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首页> 外文会议>Vehicle aerodynamics, 2012. >Assessment of a Vehicle's Transient Aerodynamic Response
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Assessment of a Vehicle's Transient Aerodynamic Response

机译：评估车辆的瞬态空气动力响应

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A vehicle on the road encounters an unsteady flow due to turbulence in the natural wind, due to the unsteady wakes of other vehicles and as a result of traversing through the stationary wakes of roadside obstacles. There is increasing concern about potential differences between the steady flow conditions used for development and the transient conditions that occur on the road. This paper seeks to determine if measurements made under steady state conditions can be used to predict the aerodynamic behaviour of a vehicle on road in a gusty environment. The project has included measurements in two full size wind tunnels, including using the Pininfarina TGS, steady-state and transient inlet simulations in Exa Powerflow, and a campaign of testing on-road and on-track. The particular focus of this paper is on steady wind tunnel measurements and on-road tests, representing the most established development environment and the environment experienced by the customer, respectively. Measurements of the surface pressure on the front sideglass were used for comparisons as this area exhibits a complex flow which is highly sensitive to yaw angle and which is also an important region, for wind noise considerations in particular. It was found that, if the transient on-road environment is known then steady-state wind tunnel measurements can be used to predict accurately the transient surface pressures, provided the methodology is sufficiently rigorous. Admittance or transfer function techniques are commonly used to compare transient and steady-state results and the limitations of these methods are shown here when the spectra of self-excited and externally imposed unsteadiness overlap. A new method is introduced to obtain a "true" transfer or admittance function, unconfused by the presence of self-excited unsteadiness. The aerodynamic admittance was found to be close to unity up to a frequency of 2-10 Hz and it then drops progressively.
机译：由于自然风的湍流，其他车辆的不规则尾迹以及横穿路边障碍物的固定尾迹，导致道路上的车辆遇到不稳定的流动。人们越来越关注用于开发的稳定流量条件和道路上发生的瞬态条件之间的潜在差异。本文试图确定在稳态条件下进行的测量是否可用于预测大风环境下车辆在道路上的空气动力学行为。该项目包括在两个全尺寸风洞中进行的测量，包括使用Pininfarina TGS，Exa Powerflow中的稳态和瞬态进气道仿真，以及一项在道路和轨道上进行测试的活动。本文的重点是稳定的风洞测量和道路测试，分别代表最成熟的开发环境和客户所体验的环境。前侧玻璃上的表面压力的测量用于比较，因为该区域显示出复杂的流动，该流动对偏航角高度敏感，并且这也是重要的区域，尤其是考虑到风噪声。已经发现，如果已知瞬态道路环境，则稳态风洞测量可用于精确预测瞬态表面压力，前提是该方法足够严格。导纳或传递函数技术通常用于比较瞬态和稳态结果，当自激和外部施加的非稳态光谱重叠时，此处显示了这些方法的局限性。引入了一种新方法来获得“真实的”传递或导纳函数，而不会因存在自激不稳定而感到困惑。发现空气动力学导纳在频率为2-10 Hz时接近统一，然后逐渐下降。

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