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Purpose – The purpose of this paper is to investigate the cooling effect of these features. Japanese traditional buildings have many features, which are effective for cooling the interior of the building. Design/methodology/approach – This paper first of all describes the characteristics of indoor thermal environment and the cooling effect of four traditional buildings, located in the Miyagi Prefecture in the northern area in Japan. The investigated buildings include traditional farmhouses and renovated farmhouses for the improvement of indoor thermal environment. Second, the cooling effect of traditional technologies was studied by the means of computer simulation using a model house, which takes the multi‐zone effects of heat transfer and air flow distribution into consideration. Findings – The paper finds that the cooling technologies of traditional buildings, such as solar shading by thatched roof decreases indoor temperature. The computer simulation revealed that natural ventilation, solar shading by thatched roof and the thermal mass by earthen floor are effective for interior cooling. Practical implications – This paper reveals the cooling effect of traditional technologies quantitatively. From the points of view of energy saving and environment symbiosis based on the understanding of physical principle, it is important to apply these traditional technologies to modern buildings. Originality/value – From the viewpoint of solution of global environmental problems, we can learn a lot from these vernacular technologies inherited from the past. This paper provides valuable information about building based on environmental design methodologies, which promote awareness about sustainable construction.

A direct numerical simulation with turbulent transport of a scalar quantity has been carried out to grasp and understand a laminarization phenomena caused by a pipe rotation. In this study, the Reynolds number, which is based on a bulk velocity and a pipe diameter, was set to be constant; Re_b=5283, and the rotating ratios of a wall velocity to a bulk velocity were set to be 0.5, 1.0, 2.0 and 3.0. A uniform heat‐flux was applied to the wall as a thermal boundary condition. Prandtl number of the working fluid was assumed to be 0.71. The number of computational grids used in this study was 256×128×128 in the z‐, r‐ and ϕ‐ directions, respectively. The turbulent quantities such as the mean flow, temperature fluctuations, turbulent stresses and pressure distribution and the turbulent statistics were obtained. Moreover, the Reynolds stress and the scalar flux budgets were also obtained for each rotating ratio. The turbulent drag decreases with the rotating ratio increase. The reason of this drag reduction can be considered that the additional rotational production terms appear in the azimuthal turbulence component. The contributions of convection and production terms to the radial scalar flux budget and also to the balance with temperature‐pressure gradient term are significant. The dissipation and viscous diffusion terms are negligible in higher rotating ratio.