An analysis and modeling of the non-local eddy viscosity for the Reynolds stress was carried out using the direct numerical simulation (DNS) of homogeneous isotropic turbulence and inhomogeneous passive vector. The profile of the exact non-local eddy viscosity was obtained numerically using the Green’s function. Non-local effects on the passive vector flux were discussed such as an overestimation of the flux by local expression and a counter-gradient diffusion of the flux near zero points. A model for the non-local eddy viscosity was proposed in a customary manner in the statistical theory of turbulence and validated by comparing the profile with the DNS data.

The effects of helicity (velocity–vorticity correlation) on scalar transport in inhomogeneous turbulence is investigated with the aid of multiple-scale renormalised perturbation theory. Helicity is ubiquitously present in geophysical, astrophysical, and engineering flows where vorticity, rotation and density stratification play key roles. It is suggested that the inhomogeneity of turbulent helicity represented by ∇⟨u′⋅∇×u′⟩ (u′: velocity fluctuation) coupled with the non-uniform scalar ∇Θ gives a contribution to the turbulent scalar flux ⟨u′θ′⟩ (Θ: mean scalar, θ′: fluctuating scalar). In the inhomogeneous turbulence, this helicity effect alters the turbulent scalar flux as compared with the non-helical turbulence. It is also pointed out that non-similar spatial distributions between the turbulent energy and turbulent helicity should be important for this helicity effect.

In this study, we carried out a direct numerical simulation of a magnetohydrodynamic (MHD) turbulent channel flow. The production terms of the transport equation for the turbulent electromotive force are evaluated accurately, and also related with the model terms of the turbulent electromotive force model equation. Unlike the cross-helicity effect, the pumping effect had not been examined clearly in the present flow, we systematically examined its contribution and clarified its physical mechanism. Furthermore, we accurately evaluated several transport equations of turbulent residual energy related to the pumping effect, and clarified the mechanism and interrelations of its production, transfer, and dissipation.

Estimation of three-dimensional unsteady flow field within based on limited measurement data is a quite challenging task. Generally, experimental measurements are constrained by temporal and spatial resolutions and measurement range, while conducting simulation requires initial and boundary conditions. Data assimilation allows to reconstruct the flow field from limited measurement data by integrating measurement data into simulation to compensate for the shortcomings of the two approaches. This study focuses on the three-dimensional flow field around a cylinder in a duct. Simultaneous PIV (Particle Image Velocimetry) is performed on two planes at different spanwise positions. By assimilating the measurement data in one plane, the velocity distribution on the other plane is predicted by the adjoint method. The estimation performance is validated by comparing the prediction with the measurement.

This study aims to identify heat-stress mitigation strategies with higher regional potential under near-future heatwaves in the Tokyo Megalopolis. Heatwave events during 2025–2044 were detected from CMIP6 projections (SSP2-4.5) and dynamically downscaled. Globe temperature was calculated using a convective–radiative heat balance model, replacing the empirical formulation commonly used in Wet Bulb Globe Temperature (WBGT). Sensitivity experiments were then conducted by perturbing key meteorological variables to quantify their individual impacts on WBGT. The results show that enhancing ventilation yields a considerably larger WBGT reduction in low-wind areas than in other areas, whereas cooling and dehumidification exhibit minimal spatial variability in mitigation potential. In addition, shading and ventilation show strong spatial consistency in mitigation potential, indicating that co-optimizing both could help balance trade-offs and improve net cooling benefits.

Short-term prediction of meteorological variables provides timely weather information to assist urban residents in avoiding potential meteorological hazards. A high-resolution meteorological field implies large data sizes, posing challenges for training models. Proper orthogonal decomposition (POD)-based dimensionality reduction was used to separate the spatio-temporal features. Linear stochastic estimate with multiple delay-time inputs (MLSE) and Transformer achieve a short-term prediction. The performances of the two methods were evaluated using high-resolution local objective data. POD-MLSE outperforms POD-Transformer in prediction. The main reason is Transformer poorly predicts coherence in the dominant-frequency range, although the predicted power spectral density is superior to that of MLSE.

