The nonlocal eddy diffusivity representation for the turbulent scalar flux was validated by using direct numerical simulation (DNS) data of homogeneous isotropic turbulence with an inhomogeneous mean shear. The DNS results showed the counter-gradient diffusion phenomenon and it was accounted for by the nonlocal effect. The behavior of the nonlocal eddy diffusivity was evaluated and its model was proposed by following the statistical theory of turbulence. The profile of the nonlocal eddy diffusivity obtained from the model agrees well with the DNS value, and the nonlocal model reproduces the scalar flux.

Rotation and density stratification are basic ingredients of astrophysical and geophysical flows. Large-scale structure formation and turbulent transport in rotating and stratified turbulence are expected to be described by the helicity subgridscale (SGS) turbulence model. The validity of the helicity SGS model is investigated with the aid of high-resolution direct numerical simulations. It is shown that, for the modeling of SGS turbulence, with large-scale helicity being injected by forcing, the SGS helicity effect should be incorporated into the model, as well as the eddy-viscosity-type Smagorinsky model.

Turbulent helicity is known to be generated in the boundary layer when the system is rotated perpendicular to the wall. In the previous study, we showed that the sign of three terms of the turbulent helicity did not necessarily coincide with that of corresponding dissipation rates near the wall using the LES of rotating channel turbulence. In this study, we discussed this issue by spectral decomposition of the three terms of the turbulent helicity. It was shown that only the high wavenumber component of the spectrum cannot account for the sign of the dissipation rate.

It is known that K－ε model which has identical form to one for incompressible flow overestimates turbulent kinetic energy downstream of the shock when it is applied to a flow with shock/turbulence interaction. In this study, we analyze the results of direct numerical simulation by previous work and focus on terms which reflect compressibility effects directly to propose a turbulence model which incorporates them. We apply derived model to the flow with a shock to show that this model alleviates the overestimation of turbulent kinetic energy compared to the conventional K－ε model.

The effect of helicity, a physical quantity that describes the state of motion of a fluid, on fluid motion is studied. In this study, we predict the turbulent helicity taking advantage of the DNS database of the Ekman boundary layer. By modeling the turbulent-diffusion term due to pressure-vorticity correlation that appear in the transport equation for turbulent helicity, we attempt to predict the phenomenon more reproducibly than in previous studies. As a result, the two models employed reproduced the near-wall data reasonably well, but their upper-layer behavior differed from each other.

Since turbulence plays important roles in enhancing the skin friction drag of high speed transport systems and pipelines, its understanding and flexible control are of great significance in various engineering applications. In this study, we optimize the spatio-temporal distribution of the body force in a low Reynolds number turbulent channel flow by leveraging the adjoint analysis in order to understand turbulence physics and to develop a new control strategy. The optimal control input is found to effectively reduce the skin friction drag by actively manipulating near-wall coherent structures, which are essential for the self-sustaining processes of wall turbulence.

Calculating the hydrodynamic forces experienced by ships passing through the frozen sea area requires numerical study. In this study, tank experiments conducted under dense brash ices—whose effects were disregarded by earlier calculations—are used to validate the numerical results. As a result, the hydrodynamic force of a single piece of ice was successfully reproduced. In the case of two vertically aligned ices, the effects of ice spacing on the hydrodynamic forces acting on the rear ice were qualitatively reproduced. One of the ices in the dense brash ices experienced inconsistent hydrodynamic forces between experiment and calculation. Different flow fields between them are the primary reason because the relationship between the flow velocity around the ice and the pressure on it made sense in the calculation.

The water and benthic qualities were investigated, and numerical simulation using a hydrodynamic and ecosystem coupled model, incorporating the aquaculture model, was performed to evaluate the environmental impacts of aquaculture in an exposed sea. The simulation results show slight variations in the total nitrogen concentration due to the waste of farmed fish, whereas the observation results represent little variations, indicating that the impacts on water quality are not significant. The sulfide concentration, which is an indicator of benthic quality, increases a little in the farm, but it is well below the standard for aquatic water, indicating that the impacts on benthic quality are limited.

To evaluate the effectiveness of air cleaners by considering the airflow characteristics of indoor spaces, we proposed a CFD-based analysis method for the age of air of the blowing airflow and the residual lifetime of air of the intake airflow of air cleaners. Using this method, we conducted an analysis of an indoor space in which a portable air cleaner was installed. The results showed that the spatial distribution of age and the residual lifetime of air of the air cleaner alone can be analyzed separately from those of the ventilation system. This method enables us to evaluate not only the effectiveness of air cleaners in reducing pollutant concentration but also how quickly they can remove pollutants and deliver clean air in response to non-steady and sudden incidents of pollutant generation.

Automated Driving itself is not a purpose, but it should contribute for enhancing social welfare. Although vehicle automation levels are classified from Level 0 to Level 5, the aims and applicable operational design domains are totally different for private owned cars and service fleets such as buses and trucks. Based on the concept of functional road and street hierarchy, this article describes four possible vehicle types and/or services, which could be realized in the near future, and how to promote diffusion of such vehicles and services based on the applications with hierarchical concept of roads and streets.

