Using the event-by-event viscous hydrodynamics VISH2+1 with MC-Glauber, MC-KLN, and AMPT initial conditions, we investigate the correlations of flow harmonics, including the symmetric cumulants SC v (m, n), the normalized symmetric cumulants N SC(m, n), and the Pearson correlation coefficients C(v 2 m , v 2 n ) in 2.76A TeV Pb-Pb collisions. We find SC v (m, n) is sensitive to both initial conditions and the specific shear viscosity η/s. A comparison with the recent ALICE data show that our hydrodynamic calculations can qualitatively describe the data of SC v (3, 2) and SC v (4, 2) for various initial conditions, which demonstrate that v2, v4 are correlated and v2, v3 are anti-correlated. Meanwhile, the predicted symmetric cumulants SC v (5, 2), SC v (5, 3), and SC v (4, 3) reveal that v2 and v5, v3 and v5 are correlated, v3 and v4 are anti-correlated in most centrality classes. We also find N SC v (3, 2) and C(v 2 3 , v 2 2 ), which are insensitive to η/s, are mainly determined by corresponding N SC ε (3, 2) and C(ε 2 3 , ε 2 2 ) correlators from the initial state. In contrast, other N SC v (m, n) and C(v 2 m , v 2 n ) correlators are influenced by both initial conditions and η/s, which illustrates the non-linear mode couplings in higher flow harmonics with n ≥ 4.