Concept Design and Data-Reduction Algorithms for a 20-hole Omnidirectional Probing Sphere

Abstract

Multi-hole pressure probe measurement method is the only way to measure velocity, static and total pressure at the same time in three-dimensional flows. This study presents the construction of a 20-hole omnidirectional pressure probe model with a high enough frequency response to measure an angular range that is really omnidirectional, while the measurement angle range of the pneumatic probe is limited. The probing sphere is suitable for both steady and unsteady three-dimensional flow measurement with a cutoff frequency of 2000Hz approximately. A data-reduction algorithm is developed for the 20-hole pressure probing sphere, which is based on interpolation method for conventional multi-hole probe by using maximal pressure zone detection technique, one set of well-behaved pressure coefficients are defined and presented. Then, the performance of the developed coefficients and data-reduction procedures is demonstrated. The standard deviations of the predicted errors are on the order of degree for the flow angles and for the velocity magnitude, which satisfies Gaussian distribution approximately.