Extended Angular Range of a Three-Hole Cobra Pressure Probe for Incompressible Flow

Abstract

This paper analyzes the operative characteristics of a three-hole cobra type probe especially designed to attain an angular range higher than 180deg for planar turbulent flows. A new calibration and data reduction method are also introduced, discriminating three different zones inside the angular range of the calibration. This methodology improves the probe performance, extending its operative angular range from the typical ±30degto±105deg. In addition, the transmission of the uncertainty—from the pressure measurements to the flow variables—is estimated, showing reasonably low levels for the whole angular range. Furthermore, the sensibility of the probe calibration to the Reynolds number and the pitch angle is considered, and the influence of the turbulence level is outlined. Regarding these factors, the probe precision in the extended angular range is found to be similar to that of the traditional range. Finally, the probe is tested in a flow field with large variations of the incidence angle, and the results obtained with the new method are compared to those given by the traditional calibration.