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Journal Articles

Simulation of Lagrangian pollutant in Jakarta urban district using Lattice Boltzmann method

Yokouchi, Hiroshi*; Inagaki, Atsushi*; Kanda, Manabu*; Onodera, Naoyuki

Doboku Gakkai Rombunshu, B1 (Suikogaku) (Internet), 76(2), p.I_253 - I_258, 2020/00

Hight-resolution pollutant model embedded into Lattice Boltzmann method (LBM) is constructed. We focuses on Particle pollutants. Flow field is calculated using D3Q27 model of LBM and particle is calculated by Lagrangian method. Using this model, we discuss the change in concentration distribution when there is a huge building (GARUDA) in Jakarta as a application. As a result, we can find the relation of differences in particle density and differences in flow velocity due to GARUDA. When the velocity in the case w/o GARUDA is faster than the other, particle velocity in the case w/o GARUDA is reduced. And also, we can find the velocity near the solid boundary is underestimated and the particle density is higher than theoretical value. However, this model is valid far away from the solid boundary.

Journal Articles

Inner and outer-layer similarity of the turbulence intensity profile over a realistic urban geometry

Inagaki, Atsushi*; Wangsaputra, Y.*; Kanda, Manabu*; Y$"u$cel, M.*; Onodera, Naoyuki; Aoki, Takayuki*

SOLA (Scientific Online Letters on the Atmosphere) (Internet), 16, p.120 - 124, 2020/00

 Times Cited Count:1 Percentile:5.1(Meteorology & Atmospheric Sciences)

The similarity of the turbulence intensity profile with the inner-layer and the outer-layer scalings were examined for an urban boundary layer using numerical simulations. The simulations consider a developing neutral boundary layer over realistic building geometry. The computational domain covers an 19.2 km by 4.8 km and extends up to a height of 1 km with 2-m grids. Several turbulence intensity profiles are defined locally in the computational domain. The inner- and outer-layer scalings work well reducing the scatter of the turbulence intensity within the inner- and outer-layers, respectively, regardless of the surface geometry. Although the main scatters among the scaled profiles are attributed to the mismatch of the parts of the layer and the scaling parameters, their behaviors can also be explained by introducing a non-dimensional parameter which consists of the ratio of length or velocity.

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:25 Percentile:72.08(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.

Oral presentation

Large Eddy Simulation of thermal atmospheric environment in urban boundary layer

Inagaki, Atsushi*; Onodera, Naoyuki; Kanda, Manabu*; Aoki, Takayuki*

no journal, , 

Since urban atmospheric environment is strongly controlled by multi-scale flow dynamics, simulation of the urban atmospheric boundary layer requires fine grid spacing and huge computational domain. We accomplished to simulate an urban atmospheric boundary layer using a Large Eddy Simulation model running on TSUBAME super computing system. Flow characteristics within and above a building canopy were successfully examined.

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