Predictive large eddy simulations for urban flows: Challenges and opportunities

García‐Sánchez, Clara; Beeck, Jeroen van; Gorlé, Catherine

doi:10.1016/j.buildenv.2018.05.007

Cited by 64 publications

(32 citation statements)

References 30 publications

(47 reference statements)

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“…We hypothesize that the omission of trees and bushes in the model, together with a less dense building layout, is responsible for the turbulence underprediction at that location. The overall performance in predicting TKE is reasonable, given all the challenges already mentioned, and is essentially the same as the one by García‐Sánchez et al (2018) using a solid wall approach (body‐fitted grid) to model the buildings (see Table 1), in both cases finding a positive fractional bias (underprediction) of TKE, attributed to the reasons already discussed.…”

Section: Urban Environment Flow Turbulence and Dispersion During Thsupporting

confidence: 79%

“…One of the advantages of LES of urban canopies versus other more simplified types of models is its superior performance in predicting turbulence related quantities (e.g., García‐Sánchez et al, 2018). Moreover, LES has the advantage that is inherently unsteady and thus reproduces the spectral distribution of eddy motions that can be resolved by a given grid spacing.…”

Section: Urban Environment Flow Turbulence and Dispersion During Thmentioning

confidence: 99%

“…Explicit representation of urban microscale features does require very fine grid spacings, Δ∼ 10 −1 −10 1 m, typically preventing building‐resolving simulations from being routinely carried out with microscale models due to the nearly prohibitive high‐performance computing resources required. As a result, building‐resolving simulations have been thus far restricted primarily to exploratory fundamental research efforts (e.g., Auguste et al, 2019; Chan & Leach, 2007; Cheng & Porté‐Agel, 2015; García‐Sánchez et al, 2018; Jiang et al, 2017; Kanda, 2006; Lee et al, 2019; Lundquist et al, 2012; Park et al, 2015; Smolarkiewicz et al, 2007; Tomas et al, 2016; Wyszogrodzki et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Inclusion of Building‐Resolving Capabilities Into the FastEddy® GPU‐LES Model Using an Immersed Body Force Method

Muñoz‐Esparza

Sauer

Shin

et al. 2020

J Adv Model Earth Syst

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As a first step toward achieving full physics urban weather simulation capabilities within the resident-GPU large-eddy simulation (LES) FastEddy ® model, we have implemented and verified/validated a method for explicit representation of building effects. Herein, we extend the immersed body force method (IBFM) from Chan and Leach (2007, https://doi.org/10.1175/2006JAMC1321.1) to (i) be scale independent and (ii) control building surface temperatures. Through a specific drag-like term in the momentum equations, the IBFM is able to enforce essentially zero velocities within the buildings, in turn resulting in a no-slip boundary condition at the building walls. In addition, we propose similar forcing terms in the energy and mass conservation equations that allow an accurate prescription of the building temperature. The extended IBFM is computationally efficient and has the potential to be coupled to building energy models. The IBFM exhibits excellent agreement with laboratory experiments of an array of staggered cubes at a grid spacing of Δ = 1 mm, demonstrating the applicability of the method beyond the atmospheric scale. In addition, the IBFM is validated at atmospheric scale through simulations of downtown Oklahoma City (Δ = 2 m) using data collected during the Joint Urban 2003 (JU03) field campaign. Our LES IBFM results for mean wind speed, turbulence kinetic energy, and SF 6 transport and dispersion compare well to observations and produce turbulence spectra that are in good agreement with sonic anemometer data. Statistical performance metrics for the JU03 simulations are within the range of other LES models in the literature. Plain Language Summary A significant majority of social and economic activities are logically concentrated around densely populated urban areas. Consequently, accurate modeling and prediction of urban-scale weather entails a tremendous benefit to society in many ways. Herein, we extend the immersed body force method (IBFM), which allows explicit representation of building effects in microscale numerical models, to be applicable to disparate scales and to effectively control building surface temperatures. This computationally efficient method is implemented into the GPU-accelerated large-eddy simulation (LES) FastEddy ® model, with the purpose of facilitating a path toward realistic street-scale operational weather forecasting in the near future. We validate the extended IBFM with observations at laboratory scale and urban-scale field measurements over downtown Oklahoma City during the Joint Urban 2003 field campaign. Our LES IBFM results for mean wind speed, turbulence kinetic energy, and SF 6 transport and dispersion compare well to observations, and the corresponding statistical performance metrics are within the range of other LES models in the literature employing body fitted and immersed boundary approaches.

