A High Performance Airfoil-Profile Deflector for Open Sunroof Wind Noise

A high performance rigid airfoil profile sunroof wind deflector has been developed for high speed freeway driving with the sunroof open. This deflector is clearly superior to the conventional bar type deflector and less expensive compared to tall flexible fabric mesh deflectors applied on high end vehicles today. It provides superior speech intelligibility under high speed driving with sunroof open. The criterion for designing this deflector was to get the highest airspeed possible to span the sunroof opening under all conditions. The customized shape also utilizes flow unsteadiness, including those at the onset of buffeting, in order to condition the shear layer. The airfoil profiled deflector yielded superior mid and high frequency acoustic performance with acceptable low frequency performance. A shorter airfoil deflector was sufficient to keep the external airflow from entering the forward tilted sunroof opening on a mid-size SUV under test. Strategically located micron-scale ridges on the airfoil deflector help speed up the airflow while a notched trailing edge in the mid-section attenuates coupling of the shear-layer with the cavity resonance modes. At 120 km/ h with a fully open sunroof, the airfoil profile deflector was able to improve the articulation index (AI) by ∼25% over a conventional castled bar type deflector while the overall A-weighted sound pressure levels dropped by ∼8 dB. The AI values achieved with the airfoil deflector were better than those on comparable SUVs (Sport Utility Vehicle) in the segment that employed much taller mesh deflectors, without compromising low frequency performance with the original deflector.