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Literatura académica sobre el tema "Anabatic flows"
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Artículos de revistas sobre el tema "Anabatic flows"
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Princevac, M. y H. J. S. Fernando. "A criterion for the generation of turbulent anabatic flows". Physics of Fluids 19, n.º 10 (octubre de 2007): 105102. http://dx.doi.org/10.1063/1.2775932.
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Cintolesi, Carlo, Dario Di Santo, Francesco Barbano y Silvana Di Sabatino. "Anabatic Flow along a Uniformly Heated Slope Studied through Large-Eddy Simulation". Atmosphere 12, n.º 7 (30 de junio de 2021): 850. http://dx.doi.org/10.3390/atmos12070850.
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Anabatic flows are common phenomena in the presence of sloping terrains, which significantly affect the dynamics and the exchange of mass and momentum in the low-atmosphere. Despite this, very few studies in the literature have tackled this topic. The present contribution addresses this gap by utilising high-resolved large-eddy simulations for investigating an anabatic flow in a simplified configuration, commonly used in laboratory experiments. The purpose is to analyse the complex thermo-fluid dynamics and the turbulent structures arising from the anabatic flow near the slope. In such a flow, three main dynamic layers are identified and reported: the conductive layer close to the surface, the convective layer where the most energetic motion develops, and the outer region, which is almost unperturbed. The analysis of instantaneous fields reveals the presence of thermal plumes, which are stable turbulent structures enhancing vertical transport and mixing of momentum and temperature. Such structures are generated by thermal instabilities in the conductive layer that trigger the rise of the plumes above them. Their evolution along the slope is described, identifying three regions responsible for the plumes generation, stabilisation, and merging. To the best of the authors’ knowledge, this is the first numerical experiment describing the along-slope behaviour of the thermal plumes in the convective layer.
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Giometto, M. G., G. G. Katul, J. Fang y M. B. Parlange. "Direct numerical simulation of turbulent slope flows up to Grashof number". Journal of Fluid Mechanics 829 (22 de septiembre de 2017): 589–620. http://dx.doi.org/10.1017/jfm.2017.372.
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Stably stratified turbulent flows over an unbounded, smooth, planar sloping surface at high Grashof numbers are examined using direct numerical simulations (DNS). Four sloping angles ($\unicode[STIX]{x1D6FC}=15^{\circ },30^{\circ },60^{\circ }$ and $90^{\circ }$) and three Grashof numbers ($\mathit{Gr}=5\times 10^{10},1\times 10^{11}$ and $2.1\times 10^{11}$) are considered. Variations in mean flow, second-order statistics and budgets of mean- (MKE) and turbulent-kinetic energy (TKE) are evaluated as a function of $\unicode[STIX]{x1D6FC}$ and $Gr$ at fixed molecular Prandtl number $(Pr=1)$. Dynamic and energy identities are highlighted, which diagnose the convergence of the averaging operation applied to the DNS results. Turbulent anabatic (upward moving warm fluid along the slope) and katabatic (downward moving cold fluid along the slope) regimes are identical for the vertical wall set-up (up to the sign of the along-slope velocity), but undergo a different transition in the mechanisms sustaining turbulence as the sloping angle decreases, resulting in stark differences at low $\unicode[STIX]{x1D6FC}$. In addition, budget equations show how MKE is fed into the system through the imposed surface buoyancy, and turbulent fluctuations redistribute it from the low-level jet (LLJ) nose towards the boundary and outer flow regions. Analysis of the TKE budget equation suggests a subdivision of the boundary layer of anabatic and katabatic flows into four distinct thermodynamical regions: (i) an outer layer, corresponding approximately to the return flow region, where turbulent transport is the main source of TKE and balances dissipation; (ii) an intermediate layer, bounded below by the LLJ and capped above by the outer layer, where the sum of shear and buoyant production overcomes dissipation, and where turbulent and pressure transport terms are a sink of TKE; (iii) a buffer layer, located at $5\lessapprox z^{+}\lessapprox 30$, where TKE is provided by turbulent and pressure transport terms, to balance viscous diffusion and dissipation; and (iv) a laminar sublayer, corresponding to $z^{+}\lessapprox 5$, where the influence of viscosity is significant. $(\cdot )^{+}$ denotes a quantity rescaled in inner units. Interestingly, a zone of global backscatter (energy transfer from the turbulent eddies to the mean flow) is consistently found in a thin layer below the LLJ in both anabatic and katabatic regimes.
