Abstract
Experiments and numerical simulations have been used in this work to understand the step response characteristics of Polymer/Ceramic Pressure-Sensitive Paint (PC-PSP). A recently developed analytical model describing the essential physics in PC-PSP quenching kinetics is used, which includes the effect of both diffusion time scale and luminescent lifetime on the net response of PC-PSP. Step response simulations using this model enables an understanding of the effects of parameters, such as the diffusion coefficient of O2 in the polymer/ceramic coating, attenuation of excitation light, ambient luminescent lifetime, sensitivity, and the magnitude and direction of pressure change on the observed response time scales of PC-PSP. It was found that higher diffusion coefficient and greater light attenuation lead to faster response, whereas longer ambient lifetime and larger sensitivity lead to slower response characteristics. Due to the inherent non-linearity of the Stern-Volmer equation, response functions also change with magnitude and direction of the pressure change. Experimental results from a shock tube are presented where the effects of varying the roughness, pressure jump magnitude and luminophore probe have been studied. Model parameters have been varied to obtain a good fit to experimental results and this optimized model is then used to obtain the response time for a step decrease in pressure, an estimate of which is currently not obtainable from experiments.
Highlights
Pressure-sensitive paint (PSP) is an optical method for determining a quantitative description of surface pressure distribution on aerodynamic bodies
This leads to improved porosity and larger scattering of excitation light, which decreases the effective thickness of the Polymer/Ceramic Pressure-Sensitive Paint (PC-PSP) coating, thereby decreasing the response times to pressure changes
PSPs based on platinum tetra (pentafluorophenyl) porphyrin (PtTFPP) and RuDPP using experiments and numerical simulations
Summary
Pressure-sensitive paint (PSP) is an optical method for determining a quantitative description of surface pressure distribution on aerodynamic bodies. The intensity of the excited-state luminescence is modulated based on the concentration of oxygen in the vicinity of the excited luminophores (Figure 1) This dependence of intensity on local pressure is exploited to obtain the pressure information. PC-PSP uses a heavy loading of ceramic particles, which creates voids in the continuum of the polymer/ceramic coating. This leads to improved porosity and larger scattering of excitation light, which decreases the effective thickness of the PC-PSP coating, thereby decreasing the response times to pressure changes. Since PC-PSP imposes no limitation on the model material, it has received wide interest among researchers to characterize unsteady flows
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