An Overview of Turbulent Inflow Boundary Conditions for Large Eddy Simulations (Invited)

2015 ◽  
Author(s):  
Nitin S. Dhamankar ◽  
Gregory A. Blaisdell ◽  
Anastasios S. Lyrintzis
Keyword(s):  
Boundary Conditions ◽  
Large Eddy Simulations ◽  
Turbulent Inflow ◽  
Large Eddy

scholarly journals Overview of Turbulent Inflow Boundary Conditions for Large-Eddy Simulations

AIAA Journal ◽  
2018 ◽  
Vol 56 (4) ◽  
pp. 1317-1334 ◽  
Author(s):  
Nitin S. Dhamankar ◽  
Gregory A. Blaisdell ◽  
Anastasios S. Lyrintzis
Keyword(s):  
Boundary Conditions ◽  
Large Eddy Simulations ◽  
Turbulent Inflow ◽  
Large Eddy

scholarly journals Large-Eddy Simulations of Real-World Episodes in Complex Terrain Based on ERA-Reanalysis and Validated by Ground-Based Remote Sensing Data

2019 ◽  
Vol 147 (12) ◽  
pp. 4325-4343 ◽  
Author(s):  
Cornelius Hald ◽  
Matthias Zeeman ◽  
Patrick Laux ◽  
Matthias Mauder ◽  
Harald Kunstmann
Keyword(s):  
Remote Sensing ◽  
Boundary Conditions ◽  
Complex Terrain ◽  
Computing Time ◽  
Remote Sensing Data ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Sensing Data ◽  
Large Eddy ◽  
Local Weather

Abstract A computationally efficient and inexpensive approach for using the capabilities of large-eddy simulations (LES) to model small-scale local weather phenomena is presented. The setup uses the LES capabilities of the Weather Research and Forecasting Model (WRF-LES) on a single domain that is directly driven by reanalysis data as boundary conditions. The simulated area is an example for complex terrain, and the employed parameterizations are chosen in a way to represent realistic conditions during two 48-h periods while still keeping the required computing time around 105 CPU hours. We show by evaluating turbulence characteristics that the model results conform to results from typical LES. A comparison with ground-based remote sensing data from a triple Doppler-lidar setup, employed during the “ScaleX” campaigns, shows the grade of adherence of the results to the measured local weather conditions. The representation of mesoscale phenomena, including nocturnal low-level jets, strongly depends on the temporal and spatial resolution of the meteorological boundary conditions used to drive the model. Small-scale meteorological features that are induced by the terrain, such as katabatic flows, are present in the simulated output as well as in the measured data. This result shows that the four-dimensional output of WRF-LES simulations for a real area and real episode can be technically realized, allowing a more comprehensive and detailed view of the micrometeorological conditions than can be achieved with measurements alone.

scholarly journals Impact of Surface Flux Formulations and Geostrophic Forcing on Large-Eddy Simulations of Diurnal Atmospheric Boundary Layer Flow

2010 ◽  
Vol 49 (7) ◽  
pp. 1496-1516 ◽  
Author(s):  
Vijayant Kumar ◽  
Gunilla Svensson ◽  
A. A. M. Holtslag ◽  
Charles Meneveau ◽  
Marc B. Parlange
Keyword(s):  
Boundary Layer ◽  
Boundary Condition ◽  
Boundary Conditions ◽  
Surface Temperature ◽  
Surface Flux ◽  
Large Eddy Simulations ◽  
Surface Boundary ◽  
Temperature Boundary ◽  
Large Eddy ◽  
Temperature Boundary Condition

Abstract The impact of surface flux boundary conditions and geostrophic forcing on multiday evolution of flow in the atmospheric boundary layer (ABL) was assessed using large-eddy simulations (LES). The LES investigations included several combinations of surface boundary conditions (temperature and heat flux) and geostrophic forcing (constant, time varying, time and height varying). The setup was based on ABL characteristics observed during a selected period of the Cooperative Atmosphere–Surface Exchange Study—1999 (CASES-99) campaign. The LES cases driven by a constant geostrophic wind achieved the best agreement with the CASES-99 observations specifically in terms of daytime surface fluxes and daytime and nighttime profiles. However, the nighttime fluxes were significantly overestimated. The LES cases with the surface temperature boundary condition and driven by a time- and height-varying geostrophic forcing showed improved agreement with the observed nighttime fluxes, but there was less agreement with other observations (e.g., daytime profiles). In terms of the surface boundary condition, the LES cases driven by either surface temperature or heat fluxes produced similar trends in terms of the daytime profiles and comparisons with data from soundings. However, in reproducing the fluxes and nighttime profiles, the agreement was better with imposed temperature because of its ability to interact dynamically with the air temperature field. Therefore, it is concluded that surface temperature boundary condition is better suited for simulations of temporally evolving ABL flow as in the diurnal evolution of the ABL.

