Chevron Flow Scenario

[Scott Haney]

Hi everyone,

I have attached a PDF file summarizing my take on a paper [1] describing 
a finite-difference approach to a flow simulation that was of interest 
to Chevron. If people would like copies of the original paper, please 
supply a FAX number.

This simulation is interesting for a couple of reasons. First, it 
requires a staggered, non-orthogonal grid and a flux field with a unique 
face-like centering. Ultimately, it introduces multi-block meshes and 
fields to obtain geometries that are locally structured, but globally 
unstructured. Second, their paper shows how complicated, inflexible, and 
hard-to-follow things can get if you use the wrong abstractions (they 
linearized indices of control volumes, thereby locking them to 3D and 
forcing the use of indirection lists).

While the authors clearly messed up the abstractions, it isn't so clear 
what the correct abstractions are. After thinking about this a long 
time, I think I have at least some of the vocabulary:

mesh
sub-mesh
cells
faces
edges
sub-cells
sub-faces
sub-edges
vertices
centering points
neighborhoods
orientation
nearest
reduction

Note that there are no array-like concepts in here like Intervals, 
Ranges, etc. One reason is that field operations inherently involve 
centering points and, specifically, mappings between centering points 
and our rectangular domains are not the very good at expressing this. 
Another reason is that if one expresses operations in terms of 
geometrical concepts, the code is born dimension independent.

Based on Jeffrey's excellent discussion, I think that the Caramana 
hydrodynamics kernel has a similar flavor and is therefore described by 
similar language.

Let me emphasize that I'm talking about USER interface here. When push 
comes to shove, everything needs to turn into indexing.

Questions? Comments?

Scott

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--
Scott W. Haney
Development Manager
Proximation LLC
2960 Rodeo Park Drive West
Santa Fe, NM 87505
Voice: 505-424-3809 x101
FAX: 505-438-4161
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