Thermodynamic Effects on Gas Dynamics in Non-Ideal Compressible Flow

Accurate prediction of shock behaviour in non-ideal compressible flows is essential for the analysis and design of turbomachinery components operating with fluids that exhibit strong departures from ideal-gas thermodynamics. This study examines how thermodynamic property variations along the flow in a non-ideal regime influence canonical gas-dynamic behaviour, with emphasis on the coupling between compressibility, density response, and the equilibrium position of a standing shock. Three-dimensional scale-resolving Navier–Stokes simulations are performed for CO₂ flow through a convergent-divergent nozzle, using a REFPROP-based equation of state to represent non-ideal thermodynamic effects with high fidelity. By systematically varying the inlet conditions, these simulations isolate the influence of non-ideal thermophysical properties on effective flow blockage, shock stability, and shock location, resolving the coupled unsteady dynamics and thermodynamic non-ideality across the shock. To assess the predictive capability, the results are compared with Reynolds-averaged Navier-Stokes (RANS) simulations and a corresponding quasi-one-dimensional inviscid quasi-analytical solution. The combined analysis shows that non-ideal thermodynamics significantly influences shock strength, stability, and position even in geometrically simple configurations. The results clarify the role of thermophysical properties in governing canonical shock behaviour and provide a foundation for future investigations of non-ideal shock--boundary-layer interaction relevant to turbomachinery applications.