An Investigation into the Bias Error Caused by Anomalies in Static Pressure Taps
Abstract
Static pressure taps are widely used in studying aerodynamics. They are used both in the design process (wind tunnel testing) and for controlling the aircraft (FADS). With the high levels of accuracy possible from current pressure measurement devices and the precise controls required for high-speed flights, bias caused by anomalies in pressure taps needed to be quantified. The parameters investigated in this study were the yaw angle, off-normal angle, and the diameter. The yaw angle was measured relative to the direction of air flow and varied between 0 and 360 degrees. The off-normal angles were measured relative to an axis perpendicular to the surface and were: 30, 20, and 10 degrees. The diameter of the pressure tap was varied up to 50% of the boundary layer thickness. For all of these a 0.026" diameter tap was used as a reference this corresponded to approximately 10% of the boundary layer thickness. It was discovered that a 30 degree off-normal tap with a yaw angle of 0 degrees gave a bias error of 0.3% of the dynamic pressure. Other off-normal and yaw angles gave smaller bias errors. Yaw angles of between 0 and 90 degrees gave positive bias errors and yaw angles between 90 and 180 degrees gave negative bias errors. These errors decreased as the off-normal angle decreased. It was also found that larger diameter taps gave larger pressure bias errors. Taps with a diameter smaller than the reference gave negative bias relative to the reference tap pressure. All results were non-dimensionalized by the boundary layer thickness, or the dynamic pressure.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 2014
- Bibcode:
- 2014PhDT........66O
- Keywords:
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- Engineering, Mechanical;Engineering, Aerospace