Resolving urban canopy flows: Scales, turbulence and boundary conditions in obstacle-resolving numerical models

2021 ◽  
Author(s):  
Benedikt Seitzer ◽  
Bernd Leitl ◽  
Frank Harms
Keyword(s):  
Boundary Layer ◽  
Boundary Conditions ◽  
Atmospheric Boundary Layer ◽  
Similarity Theory ◽  
Urban Canopy ◽  
Large Eddy Simulations ◽  
Roughness Sublayer ◽  
Boundary Layer Meteorol ◽  
Large Eddy ◽  
Near Wall

<p>Large-eddy simulations are increasingly used for studying the atmospheric boundary layer. With increasing computational resources even obstacle-resolving Large-eddy simulations became possible and will be used in urban climate studies more frequently. In these applications, grid sizes are in the order of a few meters. Whereas major urban structures can be resolved in general, details like aerodynamically rough surface structures can not be resolved explicitly. Based on the original fields of application, boundary conditions in Large-eddy simulations were initially formulated for surfaces of homogeneous roughness and for wall-distances much larger than the roughness sublayer height (Hultmark et al., 2013). The height of the roughness sublayer depends on the size of small-scale obstacles present on the surface exposed to the flow (Raupach et al., 1991). Typically, boundary conditions are evaluated between the surface and the first grid level. Thus, grid resolution in obstacle-resolved Large-Eddy simulations should also be a question of scales and therefore has to be chosen carefully (Basu and Lacser, 2017; Maronga et al., 2020). <br />In several wind tunnel experiments presented here, we measured the near-wall influence of differently scaled and shaped objects on a flow and its turbulence characteristics. Experimental setups were replicated numerically using the PALM model (Maronga et al. 2019). In a first, more generic experiment, the flow over horizontally homogeneous surfaces of different roughness was investigated. In a second experiment, the spatial separation of the turbulence scales was investigated in a more complex flow case. These experiments lead to considerations on model grid sizes in urban type Large-eddy simulations. The limitations of interpreting simulation results within the urban canopy layer are highlighted. There is an urgent need to reconsider how near-wall results of urban large-eddy simulations are generated and interpreted in the context of practical applications like flow and transport modelling in urban canopies. <br /><br /><em><strong>References</strong></em><br /><em>Basu, S. and Lacser, A. (2017). A Cautionary Note on the Use of Monin–Obukhov Similarity Theory in Very High-Resolution Large-Eddy Simulations. Boundary-Layer Meteorol, 163(2):351–355.</em></p> <p><em>Hultmark, M., Calaf, M., and Parlange, M. B. (2013). A new wall shearstress model for atmospheric boundary layer simulations. J Atmos Sci,70(11):3460–3470.</em></p> <p><em>Maronga, B., et al. (2020). Overview of the PALM model system 6.0. Geosci Model Dev Discussions, 06(June):1–63.</em></p> <p><em>Maronga, B., Knigge, C., and Raasch, S. (2020). An Improved Surface Boundary Condition for Large-Eddy Simulations Based on Monin–Obukhov Similarity Theory: Evaluation and Consequences forGrid Convergence in Neutral and Stable Conditions. Boundary-Layer Meteorol, 174(2):297–325.</em></p> <p><em>Raupach, M. R., Antonia, R. A., and Rajagopalan, S. (1991). Rough-wall turbulent boundary layers. Appl Mech Rev, 44(1):1–25</em></p>

Subgrid-Scale Diffusivity: Wall Behavior and Dynamic Methods

2004 ◽  
Vol 73 (3) ◽  
pp. 360-367 ◽  
Author(s):  
Guillaume Brillant ◽  
Sabine Husson ◽  
Françoise Bataille
Keyword(s):  
Prandtl Number ◽  
Boundary Conditions ◽  
Turbulent Channel Flow ◽  
Constant Heat Flux ◽  
Large Eddy Simulations ◽  
Subgrid Scale ◽  
Adiabatic Wall ◽  
Thermal Boundary Conditions ◽  
Dynamic Methods ◽  
Large Eddy

This study concerns the near-wall behavior of the subgrid-scale diffusivity. This is shown to depend on the thermal boundary conditions. Therefore, the constant subgrid-scale Prandtl number hypothesis is questionable and a direct modeling of the subgrid-scale diffusivity is considered instead. Large-eddy simulations are carried out using the Trio U code in a turbulent channel flow configuration with the three classical thermal boundary conditions (constant temperature, constant heat flux, and adiabatic wall). Different dynamic methods are used to model the subgrid-scale diffusivity and results are compared with constant subgrid-scale Prandtl number large-eddy simulations and with direct numerical simulations.

Inlet and Outlet Characteristics Boundary Conditions for Large Eddy Simulations of Turbomachinery

2019 ◽  
Author(s):  
Nicolas Odier ◽  
Thierry Poinsot ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Stéphane Moreau
Keyword(s):  
Boundary Conditions ◽  
Total Pressure ◽  
Static Pressure ◽  
Flow Direction ◽  
Essential Elements ◽  
Large Eddy Simulations ◽  
Large Eddy ◽  
Total Temperature ◽  
Industrial Use ◽  
Inlet Boundary Condition

Abstract Inlet an outlet boundary conditions are essential elements of any CFD predictions and this is even more so for turbomachinery Large Eddy Simulations, either applied to academic or industrial configurations. For compressible solvers, non-reflecting, characteristic inlet boundary condition imposing total pressure, total temperature and flow direction is usually needed, while an outlet relaxation methodology that automatically adapts the outlet static pressure as a function of the desired mass-flow rate rate is used for turbomachinery flow predictions. Establishing such a framework is clearly desirable especially for industrial use of LES. Development and validations remain necessary in such a fully unsteady context as detailled hereafter.

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