  The massive star-forming region G332.83-0.55 contains at least two levels of
hub-filament structures. The hub-filament structures may form through the
"gravitational focusing" process. High-resolution LAsMA and ALMA observations
can directly trace the gas inflows from cloud to core scales. We investigated
the effects of shear and tides from the protocluster on the surrounding local
dense gas structures. Our results seem to deny the importance of shear and
tides from the protocluster. However, for a gas structure, it bears the tidal
interactions from all external material, not only the protocluster. To fully
consider the tidal interactions, we derived the tide field according to the
surface density distribution. Then, we used the average strength of the
external tidal field of a structure to measure the total tidal interactions
that are exerted on it. For comparison, we also adopted an original
pixel-by-pixel computation to estimate the average tidal strength for each
structure. Both methods give comparable results. After considering the total
tidal interactions, the slope of the $\sigma-N*R$ relation changes from 0.20 to
0.52, close to 0.5 of the pure free-fall gravitational collapse, and the
correlation also becomes stronger. Thus, the deformation due to the external
tides can effectively slow down the pure free-fall gravitational collapse of
gas structures. The external tide tries to tear up the structure, but the
external pressure on the structure prevents this process. The counterbalance
between the external tide and external pressure hinders the free-fall
gravitational collapse of the structure, which can also cause the pure
free-fall gravitational collapse to be slowed down. These mechanisms can be
called "tide-regulated gravitational collapse."
