This paper presents the results of an investigation of the near wake of isolated, cambered and un-cambered 40 % scale, non-deformable Champ Car wheels rotating in ground contact. The results of this study suggest that the vortex structure surrounding an isolated wheel rotating in ground contact differs from the theoretical proposal in that: 1. The vortex shed from the hub, on the side of the support strut, is suppressed; 2. The vortices shed from the hub on the opposite side to the support strut, and from the upper tyre shoulder of that side are suppressed by entrainment of flow from inside the wheel hub; 3. The jetting vortices emanating from in front of the tyre contact patch have lower vorticity than those from the upper tyre shoulders. The above points apply to both the parallel and cambered wheels. However the results of the cambered wheels generally showed more defined, higher intensity vortex structures. Correspondingly, the cambered wheel was found to have approximately a 12% higher drag coefficient than a parallel wheel, based on respective frontal areas. The vortices persisted to 100 mm downstream of the wheel. By this downstream station, however, the vortical structures on the side opposite to the support sting were beginning to coalesce. A region of reversed flow was noted at every measurement station except 100 mm downstream of the parallel wheel. In every case this area was concentrated, or skewed towards, the lower left shoulder of the projected wheel profile. The region was more pronounced in the cambered wheel results and extended outside the projected area of the wheel into the freestream. The cause of the reversed flow could not be determined from the experimental data but also appears to be present in other published research. Further work using alternative, instantaneous velocity measurement techniques will be required to resolve the causes of this interesting flow feature.
On the near wake of rotating, 40%-scale champ car wheels
Über die Nachlaufströmung der Rotation bei Reifen von 40%-Rennautomodellen
2002
9 Seiten, 6 Bilder, 1 Tabelle, 10 Quellen
Conference paper
English
On the Near Wake of Rotating, 40%-Scale Champ Car Wheels
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