Collective Expansion at the LHC: selected ALICE anisotropic flow measurements

The collective expansion of matter created in collisions of heavy-ions, ranging from collision energies of tens of MeV to a few TeV per nucleon pair, proved to be one of the best probes to study the detailed properties of these unknown states of matter. Collective expansion originates from the initial pressure gradients in the created hot and dense matter. These pressure gradients transform the initial spatial deformations and inhomogeneities of the created matter into momentum anisotropies of the final state particle production, which we call anisotropic flow. These momentum anisotropies are experimentally characterised by so-called flow harmonics. In this paper I review ALICE measurements of the flow harmonics at the CERN Large Hadron Collider and discuss some of the open questions.