Development ofLOcal-scaleHigh-resolution atmosphericDIspersionModel usingLarge-EddySimulation. Part 5: detailed simulation of turbulent flows and plume dispersion in an actual urban area under real meteorological conditions

Nakayama, Hiromasa; Takemi, Tetsuya; Nagai, Hiroki

doi:10.1080/00223131.2015.1078262

Cited by 19 publications

(11 citation statements)

References 35 publications

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“…The grid spacing is 20 m in the horizontal directions and 2.5-64 m stretched in the vertical direction based on an orthogonal grid system. In the previous study, we conducted LESs of urban boundary layer flows in the urban central district by coupling with a MM model and showed reasonable results in comparison to the field experimental data of vertical profiles of wind speeds and directions (Nakayama et al, 2015). Those calculation conditions such grid resolution and computational domain were almost the same as the present ones.…”

Section: Les Computational Conditionsmentioning

confidence: 74%

“…Therefore, first, we proposed the treatment of the inflow boundary conditions in order to automatically input wind velocity data obtained by the MM model into the LES model under neutral stability conditions, depending on mean wind directions in the meteorological field (Nakayama et al, 2012(Nakayama et al, , 2015. Figure 1 shows a schematic diagram of the treatment of inflow boundary conditions in the LES model.…”

Section: Generation Of Turbulent Inflows From MM Outputsmentioning

confidence: 99%

“…The meso-scale meteorological simulation model used here is the Weather Research and Forecasting (WRF) model, the Advanced Research WRF Version 3.3.1 (Skamarock et al, 2008) to provide the input data for the LES model. We use a nesting capability to resolve the FDNPP region at a fine grid spacing by setting two-way nested, four computational domains (with the top being at the 50 hPa level).…”

Section: Meso-scale Meteorological Simulationmentioning

confidence: 99%

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Large-eddy simulation of turbulent winds during the Fukushima Daiichi Nuclear Power Plant accident by coupling with a meso-scale meteorological simulation model

2015

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Abstract. A significant amount of radioactive material was accidentally discharged into the atmosphere from the Fukushima Dai-ichi Nuclear Power Plant from 12 March 2011, which produced high contaminated areas over a wide region in Japan. In conducting regional-scale atmospheric dispersion simulations, the computerbased nuclear emergency response system WSPEEDI-II developed by Japan Atomic Energy Agency was used. Because this system is driven by a meso-scale meteorological (MM) model, it is difficult to reproduce smallscale wind fluctuations due to the effects of local terrain variability and buildings within a nuclear facility that are not explicitly represented in MM models. In this study, we propose a computational approach to couple an LES-based CFD model with a MM model for detailed simulations of turbulent winds with buoyancy effects under real meteorological conditions using turbulent inflow technique. Compared to the simple measurement data, especially, the 10 min averaged wind directions of the LES differ by more than 30 degrees during some period of time. However, distribution patterns of wind speeds, directions, and potential temperature are similar to the MM data. This implies that our coupling technique has potential performance to provide detailed data on contaminated area in the nuclear accidents.

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Section: Les Computational Conditionsmentioning

confidence: 74%

Section: Generation Of Turbulent Inflows From MM Outputsmentioning

confidence: 99%

Section: Meso-scale Meteorological Simulationmentioning

confidence: 99%

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Large-eddy simulation of turbulent winds during the Fukushima Daiichi Nuclear Power Plant accident by coupling with a meso-scale meteorological simulation model

2015

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“…One-way coupled obstacle-resolving LES has been applied to a built environment by Nakayama et al (2016) and by Vonlanthen et al (2016Vonlanthen et al ( , 2017. Also the present PALM implementation has already been demonstrated by MAronga et al (2019); Maronga et al (2020) and applied to obstacle-resolving urban studies (Kurppa et al, 2019;Auvinen et al, 2020a;Karttunen et al, 2020;Kurppa et al, 2020) using the one-way coupling.…”

mentioning

confidence: 76%

A Nested Multi-Scale System Implemented in the Large-Eddy Simulation Model PALM model system 6.0

