  The STAR Collaboration reported measurements of di-hadron azimuthal
correlation in medium-central Au+Au collisions at 200 A$\,$GeV, where the data
are presented as a function of the trigger particle's azimuthal angle relative
to the event plane $\phi_s $. In particular, it is observed that the away-side
correlation evolves from single- to double-peak structure with increasing
$\phi_s$. In this work, we present the calculated correlations as functions of
both $\phi_s$ and particle transverse momentum $p_T $, using the hydrodynamic
code NeXSPheRIO. The results are found to be in reasonable agreement with the
STAR data. We further argue that the above $\phi_s$ dependence of the
correlation structure can be understood in terms of one-tube model, as due to
an interplay between the background elliptic flow caused by the initial state
global geometry and the flow produced by fluctuations.
