Advanced pneumatic method for gradient flow analysis

Abstract

Pneumatic 5-hole probes are widely known reliable sen-!~ ko/(rfis) sors for the analysis of three-dimensional flow fields. Since the v m2/s accuracy of such measurements depends strongly on the volume of p ky/m 3 the probe and the gradients in the flow, a miniature spherical ~b o five-hole-probe with an improved analysis method was developed. With the new method, the complete physically reasonable angle measurement range can be used now by introducing modified calibration functions. A dimensionless examination of the flow around Subscripts spheres shows the independence of the calibration functions within abs a wide range of flow velocities. Misrepresentations in flows with high meas gradients caused by the volume of the probe are estimated by ref a geometry based correction method. The quality of the method is st analysed by an extensive error calculation. Results of measurements s in a three-dimensional model combustor are discussed. dynamic viscosity kinematic viscosity = #/p density separation angle * depends on quantity absolute measured reference static surrounding List of symbols Ap m 2 a m/s c m/s C o --Dm dm Kp, iKo, K~ -km M m X * n p N/m 2 q N/m 2 R J/(koK ) Rer, O, z m S X *