Low-Speed Wind-Tunnel Tests of Two Weathercocking Sensors

Two blunt-nosed weathercocking wind direction sensors, one stabilized by a ring tall and the other by swept cruciform fins, were tested in a low-speed wind tunnel to investigate possible aerodynamic interference between these wind direction sensors and the vehicles in front of which they were to be mounted. In these low speed tests, sensor support shaft diameter and vehicle nose tip geometry both caused significant errors in the ring-tailed sensors alignment to the free stream when the vehicle was at angle of attack. A disk baffle placed on the shaft behind the sensor base was found to reduce sensor misalignment significantly at small angles of attack. Alignment errors for the cruciform sensor were much smaller than those of the ring-tailed sensor at small angles of attack, and these smaller errors were further reduced when a baffle was placed on the shaft.