Model. The training data is taken from the reverse flow region behind a backward facing step. When applied to the classic periodic hills case, the subclass of models generated are found to greatly improve the prediction with respect to the linear model. A subclass of models is created in order to test the ability of the evolutionary algorithm. The deviation from the periodic hills reference data is quantified and used as a metric for model performance. The key finding is that improved performance of the Gene Expression Programming framework corresponded to improved prediction of the periodic hills. The final application of Gene Expression Programming, the clustering of datasets, is used to group Reynolds stress structures into distinct types. Firstly, reference Direct Numerical Simulation data obtained in a turbulent channel is categorised into six distinct groups. These groups are then compared to structures from Hybrid RANS/LES. These groups help to show that Hybrid RANS/LES structures do not correctly capture the near-wall cycle of turbulence. Instead there is an artificial cycle that is characterised by an incorrect buffer layer, defined by tall, long and thin structures. Further, streaky structures lie on the interface between Reynolds-Averaged Navier-Stokes and Large Eddy Simulation. These structures are free to move in the vertical direction and seriously contribute to discrepancies in the second order statistics.

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Ilicak, Mehmet. "Development and Applications of Second-Order Turbulence Closures for Mixing in Overflows." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/225.

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Mixing between overflows and ambient water masses is a crucial problem of deep-water formation in the down-welling branch of the meridional overturning circulation of the ocean. In this dissertation work, performance of second-order turbulence closures in reproducing mixing of overflows is investigated within both hydrostatic and non-hydrostatic models. First, a 2D non-hydrostatic model is developed to simulate the Red Sea overflow in the northern channel. The model results are compared to the Red Sea Outflow Experiment. It is found that the experiments without sub-grid scale models cannot reproduce the basic structure of the overflow. The k-ε model yields unrealistically thick bottom layer (BL) and interfacial layer (IL). A new technique so-called very large eddy simulation (VLES) which allows the use of k-ε model in non-hydrostatic models is also employed. It is found that VLES results the most realistic reproduction of the observations. Furthermore, the non-hydrostatic model is improved by introducing laterally average terms, so the model can simulate the constrictions not only in the z-direction but also in the y-direction. Observational data from the Bosphorus Strait is employed to test the spatially average 2D non-hydrostatic model (SAM) in a realistic application. The simulations from SAM with a simple Smagorinsky type closure appear to be excessively diffusive and noisy. We show that SAM can benefit significantly from VLES turbulence closures. Second, the performance of different second-order turbulence closures is extensively tested in a hydrostatic model. Four different two-equation turbulence closures (k-&epsilon, k-&omega, Mellor-Yamada 2.5 (MY2.5) and a modified version of k- &epsilon) and K-Profile Parameterization (KPP) are selected for the comparison of 3D numerical simulations of the Red Sea overflow. All two-equation turbulence models are able to capture the vertical structure of the Red Sea overflow consisting of the BL and IL. MY2.5 with Galperin stability functions produce the largest salinity deviations from the observations along two sections across the overflow and the modified k-&epsilon exhibits the smallest deviations. The rest of the closures fall in between, showing deviations similar to one another. Four different closures (k- &epsilon, k-&omega, MY2.5KC and KPP) are also employed to simulate the Mediterranean outflow. The numerical results are compared with observational data obtained in the 1988 Gulf of Cadiz Expedition. The simulations with two-equation closures reproduce the observed properties of the overflow quite well, especially the evolution of temperature and salinity profiles. The vertically integrated turbulent salt flux displays that the overflow goes under significant mixing outside the west edge of the Strait of Gibraltar. The volume transport and water properties of the outflow are modified significantly in the first 50 km after the overflow exits the strait. The k-&epsilon and k-&omega cases show the best agreement with the observations. Finally, the interaction between the Red Sea overflow and Gulf of Aden (GOA) eddies has been investigated. It is found that the overflow is mainly transported by the undercurrent at the west side of the gulf. The transport of the overflow is episodic depending strength and location of GOA eddies. The most crucial finding is that the Red Sea overflow leaves the Gulf of Aden in patches rather than one steady current. Multiple GOA eddies induce lateral stirring, thus diapycnal mixing of the Red Sea outflow.

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Shen, Bing. "The application of second-moment turbulence closures to 2D pulverised-coal flames." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420722.

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Pascau, Benito Antonio. "The application of second order turbulence closures to isothermal and combusting swirling flows." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46491.

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Marquis, Andrew James. "The application of high order convection approximations and second order turbulence closures to recirculating flows." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38095.

