NAFEMS International Journal of CFD Case Studies

Volume 1, January 1998

ISSN 1462-236X

The Use of an Unstructured Adaptive Mesh Code to Perform Resolved Obstacle Computations for Confined Explosion Hazards

P. Birkby, F. M. Sinclair, A. M. Savill, R. S. Cant and W. N. Dawes
Engineering Department, Cambridge University, Trumpington Street, Cambridge CB2 JPZ UK

https://doi.org/10.59972/yzxn5vgx

Keywords: Unstructured Adaptive Mesh Code, Resolved-Obstacle Computations, Explosion Hazards and CFD

Introduction

The establishment of safety cases for oil and gas installations requires accurate estimations of the effects of confined explosions and in particular the over-pressures generated. The shortcomings of the current understanding, traditional semi-empirical methods, and Computational Fluid Dynamic (CFD) techniques have been clearly highlighted in many cases, including the recent SCI full-scale evaluation exercise, where over-pressures were severally underpredicted.
Despite this, there is a growing recognition that CFD has an important role to play and a number of different techniques are currently being developed for confined explosions, e.g. see [1-4]. Structured mesh codes can typically handle only about 10 obstacles. Extension of such codes to larger numbers of obstacles is limited by computer resources required to ensure at least 10 cell resolution of the obstacles and more importantly their shear layers [1]. For real installation modules, containing several hundred or even thousands of obstacles, unresolved calculations using Porosity, Distributed Resistance (PDR) models are currently the only CFD option. In this approach obstacles are not resolved, but are represented by resistance terms appended to the mean and turbulent sources, and these methods are limited by the accuracy of these terms, which can only be improved by access to detailed parametric data or high quality resolved computational results. Formulating resistance terms is thus very difficult for complex geometries...

References

[1] A. M. Savill and T. Solberg, Proc. ERCOFTAC/IMA Conference on Flow and Dispersion Though Groups of Obstacles, Cambridge, 1994

[2] D. K. Pritchard, D. J. Freeman and P. W. Guilbert, Journal of Loss Prevention in the Process Industry, 9, p. 205, 1996.

[3] C. A. Catlin, M. Fairweather and S.S. Isbrahim, Combustion and Flame, 102, p. 115, 1995.

[4] J. K. Watterson, A. M. Savill, W. N. Dawes and K. N. C. Bray, Joint Meeting of the Portuguese, British and Spanish Sections of the Combustion Institute, 1996.

[5] W. N. Dawes, AIAA/ASME/SAE ASEE 27th Joint Propulsion Conference, Paper 91-2469-CP, 1991.

[6] W. N., Dawes, Progress in Aerospace Science, 29, p. 221, 1993.

[7] W. N. Dawes, ASME-IGTI Conference, Paper 93-GT-104, 1993.

[8] I. J. Connell, J. K. Watterson, A. M. Savill, W. N. Dawes and K. N. C. Bray, Proceedings of the 2nd International Specialists Meeting in Fuel-Air Explosions, June 1996.

[9] I. J. Connell, J. K. Watterson, A. M. Savill and W. N. Dawes, Poster Presentation at the 26th Symposium (International) on Combustion, Naples, 1996.

[10] I. J. Connell, J. K. Watterson, A. M. Savill and W. N. Dawes, Abstracts International Congress of Theoretical and Applied Mechanics, Kyoto and Submitted to International Journal of Numerical Methods in Fluids, 1996.

[11] A. P. Watkins, S-P. Li and R. S. Cant, SAE Paper No.961190, 1996.

[12] G. M. Am-Orf, PhD Thesis, UMIST, 1996

Cite this paper

P. Birkby, F.M. Sinclair, A.M. Savill, R.S. Cant, W.N. Dawes, The Use of an Unstructured Adaptive Mesh Code to Perform Resolved Obstacle Computations for Confined Explosion Hazards, NAFEMS International Journal of CFD Case Studies, Volume 1, 1998, Pages 59-66, https://doi.org/10.59972/yzxn5vgx