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

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.