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Kirwin, P. J. "Investigation and development of two-equation turbulence closures with reference to mixed convection in vertical pipes." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525619.

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Rasam, Amin. "Anisotropy-resolving subgrid-scale modelling using explicit algebraic closures for large eddy simulation." Doctoral thesis, KTH, Turbulens, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142401.

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The present thesis deals with the development and performance analysis ofanisotropy-resolving models for the small, unresolved scales (”sub-grid scales”,SGS) in large eddy simulation (LES). The models are characterised by a descriptionof anisotropy by use of explicit algebraic models for both the subgridscale(SGS) stress tensor (EASSM) and SGS scalar flux vector (EASSFM). Extensiveanalysis of the performance of the explicit algebraic SGS stress model(EASSM) has been performed and comparisons made with the conventionalisotropic dynamic eddy viscosity model (DEVM). The studies include LES ofplane channel flow at relatively high Reynolds numbers and a wide range ofresolutions and LES of separated flow in a channel with streamwise periodichill-shaped constrictions (periodic hill flow) at coarse resolutions. The formersimulations were carried out with a pseudo-spectral Navier–Stokes solver, whilethe latter simulations were computed with a second-order, finite-volume basedsolver for unstructured grids. The LESs of channel flow demonstrate that theEASSM gives a good description of the SGS anisotropy, which in turn gives ahigh degree of resolution independence, contrary to the behaviour of LES predictionsusing the DEVM. LESs of periodic hill flow showed that the EASSMalso for this case gives significantly better flow predictions than the DEVM.In particular, the reattachment point was much better predicted with the EASSMand reasonably well predicted even at very coarse resolutions, where theDEVM is unable to predict a proper flow separation.The explicit algebraic SGS scalar flux model (EASSFM) is developed toimprove LES predictions of complex anisotropic flows with turbulent heat ormass transfer, and can be described as a nonlinear tensor eddy diffusivity model.It was tested in combination with the EASSM for the SGS stresses, and itsperformance was compared to the conventional dynamic eddy diffusivity model(DEDM) in channel flow with and without system rotation in the wall-normaldirection. EASSM and EASSFM gave predictions of high accuracy for meanvelocity and mean scalar fields, as well as stresses and scalar flux components.An extension of the EASSM and EASSFM, based on stochastic differentialequations of Langevin type, gave further improvements. In contrast to conventionalmodels, these extended models are able to describe intermittent transferof energy from the small, unresolved scales, to the resolved large ones.The present study shows that the EASSM/EASSFM gives a clear improvementof LES of wall-bounded flows in simple, as well as in complex geometriesin comparison with simpler SGS models. This is also shown to hold for a widerange of resolutions and is particularly accentuated for coarse resolution. The advantages are also demonstrated both for high-order numerical schemes andfor solvers using low-order finite volume methods. The models therefore havea clear potential for more applied computational fluid mechanics.

QC 20140304

Explicit algebraic sub-grid scale modelling for large-eddy simulations

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Sotgiu, Corrado [Verfasser]. "An investigation of anisotropic RANS turbulence closures for the heat transfer prediction in ribbed cooling passages / Corrado Sotgiu." München : Verlag Dr. Hut, 2021. http://d-nb.info/123842273X/34.

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Nenja, A. "Turbulence closure models." Thesis, Вид-во СумДУ, 2005. http://essuir.sumdu.edu.ua/handle/123456789/19821.

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Zonato, Andrea. "Modeling the Urban Boundary Layer in Complex Terrain." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/323566.

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In this work, various topics regarding (urban) boundary simulations for a city situated in the alps will be discussed. First of all, we will present novel parameterization adopted to take into account the effect of mitigation strategies, such as rooftop Photovoltaic Panels and Green Roofs, on the urban environment, and their effect on average temperature and energy consumption by buildings. Secondly, a new turbulence closure, that adopts a diagnostic equation for dissipation rate, and then independent on mixing length scales, will be introduced. The new turbulence closure, implemented into the WRF model, has been coupled with multi-layer urban parameterization schemes and compared with high-resolution CFD and LES simulations.

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Книги з теми "Turbulence Closures"

1930-, Lumley John L., and Lewis Research Center. Institute for Computational Mechanics in Propulsion., eds. Applications of direct numerical simulation of turbulence in second order closures. Cleveland, Ohio: Lewis Research Center, Institute for Computational Mechanics in Propulsion, 1995.

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So, Ronald M. C. A review of near-wall Reynolds-stress closures. Hampton, Va: Langley Research Center, 1991.

