The structure of supercritical fluid free‐jet expansions

Experimental and numerical studies are reported on the structure of supersonic free‐jet expansions of supercritical CO2 impacting on a flat plate. Numerical calculations for the axisymmetric, two‐dimensional (2‐D) expansion use a time‐dependent finite difference method known as the two‐step Lax‐Wendroff technique, incorporating the Redlich‐Kwong equation of state to model CO2. The numerical results are compared with experimental optical shadowgraph measurements of the jet and shock wave structure, impact pressure and temperature measurements along the plate, and a thermocouple probe of the expansion. Approximations based on ideal gases and quasi‐1‐D flow analysis, often used by researchers, are found to be useful for these supercritical fluid flows.