The total number of runs from all four parts of the proposed studies
amounts to of the order of ten, with the exact number determined in
part by earlier results: novel initial results might compel us to invest more
time in few high resolution runs, or a broader exploration of parameter
space. Either way, trial runs on the Origin 2000s at both OSC and NCSA
provide us with a dependable estimate of the resources required.
We note the very important point that because of our use of Adaptive Mesh
Refinement, low resolution 3D runs can be made on workstation class machines
with 128Mb of memory. Such runs have insufficient resolution to address the
questions set out above, but provide invaluable insight into which initial
conditions and parts of parameter space are most appropriate choices for
production runs at OSC. We thus expect to need little or no experimentation,
and will make efficient use of OSC facilities.
Runs will require typically 1 -- 2 Gb of memory (which is available through a
queue -- Q95.2g36000 -- set up at our request in October 1998). Figure-N
shows the results of an exploratory run with a precessing jet; this required
0.7 Gb on the Origin 2000, and employs 2 levels of refinement on a base grid
of size #tex2html_wrap_inline145#. Although interesting, and indeed capable of
giving insight into the dynamics of the flow, the resolution is clearly
insufficient. An additional level of refinement alone would lead to
untenable memory requirements, but an additional level in conjunction with
more selective refinement criteria -- restricting refinement to key portions
of the flow -- would increase the memory required by no more than #tex2html_wrap_inline147#.