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Fedorovich, Evgeni y Alan Shapiro. "Structure of numerically simulated katabatic and anabatic flows along steep slopes". Acta Geophysica 57, n.º 4 (1 de agosto de 2009): 981–1010. http://dx.doi.org/10.2478/s11600-009-0027-4.
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Hannah, David M. y Glenn R. McGregor. "Evaluating the impact of climate on snow- and ice-melt dynamics in the Taillon basin, French Pyrénées". Journal of Glaciology 43, n.º 145 (1997): 563–68. http://dx.doi.org/10.1017/s0022143000035176.
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AbstractThis pilot study adopts a computer-assisted synoptic typing methodology to evaluate the totality of climatic influences on snow- and ice-melt dynamics within a small cirque basin in the French Pyrénées. The synoptic categories identified possess contrasting large-scale atmospheric circulation patterns and surface energy budgets which generate differential ablation responses. Continental air masses yield consistently high melt. Advection of moist maritime air also produces elevated but more variable ablation due to air-mass transitions. The two observed local valley circulation types show melt to be higher under nocturnal katabatic drainage than for anabatic wind flows associated with development of daytime ridge-top cumulus.
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Hannah, David M. y Glenn R. McGregor. "Evaluating the impact of climate on snow- and ice-melt dynamics in the Taillon basin, French Pyrénées". Journal of Glaciology 43, n.º 145 (1997): 563–68. http://dx.doi.org/10.3189/s0022143000035176.
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AbstractThis pilot study adopts a computer-assisted synoptic typing methodology to evaluate the totality of climatic influences on snow- and ice-melt dynamics within a small cirque basin in the French Pyrénées. The synoptic categories identified possess contrasting large-scale atmospheric circulation patterns and surface energy budgets which generate differential ablation responses. Continental air masses yield consistently high melt. Advection of moist maritime air also produces elevated but more variable ablation due to air-mass transitions. The two observed local valley circulation types show melt to be higher under nocturnal katabatic drainage than for anabatic wind flows associated with development of daytime ridge-top cumulus.
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Lesouëf, D., F. Gheusi, R. Delmas y J. Escobar. "Numerical simulations of local circulations and pollution transport over Reunion Island". Annales Geophysicae 29, n.º 1 (6 de enero de 2011): 53–69. http://dx.doi.org/10.5194/angeo-29-53-2011.
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Abstract. A series of high-resolution (1 km) numerical simulations with a limited-area numerical model has been performed over Reunion Island. In the dynamical context of a regular maritime flow perturbed by a major topographic obstacle such as Reunion Island, the objectives are to identify the main atmospheric circulations at local-scale over the island and to improve the understanding of local-scale transport and dispersion of pollutants emitted from local sources. To investigate the effects of topography and land surface heating on low-level flows over the island, simulations representative of austral winter were performed in idealized conditions keeping the radiative forcing plus a background east-south-easterly synoptic flux of varying strengths, typical of the prevailing trade-wind conditions. The numerical experiments show mainly that flow splitting of the trade-wind occurs around the island, with enhanced winds blowing along the coast lines parallel to the synoptic flux, due to the lateral constriction of the flow by the island and resulting Venturi effect. Blocking occurs on the island side facing the trade-wind. The north-western area on the leeside is screened from the trade-wind by high mountains, and this enables the development of diurnal thermally-induced circulations, combining downslope and land-breeze at night, and upslope and sea breeze at daytime. Flow splitting is modulated by radiative convergence toward the island at daytime, and divergence from the island at night. Stronger winds than the large-scale trade-wind occur along the coast at daytime (Venturi effect), whereas at night, the trade-wind flow is pushed few kilometres offshore by divergence of cooled air from the land. At night, the trade-wind flow is pushed few kilometres offshore by divergence of cooled air from the land. Consequently, a number of processes of pollution transport and dispersion have been identified. Vortices in the wake of the island were found to cause counterflow circulation and trapping of polluted air masses near the north-western coast. These air masses may in turn be sucked by anabatic wind systems during daytime (upslope and sea breezes) in the cirques and up to the summits of the island, and especially to Piton Maïdo (2200 m) where a new observatory of the Indian Ocean background atmosphere is being built. A "cap effect" above the mountains downstream from the volcano (to the south-east of the island), and especially above Piton Maïdo, might occur in case of development of inland and upslope breezes on the west coast. In this case, air pumped from lower layers may protect the observatory from the volcanic plume forced to pass over a "cap" of low-level air clean of volcanic emissions.
