Instability mechanisms in meandering streamwise vortex pairs of upswept afterbody wakes
Article dans une revue avec comité de lecture
Date
2022-07Journal
European Journal of Mechanics - B/FluidsAbstract
Wakes of upswept afterbodies are often characterized by counter-rotating streamwise vortex pairs which meander in space. One application concerns aft regions of cargo aircraft, which are characterized by a relatively flat upswept base. Here we consider a canonical configuration comprised of a cylinder with upswept basal surface. The resulting longitudinal vortices, which are much closer to each other than wing-tip vortices, can adversely influence paratrooper and cargo drop operations as well as trailing aircraft. The unsteady dynamics of these vortices are examined using spatio-temporally resolved Large-Eddy Simulations (LES) and stability considerations. Emphasis is placed on understanding the potential instability dynamics responsible for meandering, which was observed, characterized and quantified at a representative location downstream of the body. The dynamics is then successfully mapped to a matched Batchelor vortex pair, and spatial and temporal stability analyses are performed with both counter-rotating vortices in the computational domain. Both spatial and temporal analyses
reveal dipole structures associated with |m| = 1 elliptic modes as dominant modes in afterbody vortices. A short-wave elliptic instability mode is found to dominate the meandering motion in the vortex pair; this mode was stable in the case of an isolated vortex. Further, the strain due to axial velocity plays a key role in the instability and therefore breakdown. The low frequency of the unstable mode (Strouhal number StD ≃ 0.3 based on cylinder diameter) is consistent with the spectral analysis of meandering in the LES. Stability analyses at very low-wavenumber do not exhibit any unstable mode suggesting an absence of the Crow instability.
Files in this item
- Name:
- DYNFLUID_EJM-B-F_2022_ROBINET.pdf
- Size:
- 3.774Mb
- Format:
- Description:
- Instability mechanisms in ...
Collections
Related items
Showing items related by title, author, creator and subject.
-
Article dans une revue avec comité de lectureLOISEAU, Jean-Christophe; ROBINET, Jean-Christophe; CHERUBINI, Stefania; LERICHE, Emmanuel (Elsevier, 2015)The linear global instability and resulting transition to turbulence induced by a cylindrical roughness element of heighth and diameter d=3h immersed within an incompressible boundary layer flow along a flat plate is ...
-
Ouvrage scientifiqueLOISEAU, Jean-Christophe; CHERUBINI, Stefania; ROBINET, Jean-Christophe; LERICHE, Emmanuel (Springer, 2015)lobal instability analysis of the three-dimensional flow past two rough- ness elements of different shape, namely a cylinder and a bump, is presented. In both cases, the eigenspectrum is made of modes characterised by a ...
-
Article dans une revue avec comité de lectureBENGANA, Y.; LOISEAU, Jean-Christophe; ROBINET, Jean-Christophe; TUCKERMAN, L. S. (Cambridge University Press (CUP), 2019)A comprehensive study of the two-dimensional incompressible shear-driven flow in an open square cavity is carried out. Two successive bifurcations lead to two limit cycles with different frequencies and different numbers ...
-
Article dans une revue avec comité de lectureDUCOIN, A.; LOISEAU, Jean-Christophe; ROBINET, Jean-Christophe (Elsevier, 2016)The objective of this work is to investigate numerically the different physical mechanisms of the transition to turbulence of a separated boundary-layer flow over an airfoil at low angle of attack. In this study, the ...
-
Chapitre d'ouvrage scientifiqueLOISEAU, Jean-Christophe; BUCCI, Michele Alessandro; CHERUBINI, Stefania; ROBINET, Jean-Christophe (Springer, 2018)With the ever increasing computational power available and the development of high-performances computing, investigating the properties of realistic very large-scale nonlinear dynamical systems has become reachable. It ...