Distortion correction for low sonic boom wind tunnel model measurements is determined from measuring a calibration model with a flat-top signature shape. Accurate pressure measurement hardware must first be created that avoids unwanted reflected shocks. Then the delta pressure measurement of the model's sonic boom includes 20-50% magnitude distortions from the wind tunnel's flow field variations. A slope and zero (intercept) correction is determined from translating the flat-top model's three DP/P flat signature portions-positive flat, negative flat and trailing zero flat-to overlap the desired measurement range on the measurement hardware. Application of the correction reduced distortion by a factor of three and improved the repeatability of corrected model measurements. When used with the best practice "spatial averaging" measurement method of ref. 1, the calibration improves accuracy, requiring fewer measurements for the same accuracy. However, results indicate that the extra time required for calibration measurements is not as time/cost effective as taking more spatial averaging measurements. Possibly less effective because any variation in tunnel distortion patterns between run series, limit calibration accuracy. Howerver, calibration measurements do provide more understanding of test section flow conditions.
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