Hellsten¹,

Ketelsen²,

Sühring³

et al. 2020

Preprint

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Abstract. Large-eddy simulation provides a physically sound approach to study complex turbulent processes within the atmospheric boundary layer including urban boundary layer flows. However, such flow problems often involve a large separation of turbulent scales, requiring a large computational domain and very high grid resolution near the surface features, leading to prohibitive computational costs. To overcome this problem, an online LES-LES nesting scheme is implemented into the PALM model system 6.0. The hereby documented and evaluated nesting method is capable of supporting multiple child domains which can be nested within their parent domain either in a parallel or recursively cascading configuration. The nesting system is evaluated by simulating first a purely convective boundary layer flow system and then three different neutrally-stratified flow scenarios with increasing order of topographic complexity. The results of the nested runs are compared with corresponding non-nested high- and low-resolution results. The results reveal that the solution accuracy within the high-resolution nest domain is clearly improved as the solutions approach the non-nested high-resolution reference results. In obstacle-resolving LES, the two-way coupling becomes problematic as anterpolation introduces a regional discrepancy within the obstacle canopy of the parent domain. This is remedied by introducing canopy-restricted anterpolation where the operation is only performed above the obstacle canopy. The test simulations make evident that this approach is the most suitable coupling strategy for obstacle-resolving LES. The performed simulations testify that nesting can reduce the CPU time up to 80 % compared to the fine-resolution reference runs while the computational overhead from the nesting operations remained below 16 % for the two-way coupling approach and significantly less for the one-way alternative.

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“…This implies that it is difficult to ensure the representativeness of the observations at a stationary point to be assimilated into turbulent flows and plume dispersion in the complex urban environments. Nakayama et al (2016) conducted LESs of plume dispersion in the urban central district of Oklahoma City under realistic atmospheric conditions during the field campaign Joint Urban 2003 by coupling the LES model with a mesoscale meteorological simulation (MMS) model and concluded that the prediction accuracy of the high-resolution simulations highly depends on the quality and reproducibility of the wind speed and direction simulated by the mesoscale model against the observed data during the field experiments.…”

Section: Introductionmentioning

confidence: 99%

Development of a Data Assimilation Method Using Vibration Equation for Large‐Eddy Simulations of Turbulent Boundary Layer Flows

Nakayama

Takemi

2020

J Adv Model Earth Syst

Self Cite

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In order to improve the simulation accuracy, it is effective to use a data assimilation technique which is capable of reproducing more realistic simulated states by incorporating observational data into simulation models. One of the simplest ones among data assimilation techniques is a Newtonian relaxation‐type nudging method which has been widely used in mesoscale meteorological models. In this study, we proposed a data assimilation method using a vibration equation which can incorporate turbulence winds toward target mean winds while maintaining small‐scale turbulent fluctuations as a different approach from the conventional nudging method. First, we conducted test simulations in which nudging is applied in a basic turbulent boundary layer (TBL) flow toward a target one. It is shown that the basic TBL flow can be reasonably nudged toward the target one while maintaining the turbulent fluctuations well when prescribing the natural frequency in the vibration equation smaller than the spectral peak frequency in the TBL flow. Then, we applied the proposed nudging method by incorporating data obtained from meteorological observations located in the actual city of Kyoto. The mean wind velocity profiles were reasonably nudged toward the target observed profile and the turbulence statistics were also favorably maintained. It is concluded that the data assimilation method using the vibration equation successfully nudges toward the target mean winds while maintaining small‐scale turbulent fluctuations well.

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Development ofLOcal-scaleHigh-resolution atmosphericDIspersionModel usingLarge-EddySimulation. Part 5: detailed simulation of turbulent flows and plume dispersion in an actual urban area under real meteorological conditions

Cited by 19 publications

References 35 publications

Large-eddy simulation of turbulent winds during the Fukushima Daiichi Nuclear Power Plant accident by coupling with a meso-scale meteorological simulation model

Large-eddy simulation of turbulent winds during the Fukushima Daiichi Nuclear Power Plant accident by coupling with a meso-scale meteorological simulation model

A Nested Multi-Scale System Implemented in the Large-Eddy Simulation Model PALM model system 6.0

Development of a Data Assimilation Method Using Vibration Equation for Large‐Eddy Simulations of Turbulent Boundary Layer Flows

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