Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro
Dai-34-Kai Suchi Ryutai Rikigaku Shimpojiumu Koen Rombunshu (Internet), 3 Pages, 2020/12
We developed a real-time ensemble simulation code for analyzing urban wind conditions and plume dispersion using a locally mesh-refined lattice Boltzmann method. We validated the developed code against the wind tunnel experiment by AIST, and against the field experiment JU2003 in Oklahoma City. In the case of the wind tunnel experiment, the wind condition showed a good agreement with the experiment, and 61.2% of the tracer gas concentration data observed on the ground satisfied the FACTOR2 condition, that is an accuracy criterion given by the environmental assessment guideline. In the case of the field experiment JU2003, the instantaneous wind speed showed a good agreement with the experiment, while the wind direction showed a difference up to 100
. The means of the tracer gas concentration satisfied the FACTOR2 condition at all observation interval. These results demonstrate that the developed code is accurate enough for the environmental assessment.
Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro
Keisan Kogaku Koenkai Rombunshu (CD-ROM), 25, 4 Pages, 2020/06
We developed a GPU-based CFD code using a mesh-refined lattice Boltzmann method (LBM), which enables ensemble simulations for wind and plume dispersion in urban cities. The code is tuned for Pascal or Volta GPU architectures, and is able to perform real-time wind simulations with several kilometers square region and several meters of grid resolution. We examined the developed code against the field experiment JU2003 in Oklahoma City. In the comparison, wind conditions showed good agreements, and the ensemble-averaged and maximum values of tracer concentration satisfied the factor 2 agreements.
Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro
no journal, ,
A wind simulation code "CityLBM" has been developed for the prediction of plume dispersion in urban areas. CityLBM utilizes a locally mesh-refined lattice Boltzmann method, where turbulent winds near the ground is captured by refining the mesh on low altitude region, and be able to perform real-time wind simulations with a meter-resolution using GPU-accelerated systems. In this study, we validated an ensemble simulation against the field experiment in Oklahoma City (JU2003) with the 100 ensemble members, computational region of 4096 m 
4096 m (horizontal) 2560 m (vertical) and the mesh resolution of 4 m near the ground and buildings. In the comparison between the ensemble simulation and the field experiment, wind speed showed good agreements within the range of 1
(where is variance of ensemble simulation), and the average value of the tracer gas concentration satisfied the factor2 agreements.
Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro
no journal, ,
Towards the prediction of the plume dispersion in the urban area, we are developing the urban wind simulation code CityLBM which is based on the lattice Boltzmann method with GPU computing. In this presentation, we implemented the ensemble simulation with MPI parallelization, and estimated the uncertainty of the plume dispersion simulation. The ensemble simulation with 100 members was performed, and the dependency of the simulation against the number of ensemble members was tested. We confirmed that the ensemble simulation can be statistically assessed with the number of ensemble members being 10.
Hasegawa, Yuta
no journal, ,
We explain the research plan for the exascale computational fluid dynamics (CFD) in Japan Atomic Energy Agency, Center for Computational Science and e-Systems (JAEA-CCSE). JAEA-CCSE has been promoting the development of 1m scale real-time urban wind simulation code, "CityLBM." In this presentation, we show our past studies that accelerate the CFD code, and our recent research which introduces ensemble data assimilation toward the digital twin of the urban wind. The outlook for the exascale computing with them is also described.