非稳定流条件下艾哈迈德体的气动性能和近尾流

IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL
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引用次数: 0

摘要

本文通过分析全局力和详细的尾流效应,对艾哈迈德体周围的非稳态效应和流场进行了实验描述。实验结果与稳定条件下获得的结果进行了比较,风洞速度不同,模型与自由流之间的偏航角也不同。非稳态场是通过位于试验段入口处的振荡叶片产生的,其振幅和频率很容易控制。具体来说,考虑的是低频,约为几赫兹,这是在车辆上产生负载振荡的典型范围。通过对测力平衡获得的力系数结果和粒子图像测速仪获得的速度场结果进行处理,以得出时间平均统计量和相位平均统计量,这与强制叶片的瞬时定位有关。由于测量系统的时间分辨率很高,力测量的时间分辨率约为 100 Hz,速度测量的时间分辨率约为 4000 Hz,因此可以进行此类分析。作为风洞速度和偏航角的函数,稳定条件下的结果与之前参考文献中的结果进行了很好的比较。在非稳态条件下,无论考虑何种振幅,时间平均阻力和升力系数及其与偏航角的关系都低于稳态情况。与时间平均值相比,非稳态条件下的相位平均系数可波动约 20%,这些波动与偏航角和振幅密切相关,因此表明它们都对瞬时载荷有影响。目前的研究与辅助驾驶(自动驾驶)车辆控制系统设置的改进有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Aerodynamic performances and near wake of an Ahmed body under unsteady flow conditions

This paper experimentally characterizes unsteady effects and flow fields around the Ahmed Body, by analyzing global forces and detailed wake effects. The results are compared to those obtained under steady conditions, with varying wind tunnel velocities and different yaw angles between the model and the free stream. Unsteady fields are generated by means of oscillating blades positioned at the inlet of the test section, whose amplitudes and frequencies can be easily controlled. Specifically, low frequencies, around a few Hertz, as those in the typical range generating load oscillations on vehicles, are considered. The results in terms of force coefficients, obtained by a dynamometric balance, and velocity fields, obtained by Particle Image Velocimetry, are processed in order to derive time-average statistics and also phase-average statistics, as related to forcing blade instantaneous positioning. This type of analysis can be performed thanks to the high temporal resolution of measurement systems, around 100 Hz for the force measurements and around 4000 Hz for the velocity measurements. Results in steady conditions well compare with previous results in references, both as functions of wind tunnel velocity and yaw angles. In unsteady conditions, whatever amplitude is considered, time-average drag and lift coefficients and their dependence on yaw angle are consistently lower compared to the steady case. Phase-averaged coefficients in unsteady conditions can oscillate by around 20 % in comparison to time-average values and these fluctuations are strongly dependent on yaw angle and amplitude of oscillations, thus suggesting that they both contribute to instantaneous loads. Present investigations are related to improvements in set-up of control systems in assisted-driving (self-driving) vehicles.

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来源期刊
Experimental Thermal and Fluid Science
Experimental Thermal and Fluid Science 工程技术-工程:机械
CiteScore
6.70
自引率
3.10%
发文量
159
审稿时长
34 days
期刊介绍: Experimental Thermal and Fluid Science provides a forum for research emphasizing experimental work that enhances fundamental understanding of heat transfer, thermodynamics, and fluid mechanics. In addition to the principal areas of research, the journal covers research results in related fields, including combined heat and mass transfer, flows with phase transition, micro- and nano-scale systems, multiphase flow, combustion, radiative transfer, porous media, cryogenics, turbulence, and novel experimental techniques.
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