Impact of turbulence models and roughness height in 3D steady RANS simulations of wind flow in an urban environment

Ricci, Alessio; Kalkman, I Ivo; Blocken, Bje Bert; Burlando, Massimiliano; Repetto, Maria Pia

doi:10.1016/j.buildenv.2019.106617

Cited by 79 publications

(8 citation statements)

References 121 publications

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“…Inlet wind conditions were simulated using Equations –(3) (Delgado‐Fernandez et al, 2018; Hesp et al, 2015; Richards & Hoxey, 1993)

normalU ((), z) goodbreak= \frac{normalu *}{κ} \ln ((), \frac{z + {normalz}_{0}}{z_{0}})

normalk ((), z) goodbreak= \frac{normalu *^{2}}{\sqrt{C_{μ}}}

normalε ((), z) goodbreak= \frac{normalu *^{3}}{normalκ ((), normalz goodbreak+ z_{0})}

where U (z), k (z) and ε (z) are wind speed, turbulence kinetic energy and turbulence dissipation rate at elevation z , respectively; u * is wind shear velocity (m s −1 ); z 0 is aerodynamic roughness length at the ocean surface (0.0002 m) (WMO, 2018); κ is the von Karman's constant (0.4187); C μ is a model constant (0.09) (Richards & Hoxey, 1993). The aerodynamic roughness length was selected as 0.05 m and 0.24 m for an area covered by sand and marram grass, respectively (Wakes et al, 2010), and 0.0013 m for John Wilson Drive (road surface) (Ricci et al, 2020). U * = 0.6 m s −1 (which gives incident wind speed U C = 15.2 m s −1 ; Figure 4a) and incident wind approach angle WA C = 40° (Figure 4b) is used in this study.…”

Section: Methodology and Methodsmentioning

confidence: 99%

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Aeolian sand transport thresholds in excavated foredune notches

Nguyen

Hilton

Wakes

2021

Earth Surf Processes Landf

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Excavation of 'notches' in foredunes aims to facilitate sand transport through the foredune zone to enhance biodiversity and increase foredune resilience. Recent research has examined notch morphodynamics, however, the underlying aeolian processes in relation to sand transport have not been examined. This study determines:(i) the critical incident wind conditions resulting in sand transport inside the notch; and (ii) the pattern of wind flow and sand deposition/erosion inside the notch.Secondary winds are recorded using 12 ultrasonic anemometers deployed at crossnotch stations and compared with incident winds measured on a mast 6.5 m above foredune crest. Instantaneous sand transport is recorded using 12 laser particle counters located on four masts across the notch. Sand deposition is measured using erosion pins and digital surface models derived from remotely piloted aerial system.Field data are used to validate Computational Fluid Dynamic wind flow simulations to provide three-dimensional wind direction and speed contours in the notch. The study area is

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“…Inlet wind conditions were simulated using Equations –(3) (Delgado‐Fernandez et al, 2018; Hesp et al, 2015; Richards & Hoxey, 1993)

normalU ((), z) goodbreak= \frac{normalu *}{κ} \ln ((), \frac{z + {normalz}_{0}}{z_{0}})

normalk ((), z) goodbreak= \frac{normalu *^{2}}{\sqrt{C_{μ}}}

normalε ((), z) goodbreak= \frac{normalu *^{3}}{normalκ ((), normalz goodbreak+ z_{0})}

Section: Methodology and Methodsmentioning

confidence: 99%

“…road surface)(Ricci et al, 2020). U* = 0.6 m s À1 (which gives incident wind speed U C = 15.2 m s À1 ; Figure4a) and incident wind approach angle WA C = 40 (Figure4b) is used in this study.CFD-simulated winds were validated with field observation in experiment 1 at all wind mast locations (Figure4c-e).…”

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confidence: 99%

Aeolian sand transport thresholds in excavated foredune notches

Nguyen

Hilton

Wakes

2021

Earth Surf Processes Landf

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“…The Reynolds-averaged Navier-Stokes (RANS) turbulence models are widely used in the simulation of urban and indoor air movement. [30][31][32][33][34] In the preliminary computation, three RANS models, namely, standard k-e model, RNG k-e model and realisable k-e model were adopted and the results were compared. The calculation results using three turbulence models are not much different, but the standard k-e model can achieve convergence faster than the other two models.…”

Section: Numerical Modelmentioning

confidence: 99%

Numerical evaluation of contaminants mixing uniformity in a full-scale test chamber with mixing fan

Zhang

et al. 2020

Indoor and Built Environment

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Most existing models and standards for volatile organic compounds emission assume that contaminants are uniform in the testing devices. In this study, a three-dimensional transient numerical model was proposed to simulate the mass transport process based on a full-scale test chamber with a mixing fan, and the airflow field and contaminants concentration distribution were obtained within the chamber under airtight and ventilated conditions. The model was validated by comparing the numerical results with experimental data. The numerical results show that the contaminant source position and the airflow field characteristics have significant impact on the contaminant mixing, and the fan rotation has an important role in accelerating mixing. In the initial mixing stage, the concentration distribution is obviously uneven; as the mixing progresses, it gradually reaches acceptable uniformity except for some sensitive regions, such as high concentration region at the injection point of the contaminants and low concentration region at the air inlet. To ensure test accuracy, the monitor should avoid above sensitive regions; and some special regions are recommended where contaminant concentration uniformity can be reached sooner. The ventilated chamber results indicate that the mixture of contaminants in the chamber is actually better than the results shown by conventional test method.

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“…However, the RANS simulation has shown acceptable predication accuracy in wind-driven singlesided natural ventilation 15 and there are also some similar studies in urban wind flow simulation. [24][25][26][27][28] Further, Blocken et al 29 stated that the RANS simulation can provide sufficient accuracy in modelling airflows in a built environment. Considering that this study only focuses on mean wind flow (i.e.…”

Section: Introductionmentioning

confidence: 99%

Performance evaluation of climate-adaptive natural ventilation design: A case study of semi-open public cultural building

Wei

2020

Indoor and Built Environment

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Naturally ventilated buildings play a vital role in mitigating climate change since they produce lower CO2 emissions compared to mechanically ventilated alternatives. Also, occupants have better experiences in naturally ventilated buildings than in mechanically ventilated buildings. However, the application of natural ventilation design is often hindered by extreme weather conditions. To cope with such problems, this paper proposes climate adaptive natural ventilation designs which utilize and adapt to the local climate. The ventilation performance of this design is quantitatively evaluated using a computational fluid dynamics (CFD) approach. The CFD simulation is first validated against experiments and then utilized to reproduce the wind flow inside the building for all four seasons. The evaluation parameters include air changes per hour (ACH), wind speed at the pedestrian level and wind flow patterns indoors. Results showed that this climate adaptive natural ventilation meets the requirements of the Chinese green building assessment standards (GB/T50378-2019) with the highest ACH value of up to 15.8 times per hour. Furthermore, the wind speed at pedestrian level varies from 0.08 m/s to 0.39 m/s. The practice and findings reported in this paper can be useful for future development of sustainable, climate-adaptive buildings.

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Impact of turbulence models and roughness height in 3D steady RANS simulations of wind flow in an urban environment

Cited by 79 publications

References 121 publications

Aeolian sand transport thresholds in excavated foredune notches

Aeolian sand transport thresholds in excavated foredune notches

Numerical evaluation of contaminants mixing uniformity in a full-scale test chamber with mixing fan

Performance evaluation of climate-adaptive natural ventilation design: A case study of semi-open public cultural building

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