Numerical Analysis on Radiation Effects in Shock Tunnel Experiments

This study investigates radiative heat flux contributions in high-enthalpy shock tunnel experiments through a combined experimental and numerical approach. Experiments were conducted in the High Enthalpy Shock Tunnel Göttingen (HEG) using a flat-faced cylinder equipped with heat flux and radiation sensors, while Computational Fluid Dynamics (CFD) simulations were performed with the DLR TAU solver and the next-generation HyperCODA code. Radiation modeling employed both infinite-slab and photon Monte Carlo methods in conjunction with the PARADE database to quantify contributions from shock-layer emission and hot-gas radiation near the nozzle throat. The results indicate that shock-induced radiation accounts for approximately 2% of the convective heat flux at the stagnation point, whereas nozzle-throat contributions are strongly reduced by wall absorption effects and remain of secondary importance. Additional modeling of iron particle radiation suggests that suspended contaminants may dominate radiative heating, potentially explaining the long-observed heat flux anomalies in high-enthalpy facilities. The work confirms the consistency of HyperCODA with TAU for high-enthalpy conditions and highlights the need for further diagnostics of particulate contamination in shock tunnels.