Left: typical example of RWI triggered in an accretion disc at r_b = 8.5r_g around a black hole whose spin parameter is set to 0.5. Density perturbations are displayed exhibiting the occurrence of vortices located at r_b from the black hole at a late stage of the simulation. Identified vortices are all anti-cyclonic according to the rotation of the disc as anticipated when one considers the RWI. Right: synthetic image from the simulation displayed on the left panel. The GRHD simulation is performed by the GR-AMRVAC code while the image is processed using the GYOTO general relativistic ray-tracing code. This image considers photons (with energy of 2 keV) reaching a remote observer standing far from the black hole.