Abstract
Highlights
Jets in cross-flows are canonical flows consisting of a boundary-layer flow in which a jet is exiting from the wall, originally orthogonal to the free-stream velocity
We have investigated the stability of a jet in cross-flow using several techniques
Nonlinear simulations were performed in order to locate the stability region of the flow in the parameter space. Those results indicate that, at the relatively low Reynolds numbers investigated, the flow is stable at low jet velocity ratios, and a global instability leading to the formation of hairpin vortices in the wake appears as the velocity ratio is increased between 0.35 and 0.375
Summary
Jets in cross-flows are canonical flows consisting of a boundary-layer flow in which a jet is exiting from the wall, originally orthogonal to the free-stream velocity. Less is known for very low velocity ratios, typically below 0.5, where the jet trajectory remains close to the boundary-layer edge and interacts with it more strongly In this regime, the main unsteady feature of the wake is hairpin vortices, that are periodic for low Reynolds numbers (Mahesh 2013). A study with the spectral element method (Peplinski, Schlatter & Henningson 2015a) reproducing this set-up with inflow/outflow conditions instead of the periodic domain found the dynamics of the jet to be significantly different and the critical peak velocity ratio to be close to R = 1.55, corresponding to a bulk velocity ratio of R = 0.49 with their velocity profile Those simulations all used a parallelepipedic box omitting the pipe and modelled the pipe by a non-homogeneous Dirichlet condition on the boundary of the box. A global linear stability analysis is performed, first using an eigenmode formulation, and through non-modal analysis techniques
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