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Recent LHC results on the appearance of sub-leading flow modes in PbPb collisions at 2.76 TeV,related to initial-state fluctuations,are analyzed and interpreted within the HYDJET++ model.Using the newly introduced Principal Component Analysis (PCA) method applied to two-particle azimuthal correlations extracted from the model calculations,the leading and sub-leading flow modes are studied as a function of the transverse momentum (pT) over a wide centrality range.The leading modes of the elliptic (v2(1)) and triangular (v3(1)) flow calculated with the HYDJET++ model reproduce rather well the v2{2} and v3{2} coefficients measured experimentally using the two-particle correlations.Within the pT ≤ 3 GeV/c range,where hydrodynamics dominates,the sub-leading flow effects are greatest at the highest pT of around 3 GeV/c.The sub-leading elliptic flow mode (v2(2)),which corresponds to the n=2 harmonic,has a small non-zero value and slowly increases from central to peripheral collisions,while the sub-leading triangular flow mode (v3(2)),which corresponds to the n=3 harmonic,is even smaller and does not depend on centrality.For n=2,the relative magnitude of the effect measured with respect to the leading flow mode shows a shallow minimum for semi-central collisions and increases for very central and for peripheral collisions.For the n=3 case,there is no centrality dependence.The sub-leading flow mode results obtained from the HYDJET++ model are in rather good agreement with the experimental measurements of the CMS Collaboration.