Ri − β relation in our cluster sample. The radial bias is an imprint that the dynamics is dominated by radial motions, driven by the accretion. In this sense, the Richardson number does not have a predictive power about the real dynamics of the ICM. The orange line is used to highlight the turbulence (left) and buoyancy (right) dominated regime, while the blue line distinguishes a radially (β > 0) from a tangentially (β < 0) bias.