The Nature of Flammable Cloud Volumes in Semi-confined Environment under the Influence of Flow of Air

PresentationIn the Explosion Risk Analysis (ERA), ventilation and dispersion calculations using Computational Fluid Dynamics (CFD) are usually considered when the level of confinement and congestion cannot be neglected. As far as the dispersion analysis is considered, alternative approaches are sought when a large number of simulations are required. Setting many scenarios and simulate them all is not always suitable within the timeframe of real engineering design. As a result, semi-empirical dispersion models and several procedures based on statistical approaches using CFD have been proposed to improve the robustness and the accuracy of prediction of the flammable gas cloud volume. In addition, notwithstanding the use of Response Surface Method (RSM) and Frozen Cloud Approach (FCA), it is convenient to address the problem on the basis of the physics underlying the dispersion of a scalar in the chemical process area. Following this line of reasoning, we propose a new dimensionless number balancing the transport of the flammable cloud and the accidental leak rate. Numerical experiments have shown that the dimensionless number is related to the angle of the wind direction as the angles in a circle are related to the phase angle in a sine wave, V ∼ sin (kφ/π+ β) , where V̂ is the nondimensional flammable cloud volume and φ the phase angle. The numerical findings suggest a periodic function comprising harmonically sinusoids in the same fashion put forward by Fourier and observed in the analytical solutions of diffusive transport equations