Aerospace applications of luminescent paint Part one: Pressure measurement

Luminescent paints allow non-intrusive measurement of pressure and temperature at high spatial resolution without prior knowledge of the flow-field. Experiments have demonstrated that a 'standard' luminescent paint technique. developed by BAE Systems, can simultaneously measure steady pressure and temperature. This is achieved through knowledge of the paint phosphorescence lifetime rather than the absolute intensity. which increases the measurement accuracy. In addition, a new 'fast' paint has been calibrated at the University of Bath for the measurement of unsteady pressure using a variable frequency pulsing air jet. Pressure measurements were made with both paints in the wake of various excrescences, sized to produce vortex shedding in the frequency range 500-4,200Hz, in a transonic tunnel. The extent of the wakes was determined from a flow visualisation technique. Time-averaged measurements, using both luminescent paints, and transient measurements of the unsteady pressure field, made with the fast paint, were compared with transducer data. For all cases the luminescent paint data compared well with the conventional measurements and the Strouhal number agreed well with data from the literature. The use of luminescent paint for the simultaneous measurement of pressure and temperature over a NACA 0012 aerofoil, as well as the quantification of convective heat transfer is examined in Part 2.