Bridging the Gap between Pressure-Sensitive Paint and Balance Measurements

摘要

We consider the question of how to reconcile integrated forces and moments from a pressure-sensitive paintnmeasurement withmeasured forces andmoments froma balance.We showthat it is possible to compute the smallestnchange in pressure distribution thatwould be required to bring the two sets of data into agreement.We refer to this asnthe gap distribution and show that it can be expressed in terms of a set of basis functions that are determined by thengeometry of the test article. The use of these gap basis functions allows discrepancies in forces and moments to benexpressed in terms of a common unit ofmeasure, namely themagnitude of the implied gap distribution.We apply thisngap analysis to data froma wind-tunnel test of the NASAOrion commandmodule, for which both pressure-sensitivenpaint data and balance data are available. Results of the analysis confirmearlier suspicions that there was a problemnwith the normal component of force of the balance. Still, it is shown that application of the gap correction leads tonimproved pressure-sensitive paint data, as determined by the level of agreement with pressure tap data. The analysisnprocedure involving a pressure-gap distribution should be applicable to the comparison of balance data to integratednforces and moments from computational fluid dynamics calculations and other techniques.