Determination of instantaneous pressure in a transonic base flow using four-pulse tomographic PIV

A tomographic four-pulse PIV system is used in a transonic axisymmetric base flow experiment at a nominal free stream Mach number of 0.7, with the objective to obtain flow acceleration and pressure data. The PIV system, consisting of two double-pulse lasers and twelve cameras, allows acquiring two velocity fields with time separations as small as 2.5 ?s. A performance assessment is carried out and provides a typical average error estimate below 0.025 U? (0.3 voxel). The ability to use these velocity measurements to determine instantaneous, volumetric pressure distributions is assessed. To provide insitu validation, fast-response pressure transducers are used concurrent with the PIV measurements. PIV was found to yield a mean pressure profile with a similar shape as the mean pressure profile obtained with transducers and as reported in literature. The levels of pressure fluctuation were however found to be substantially higher. From this comparison it is concluded that the present PIV-based pressure determination procedure requires improvements to obtain more reliable pressure data. Such improvements may be obtained by optimizing the time separation between consecutive velocity fields and by making use of the temporal coherence between consecutive particle images through more advanced processing algorithms.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin