EXPLOITS: The PHOENICS-based Software Package for
the Simulation of Gas Dispersion and Explosions,
and Their Consequences, in
Off-shore Oil Platforms

by
D B Spalding
of
Concentration, Heat and Momentum Ltd
November 1996

Contents

• Abstract

1. Introduction

2. The scientific basis of computational fluid dynamics (ie CFD)

3. CFD applied to gas-dispersion

4. CFD applied to explosions

5. CFD applied to explosion or blast damage and missile projection

6. CFD applied to fire-spread phenomena

7. What is special about EXPLOITS; setting up the problem

8. What is special about EXPLOITS; performing the simulations

9. What is special about EXPLOITS; inspecting the results

10. What credence to accord to the results

11. Concluding remarks

12. References

-------- ABSTRACT ---------

EXPLOITS is a customised version of the PHOENICS flow-simulation software package, which is being developed by CHAM during 1996, for the prediction of:-

• gas-dispersion phenomena which may give rise to explosions within partly-ventilated enclosures containing solid objects;

• the pressure, velocity and temperature fields in an enclosure after ignition of the gas-air mixture;

• the consequent damage to solid objects which leads to the projection of missiles; and

• the spread of fire which may result from subsequent oil spillages.

EXPLOITS differs from other ostensibly-similar software packages by way of:-

• its ability to employ the full scientific-model and computer- methods capabilities of a powerful and well-validated general- purpose computer code (namely PHOENICS), so taking account of:
  • multi-phase effects (water sprays, or missiles; gas-liquid interfaces);
  • simultaneous modelling of stresses in solids;
  • automatic selection of numerical settings;
  • parallel-computing capabilites;

• its possession of a Virtual-Reality user interface, for setting up problems and displaying results;

• its availability for purchase and direct use, by sufficiently confident users; and, for "assisted and metered use", at remote sites with resident human experts, by other users possessing personal computers equipped with modems.

EXPLOITS is also supplied with novel and unique turbulence and combustion models, which enable it to replace guesswork by computation in important parts of the prediction process.

One feature of these models is that they permit numerical-error estimates to be made.

However, EXPLOITS is not claimed by CHAM to be able to do more than indicate what will PROBABLY happen.

The reasons are that the science of turbulence, whether the fluid is reactive or inert, is not sufficiently far advanced to make certainty justifiable, even in much more simple circumstances than those of off-shore oil platforms.

The wise user of EXPLOITS therefore keeps in mind two mnemonics:
NOKFOS (meaning NObody Knows FOr Sure); and
BATWEC (meaning Best Available Technique Without Excessive Cost).

"Because of NOKFOS, EXPLOITS represents the BATWEC"

wbs