  The rising part of a tidal disruption event light curve provides unique
insight into early emission and the onset of accretion. Various mechanisms are
proposed to explain the pre-peak emission, including shocks from debris
interaction and reprocessing of disk emission. We study the pre-peak emission
and its influence on the gas circularization by a series of gray radiation
hydrodynamic simulations with varying black hole mass. We find that given a
super-Eddington fallback rate of 10\dot{M}_{Edd}, the stream-stream collision
can occur multiple times and drive strong outflows of up to 9\dot{M}_{Edd}. By
dispersing gas to \gtrsim 100rs, the outflow can delay gas circularization and
leads to sub-Eddington accretion rates during the first few stream-stream
collisions. The stream-stream collision shock and circularization shock can
sustain a luminosity of ~10^{44}erg/s for days. The luminosity is generally
sub-Eddington and shows a weak correlation with accretion rate at early time.
The outflow is optically thick, yielding a reprocessing layer with a size of
~10^{14} cm and photospheric temperature of ~4\times10^{4}K.
