(Top) Energy dependence of $v_2$ for midcentral heavy-ion collisions integrated over $p_{\rm T}$ . (Bottom) Decomposition of the two-particle correlation function in terms of even and odd anisotropic flow harmonics ($v_{\rm n}$) from very central Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=$ 2.76 TeV .