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Institute for Computer Applications in Science and Engineering. and United States. National Aeronautics and Space Administration., eds. Some results relevant to statistical closures for compressible turbulence. Hampton, VA: Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, 1998.

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Ridha, Abid, Blaisdell Gregory A, and Institute for Computer Applications in Science and Engineering., eds. On the consistency of Reynolds stress turbulence closures with hydrodynamic stability theory. Hampton, VA: Institute for Computer Applications in Science and Engineering, NASA Langley Research Center, 1995.

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Speziale, Charles G. New results on the realizability of Reynolds stress turbulence closures. Hampton, Va: Institute for Computer Applications in Science and Engineeering, 1993.

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Ridha, Abid, Durbin Paul A, and Langley Research Center, eds. New results on the realizability of Reynolds stress turbulence closures. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1993.

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Speziale, Charles G. Analytical methods for the development of Reynolds stress closures in turbulence. Hampton, Va: Institute for Computer Applications in Science and Engineering, 1990.

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Speziale, Charles G. Evaluation of Reynolds stress turbulence closures in compressible homogenous shear flow. Hampton, Va: Institute for Computer Applications in Science and Engineering, 1994.

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1948-, Speziale C. G., and Langley Research Center, eds. Predicting equilibrium states with Reynolds stress closures in channel flow and homogeneous shear flow. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1992.

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Частини книг з теми "Turbulence Closures"

Pope, S. B. "Mapping Closures for Turbulent Mixing and Reaction." In Studies in Turbulence, 152–53. New York, NY: Springer New York, 1992. http://dx.doi.org/10.1007/978-1-4612-2792-2_9.

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Savill, A. M. "One-Point Closures Applied to Transition." In Turbulence and Transition Modelling, 233–68. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8666-5_6.

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Herring, Jackson R., and Robert M. Kerr. "Small-Scale Structures in Turbulence: Their Implications for Turbulence Closures." In New Approaches and Concepts in Turbulence, 367–76. Basel: Birkhäuser Basel, 1993. http://dx.doi.org/10.1007/978-3-0348-8585-0_21.

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Hanjalić, K., and S. Jakirlić. "A Model of Stress Dissipation in Second-Moment Closures." In Advances in Turbulence IV, 513–18. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1689-3_80.

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Shih, T. H. "Constitutive Relations and Realizability of Single-Point Turbulence Closures." In Turbulence and Transition Modelling, 155–92. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8666-5_4.

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Leschziner, M. A. "The Computation of Turbulent Engineering Flows with Turbulence-Transport Closures." In Advanced Turbulent Flow Computations, 209–77. Vienna: Springer Vienna, 2000. http://dx.doi.org/10.1007/978-3-7091-2590-8_5.

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Ristorcelli, J. R. "Some Results Relevant to Statistical Closures for Compressible Turbulence." In ICASE/LaRC Interdisciplinary Series in Science and Engineering, 297–327. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4724-8_17.

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Leschziner, Michael. "Modelling Separation from Curved Surfaces with Anisotropy-Resolving Turbulence Closures." In Modelling Fluid Flow, 23–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-08797-8_2.

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Ventikos, Y., F. Sotiropoulos, and V. C. Patel. "Modelling Complex Draft-Tube Flows using Near-Wall Turbulence Closures." In Hydraulic Machinery and Cavitation, 140–49. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-010-9385-9_13.

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Hallbäck, Magnus, Torbjörn Sjögren, and Arne V. Johansson. "Modelling of Intercomponent Transfer in Reynolds Stress Closures of Homogeneous Turbulence." In Turbulent Shear Flows 9, 21–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78823-9_3.

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Тези доповідей конференцій з теми "Turbulence Closures"

McCOMB, DAVID. "TWO-POINT TURBULENCE CLOSURES REVISITED." In Proceedings of the COSNet/CSIRO Workshop on Turbulence and Coherent Structures in Fluids, Plasmas and Nonlinear Media. WORLD SCIENTIFIC, 2007. http://dx.doi.org/10.1142/9789812771025_0013.

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Bertoglio, Jean Pierre. "TWO-POINT CLOSURES AND TURBULENCE MODELING." In Third Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2003. http://dx.doi.org/10.1615/tsfp3.1440.

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FREDERIKSEN, JORGEN S., and TERENCE J. O'KANE. "TURBULENCE CLOSURES AND SUBGRID-SCALE PARAMETERIZATIONS." In Proceedings of the COSNet/CSIRO Workshop on Turbulence and Coherent Structures in Fluids, Plasmas and Nonlinear Media. WORLD SCIENTIFIC, 2007. http://dx.doi.org/10.1142/9789812771025_0014.

