  Matter mixing is one important topic in the study of core-collapse supernova
(CCSN) explosions. In this paper, we perform two-dimensional hydrodynamic
simulations to reproduce the high velocity $^{56}$Ni clumps observed in SN
1987A. This is the first time that large density perturbation is proposed in
the CCSN progenitor to generate Rayleigh-Taylor (RT) instability and make the
effective matter mixing. In the case of a spherical explosion, RT instability
is efficient at both C+O/He and He/H interfaces of the SN progenitor. Radial
coherent structures shown in perturbation patterns are important for obtaining
high velocity $^{56}$Ni clumps. We can also obtain matter mixing features and
high velocity $^{56}$Ni clumps in some cases of aspherical explosion. We find
that one of the most favorable models in our work has a combination of bipolar
and equatorially asymmetric explosions in which at least 25\% of density
perturbation is introduced at different composition interfaces of the CCSN
progenitor. These simulation results are comparable to the observational
findings of SN 1987A.
