3/4开口式模型风洞的被动式湍流发生器研究

Research on Passive Turbulence Generator Based on 3/4 Open Model Wind Tunnel

摘要:

为适应大多数汽车行驶工况的试验模拟，通常风洞试验段内要求湍流度较低，但随着道路交通研究的不断深入和细化，行驶车辆的来流工况不能再单一地简化为低湍流度均匀来流工况，而汽车在湍流度较高的实际环境中，其气流结构和增阻机理等都会发生变化。为了能够提供更加符合这种道路工况的流场，本研究设计了一种被动式湍流发生器，用以模拟特殊工况下较高湍流度的自然来流情况。首先，使用数值仿真方法分析湍流发生器产生的湍流效果，并对比其与实际道路风谱的吻合度。然后，对风洞测试段的流场品质和射流剪切层特性进行分析，发现湍流发生器会使低频颤振现象变得明显，为此结合抑振型海豹胡须喷口结构来进一步优化其湍流效果及流场特性。最后，通过模型风洞试验对仿真结果以及所产生的湍流效果进行验证。结果表明，被动式湍流发生器能够很好地模拟较高湍流度的自然来流，同时仍然能维持风洞内较低的低频颤振水平。

Abstract:

Wind tunnel testing is a pivotal methodology for investigating automotive aerodynamics. In order to simulate test scenarios encompassing a broad spectrum of real-world driving conditions， wind tunnel test sections typically demand a relatively low level of turbulence intensity. However， as road traffic research becomes increasingly intricate， the notion of simplifying vehicle inflow conditions to uniformly low turbulence is no longer adequate. On one hand， the evolution of autonomous driving technologies has led to reduced inter-vehicle spacing at high speeds， even giving rise to platooning scenarios. Under such conditions， the trailing vehicle contends with inflow characterized by heightened turbulence intensity. On the other hand， vehicles navigating through non-open-road environments， like those flanked by trees or buildings， confront inflow conditions that are far from being characterized by low， uniform turbulence. The aerodynamic flow structures and drag-increasing mechanisms experienced by vehicles in these high-turbulence real-world settings undergo transformation. To furnish a flow environment more closely aligned with these road conditions， this study has devised a passive turbulence generator， aimed at emulating elevated turbulence intensity scenarios prevalent in specific driving conditions. Initially， numerical simulation techniques were employed to assess the turbulence-generating efficacy of the generator， and its resemblance to actual road flow spectra was examined. Subsequently， an analysis of the wind tunnel test section's flow field quality and jet shear layer characteristics revealed the amplification of low-frequency flutter phenomena attributed to the turbulence generator. To address this issue， a vibration-damping variant of the harbor seal whisker nozzle structure was incorporated， further investigating its impact on turbulence and flow field characteristics. Finally， model-scale wind tunnel experiments were conducted to validate both the simulation outcomes and the generated turbulence effects. The results underscore the capability of the passive turbulence generator to aptly emulate the higher turbulence intensity natural inflow conditions while still maintaining low-frequency flutter at manageable levels within the wind tunnel environment.