- Akustik von Blasen: Anwendung in der Vulkanologie
- Akustik und Dynamik von turbulenten Strahlen und Schockwellen
- Identifizierung von transportdominierten großräumigen Strukturen in turbulenten wandbegrenzten Strömungen
[Gastvortrag am 17.2.2022 16-18 Uhr c.t. im H32]
The whistling mechanism of a the jet flow through a circular hole in a thick plate. David Fabre Institut de Mécanique des Fluides de Toulouse (IMFT),
Allée du prof. Soula, Toulouse The flow through a hole in a thick plate (or a series of holes) is known to be a powerful source of sound emission. I most cases regarding industrial appluications, this situation should be avoided because of the strong loads exerted on the structures. In the past years, a number of studies (mostly numerical/theoretical) have been conducted in IMFT to explore the mechanisms responsible for whistling. In this talk I will focus on the situation with a single circular hole in a thick plate. We show that the whistling potential can be explored using the concept of impedance, and that a Nyquist criterion and show that it is able to quantify the effect of the Mach number and the volume of the upstream volume cavity on the instabilities. We show that using that Linearised Navier-Stokes Equations (LNSE) starting from incompressible description is an efficient mean to predict this impedance, leading to accurate predictions even when Mach number is moderate and in the case where the spatial evolution of the perturbations is rapidly dominated by nonlinear effects. This efficiency to predict whistling is demonstrated by comparison with nonlinear simulations and global stability analysis conducted in the fully compressible case. Our approach is particularly suitable to perform a parametric analysis aimed to investigate the onset of instabilitie, and we willdiscuss its potential application to other related situations.