John Donovan

Aerodynamic applications of pressure sensitive paint

A pressure measurement technique based on a photoluminescent coating is being developed and used for aerodynamic applications. Visible light excites probe molecules in the paint and their luminescence is related to the static pressure. Details of the illumination, luminescence detection, and data reduction for this technique are presented. These include key issues such as temperature effects, camera calibration, and model movement. Results from this technique in a variety of flowfields are given. Comparisons with pressures measured using standard wall taps show good agreement

Experimental investigation of terminal shock sensors for mixed-compression inlets

This paper describes experimental investigations of devices designed for the nonintrusive detection of terminal shock location in mixed-compression inlets at high supersonic flight speeds. Systems based on sensing wall pressures by an array of wall-mounted transducers were selected for detailed study. Pressure signals were processed by three different methods: (1) interpretation of instantaneous pressure distributions, (2) detection of the turbulent intensity amplification occurring at the shock, and (3) determination of the upstream limit to which a search-tone, introduced at the downstream end of the channel, can propagate. The first two of these methods were tested in real time. The third method appeared feasible for weak shocks only; at high shock strengths, propagation upstream of the source could not be detected.

Pressure Sensitive Paint in Transonic Wind-Tunnel Testing of the F-15

The pressure sensitive paint (PSP) technique has been used to measure surface static pressures on a 4.7% scale F-15E model with complex store loadings during a high-speed wind-tunnel test. Successful employment of the technique required an integrated process of paint formulation, model preparation, test procedure, data acquisition, and data reduction. Testing a total of 107 different combinations of configuration s and flight conditions has provided an invaluable database. The data have immediate qualitative utility as surface flow visualization. Details of the measured pressure distribution were readily correlated with specific geometric features of the model. Absolute accuracy, and hence, quantitative utility is determined presently by the paint calibration. The digital data can be processed readily by appropriate software to provide pressure distribution plots, pressure increments, and integrated loads. This tests combination of duration, variety of flight conditions and configurations, and quick data turnaround represent a milestone in the practical application of PSP in aerospace testing.

The application of the pressure sensitive paint technique to high speed wind tunnel testing of a fighter aircraft configuration with complex store loadings

The Pressure Sensitive Paint (PSP) technique has been used to measure surface static pressures on a 4.7% scale F15E model with complex store loadings during a high speed wind tunnel test. Successful employment of the technique required an integrated process of paint formulation, model preparation, test procedure, data acquisition, and data reduction. Testing a total of 107 different combinations of configuration and flight condition has provided an invaluable database. The data have immediate qualitative utility as surface flow visualization. Details of the measured pressure distribution were readily correlated with specific geometric features of the model. Absolute accuracy and hence quantitative utility is determined presently by the paint calibration. The digital data can be processed readily by appropriate software to provide pressure distribution plots, pressure increments, and integrated loads. This tests combination of duration, variety of flight conditions and configurations, and quick data turnaround represents a milestone in the practical application of PSP in aerospace testing.

Recent Improvements in Pressure-Sensitive Paint Measurement Accuracy at Boeing

The accuracy of pressure measurements made with the Boeing Pressure-Sensitive Paint system has been re-assessed. The evaluation was done in light of recent system improvements, which include a new paint formulation and the addition of feedback control for the excitation lamps. A highly rigid test installation that minimized model displacements in the light field was also a factor. The observed accuracies for transonic test conditions range from 0.012 to 0.033 in terms of pressure coefficient. These results represent an improvement of 50 percent. Background and motivation Reference 1 documented the accuracy achieved by the Boeing Pressure-Sensitive Paint (PSP) system late in the year 2000. Uncertainty estimates were obtained from a statistical analysis of over 44,000 comparisons between measurements from PSP and those obtained from conventional pressure transducers. The standard uncertainty of the data from the intensity-based system with in-situ calibration, in a production wind tunnel, ranged from 0.16 to 0.45 psi. In terms of pressure coefficient, this is equivalent to 0.04 to 0.1. In addition, the variable-density capability of the tunnel was utilized to apply several levels of known, constant pressure to the model under quiescent conditions. The uncertainty for these wind-off test points was only 0.14 psi. ∗ Copyright c