Flow Separation in Four Configurations of Three Tandem Minibus Models

This paper presents an investigation of the pressure coefficients and flow separation in four configurations of three tandem minibus models through experiments and CFD simulations. The wind tunnel was used to measure the pressure distribution by installing 14 taping positions around the three minibusses' walls, and then the tapings were connected to a manometer. The 43mm 45mm dimensions of each model are 121mm (length, width, and height), and the ratio between the model and prototype is 1:40. The models are manufactured from iron with a thickness of 1 mm. Car 1 and car 2 are arranged in series at a constant distance (L) of 121 mm, while car 3 is installed in parallel with car 1 and car 2 with varying distances according to the configurations. The distances in the Y and X direction are denoted as M and N, respectively. N is set constant for each configuration. For configuration I, N is 0 mm. Furthermore, for configuration II, III, and IV, N is set at 121 mm, 242 mm, and 363 mm, respectively. Each configuration is given 6 M changes, with a constant airflow velocity (U) of 20 m/s or 72 km/h. The research was done at the Reynolds number (Re) of 55,120, which showed a significant change in the flow separation characteristics of the four configurations. Most values of the optimum pressure coefficient are positive, where the flow separation is smaller at the same M/D=0.57, in the following configuration order III, II, I, and IV subsequently.