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Journal Articles

CityTransformer; A Transformer-based model for contaminant dispersion prediction in a realistic urban area

Asahi, Yuichi; Onodera, Naoyuki; Hasegawa, Yuta; Shimokawabe, Takashi*; Shiba, Hayato*; Idomura, Yasuhiro

Boundary-Layer Meteorology, 186(3), p.659 - 692, 2023/03

 Times Cited Count:0 Percentile:0.01(Meteorology & Atmospheric Sciences)

We develop a Transformer-based deep learning model to predict the plume concentrations in the urban area under uniform flow conditions. Our model has two distinct input layers: Transformer layers for sequential data and convolutional layers in convolutional neural networks (CNNs) for image-like data. Our model can predict the plume concentration from realistically available data such as the time series monitoring data at a few observation stations and the building shapes and the source location. It is shown that the model can give reasonably accurate prediction with orders of magnitude faster than CFD simulations. It is also shown that the exactly same model can be applied to predict the source location, which also gives reasonable prediction accuracy.

Journal Articles

MPS-based axisymmetric particle method for bubble rising with density and pressure discontinuity

Wang, Z.; Sugiyama, Tomoyuki

Engineering Analysis with Boundary Elements, 144, p.279 - 300, 2022/11

 Times Cited Count:3 Percentile:61.71(Engineering, Multidisciplinary)

Journal Articles

On the free surface boundary of moving particle semi-implicit method for thermocapillary flow

Wang, Z.; Sugiyama, Tomoyuki

Engineering Analysis with Boundary Elements, 135, p.266 - 283, 2022/02

 Times Cited Count:4 Percentile:52.33(Engineering, Multidisciplinary)

Journal Articles

Coherent eddies transporting passive scalars through the plant canopy revealed by Large-Eddy simulations using the lattice Boltzmann method

Watanabe, Tsutomu*; Takagi, Marie*; Shimoyama, Ko*; Kawashima, Masayuki*; Onodera, Naoyuki; Inagaki, Atsushi*

Boundary-Layer Meteorology, 181(1), p.39 - 71, 2021/10

 Times Cited Count:6 Percentile:45.38(Meteorology & Atmospheric Sciences)

A double-distribution-function lattice Boltzmann model for large-eddy simulations of a passive scalar field is described within and above a plant canopy. For a top-down scalar, for which the plant canopy serves as a distributed sink, the flux of the scalar near the canopy top are predominantly determined by sweep motions originating far above the canopy. By contrast, scalar ejection events are induced by coherent eddies generated near the canopy top. In this paper, the generation of such eddies is triggered by the downward approach of massive sweep motions to existing wide regions of weak ejective motions from inside to above the canopy.

Journal Articles

Real-time tracer dispersion simulations in Oklahoma City using the locally mesh-refined lattice Boltzmann method

Onodera, Naoyuki; Idomura, Yasuhiro; Hasegawa, Yuta; Nakayama, Hiromasa; Shimokawabe, Takashi*; Aoki, Takayuki*

Boundary-Layer Meteorology, 179(2), p.187 - 208, 2021/05

 Times Cited Count:13 Percentile:73.61(Meteorology & Atmospheric Sciences)

A plume dispersion simulation code named CityLBM enables a real time simulation for several km by applying adaptive mesh refinement (AMR) method on GPU supercomputers. We assess plume dispersion problems in the complex urban environment of Oklahoma City (JU2003). Realistic mesoscale wind boundary conditions of JU2003 produced by a Weather Research and Forecasting Model (WRF), building structures, and a plant canopy model are introduced to CityLBM. Ensemble calculations are performed to reduce turbulence uncertainties. The statistics of the plume dispersion field, mean and max concentrations show that ensemble calculations improve the accuracy of the estimation, and the ensemble-averaged concentration values in the simulations over 4 km areas with 2-m resolution satisfied factor 2 agreements for 70% of 24 target measurement points and periods in JU2003.

