Frédéric OLIVON, Antoine CHÉDIN, Jean-Etienne DURAND, Aurélien GENOT, Estelle PIOT
DOI Number: N/A
Conference number: HiSST-2025-042
The indirect entropy noise generation in a thermally choked flow nozzle, induced by the convection of 2D circular entropy spots, is investigated. Two configurations are examined: a thermal throat formed by non-uniform volumetric heat addition, and an equivalent isentropic nozzle with a geometric throat. Both are designed to produce the same steady Mach number distribution, in order to isolate the influence of heat addition on the acoustic response. The analysis combines two-dimensional CFD simulations with two asymptotic one-dimensional models: the quasi-steady (QSS) model, adapted for large spots, and the point-mass (PM) inertial model, for small spots. For the geometric-throat case, the CFD results
show fair agreement with both the QSS and PM predictions in their respective asymptotic regimes. For the thermal-throat case, the QSS regime is reached for spots larger than 100 throat radius, which is a value lower than that of the geometric configuration. Then, the acoustic response exceeds QSS predictions (∼ 20%), which is certainly due to the invalidity of the assumption of no Mach fluctuations at the throat. In the small-spot limit, the PM model predicts the inertial regime with reasonable accuracy for both configurations, but at different spot radii. The thermal-throat case, however, deviates from the PM prediction, highlighting fundamental differences between heated and isentropic nozzles and the need to
extend asymptotic models to non-isentropic base flows.