In fields such as MaaS, demand-responsive transport, and autonomous driving, various POC trials have been conducted but there is still no "killer app" or a commercially viable "business model". The road to social implementation is not clear. In this paper, through a case study of the on-demand transportation service developed by the WILLER group, we examine business issues (rather than technical issues) and possible measures for the social implementation of MaaS.

As one of the efforts toward the social implementation of automated driving, the commercial launch of automated valet parking services in parking lots has been targeted, and in November 2018, a functional demonstration experiment was conducted using an actual parking lot. However, there are currently no examples of practical social implementation of automated valet parking services using automated driving technology in Japan. In this paper, we review the activities related automated valet parking in Japan, and discuss the challenges for social implementation, including the formation of an ecosystem from a business perspective, the establishment of a revenue model based on users’ value, and social implementation scenarios.

In the social implementation of automated driving technology, in addition to technical issues and legal/institutional issues, the improvement of social acceptance is identified as one of key factors. This paper reports on the results of a questionnaire survey conducted to analyze the expectations, level of acceptance and recognized challenges of the participants of a student business model contest on automated driving services, in order to clarify the effective measures to improve the acceptance of automated driving. The results showed that students' expectations regarding the introduction of automated driving increased over the course of the contest. The results also showed that observers from support companies may have changed their evaluation on issues regarding economic viability and business model over the course of the contest.

In Japan, where the population is expected to be aging and unevenly distributed, there is a need for the practical application of automated driving technology, especially in rural areas. To achieve this purpose, automated technology for passing through level crossings is important. However, most of the current automated driving technologies for level crossings require facilities on the infrastructure side and are not practical due to cost and other factors. In this paper, we propose a new method of automated driving technology with autonomy for passing level crossings and report the results of experiments using actual vehicles. Based on these results, we continue to aim to realize the driving assist and automated driving technology, which is autonomous and relatively easy to spread.

Implementation of Automated Driving Vehicle is discussed in these days. Actual current condition of automated driving development is well understood by experts, however difficult to see from lots of people in society. Analysis and visualization of actual running scenario on real road environment is required to show the automated drive current condition. A field operational test of automated bus with SAE Level 2 system has been conducted at Kashiwa-no-ha area, Kashiwa-city in Japan since 2019. This activity is operated as commercial services with safety driver. This paper introduces visualization results and some situations that safety drivers take over automated driving system running. The data shows outline of overtaking situation and detailed situation when they occurred. Also, this data processing challenge show the discussion points to explain to the society about the automated driving implemented with data.

Expectations are high for autonomous vehicles and electric vehicles utilizing infrastructure system installed on road. Vehicle localization system using magnetic markers embedded on road （Magnetic Positioning System） is being used in many autonomous vehicle tests. Research and development is going on to enable wireless power transfer to electric vehicles using coils embedded on road. Both systems emit electro-magnetic waves from the embedded system on road, but their cross effect has not been investigated. We have done preliminary testing to see their effects. Under static conditions, both systems did not show major influence that can inhibit the function of each other.

This study proposed a method for estimating pedestrian trust in an automated vehicle based on pedestrian behavior. It conducted pedestrian crossing experiments in VR where an automated vehicle approached a pedestrian crossing without a signal on a single road section to observe pedestrian behaviors. The experimental participants rated their trust in the vehicle at three levels in real time. The proposed method used the ratings to estimate their trust by using a deep learning method (LSTM) based on the skeletal coordinates extracted from the pedestrian observed by video camera, the pedestrian's position in the crossing direction, the vehicle's position, and speed in the direction of travel. The estimation accuracy rate was 61%.

A previous study classified appropriate stop position and method depending on the situation for each trigger of minimal risk maneuver (MRM), such as driver malfunction, based on a simple operational design domain (ODD). However, ODD can be set in various ways from the viewpoint of the driving environment, etc., and the events included in the ODDs vary. Therefore, this study assumes that the appropriate stop position and method differ when the MRM trigger occurs and shows how the appropriate stop position and method by MRM change depending on the difference in ODD.

Inactivation and decline of the rural or suburban areas by aging and depopulation have been clearer in the current Japan, which has become a super aging society. It is said that it is partly because inconvenience of short-range mobility causes the situation. The authors show that micro-EV (electric vehicle) cars are convenient for the daily short-range use in such areas shown above. We brought several micro-EV cars into a rural area near Tokyo, and we will show the situation and results with them. Theoretical conditions that make the micro-EV’s installed without problems are shown at the same time.

The capillary blood vessel plays a key role to maintain the physiological function by the nutrition supply to tissues, the removal of the metabolic decomposition product, and the immunocytic transportation. Structure of the capillary blood vessel is stabilized by physical and chemical interaction between vascular endothelial cells and pericytes. However, ‘pericyte loss’ which happens by aging, disruption of lifestyle habits, and inflammatory response increase vascular permeability, resulting in the dysfunction of the capillaries. In this study, we evaluated effect foods containing long pepper extract and gingko leaf extract on vascular permeability by using in vitro 3D capillary blood vessel model.