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Section: Urban Environment Flow Turbulence and Dispersion During Thsupporting

confidence: 79%

Section: Urban Environment Flow Turbulence and Dispersion During Thmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Inclusion of Building‐Resolving Capabilities Into the FastEddy® GPU‐LES Model Using an Immersed Body Force Method

Muñoz‐Esparza

Sauer

Shin

et al. 2020

J Adv Model Earth Syst

View full text Add to dashboard Cite

show abstract

“…While being computationally more expensive than RANS, LES has been shown to perform better in resolving instantaneous turbulence structures in a complex urban environment (García-Sánchez et al, 2018;Salim et al, 2011). Further, air pollutant concentrations can be significantly modified by their chemical and physical processes (Kurppa et al, 2019;Nikolova et al, 2016;Zhong et al, 2020), especially as the residence time of air pollutants is increased in a complex urban environment (Gronemeier and Sühring, 2019;Ramponi et al, 2015). Therefore, a detailed module describing the characteristics of air pollutants and their dynamics is needed to enable modelling aerosol particles of different size, chemical composition and harmfulness.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of spatial aerosol particle distributions to the boundary conditions in the PALM model system 6.0

et al. 2020

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Abstract. High-resolution modelling is needed to understand urban air quality and pollutant dispersion in detail. Recently, the PALM model system 6.0, which is based on large-eddy simulation (LES), was extended with the detailed Sectional Aerosol module for Large Scale Applications (SALSA) v2.0 to enable studying the complex interactions between the turbulent flow field and aerosol dynamic processes. This study represents an extensive evaluation of the modelling system against the horizontal and vertical distributions of aerosol particles measured using a mobile laboratory and a drone in an urban neighbourhood in Helsinki, Finland. Specific emphasis is on the model sensitivity of aerosol particle concentrations, size distributions and chemical compositions to boundary conditions of meteorological variables and aerosol background concentrations. The meteorological boundary conditions are taken from both a numerical weather prediction model and observations, which occasionally differ strongly. Yet, the model shows good agreement with measurements (fractional bias <0.67, normalised mean squared error <6, fraction of the data within a factor of 2 >0.3, normalised mean bias factor <0.25 and normalised mean absolute error factor <0.35) with respect to both horizontal and vertical distribution of aerosol particles, their size distribution and chemical composition. The horizontal distribution is most sensitive to the wind speed and atmospheric stratification, and vertical distribution to the wind direction. The aerosol number size distribution is mainly governed by the flow field along the main street with high traffic rates and in its surroundings by the background concentrations. The results emphasise the importance of correct meteorological and aerosol background boundary conditions, in addition to accurate emission estimates and detailed model physics, in quantitative high-resolution air pollution modelling and future urban LES studies.

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“…Detailed information on the variability of urban air pollutant concentrations are, however, highly valuable to urban planning to design healthy living environments (Giles-Corti et al, 2016;Kurppa et al, 2018), to air quality monitoring network design, and to conducting exposure studies. Therefore, a building-resolving tool for simulating and predicting air quality in real complex urban environments in current and future conditions is needed.…”

Section: Introductionmentioning

confidence: 99%

Implementation of the sectional aerosol module SALSA2.0 into the PALM model system 6.0: model development and first evaluation

et al. 2019

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Abstract. Urban pedestrian-level air quality is a result of an interplay between turbulent dispersion conditions, background concentrations, and heterogeneous local emissions of air pollutants and their transformation processes. Still, the complexity of these interactions cannot be resolved by the commonly used air quality models. By embedding the sectional aerosol module SALSA2.0 into the large-eddy simulation model PALM, a novel, high-resolution, urban aerosol modelling framework has been developed. The first model evaluation study on the vertical variation of aerosol number concentration and size distribution in a simple street canyon without vegetation in Cambridge, UK, shows good agreement with measurements, with simulated values mainly within a factor of 2 of observations. Dispersion conditions and local emissions govern the pedestrian-level aerosol number concentrations. Out of different aerosol processes, dry deposition is shown to decrease the total number concentration by over 20 %, while condensation and dissolutional increase the total mass by over 10 %. Following the model development, the application of PALM can be extended to local- and neighbourhood-scale air pollution and aerosol studies that require a detailed solution of the ambient flow field.

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Predictive large eddy simulations for urban flows: Challenges and opportunities

Cited by 64 publications

References 30 publications

Inclusion of Building‐Resolving Capabilities Into the FastEddy® GPU‐LES Model Using an Immersed Body Force Method

Inclusion of Building‐Resolving Capabilities Into the FastEddy® GPU‐LES Model Using an Immersed Body Force Method

Sensitivity of spatial aerosol particle distributions to the boundary conditions in the PALM model system 6.0

Implementation of the sectional aerosol module SALSA2.0 into the PALM model system 6.0: model development and first evaluation

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