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Demko, J. Cory y Bart Geerts. "A Numerical Study of the Evolving Convective Boundary Layer and Orographic Circulation around the Santa Catalina Mountains in Arizona. Part I: Circulation without Deep Convection". Monthly Weather Review 138, n.º 5 (1 de mayo de 2010): 1902–22. http://dx.doi.org/10.1175/2009mwr3098.1.
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Abstract The daytime evolution of the thermally forced boundary layer (BL) circulation over an isolated mountain, about 30 km in diameter and 2 km high, is examined by means of numerical simulations validated with data collected in the Cumulus Photogrammetric, In Situ, and Doppler Observations (CuPIDO) field campaign. Two cases are presented, one remains cloud free in the simulations, and the second produces orographic convection just deep enough to yield a trace of precipitation. The Weather Research and Forecasting version 3 simulations, at a resolution of 1 km, compare well with CuPIDO observations. The simulations reveal a solenoidal circulation mostly contained within the convective BL, but this circulation and especially its upper-level return flow branch are not immediately apparent since they are overwhelmed by BL thermals. A warm anomaly forms over the high terrain during the day, but it is rather shallow and does not extend over the depth of the convective BL, which bulges over the mountain. Low-level mountain-scale convergence (MSC), driven by an anabatic pressure gradient, deepens during the day. Even relatively shallow and relatively small cumulus convection can temporarily overwhelm surface MSC by cloud shading and convective downdraft dynamics. In the evening drainage flow develops near the surface before the anabatic forcing ceases, and anabatic flow is still present in the residual mixed layer, decoupled from the surface. The interaction of the boundary layer circulation with deep orographic convection is examined in Part II of this study.
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Catalano, Franco y Antonio Cenedese. "High-Resolution Numerical Modeling of Thermally Driven Slope Winds in a Valley with Strong Capping". Journal of Applied Meteorology and Climatology 49, n.º 9 (1 de septiembre de 2010): 1859–80. http://dx.doi.org/10.1175/2010jamc2385.1.
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Abstract The complete day–night cycle of the circulation over a slope under simplified idealized boundary conditions is investigated by means of large-eddy simulations (LES). The thermal forcing is given with a time-varying law for the surface temperature. A surface layer parameterization based on the Monin–Obukhov similarity theory is used as a wall layer model. The domain geometry is symmetric, having an infinitely long straight valley in the y direction. Since the depth of the katabatic flow in midlatitude climates is limited to 5–30 m, the authors introduced a vertically stretched grid to obtain a finer mesh near the ground. The length scale for the calculation of eddy viscosities is modified to take into account the grid anisotropy. A preintegration of 24 h is made to obtain a capping inversion over the valley. Results show that the model is able to reproduce microscale circulation dynamics driven by thermal forcing over sloping terrain. The diurnal growth of the convective boundary layer leading to the development of the anabatic wind as well as the evolution of the cold pool in the valley during the night and its interaction with the katabatic flow are shown. Waves develop at the interface between the anabatic current and the return flow. During the day, as a combined effect of the geometry and the forcing, a horizontal breeze develops directed from the middle of the valley toward the ridges. The impact of the gravity current on the quiescent atmosphere in the valley generates a weak hydraulic jump during the night.
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Demko, J. Cory y Bart Geerts. "A Numerical Study of the Evolving Convective Boundary Layer and Orographic Circulation around the Santa Catalina Mountains in Arizona. Part II: Interaction with Deep Convection". Monthly Weather Review 138, n.º 9 (1 de septiembre de 2010): 3603–22. http://dx.doi.org/10.1175/2010mwr3318.1.