Cyclone separators are widely used in industry, but conventional research has primarily focused on centrifugal force. When separating aggregated flocs containing fine particles, low-speed operation is necessary to prevent floc breakup due to centrifugal force; however, knowledge under these conditions remains insufficient. This study aims to clarify the flow characteristics of low-speed cyclones and the effects of vortex generators on the flow field through numerical simulations of liquid cyclones. Five cases were analyzed using OpenFOAM. The results showed that the velocity distribution pattern above the vortex generator was similar regardless of inlet velocity, while it varied significantly below the generator depending on inlet velocity. Additionally, the effect of vortex generator installation height on the flow field was found to be minimal.

This study investigates the flow field within a marine semi-closed circulation aquaculture cage by observations and numerical simulations. The numerical simulation results represent that circulation flows were formed depending on the number and location of operating submersible pumps, whereas no clear circulation flows were observed. Possible reasons for this include differences in seawater injection conditions, the effects of deformation and sloshing of the flexible sheet, and observation accuracy. In the future, the consistency between the observed and simulated results should be improved, and then comprehensive observations and numerical simulations should be carried out including the chemical and biological processes inside the cage.

This study develops a method to evaluate the effectiveness of Zone 30 Plus safety measures on residential streets using nationwide ETC2.0 probe data. Comparing pre- and post-implementation data across multiple cities, the analysis found that installing more physical devices tends to reduce accidents on street segments, while zone area and shape index are related to accident decreases at intersections. Regardless of local conditions, the share of vehicles exceeding 30 km/h declined, and factors such as zone area, total link length, and the number of three-way intersections were associated with reductions in the 85th-percentile speed.

This study investigates driver behavior under varying visibility constraints at midblock crosswalks, focusing on bulb-outs. A field experiment was conducted on a closed test road with normal and bulb-out crosswalks, involving ten participants across twenty driving scenarios with different pedestrian and parked vehicle conditions. A regression-based speed profile model quantified the impacts of crosswalk geometry and visibility constraints on driver deceleration. The results suggest that bulb-outs facilitated earlier onset of deceleration when pedestrians were hidden by on-street parking. Eye gaze data was also analyzed to understand drivers’ visual attention under limited visibility.

In order to enhance the vitality of a town, a critical component of its development, it is imperative to understand the circumstances under which visitors linger in the surrounding area after utilizing a facility. The objective of this study is to understand the phenomenon of people’s lingering by conducting a post-match analysis of the behavior exhibited by spectators attending sports events held at facilities in proximity to railway stations. The utilization of sports event data, encompassing the time at which the game concluded, and transportation IC card data, including the times at which tickets were presented at the gate and personal attributes, is undertaken with the objective of elucidating the relationship between the time from the conclusion of the game and the time at which tickets were presented at the gate, as well as other pertinent variables.

Currently, a Level 2 automated bus demonstration experiment is underway between the University of Tokyo’s Kashiwa Campus and Kashiwa-no-ha Campus Station. Automated buses are expected to operate at low speeds due to technical challenges and to prevent in-vehicle accidents. This study uses the traffic flow simulator MicroAVENUE to evaluate the impact on traffic flow when low-speed automated buses mix with other transportation modes. It also verifies the effectiveness of measures such as road parking countermeasures. These analyses aim to contribute to planning measures for future demonstration tests and practical implementation of automated vehicles.

To realize cities where everyone can travel safely and comfortably, it is essential to establish pedestrian protection zones in a systematic rather than ad-hoc manner. This study develops a multi-objective optimization model that incorporates composite indicators such as safety, mobility, comfort, and connectivity. The model simultaneously derives the allocation of street hierarchies corresponding to pedestrian protection zones and collector-distributor roads. Applications to actual urban road networks demonstrate the trade-off characteristics among the indicators and suggest the possibility of context-sensitive prioritization that accommodates both community perspectives and policy decisions. The proposed framework is expected to contribute to the advancement of urban traffic management techniques.