Journal Articles

A Numerical study of turbulence statistics and the structure of a spatially-developing boundary layer over a realistic urban geometry

Inagaki, Atsushi*; Kanda, Manabu*; Ahmad, N. H.*; Yagi, Ayako*; Onodera, Naoyuki; Aoki, Takayuki*

Boundary-Layer Meteorology, 164(2), p.161 - 181, 2017/08

 Times Cited Count:30 Percentile:73.33(Meteorology & Atmospheric Sciences)

The applicability of outer-layer scaling is examined by numerical simulation of a developing neutral boundary layer over a realistic building geometry of Tokyo. Large-eddy simulations are carried out over a large computational domain 19.2 km $$times$$ 4.8 km $$times$$1 km, with a fine grid spacing (2 m) using the lattice-Boltzmann method with massively parallel graphics processing units. Results from simulations show that outer-layer features are maintained for turbulence statistics in the upper part of the boundary layer, as well as the width of predominant streaky structures throughout the entire boundary layer. This is caused by the existence of very large streaky structures extending throughout the entire boundary layer, which follow outer-layer scaling with a self-preserving development. We assume the top-down mechanism in the physical interpretation of results.

Journal Articles

Comparative studies in the local circulations induced by land-use and by topography

Lee, S.; Kimura, Fujio*

Boundary-Layer Meteorology, 101(2), p.157 - 182, 2001/11

 Times Cited Count:53 Percentile:74.53(Meteorology & Atmospheric Sciences)

no abstracts in English

Journal Articles

Preparation of piezoelectric paints and application to smart materials and structures

Egusa, Shigenori

Boundary, 12(8), p.7 - 11, 1996/08

no abstracts in English

Journal Articles

Three-dimensional thermal stress numerical convergence analysis of a hot spot in a thin pipe using the boundary element method

Bains, R.S.*; Sugimoto, Jun

Engineering Analysis with Boundary Elements, 14, p.267 - 275, 1994/00

 Times Cited Count:4 Percentile:76.68(Engineering, Multidisciplinary)

no abstracts in English

Journal Articles

Source iterative multiple reciprocity techniques for Helmholtz eigenvalue problems with boundary elements

; C.A.Brebbia*

Boundary Element Methods, p.79 - 88, 1993/00

no abstracts in English

Journal Articles

Multiple reciprocity boundary element formulation for one-group fission neutron source iteration problems

; C.A.Brebbia*

Engineering Analysis with Boundary Elements,11, p.39 - 45, 1993/00

no abstracts in English

Journal Articles

Generation of higher order fundamental solutions to the two-dimensional modified Helmholtz equation

; C.A.Brebbia*

Engineering Analysis with Boundary Elements,11, p.87 - 90, 1993/00

no abstracts in English

Journal Articles

Round-off error accumulation observed in a neutron diffusion calculation using the multiple reciprocity boundary element method

; C.A.Brebbia*

Boundary Elem. Abstr. Newsl., 3(2), p.67 - 70, 1992/03

no abstracts in English

Journal Articles

Dual and multiple reciprocity formulations applied to fission neutron source problems

; C.A.Brebbia*

Boundary Elements XIV, Vol.1; Field Problems and Applications, p.25 - 38, 1992/00

no abstracts in English

Journal Articles

Remedy for round-off error accumulation observed in a neutron diffusion calculation using the multiple reciprocity boundary element method

; C.A.Brebbia*

Engineering Analysis with Boundary Elements, 10, p.345 - 352, 1992/00

 Times Cited Count:9 Percentile:73.03(Engineering, Multidisciplinary)

no abstracts in English

Journal Articles

Boundary element formulation of fission neutron source problems using only boundary integrals

; C.A.Brebbia*

Engineering Analysis with Boundary Elements, 8(5), p.239 - 244, 1991/10

 Times Cited Count:9 Percentile:76.25(Engineering, Multidisciplinary)

no abstracts in English

Journal Articles

Boundary element method applied to neutron diffusion problems of a thin layer sandwiched between two zones

; C.A.Brebbia*

Boundary Elements XII, Vol.1; Applications in Stress Analysis, Potential and Diffusion, p.227 - 239, 1990/00

no abstracts in English

Journal Articles

Boundary element method applied to neutron diffusion problems

; C.A.Brebbia*

Boundary Elements, X, Vol.2, 12 Pages, 1988/00

no abstracts in English

18 (Records 1-18 displayed on this page)
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