Gas properties' impact on flow dynamics and thermal characteristics in a Hartmann–Sprenger tube

The Hartmann–Sprenger (H–S) tube has attracted considerable attention due to its applicability in acoustics and ignition studies. Although its operational mechanisms have been extensively investigated, the influence of gas properties on its performance remains insufficiently characterized. This study numerically examines the flow and thermal behavior of eight different gases and hydrogen–oxygen mixtures in an H–S tube over different nozzle pressure ratios (NPRs), using a two-dimensional axisymmetric model with explicit time discretization and a second-order upwind spatial scheme. The results show that the gas specific heat ratio and molecular mass primarily govern the temperature evolution, response time, and transition from initial transients to quasi-harmonic oscillations, whereas the overall pressure amplitude depends mainly on NPR and geometry constraints. Monatomic gases yield higher temperature rises, but the maximum pressure remains relatively insensitive to gas type under identical driving conditions (NPR). When the time histories are normalized by the characteristic sound speed factor (γ/M), the pressure and temperature oscillations of different gases exhibit similar phase patterns, indicating a scaled dynamic correspondence. Also, by normalizing temperature records using γ, all gases show almost the same levels for temperature, indicating similar changes in normalized thermal energy. These results provide a physically interpretable framework linking thermodynamic properties to oscillation frequency, temperature rise, and response time, supporting more informed selection of working gases for ignition or resonant-tube applications.