Aerodynamic characteristics have great influences on fuel economy and environmental problems nowadays. The aim of this research is to analyze the influence of configurations and diffusers of road vehicles on aerodynamic characteristics. As configuration parameters, the rear window angle and the side window angle are adopted, and together with the diffuser angle, totally 126 patterns of configurations changing from box type through fastback to notchback types are investigated by wind-tunnel experiments using the moving belt. As results, by the rear diffuser, the lift is decreased with the minimum at diffuser angle 15°, but overall the drag is increased except for diffuser angle 5°~10° with the minimum at diffuser angle 5°. The drag is greatly reduced when combined with side angles 30° and diffuser angle 5°. The well-known tendency that the drag increases steeply at rear angle from 20° to 35° appears with side angles 0° and 15° for most diffusers, while this tendency does not with side angle 30°. Visualization by the five-hole Pitot tube suggests that the drag reduction can be obtained by restraining longitudinal vortices.
In recent years, while data mining has attracted attention, formal concept analysis has the disadvantage that although it can understand the inclusion relation between attributes, it doesn’t know what kind of meaning or inclusion relation the attributes have. Therefore, in this study, the inclusion of the attributes and the visualization of the correlation are realized by combining the Hasse diagram by formal concept analysis and the layout diagram of the attribute of quantification theory type III for visualizing the meaning between the attributes. Moreover, in order to confirm usefulness of the proposed method, we developed a simultaneous visualization system of inclusion and correlation combining formal concept analysis and quantification theory type III, and evaluated the proposed method using verification data. As a result, it was confirmed that useful information that can’t be obtained only by formal concept analysis or quantification theory type III can be extracted.
This paper describes experimental visualization results of flow around a vehicle model using Global Luminescent Oil-Film Skin-Friction (GLOF) meter which can measure both skin-friction distribution and skin-friction vector by detecting luminescent intensity of an oil film on the surface. In particular, we can understand basic fluid structures such as flow separation, reattachment, and vortices and their quantitative locations based on the skin-friction-vector distribution obtained by this technique. The analysis results well capture the characteristics vortex structure in the rear window surface and the vertical vortex generated at the C-pillar. Although a few technical problems are also seen, our results show that GLOF meter is an effective tool for the quantitative visualization of the flow around the vehicle body.
Prediction of flow around a vehicle in crosswind is of great practical importance to improve stability and aerodynamic performance. Since changes in the wake structure in crosswind strongly affect the aerodynamics, a measurement technique that can observe the complicated flow field on the back side has been required. This paper describes visualization results of skin-friction vector-fields on the back side using a Global Luminescent Oil-Film Skin-Friction (GLOF) meter. Although a pair of separation bubbles with a two-dimensional structure are formed on the back at 0 yaw angle, these changes into a coherent longitudinal vortex at high yaw angle. A sharp increase and hysteresis in the aerodynamic drag are caused by the difference of these vortex structures on the back as the yaw angle changes.