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Duraisamy, Karthikeyan. "Informing Turbulence Closures With Computational and Experimental Data." In 54th AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-1556.

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Taylor, Lafayette, Ramesh Pankajakshan, W. R. Briley, and David Whitfield. "Scalable Parallel Implicit Algorithm for Advanced Turbulence Closures." In 43rd AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2005. http://dx.doi.org/10.2514/6.2005-876.

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Banerjee, Tania, Jaideep Ray, Matthew F. Barone, and Stefan P. Domino. "Qualifying Training Datasets for Data-Driven Turbulence Closures." In AIAA AVIATION 2022 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2022. http://dx.doi.org/10.2514/6.2022-3979.

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Lav, Chitrarth, and Richard D. Sandberg. "Unsteady Simulations of a Trailing-Edge Slot Using Machine-Learnt Turbulence Stress and Heat-Flux Closures." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14398.

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Abstract The trailing edge slot is a canonical representation of the pressure-side bleed flow encountered in high pressure turbines. Predicting the flow and temperature downstream of the slot exit remains challenging for RANS and URANS, with both significantly overpredicting the adiabatic wall-effectiveness. This over-prediction is attributable to the incorrect mixing prediction in cases where the vortex shedding is present. In case of RANS the modelling error is rooted in not properly accounting for the shedding scales while in URANS the closures account for the shedding scales twice, once by resolving the shedding and twice with the model for all the scales. Here, we present an approach which models only the stochastic scales that contribute to turbulence while resolving the scales that do not, i.e. scales considered as contributing to deterministic unsteadiness. The model for the stochastic scales is obtained through a data-driven machine learning algorithm, which produces a bespoke turbulence closure model from a high-fidelity dataset. We use the best closure (blowing ratio of 1.26) for the anisotropy obtained in the a priori study of Lav, Philip & Sandberg [A New Data-Driven Turbulence Model Framework for Unsteady Flows Applied to Wall-Jet and Wall-Wake Flows, 2019] and conduct compressible URANS calculations. In the first stage, the energy equation is solved utilising the standard gradient diffusion hypothesis for the heat-flux closure. In the second stage, we develop a bespoke heat-flux closure using the machine-learning approach for the stochastic heat-flux components only. Subsequently, calculations are performed using the machine-learnt closures for the heat-flux and the anisotropy together. Finally, the generalisability of the developed closures is evaluated by testing them on additional blowing ratios of 0.86 and 1.07. The machine-learnt closures developed specifically for URANS calculations show significantly improved predictions for the adiabatic wall-effectiveness across the different cases.

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Rubinstein, Robert, and Sharath Girimaji. "Two-point turbulence closures applied to variable resolution modeling." In 6th AIAA Theoretical Fluid Mechanics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-3470.

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Barakos, G., and Dimitris Drikakis. "NUMERICAL SIMULATION OF TRANSONIC BUFFET FLOWS USING VARIOUS TURBULENCE CLOSURES." In First Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 1999. http://dx.doi.org/10.1615/tsfp1.1590.

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Lav, Chitrarth, Jimmy Philip, and Richard D. Sandberg. "A New Data-Driven Turbulence Model Framework for Unsteady Flows Applied to Wall-Jet and Wall-Wake Flows." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90179.

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Abstract The unsteady flow prediction for turbomachinery applications relies heavily on unsteady RANS (URANS). For flows that exhibit vortex shedding, such as the wall-jet/wake flows considered in this study, URANS is unable to predict the correct momentum mixing with sufficient accuracy. We suggest a novel framework to improve that prediction, whereby the deterministic scales associated with vortex shedding are resolved while the stochastic scales of pure turbulence are modelled. The framework first separates the stochastic from the deterministic length scales and then develops a bespoke turbulence closure for the stochastic scales using a data-driven machine-learning algorithm. The novelty of the method lies in the use of machine-learning to develop closures tailored to URANS calculations. For the walljet/wake flow, three different mass flow ratios (0.86, 1.07 and 1.26) have been considered and a high-fidelity dataset of the idealised geometry is utilised for the sake of model development. This study serves as an a priori analysis, where the closures obtained from the machine-learning algorithm are evaluated before their implementation in URANS. The analysis looks at the impact of using all length scales versus the stochastic scales for closure development, and the impact of the extent of the spatial domain for developing the closure. It is found that a two-layer approach, using bespoke trained models for the near wall and the jet/wake regions, produce the best results. Finally, the generalisability of the developed closures is also evaluated by applying a given closure developed using a particular mass flow ratio to the other cases.