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Abstract This is the second part of a study that examines the daytime evolution of the thermally forced boundary layer (BL) circulation over a relatively isolated mountain, about 30 km in diameter and 2 km high, and its interaction with locally initiated deep convection by means of numerical simulations validated with data collected in the 2006 Cumulus Photogrammetric, In Situ, and Doppler Observations (CuPIDO) field campaign in southeastern Arizona. Part I examined the BL circulation in cases with, at most, rather shallow orographic cumulus (Cu) convection; the present part addresses deep convection. The results are based on output from version 3 of the Weather Research and Forecasting model run at a horizontal resolution of 1 km. The model output verifies well against CuPIDO observations. In the absence of Cu convection, the thermally forced (solenoidal) circulation is largely contained within the BL over the mountain. Thunderstorm development deepens this BL circulation with inflow over the depth of the BL and outflow in the free troposphere aloft. Primary deep convection results from destabilization over elevated terrain and tends to be triggered along a convergence line, which arises from the solenoidal circulation but may drift downwind of the terrain crest. While the solenoidal anabatic flow converges moisture over the mountain, it also cools the air. Thus, a period of suppressed anabatic flow following a convective episode, at a time when surface heating is still intense, can trigger new and possibly deeper convection. The growth of deep convection may require enhanced convergent flow in the BL, but this is less apparent in the mountain-scale surface flow signal than the decay of orographic convection. A budget study over the mountain suggests that the precipitation efficiency of the afternoon convection is quite low, ~10% in this case.
Tesis sobre el tema "Anabatic flows"
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Di, Santo Dario. "Study of anabatic flows using large-eddy simulations in a simplified geometry". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20762/.
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In the present work, the turbulent anabatic flow generated over a uniformly heated slope in neutral stratification is originally studied through a large-eddy simulation (LES) technique. The present study is, to the best of the author's knowledge, the first case of a LES applied to anabatic flows in neutral stratification. The simulation approach is succesfully validated against three data sets: experimental, DNS and theoretical. One of the primary objectives of the study is to characterise the instantaneous turbulent structures triggered by the vertical buoyancy force responsible for the increase the turbulent mixing in the boundary layer. Such structures are hardly detected in both field and laboratory experiments and cannot be reproduced by steady-state numerical simulations. A new expression of the characteristic length scale of the thermal boundary layer is proposed and applied to derive alternative scaling parameters. Three principal regions are detected in the near-surface temperature profiles: a conduction region that contains most of the temperature decrease, a convective region dominated by flow convection and an equilibrium region that is almost not influenced by the heated slope. The newly proposed length scale resulted to be linked to the evolution of instantaneous turbulent structures identified as Rayleigh-Taylor instabilities which are analyzed and described. Their characteristic frequency is determined through a spectral analysis and their geometric dimensions are studied and linked to the extension of the vertical mixing zone inside the convection region. Three simulations are performed at different Rayleigh numbers to understand if there is a critical value above which the anabatic flow results Rayleigh-independent. the sensitivity analysis is carried out concluding that the analyzed flows are not Rayleigh-independent.
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Franzoni, Stefano. "Large-Eddy simulation of an anabatic wind on an idealised geometry". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21930/.
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La presente tesi propone una simulazione numerica Large-Eddy Simulation (LES) con Near-Wall Resolution (NWR) in OpenFOAM di un flusso anabatico all'interno di una geometria semplificata. Il caso proposto consiste nella riproduzione del flusso che si instaura al di sopra di un piano inclinato di 30°, liscio e infinitamente esteso, avendo imposto una buoyancy costante sulla superficie, il numero di Grashof Gr=2.1x10^11 e il numero di Prandtl Pr=1. La prima parte del lavoro offre una panoramica dei principali aspetti caratterizzanti la fluidodinamica computazionale e utili a fornire un contesto teorico per il caso presentato. In particolare, si descrivono i fondamenti del metodo di discretizzazione ai volumi finiti impiegato in OpenFOAM. Con l'intento di mostrare le principali motivazioni che giustificano l'introduzione dell'approccio LES, si forniscono le basi della teoria della turbolenza di Kolmogorov. La discussione del metodo LES viene conclusa con la presentazione del modello di Smagorinsky, impiegato nella simulazione. La seconda parte si focalizza sull'esposizione del caso simulato. Una volta introdotte le equazioni che governano il sistema, si forniscono i dettagli delle impostazioni della simulazione, esponendo le modifiche apportate al solutore. Attraverso i grafici prodotti, la simulazione viene validata tramite il confronto con i risultati dalla DNS effettuata da Giometto et al. (2017). Contestualmente, si offre una discussione dei risultati dal punto di vista fisico, individuando le principali proprietà delle componenti medie e della turbolenza, nonchè mostrando le strutture che caratterizzano istantaneamente il moto.