Encyclopaedia Index

ADVICE on the use of PHOENICS

(1) Desirable background knowledge

PHOENICS can be used successfully by persons of varied experience and background; however, the probability of success is greatest if they are already familiar with the general features of computer simulation of flowing continua; in particular, they should be aware of the following:

(2) Why caution is needed

The ideal user of PHOENICS has been identified in this way in order that, should less experienced persons use it, they should have received due warning that computer simulations of fluid flow differ appreciably from calculations of the kind which are customary in, say, structural engineering or in rigid-body dynamics.

In the those fields, non-linearities are often of secondary importance, if indeed they are present at all; the computer code can therefore be left to produce the solution automatically.

Fluid-flow phenomena, by contrast, are essentially non-linear; so the user of a flow-simulating code must reconcile himself to having, on occasion, to help the code along, using his intuition and experience in the selection of the 'switches' and 'tuning knobs' of the solving procedure.

The final solution itself, i.e. the result of the solving procedure, of course must not depend upon the settings so chosen, any more than the scenery at the port of destination can depend upon the course which the ship's navigator selected.

It is WHETHER the solution is arrived at, and HOW SWIFTLY, that these steering adjustments may beneficially influence.

PHOENICS does already possess a primitive EXPERT system for making optimal adjustments of the numerical parameters as the calculation proceeds; and this auto-pilot feature is being further developed by CHAM. However what has been stated above remains true: the user of PHOENICS, or of any other CFD code, should never trust their predictions blindly, or expect them to proceed efficiently no matter how injudicious are the user's settings.