This paper introduces the new fast response aerodynamic probe, which was recently developed at the ETH Zurich. The technique provides time-resolved, three-dimensional flow measurements using the virtual four sensor technique. The concept and the evaluation of the virtual four sensor probe is discussed in detail. The basic results consist of yaw and pitch flow angles as well as the total and static pressure. They combine to form the unsteady, three dimensional flow vector. The outer diameter of the cylindrical probe head was miniaturized to 0.84mm, hence probe blockage effects as well as dynamic lift effects are reduced. The shape of the probe head was optimized in view of the manufacturing process as well as aerodynamic considerations. The optimum geometry for pitch sensitivity was found to be a cylindrical surface with the axis perpendicular to the probe shaft. The internal design of the probes led to a sensor cavity eigenfrequency of 44kHz for the yaw sensitive and 34kHz for the pitch sensitive probe. Data acquisition is done with a fully automated traversing system, which moves the probe within the test rig and samples the signal with a PC-based A/D-board. An error analysis implemented into the data reduction routines revealed acceptable accuracy for flow angles as well as pressures for many turbomachinery flows. Depending on the dynamic head of the application the yaw angle is accurate within ±0.35° and pitch angle within ±0.7°. In the final section, a comparison of time averaged results to five hole probe measurements is discussed. The advantages of the new probe, beside its unique smallness, are the complete unsteady kinematic information and the improved recording of unsteady total pressure measurement as it is pointed out in a comparison against a 2D virtual three sensor probe.

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