  Filamentary structures are ubiquitously seen in the interstellar medium. The
concentrated molecular mass in the filaments allows fragmentation to occur in a
shorter timescale than the timescale of the global collapse. Such hierarchical
fragmentation may further assist the dissipation of excessive angular momentum.
It is crucial to resolve the morphology and the internal velocity structures of
the molecular filaments observationally.
  We perform 0".5-2".5 angular resolution interferometric observations toward
the nearly face-on OB cluster forming region G33.92+0.11. Observations of
various spectral lines as well as the millimeter dust continuum emission,
consistently trace several $\sim$1 pc scale, clumpy molecular arms. Some of the
molecular arms geometrically merge to an inner
3.0$^{{\scriptsize{+2.8}}}_{{-\scriptsize{1.4}}}\cdot10^{3}$\,$M_{\odot}$, 0.6
pc scale central molecular clump, and may directly channel the molecular gas to
the warm ($\sim$50 K) molecular gas immediately surrounding the centrally
embedded OB stars. The NH$_{3}$ spectra suggest a medium turbulence line width
of FWHM$\lesssim$2\,km\,s$^{-1}$ in the central molecular clump, implying a
$\gtrsim$10 times larger molecular mass than the virial mass. Feedbacks from
shocks and the centrally embedded OB stars and localized (proto)stellar
clusters, likely play a key role in the heating of molecular gas and could lead
to the observed chemical stratification. Although (proto)stellar feedbacks are
already present, G33.92+0.11 chemically appears to be at an early evolutionary
stage given by the low abundance limit of SO$_{2}$ observed in this region.
