Flow dynamics and wall-pressure signatures in a high-Reynolds-number overexpanded nozzle with free shock separation

Numerical Analysis of Side-loads Reduction in a Sub-scale Dual-bell Rocket Nozzle

“…This objective is achieved by defining the length-scale d in (3) as where d w is the distance from the nearest wall, is the subgrid length-scale that controls the wavelengths resolved in LES mode and C DES is a calibration constant set equal to 0.65 in the original model. On the basis of previous calibration studies performed on DDES of a sub-scale rocket nozzle Martelli et al (2019Martelli et al ( , 2020 the constant C DES has been set equal to 0.20 and the function f d here employed is (1) t + ( u j )…”

“…The scope of this study is to show how the dual-bell inflection point changes the receptivity of the separation shock to the acoustic disturbances coming from the interaction between the supersonic shear layer and the second Mach disk, thus altering the aeroacoustic feed-back loop observed in the TIC. This is demonstrated through an in-depth analysis of the flow organization, wall-pressure signature and side-loads level in the dual bell nozzle, that are compared with those relative to the TIC nozzle studied by Martelli et al (2020). It is worthwhile to underline that, in real applications, conventional bell nozzles (like the TIC) operate with overexpanded flows without internal flow separation.…”

“…The present analysis focuses on the investigation of the wall-pressure signature and its spectral content, in particular in the azimuthal wave-number frequency plane, with the main aim of identifying a correlation between the forced flow separation and the energy level of the non-symmetrical azimuthal mode. By performing experimental and numerical analysis of TIC nozzles, Jaunet et al (2017) and Martelli et al (2020) have recently proposed that the side loads could be triggered by an aeroacoustic feed-back loop (screech-like phenomenon) involving the shock-cell structure and the separated shear layer present inside the nozzle. The scope of this study is to show how the dual-bell inflection point changes the receptivity of the separation shock to the acoustic disturbances coming from the interaction between the supersonic shear layer and the second Mach disk, thus altering the aeroacoustic feed-back loop observed in the TIC.…”

Exact solutions for quasi-one-dimensional compressible viscous flows in conical nozzles

“…Many fluid dynamics processes and research themes, such as the interaction between shocks and boundary layers, free shock separation in over-expanded jets (Martelli et al. 2020), entrance effects due to the developing internal flow (Kohl et al. 2005), turbulence and vorticity (Mahapatra et al.…”

“…With the development of micro-machine technology, numerous research investigations on viscous gaseous flows in micro-channels have also been carried out with one-dimensional models in the microelectronic and bioengineering fields (Atmaca, Erek & Ekren 2020; Martelli et al. 2020).…”