Recent direct drive implosion experiments, performed on the OMEGA
laser, have been analyzed by comparing full two-dimensional (2D) and
one-dimensional (1D) numerical simulations. The 2D simulations result
in a fusion yield higher than experimental results. A simple
full-mixing model, leaving only the clean region, overestimates yield
degradation. Fully turbulent mixing is expected to develop in most of
the mixing region; however regions slightly beyond the radius of the
most penetrating spike are expected to remain clean and to contribute
to fusion yield. One can correct the mixing model by redefining the
clean region. Accounting for this unmixed region results in improved
agreement with experimental results. Differences in central pressure,
density, temperature, and fusion rate in implosions dominated by low
mode number perturbations imply that mix effects might not be limited
to the mix region, and that 2D simulations are necessary to describe
the large scale flow affecting the central region. The same analysis
has been undertaken for implosions with different convergence ratios,
but with similar initial perturbation spectra. These implosions should
be compared to implosions dominated by high mode number perturbations,
which might be described by models based on 1D simulations.