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Звіти організацій з теми "Turbulence Closures"

Tanny, Josef, Gabriel Katul, Shabtai Cohen, and Meir Teitel. Application of Turbulent Transport Techniques for Quantifying Whole Canopy Evapotranspiration in Large Agricultural Structures: Measurement and Theory. United States Department of Agriculture, January 2011. http://dx.doi.org/10.32747/2011.7592121.bard.

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Original objectives and revisions The original objectives of this research, as stated in the approved proposal were: 1. To establish guidelines for the use of turbulent transport techniques as accurate and reliable tool for continuous measurements of whole canopy ET and other scalar fluxes (e.g. heat and CO2) in large agricultural structures. 2. To conduct a detailed experimental study of flow patterns and turbulence characteristics in agricultural structures. 3. To derive theoretical models of air flow and scalar fluxes in agricultural structures that can guide the interpretation of TT measurements for a wide range of conditions. All the objectives have been successfully addressed within the project. The only modification was that the study focused on screenhouses only, while it was originally planned to study large greenhouses as well. This was decided due to the large amount of field and theoretical work required to meet the objectives within screenhouses. Background In agricultural structures such as screenhouses and greenhouses, evapotranspiration (ET) is currently measured using lysimeters or sap flow gauges. These measurements provide ET estimates at the single-plant scale that must then be extrapolated, often statistically or empirically, to the whole canopy for irrigation scheduling purposes. On the other hand, turbulent transport techniques, like the eddy covariance, have become the standard for measuring whole canopy evapotranspiration in the open, but their applicability to agricultural structures has not yet been established. The subject of this project is the application of turbulent transport techniques to estimate ET for irrigation scheduling within large agricultural structures. Major conclusions and achievements The major conclusions of this project are: (i) the eddy covariance technique is suitable for reliable measurements of scalar fluxes (e.g., evapotranspiration, sensible heat, CO2) in most types of large screenhouses under all climatic conditions tested. All studies resulted with fair energy balance closures; (ii) comparison between measurements and theory show that the model is capable in reliably predicting the turbulent flow characteristics and surface fluxes within screenhouses; (iii) flow characteristics within the screenhouse, like flux-variance similarity and turbulence intensity were valid for the application of the eddy covariance technique in screenhouses of relatively dilute screens used for moderate shading and wind breaking. In more dense screens, usually used for insect exclusions, development of turbulent conditions was marginal; (iv) installation of the sensors requires that the system’s footprint will be within the limits of the screenhouse under study, as is the case in the open. A footprint model available in the literature was found to be reliable in assessing the footprint under screenhouse conditions. Implications, both scientific and agricultural The study established for the first time, both experimentally and theoretically, the use of the eddy covariance technique for flux measurements within agricultural screenhouses. Such measurements, along with reliable theoretical models, will enable more accurate assessments of crop water use which may lead to improved crop water management and increased water use efficiency of screenhouse crops.

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Trowbridge, J. H. Testing Turbulence Closure Models against Oceanic Turbulence Measurements. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada625214.

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Trowbridge, J. H. Testing Turbulence Closure Models Against Oceanic Turbulence Measurements. Fort Belvoir, VA: Defense Technical Information Center, August 2002. http://dx.doi.org/10.21236/ada626861.

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Futterman, J. A Quadratic Closure for Compressible Turbulence. Office of Scientific and Technical Information (OSTI), September 2008. http://dx.doi.org/10.2172/945679.

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Pope, Stephen B. Mapping Closures for Turbulent Combustion. Fort Belvoir, VA: Defense Technical Information Center, April 1994. http://dx.doi.org/10.21236/ada279995.

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Cloutman, L. D. Compressible turbulence transport equations for generalized second order closure. Office of Scientific and Technical Information (OSTI), May 1999. http://dx.doi.org/10.2172/9097.

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Kelley, Dan, and David Hebert. Evaluation of Turbulence-Closure Schemes for the Coastal Ocean. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada624738.

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Mellor, George L. Turbulence Closure and 3-D Ocean Modeling for CBLAST. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada625355.

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Goodman, Louis. Development of Turbulent Biological Closure Parameterizations. Fort Belvoir, VA: Defense Technical Information Center, January 2008. http://dx.doi.org/10.21236/ada505108.

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Goodman, Louis. Development of Turbulent Biological Closure Parameterizations. Fort Belvoir, VA: Defense Technical Information Center, September 2011. http://dx.doi.org/10.21236/ada598069.

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