CALL FOR PRESENTATIONS DEADLINE: 16 SEPTEMBER 2025
Solving Structural Integrity Challenges with Engineering Simulation November 2025
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Día: Martes 9 de septiembre, 12:00h
Lugar: Sala Torres Quevedo (2ª planta Edificio A ETSIAE)
Ponente: Prof. Eduardo Martini, ISAE-ENSMA
Summary: Jets exhibit many interesting, and sometimes puzzling, phenomena, including different types of instability (convective, absolute, long-ranged) depending on operational conditions (density/temperature ratios, backflow, etc). Although these trends have been mapped over the past decade, both experimentally and numerically, they have remained mostly disconnected facts.
In this talk, the role of acoustic modes in the dynamics in jets is explored using a double vortex-sheet model. By analyzing these modes we show how jets and wakes may both behave as waveguides under certain conditions, emulating acoustic ducts with soft or hard walls, with the vortex-sheet impedance providing effective ‘wall’ conditions. We consider, in particular, the role that upstream-travelling acoustic modes play in underpinning the onset of absolute instability. Providing a new perspective on the stabilizing and destabilizing effects of reverse flow, temperature ratio, and compressibility, it also clarifies the differing symmetries of jet (symmetric) and wake (antisymmetric) instabilities. An energy balance, based on the vortex-sheet impedance, is used to determine stability conditions for the acoustic modes: these may become unstable in supersonic flow due to an energy influx through the shear layers. These results provide a unified interpretation of different previously unconnected dynamics of jets (and wakes).
https://ulepicc.es/2025/05/3a-jornadas-de-doctorado-ulepicc-espana-gandia/
