What is the problem/issue being addressed?
The project aims to develop and validate computational fluid dynamics (CFD) based numerical models to facilitate the prediction of flame acceleration (FA) and Deflagration to Detonation Transition (DDT) in industrial scale explosions incorporating the turbulence effects.
Why is it important for society?
Despite increasingly stringent safety measures, explosions resulting from the accidental leaks of fuels continue to occur with higher frequency and consequences especially when DDT occurs. DDT involves transition from subsonic to supersonic flows. In practice, explosions resulting from accidental releases of flammable gases; e.g. congested chemical plants, nuclear installations or just gas leak in a residential building or underground pipelines, all involve non-uniform mixtures. The complex interaction between turbulent flame, obstacles and mixture concentration gradients all affect FA and DDT. These effects cannot be captured by the current provisions for explosion resistant design and explosion safety, which are based on the energy release mechanism of high-order explosives; they are insufficient to interpret the complex nature of vapour cloud explosions (VCE) and hence their use in facility siting and explosion protection design is problematic.
What are the overall objectives?
The objectives include:
⁃ To gain insight about the underlying physical mechanisms affecting FA and DDT in smooth channels/tubes with uniform mixtures and mixtures with concentration gradients using direct numerical simulations (DNS) with high order numerical schemes.
⁃ To repeat the above in channels/tubes with obstacles.
⁃ To assess the capability of the more efficient large eddy simulation (LES) approaches for medium scale simulations (order of several metres) and large scales (tens to hundreds of metres) to predict global safety parameters like flame speed, overpressure and onset of DDT.
⁃ To conduct large scale FA and DDT of practical scales and assess the resulting differences in the predicted likelihood of DDT and explosion impact on structures.
