New insights into how different ground simulation methods affect road vehicle aerodynamics are presented. Experiments are conducted on a 1/24th-scale model, representative of a Heavy Goods Vehicle, at a Reynolds number, based on width of 2.3 × 10 5 . Particular focus lay in characterising differences in unsteady wake development, with mean drag, base pressures, and wake velocities quantified, compared, and evaluated. Distinctly, these tests include the effects of elevated blockage ratio and wheel rotation. Results show moving ground use can have a substantial influence under these conditions, with increases in wake length and average base pressure coefficient of 17% and 9%, respectively. The dominant wake dynamics, characterised by a global streamwise oscillation commonly referenced as the bubble pumping mode, was also found dependent with asymmetric shedding frequencies from both vertical and horizontal base edges higher with static ground use. For these conditions, development of a low-frequency turbulence source, near omni-directional in nature, positioned behind the model, further contaminates the flow-field. This feature disappears with moving ground use. Both the nature and characteristics of the turbulence generated behind the wheels were also found to evolve differently, with a moving ground promoting stronger and more defined oscillatory behaviour up to model mid-height, two-and-a-half widths downstream. Overall, these results highlight that while variations in time-independent quantities to differing ground simulation can often be very subtle, prompting the interpretation of negligible overall effects, in-depth consideration from a time-dependent perspective may lead to a different conclusion.

中文翻译：

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转轮和动地使用对小型道路车辆非定常尾流的影响

提出了有关不同地面模拟方法如何影响道路车辆空气动力学的新见解。实验在代表重型货车的 1/24 比例模型上进行，雷诺数基于 2.3 × 10 5 的宽度。特别关注的是表征不稳定尾流发展的差异，量化、比较和评估平均阻力、基础压力和尾流速度。显然，这些测试包括高阻塞率和车轮旋转的影响。结果表明，在这些条件下，移动地面的使用会产生重大影响，尾流长度和平均基础压力系数分别增加 17% 和 9%。主要的尾流动力学，其特征是全局流向振荡，通常被称为气泡泵模式，还发现随着静态地面使用，垂直和水平底边的不对称脱落频率更高。在这些条件下，位于模型后面的几乎全方位的低频湍流源的发展进一步污染了流场。此功能会随着移动地面的使用而消失。还发现车轮后面产生的湍流的性质和特征发生了不同的演变，移动的地面促进了更强和更明确的振荡行为，直到模型中等高度，下游两个半宽度。总体而言，这些结果突出表明，虽然与时间无关的数量随不同地面模拟的变化通常非常微妙，从而导致对可忽略不计的整体影响的解释，