Rotor assembly and rotating machine

A rotor assembly, comprising:

• a rotor disc;
• a plurality of rotor blades fixed to the rotor disc and extending radially outward in a radial direction of the rotor disc;
• and
• at least one rolling element configured to roll on a curved surface facing inward in the radial direction of the rotor disc,
• wherein the at least one rolling element includes:
• a first rolling element configured to roll on a first curved surface as the curved surface;
• and
• a second rolling element configured to roll on a second curved surface as the curved surface, and
• wherein the rotor assembly satisfies at least one of the following conditions (A) and (C):
• (A) a first curvature radius R1 of the first curved surface is different from a second curvature radius R2 of the second curved surface;
• or
• (C) a distance d1 from a central axis of the rotor disc to the first rolling element is different from a distance d2 from the central axis of the rotor disc to the second rolling element.