Experimental investigation of aeroacoustic cabin noise in unsteady flow by means of Natural Wind Generator

Paper #:
  • 2017-01-1545

Published:
  • 2017-03-28
Abstract:
Though aeroacoustic performance of passenger vehicle under steady state has been improved, fluctuating cabin noise that passengers are more sensitive to has not been researched enough. Previous works on cabin noise in unsteady flow was conducted by road tests and wind tunnel test with devices that produce turbulent flow. Considering the difficulty in setting the condition and data reproducibility in road test, wind tunnel test is preferable.However, wind tunnel test with turbulence generating devices has also difficulty in reproduction of natural wind. Though previous researches has been conducted mainly under flow with yaw angle fluctuation, flow velocity fluctuation has not been considered because these two factors have not been generated at the same time by existing facilities. Additionally, high turbulence intensity and high frequency fluctuation of flow in road condition are not reproduced together either. Our new facilities (NWG: Natural Wind Generator),which was newly developed in Toyota wind tunnel, has solved those issues. NWG consists of two arrays of wings which can generate turbulence intensity up to 10% at 2Hz pulsation, ,and maximum frequency is 5Hz.Both velocity and yaw angle fluctuation can be generated and natural winds as in road test can be replicated too.The noise impression by means of NWG is quite similar to that of road test and artificial head data with impression result, shows that modulating cabin noise gets amplified when the yaw angle and flow velocity get larger at the same time. This shows fluctuations of both yaw angle and velocity are main cause of cabin noise fluctuation.In addition, quasi-steady state cabin noise is estimated from static data which is achieved by evaluation with yaw angle and velocity of flow change. It is shown that unsteady cabin noise is a little smaller than quasi-steady state especially with flow fluctuaion at high frequency.
Also in:
  • SAE International Journal of Passenger Cars - Mechanical Systems - V126-6
  • SAE International Journal of Passenger Cars - Mechanical Systems - V126-6EJ
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