  The disk galaxy UGC8802 has high neutral gas content and a flat profile of
star formation rate compared to other disk galaxies with similar stellar mass.
It also shows a steep metallicity gradient. We construct a chemical evolution
model to explore its growth history by assuming its disk grows gradually from
continuous gas infall, which is shaped by a free parameter -- the infall-peak
time. By adopting the recently observed molecular surface density related star
formation law, we show that a late infall-peak time can naturally explain the
observed high neutral gas content, while an inside-out disk formation scenario
can fairly reproduce the steep oxygen abundance gradient. Our results show that
most of the observed features of UGC8802 can be well reproduced by simply
`turning the knob' on gas inflow with one single parameter, which implies that
the observed properties of gas-rich galaxies could also be modelled in a
similar way.
