Raymond S. Castner is an aerospace engineer whose NASA work includes the interaction between exhaust plumes and shock waves in supersonic flow. His 2010 report describes a wind tunnel model designed to study how an exhaust nozzle changes the near-field pressure pattern associated with a sonic boom.[ref]
Wind Tunnel Model Design for the Study of Plume Effects on Sonic Boom for Isolated Exhaust Nozzles by Raymond S. Castner. NASA/TM-2010-216259, abstract and sections II–III
The apparatus places an isolated nozzle between transparent tunnel walls, allowing Schlieren photography alongside pressure measurements and comparison with computational fluid dynamics. Its geometry was chosen to leave a useful observation region before shock waves reflected from the tunnel walls reached the model centreline. This is an example of experimental design in which the measuring environment itself creates disturbances that must be separated from the physical effect under study.[ref]
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