...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>SAE International Journal of Passenger Cars - Mechanical Systems >Identification of Vortical Structure that Drastically Worsens Aerodynamic Drag on a 2-Box Vehicle using Large-scale Simulations
【24h】

Identification of Vortical Structure that Drastically Worsens Aerodynamic Drag on a 2-Box Vehicle using Large-scale Simulations

机译：使用大型模拟识别在2厢式车辆上急剧恶化的空气阻力的涡流结构

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

It is important to reduce aerodynamic drag for reducing fuel consumption. Conventionally reduction of aerodynamic drag has been carried out by shape optimization of each part of a vehicle based on the investigations of the time-averaged flows around the vehicle. However, the general tendency of drag reduction has been saturated recently and it is required to develop a new flow-control technique to achieve further reduction in aerodynamic drag. We therefore focus on the unsteadiness of the flow around a vehicle to achieve it because the aerodynamic drag of a vehicle fluctuates over time due to repetitions of generation, growth, merging and disappearance of various sizes of vortices around it. These vortices are formed by flow separations, for which the longitudinal coherent vortices inside turbulent boundary layers on vehicle surfaces are presumably playing an important role. However, there have been few studies on these vortices due to the difficulty in performing such a high-resolution flow simulation that is able to capture these small structures. In fact, the size of these vortices in the boundary layers on vehicle surfaces is estimated to be as small as 0.4 mm when the vehicle is running at 100 km/h. In the present paper, we carried out wall-resolving LES (Large Eddy Simulation) for 1/4-scale simplified 2-box car models. The Reynolds number based on the vehicle speed and the representative length of 1.06 m is set to about 0.71 million. By using K computer, which accommodates approximately 80,000 CPUs, we have realized large-scale flow computations by using approximately 2.9 billion grids. At first, we investigated appropriate grid resolution by considering the size of the longitudinal coherent vortices in the boundary layers and we have confirmed the importance to accurately resolve turbulent boundary layers in the under-floor flow of a car model. Next, we have identified critical differences in the vortical structures behind car models that have high and low aerodynamic drag. Especially, we have found that the hone-shaped vortical structures are formed behind the car model with a drastically worsened aerodynamic drag, and proposed a formation process of such vortical structures. This new finding is expected to help us achieve further reduction in aerodynamic drag of 2-box vehicles. In addition, we have found that the under-floor flow plays an important role in the above-mentioned formation process and it is essentially determined by the under-floor shape of a car model and is little affected by the flows over the roof, C pillar, or side surfaces of a car model.
机译：重要的是减少空气阻力以减少燃料消耗。传统上，已经基于对车辆周围的时间平均流量的研究，通过对车辆的每个部分的形状进行优化来减小空气阻力。然而，减阻的总体趋势近来已经饱和，并且需要开发新的流量控制技术以实现气动阻力的进一步减小。因此，我们将注意力集中在车辆周围实现流动的不稳定上，因为车辆的空气阻力随着时间的流逝而波动，这是由于周围周围各种尺寸的涡流的产生，生长，合并和消失的重复。这些涡流是通过流动分离形成的，为此，在车辆表面湍流边界层内部的纵向相干涡流可能起着重要的作用。但是，由于难以执行能够捕获这些小结构的高分辨率流模拟，因此对这些涡旋的研究很少。实际上，当车辆以100 km / h的速度行驶时，在车辆表面边界层中的这些涡流的大小估计为0.4 mm。在本文中，我们对1/4比例简化的2盒汽车模型进行了壁解析LES（大涡模拟）。基于车速和代表长度1.06 m的雷诺数设定为约71万。通过使用可容纳约80,000个CPU的K计算机，我们通过使用约29亿个网格实现了大规模的流量计算。首先，我们通过考虑边界层中纵向相干涡旋的大小来研究适当的网格分辨率，并且我们确认了准确解析汽车模型在地板下流动中湍流边界层的重要性。接下来，我们确定了具有高和低空气动力阻力的汽车模型背后的涡流结构中的关键差异。特别是，我们发现，在汽车模型的后面形成了磨削形的旋涡结构，其气动阻力急剧恶化，并提出了这种旋涡结构的形成过程。这一新发现有望帮助我们进一步降低2厢式车辆的空气阻力。此外，我们发现地板下流动在上述形成过程中起着重要作用，并且基本上由汽车模型的地板下形状决定，并且几乎不受屋顶上的流动C的影响。柱子或汽车模型的侧面。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号