Mach flow angularity probe curve fitting/calibration routine

A method of calibrating five-hole probes (mach flow angularity probes) that are used to measure local flow angles and Mach numbers in a flow field has been developed. Using a least squares curve fitting program, the misalignment angles of a mach flow angularity probe are determined using pressure data measured from all five orifices during a wind tunnel test. Calibration curves are then determined using a differential corrections technique that fits the data as a function of Mach number (pressure ratio) and total angle of attack which characterize the performance of a particular probe. Once a mach flow angularity probe has been calibrated, it can be used in the flow field of an aircraft to characterize the large variations in flow velocity and flow direction. Results are discussed from a calibration of supersonic data to illustrate the methodology used.

Other five hole probe calibration techniques are discussed to show a correlation of the method presented versus methods available. Disadvantages of using the other methods are discussed along with the advantages of using the mach flow angularity curve fitting/calibration routine.