  The Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory
observed a coronal mass ejection with an embedded filament on 2011 February 24,
reavealing quasi-periodic vortex-like structures at the northern side of the
filament boundary with a wavelength of approximately 14.4 Mm and a propagation
speed of about 310 +- 20 km/s. These structures could result from the
Kelvin-Helmholtz instability occurring on the boundary. We perform 2.5D
numerical simulations of the Kelvin-Helmholtz instability and compare the
simulated characteristic properties of the instability with the observations,
where we obtain qualitative as well as quantitative accordance. We study the
absence of Kelvin-Helmholtz vortex-like structures on the southern side of the
filament boundary and find that a magnetic field component parallel to the
boundary with a strength of about 20% of the total magnetic field has
stabilizing effects resulting in an asymmetric development of the instability.
