Abstract The effect of varying the aspect ratio of a 1:8 scaled Ground Transportation System (GTS) was numerically investigated using the steady formulation of the RANS k − ω SST model. Cases of different aspect ratios (defined as the ratio of the varying width to the baseline width (Eq. (1)), with and without a boat-tail, were considered. For the GTS without boat-tail, a quasi-linear decline in the drag coefficient was found with increasing aspect ratio, resulting from a variation in the strength of the side shear layers, and the consequent change in the vertical symmetry of the near-wake. The average length of the wake was found to increase with increasing aspect ratios, resulting from an increase in the size of high Reynolds shear stress regions in the wake. For the GTS with boat-tail, variation of aspect ratio was found to have no effect on the critical boat-tail angle, albeit the magnitude of reduction in the drag coefficient differed between low and high aspect ratio configurations. Variation of the ground clearance ( G ∗ ) of the GTS (without boat-tail) concluded a G ∗ value corresponding to minimum drag coefficient ( G ∗ = 0.083 ) , while retaining of vertical quasi-symmetry was observed for G ∗ ≥ 0.29 .

中文翻译：

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纵横比对地面交通系统流动特性影响的数值研究

摘要 使用 RANS k − ω SST 模型的稳定公式，对改变 1:8 比例地面运输系统 (GTS) 的纵横比的影响进行了数值研究。考虑了具有和不具有船尾的不同纵横比（定义为变化宽度与基线宽度的比率（等式（1））的情况。对于没有船尾的 GTS，准线性下降发现阻力系数随着纵横比的增加而增加，这是由于侧剪切层强度的变化以及随之而来的近尾流垂直对称性的变化。发现尾流的平均长度随着增加纵横比，这是由于尾流中高雷诺剪切应力区域的尺寸增加造成的。对于带船尾的 GTS，发现纵横比的变化对临界船尾角没有影响，尽管低纵横比和高纵横比配置之间阻力系数的降低幅度不同。GTS（无船尾）的离地间隙 (G*) 的变化得出对应于最小阻力系数 (G*=0.083) 的 G*值，同时观察到 G*≥0.29 的垂直准对称性的保留。