Correction of inertial effect on a sphere-probe to measure the unsteady flow

When a combined sphere-probe is used to measure the instantaneous value of velocity in the unsteady flow where both magnitude and direction of velocity vary strongly, the inertial effects on the pressure reading of the probe should be considered. A procedure is developed to secure the accurate measurement of velocity by the probe, assuming that the pressure reading is superimposed with the viscous term and the inertial term. The former is obtained by the calibration test, and the latter is predicted by the inviscid theory. The time derivative in the inertial term is determined from the time series data of the pressure reading using a digital computer. Applying this method to the experimental data, it was shown that one or two times iteration was enough for predicting the inertial term. The FORTRAN computer program is included.