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The thermal fluid field in a vehicle cabin model is analyzed by the mesh free method as well as mentioned in the Part 1. This paper focuses on the steady state indoor climate in the vehicle cabin including the effect of the buoyancy, the heat generation of the driver and heat conduction through the vehicle body surface under the maximum air-cooling condition soaked in a climate chamber in the summer condition for the demonstration of the mesh free method without not only the deformation of the 3D-CAD model but mesh generation. The solar radiation distribution and heat generation through the exhaust pipe from the engine room are simply included in the analysis. Simulated results are compared with experiments in the conditions of both moving and idling states. As a result, no significant difference in air temperature between simulation and experiments can be obtained in both conditions.

The thermal fluid field in a headlamp based on the real 3D-CAD model is analyzed by a mesh free method. The conducted method is a new CFD (Computational Fluid Dynamics) solver based on the couples of the points whose density is controlled scattered in the analysis space including the boundaries, which leads to much reduce the hand-working time in the deformation of the 3D-CAD model for the mesh generation. This paper focuses on the steady state airflow field in a headlamp under the conditions of natural ventilation including the effect of the buoyancy and the heat generation of the lamp surface for the demonstration of the conducted method without not only the deformation of the real 3D-CAD model but mesh generation. The differences of the pressure outlet conditions and heat generation of the headlamp on the amount of the ventilation are also experimented.

In the present study, two kinds of simplified vehicle models, which can reproduce flow structures around the two sedan-type vehicles in the previous study, are constructed for the object and the unsteady flow structures are extracted using Large-Eddy Simulation technique. The numerical results are validated in a stationary condition by comparing the results with a wind-tunnel experiment and details of steady and unsteady flow characteristics around the models, especially above the trunk deck, are investigated. In quasi- and non- stationary manner with regard to vehicle pitch motion, unsteady flow characteristics are also investigated and their relations to an aerodynamic stability are discussed.

This study shows an example in which the conventional aerodynamic evaluation method that focuses on “steady” aerodynamic lift coefficient is not necessarily sufficient to evaluate vehicle's straight-ahead stability at high speed, and proposes a new aerodynamic evaluation method for vehicle stability. In vehicle development, it is generally said that vehicle with lower aerodynamic lift coefficient has better straight-ahead stability at high speed. However, in some cases, straight-ahead stability differs between two vehicles with similar low aerodynamic lift coefficient. It is natural to think that this variation is caused by the difference of suspension characteristics or vehicle body rigidity. But from our experiences, different straight-ahead stability was observed between two vehicles having same suspension characteristics, same vehicle body rigidity and almost similar aerodynamic lift coefficient, but different vehicle configurations.

Experiment and CFD have been performed to clarify the distribution of wind noise sources and its generation mechanism for a production vehicle. Three noise source identification techniques were applied to measure the wind noise sources from the outside and inside of vehicle. The relation between these noise sources and the interior noise was investigated by modifying the specification of underbody and front-pillar. In addition, CFD was preformed to predict the noise sources and clarify its generation mechanism. The noise sources obtained by simulation show good agreement with experiment in the region of side window and underbody.

This paper describes results of the correlation tests between several full-scale automotive wind tunnels in Japan. The tests were carried out during FY 2003 by members of the working group for wind tunnel correlation test, which was organized in JSAE Vehicle Aerodynamics Research Committee. Five wind tunnels were selected, i.e., three open test section type wind tunnels and two closed ones. Four test models were selected, i.e., sedan, station wagon, minivan and hatch back car, all of which are current production models. Tests were done with EADE test conditions. Correlation formulas for drag coefficient, which are based on the previous methods by Mercker and Wiedemann [13] and Mercker [3, 10] respectively for open and closed test section type wind tunnels, were used. Also considered were the differences of the boundary layer thickness between five wind tunnels.

Aerodynamic noise generated in production vehicle has been evaluated using experiment and numerical simulation. Finite difference method (FDM) and finite element method (FEM) are applied to analyze the flow field, and Lighthill's analogy is employed to conduct acoustic analysis. The flow fields around front-pillar obtained by numerical simulations agree with those by experiment for two cases with different front-pillar shape. Moreover, the distribution of acoustic source predicted by FEM is consistent with that obtained by experiment. Present study ascertained the feasibility and applicability of FEM with SGS model towards prediction of aerodynamic noise generated in production vehicle.

For both notchback-type and fastback-type models, it has been found that critical geometries which increase the aerodynamic drag exist, and the time-averaged wake patterns basically consist of an arch vortex behind the rear window and trailing vortices in the wake. The unsteady characteristics of the wake seem to be directly related to aerodynamic drag. However, the unsteady characteristics of these wake patterns for notchback and fastback cars were not clear. The purpose of present paper is to clarify these phenomena. We try to analyze experimentally the unsteady characteristics by measuring the velocity fluctuations in the wake, the pressure fluctuations on the trunk deck and the drag-force fluctuations acting on the model. At the same time, the analysis of the numerical simulation was made by using the same numerical model as the experimental model. The computed flow visualization behind the rear window showed a fluctuating arch vortex.

Notchback models generally have more complicated flow patterns than box models. This leads to intricate infuluence of rear geometry of Notchback on aerodynamic drag. Therefore, based on understanding of wake structure, flow phenomena for reducing the drag can be analyzed. This paper analyzes the influence of geometry of rear portion on the drag by means of 1/5 scale notchback models. For fastback models, at certain critical angle of the rear window the drag shows a sharp peak. For notchback models, it is found that some combination of the angle of rear window and the height of trunk deck shows simillar maximum in the drag. Moreover, the flow visualization and the detailed measurements of velocity fluctuation clarify typical vortex patterns of wake, which are an arch-type vortex behind the rear window and the trailing vortex behind the trunk deck.