Calibration of a segmented friction probe flush mounted in a sphere

A calibration theory for segmented probes flush mounted in a sphere exposed to uniform fluid flow was developed. The theory was checked experimentally by towing the sphere of diameter 2R = 22.2 mm with a three-segment circular electrodiffusion probe of diameter 2R_E = 0.526 mm through a pool of aqueous solution of potassium ferro/ferricyanide. Oriented wall shear rates were detected and analysed at Reynolds number 660. Hydrodynamic models of the wall shear rate distribution along the sphere surface in a uniform stream are reviewed. The principles of the direction specific flow measurements using three-segment electrodiffusion friction probes are explained.