“…However, very few DES simulations of separated rocket nozzle flows are discussed in the open literature. Deck (2009) and Shams et al (2013) presented a delayed DES (DDES) of the end-effect regime in an axisymmetric nozzle flow characterized by RSS. While the simulation reproduced the main flow properties rather well, the most energetic frequency, as predicted by the simulation, was higher than that observed in the experiment.…”
“…However, very few DES simulations of separated rocket nozzle flows are discussed in the open literature. Deck (2009) and Shams et al (2013) presented a delayed DES (DDES) of the end-effect regime in an axisymmetric nozzle flow characterized by RSS. While the simulation reproduced the main flow properties rather well, the most energetic frequency, as predicted by the simulation, was higher than that observed in the experiment.…”
“…While this kind of nozzle flow configuration has been widely studied with Reynolds-averaged Navier-Stokes (RANS) simulations, it is worth recalling that, until very recently, only very few unsteady simulations with hybrid approaches, similar to the one adopted in the present study, have been attempted. Such unsteady simulations have been carried out in the case of planar nozzle configuration (Martelli et al 2019) or truncated ideally contoured nozzles (Deck 2009;Shams et al 2013). The first hybrid simulations of TIC nozzle flow have more recently been reported in Goncalves, Lehnasch & Herpe (2017) and then in Martelli et al (2020).…”
Section: Numerical Set-upmentioning
confidence: 99%
“…In TOC nozzles featuring the RSS regime, a far larger Mach disk is produced with more pronounced curvature levels, leading to the generation of a large recirculating region in the subsonic core of the jet downstream of this Mach disk. This large recirculation bubble presents an intrinsic complex three-dimensional dynamics (Shams et al 2013). For this regime, the position of the restricted separation regions close to the wall move downstream as the NPR increases, so that they can intermittently open to the ambient atmosphere at particular NPR values.…”
Section: Introductionmentioning
confidence: 99%
“…This so-called 'end-effect regime' is known to be associated with particularly significant levels of unsteadiness and the generation of particularly intense lateral forces (Nguyen et al 2003;Deck 2009). The integral of the pressure forces resulting from the contribution of all these potential sources of instability then generally presents a random character, mostly dominated by low-frequency side-loads activity (Deck & Guillen 2002;Shams et al 2013).…”
“…Moríñigo 27 and Deck 28 reproduced the characteristic large amplitude self-sustained oscillations observed in end-effect regime. Shams 29 studied the leading mechanisms at the origin of the first side-load peak observed in the RSS regime. Figure 2.Schematic of flow separation shock pattern: 19 (a) schematic of FSS; (b) schematic of RSS.…”
The objective of this effort is to numerically investigate the effect of the fire-in-the-hole staging event on the start-up flow separation and side loads of a conical nozzle during flight. The axisymmetric transient flow structure in nozzle was examined by time-accurate numerical method with time-varying chamber pressure and separation gap width. Three-dimensional time-accurate computations to examine the side loads due to non-nominal staging movement were conducted for two particular cases: misalignment between two stages and the angle of the nozzle thrust vector direction. Each asymmetry case comprised several specific staging state points which determined the corresponding chamber pressure and staging gap width. As presented by the simulation results, the flow separation in nozzle is significantly prolonged and intensified by the obstruction of the lower stage dome. When the flow separation location moves close to the nozzle exit, a strenuously axial oscillation of the separation shock appears and lasts for a period of time. In the three-dimensional asymmetric computations, in spite of strenuous oscillation, the time-average of nozzle side loads indicate that the asymmetric staging situation could lead to large sustained lateral disturbance forces. An essential ingredient driving the flow unsteadiness and asymmetry is related to the deflected and reversed supersonic flow by the dome and interstage wall corner of lower stage.
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