Three-dimensional direct numerical simulations of spherically propagating premixed turbulent hydrogen flames were carried out to clarify the influence of turbulence scale on propagating hydrogen/air flame. In a previous study (1), results suggested that an optimum integral length scale exists to promote flame propagation, with which the maximum burning velocity was obtained. This study investigates the influence of variation of turbulence scale on turbulent flame propagation and burning velocity within multiple turbulent flame radii. Results of the work suggest that an integral length scale was found where the maximum turbulent burning velocity exist. Also, it got larger as flame propagated.
Estimating the intentions and trajectories of other vehicles is critical to achieving stable, long-term planning and decision making in autonomous driving systems. This paper introduces a novel technique for estimating the intention and trajectory probabilities of surrounding vehicles. The first step is to use a deterministic behavior planner to identify possible trajectories and behaviors. The behavior planner models an average driver who follows the driving rules according to information provided by a road network map, and also provides the control signal used in the following step. Next, a customized particle filter is integrated with the planner to model the uncertainty of various trajectories and behaviors, using multiple sensing cues such as pose, velocity, acceleration and turn signal use. The proposed method supports various sensor modalities, depending on the availability of additional sensing information. Finally, by including the sensor data the probabilistic process is able to estimate the probabilities of various trajectories and intentions. The proposed method is generic to any driving situation supported by the behavior planner. Intentions such as ‘go forward’, ‘turn right’, ‘turn left’, ‘yield’ and ‘stop’ are supported by the proposed method. Our proposed method is evaluated using multiple, complex, simulated driving situations, and then comparing the simulation’s ground truth to the estimated probabilities. Evaluation criteria are how early and accurately our system can estimate the driving trajectory and intention probabilities of the vehicle. Our results show that the method can successfully estimate driver intention and trajectory in multiple complex situations, such as left turns, right turns and during passing, as well as at four-way intersections and bus stops.
In previous report, four-wheeled vehicle accidents in hilly and mountainous area are paid attention to Nagano Prefecture. These accidents are vehicle alone or head-on collision accidents caused by lane departure on the road with up and down slope and curve. This paper researched the risk of accidents using statistical data analysis related to road alignment. Furthermore, the authors investigated additional accident cases in hilly and mountainous area occurred in 2016, and reconstructed the accident using accident simulation to find out the influence of road alignment. In results, the risks of accidents, which are calculated the number of fatal accidents divided by the number of all accidents, at downhill with right curve and uphill with left curve in Nagano are higher than those in the whole of Japan. These accidents were caused by lane departure, and the vehicles fell to the outside road. The occupants died with multi-injured body parts by these accidents. The accident reconstruction simulation indicates the road slope affects the curve recognition time. Therefore, the road alignment becomes accident hazard factor, and is sure to indicate accident hazard map to prevent accidents in hilly and mountainous areas.
In this study, finite element models for two types of bicycles with different shapes were constructed. These deformable models were validated in quasi-static loading conditions, and were used to investigate the effect of the deformation of the bicycle body on the head injuries to its occupant. The analysis confirmed that, when deformable models are used, the kinematics of the cyclist after the contact with a vehicle changes, and the injury values are different, from those obtained by rigid models. In addition, different bicycle types produce different riding postures, which significantly change the rotational motion of the cyclist around the vertical axis, subsequently affecting head injuries.
Approximately 25% of the aerodynamic drag of passenger vehicles is contributed by the wheels. Small features in the tire geometry and the contact area between tire and ground can induce flow separation. Thus, the wheel wake features complex flow phenomena. To understand the appearing flow phenomena, a correct geometry representation of the rotating tire in CFD is essential. The model has to cover the rotating tread, the deformation due to weight and centrifugal forces. Realistic detailed and/or deformed tires are investigated with OpenFOAM® employing a hybrid approach to study the influence of geometrical features on the flow field and coefficients.
Particulate matter and – recently – particle number emissions from direct injection gasoline engines have already been regulated. The measurement techniques are well established for moderate temperature (23 ± 5 °C) but not for low temperature (e.g. -7 °C). Such an extended environmental condition has been enforced under real driving conditions but not yet for the laboratory testing. During development processes of engines and emission control systems, the testing at low temperature is of interest. This paper focuses on various challenges that need to be addressed for the developments with respect to engine calibrations and particle measurements under the extended environmental conditions.
Previously, some efforts were made to investigate the effect of combining premixed charge compression ignition (PCCI) combustion with conventional mixing controlled combustion using two injectors for single cylinder. In this experiment, the PCCI combustion was introduced by a sub injection fixed at early stage and the conventional diesel combustion was introduced by main injection starts near top dead center (TDC). The self-ignitability of sub injection fuel was modified by blending n-heptane and isooctane. Therefore, the ignition delay of PCCI combustion was extended to overlap with conventional diesel combustion near TDC by increasing the isooctane volume percentage in sub fuel. By overlapping PCCI and conventional diesel combustion, the cooling loss could be reduced. Later, the combustion and emission characteristics of the combined combustion strategy was examined. The experimental results showed that with larger PCCI combustion ratio at the fixed load, the degree of constant volume (DCV) increased. At the same time, the cooling loss was decreased slightly.
There are many studies comparing the behavior of ATD (anthropomorphic testing device) and PMHS (Post Mortality Human Subject = Cadaver) to improve the bio-fidelity of ATD. The best method to get bio-fidelity data for the development of ATD is human volunteer tests. But the human volunteer tests can be conducted only at low speeds. Previously we conducted low speed human volunteer tests, and high speed and low speed tests with ATD and PMHS. We compared the result of those tests at low speed and concluded the excursion of the human volunteer is less than the excursion of PMHS and the ATD's excursion is the least. But we could not make any conclusions about human volunteer response at high speed due to lack of data. We accessed high speed human volunteer test data which had completed in the 1970's in United States sponsored by National Highway Traffic Safety Administration (NHTSA) from NHTSA`s archives. In this report we compared these high speed human volunteer test results with our previous work and concluded the excursion of human volunteer is less than the excursion of PMHS at higher speeds, mimicking the findings at lower speeds.
In this study, we aim to develop a detection system of damaged crosswalks as a basic component of a digital map localization system. In rural areas, because the road paints of crosswalks are sometimes damaged, the features on which the existing methods focus for detecting them, such as rectangular shapes with side edges, are not clear. Thus, we focus on multi-layered faint features: existence of the white-band bottom shape, distribution of the white-band bottoms, and shape of the white-band candidates. Through an experiment on public roads, we confirm the practical performance of the proposed system.