Wind tunnel investigation on a squared–back commercial vehicle

The assessment of an appropriate methodology for a wind tunnel investigation on a square back vehicle model is presented and discussed. The CD−Re curve is evaluated in order to identify the adequate range of Reynolds number for the tests. The drag coefficient value is attested at CD = 0.465 which is in accordance with the literature results for the same category of vehicles considered. The repeatability and the accuracy of the CD have been analyzed through a campaign of measurements and an error propagation analysis is dedicated to associate the correct uncertainty to the drag coefficient values. The analysis of statistical convergence of the measured quantities is also carried out in order to fix the adequate acquisition time. The results of the experimental investigation regarding the measurement methodology, drag coefficient, base pressure distribution, position of the center of pressure, and wake measurements are presented highlighting the main natural flow features. Moreover, the pressure fluctuations measured by microphone sensors allowed to evidence the unsteadiness and possible flow configurations involving the entire rear part.