  In recent years, the decay-less regime of standing transverse oscillations in
coronal loops has been the topic of many observational and numerical studies,
focusing on their physical characteristics, as well as their importance for
coronal seismology and wave heating. However, no definitive answer has yet been
given on the driving mechanism behind these oscillations, with most studies
focusing on the use of periodic footpoint drivers as a means to excite them. In
this paper, our goal is to explore the concept of these standing waves being
self-sustained oscillations, driven by a constant background flow. To that end,
we use the PLUTO code, to perform $3$D magnetohydrodynamic simulations of a
gravitationally stratified straight flux tube in a coronal environment, in the
presence of a weak flow around the loop, perpendicular to its axis. Once this
flow is firmly set up, a transverse oscillation is initiated, dominated by the
fundamental kink mode of a standing wave, while the existence of a second
harmonic is revealed, with a frequency ratio to the fundamental mode near the
observed ones in decay-less oscillations. The presence of vortex shedding is
also established in our simulations, which is connected to the "slippery"
interaction between the oscillator and its surrounding plasma. We thus present
a proof-of-concept of a self-oscillation in a coronal loop, and we propose it
as a mechanism that could interpret the observed decay-less transverse
oscillations of coronal loops.
