Swept Collector Design for the Honda Automotive Laboratories of Ohio Wind Tunnel

Modern aeroacoustic wind tunnels are required to have flat axial static pressure distribution, very low background noise levels, and minimal low frequency pressure fluctuations. These characteristics enable accurate measurement of aerodynamic forces acting on a vehicle as well as identification of noise sources. The collector of an open-jet or ¾ open jet wind tunnel plays a critical role in achieving these goals. Collector self-generated noise contributes to the overall background noise level in the test section, and this contribution has become more significant as other noise sources, such as the main fan, have been addressed through improvements to acoustic treatment. Ever-increasing attention to detail is required to manage noise signatures as the overall facility noise floor is lowered. Furthermore, aspects of collector design that may be beneficial to aerodynamics or pressure fluctuation tend to be some of the worst offenders for noise generation. A new collector configuration was designed during construction of the Honda Automotive Laboratories of Ohio (HALO) Wind Tunnel. The collector design balances functional requirements for aerodynamics and acoustics, with development work making use of modern computational fluid dynamics techniques and sub-scale laboratory testing. The resulting collector design enabled a flat axial static pressure distribution and low background noise levels and helped minimize low frequency pressure fluctuations. A previous paper describes the HALO wind tunnel’s overall features and commissioning results. This paper focuses specifically on the challenges, engineering approach, and trade-offs that went into the collector design.