FLACS CFD Software

Geometry and Explosions

Geometry has long been identified as of key importance to understanding the consequence of explosions. Flame speed and explosion pressure strongly depends on the gas cloud and the geometrical conditions. Chris Coffey, Global FLACS Product & Strategic Business Development Manager, explains.

Obstacle generated turbulence

A number of large-scale gas-explosion experimental programmes took place in the 1980’s. One programme (GEP 80-86) investigated pressure development due to flame acceleration by obstacle generated turbulence which was identified as primarily responsible for the intensification of explosions occurring in the complex geometries typically found on offshore platforms.

The experimental data from the programme provided new insights about flame acceleration in complex geometries.

It also provided data for the validation of a new CFD code, FLACS (Flame Acceleration Simulator) the forefather of Gexcon’s FLACS-CFD software.

Size matters

The programme identified the importance of capturing small scale congestion within a CFD model.

Gexcon’s best-practice guidance is that all geometrical details down to one inch play an important role in the development of an explosion and should be captured within a CFD model.

Arrangements matter too

How the geometry is arranged is also of critical importance. Lack of symmetry and the presence of non-uniform congestion can result in significant directional effects. If these aspects are not considered when modelling explosions, then resulting overpressure may be significantly under estimated or over predicted.

The two videos below show the impact of geometry on the development of a vapour cloud explosion. In both videos an identical mixture of propane-air was ignited in the centre of the cube and the blockage ratio was the same.

The first video shows a high-congestion scenario -the blockage is achieved by a large number of ‘thin’ pipes.

The second video shows a low-congestion scenario – the blockage is achieved by a small number of ‘fat’ pipes.

The different in the result consequence can clearly be observed. Overpressure for the high-congestion are over a factor of 100 higher than the low-congestion case.

FLACS-CFD software has been developed to perform:

  • Easy handling of multiple geometry import formats
  • Powerful geometry creation and clean up with CASD
  • Powerful visualisation within CASD and Flowvis (including lighting and textures)


Learn more about our software here:

Ensuring Safe Biogas Production using CFD-based Risk Analysis

Ensuring Safe Biogas Production using CFD-based Risk Analysis

In a bid to fight the effects of climate change, focus has been placed on reducing emissions from within industrial, energy, transportation, and construction sectors to ensure that future objectives are achieved. Biogas is positioned to be a key part of a sustainable solution. With the use of biogas and the number of production facilities increasing, focus must be placed…

Overcoming DSEAR challenges during COVID

Overcoming DSEAR challenges during COVID

The past 12 months has brought many challenges to the world of process safety which has affected the way we work and raised the question ‘How can we remain compliant with safety regulations during this difficult period?’. Whilst restrictions remain in place on being able to visit some client facilities, it’s still not impossible to ensure you remain compliant and…

Learnings From the Buncefield Oil Depot explosion: The Third Key Question.

Learnings From the Buncefield Oil Depot explosion: The Third Key Question.

To mark the15th anniversary of the Buncefield Storage Oil Storage Depot explosion which injured 40 people in 2005, we reflect on the third of three key questions raised by the Health and Safety Executive at the time of the criminal prosecution. Are you getting the right information to assure yourself that these systems are working effectively? At approximately 6am on…

E-Newsletter sign-up

Gexcon Makes The World a Safer Place