  Flow harmonic coefficients, $v_n$, which are the key to studying the
hydrodynamics of the quark-gluon plasma (QGP) created in heavy-ion collisions,
have been measured in various collision systems and kinematic regions and using
various particle species. The study of flow harmonics in a wide pseudorapidity
range is particularly valuable to understand the temperature dependence of the
shear viscosity to entropy density ratio of the QGP. This paper presents the
first LHCb results of the second- and the third-order flow harmonic
coefficients of charged hadrons as a function of transverse momentum in the
forward region, corresponding to pseudorapidities between 2.0 and 4.9, using
the data collected from PbPb collisions in 2018 at a center-of-mass energy of
$5.02$ TeV. The coefficients measured using the two-particle angular
correlation analysis method are smaller than the central-pseudorapidity
measurements at ALICE and ATLAS from the same collision system but share
similar features.
