Characterisation and analysis on the instantaneous development and dynamic vortex cores of fire whirls in a fixed-frame facility. (August 2021)

• Record Type: Journal Article
• Authors: Yan, Yihuan; Fang, Xiang; Cheung, Sherman C.P.; Yan, Ping; Tu, Jiyuan
• Is Part Of: International journal of heat and mass transfer. Volume 175(2021)
• Publication Date: 2021-08
• Subjects: Fire whirl -- LES -- Vortex core -- Heat release rate -- Imposed circulation; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2021.121355
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Four approaches are developed to identify the core region of fire whirls. The hybrid swirling vector & tangential velocity method is recommended. Pattern of fire whirl's vortex core directly links to the flame behaviour. Vortex core radius and critical height are nearly proportional to heat release rate. Mass flux inside the vortex core has strong impacts on the formation of fire whirl. Abstract: In an outdoor fire accident, the fire whirl could significantly accelerate the spread of fires with the elongated flame and the rotating flame movement. Large eddy simulations were conducted to investigate the fire whirl formations in a medium-scale fixed-frame facility and their development processes under three heat release rates. Four approaches were developed to identify the size and location of fire whirl's vortex core. A hybrid swirling vector and tangential velocity refinement approach was found as the most promising approach to identify reliable vortex cores at various fire whirl development stages. The numerical outcomes revealed that the instantaneous vortex core expanded with the increased heat release rate in the fixed-frame facility, and the vortex core constructed the fire whirls' elongated flame. Also, the correlations between heat release rate and the imposed circulation could impact the flame shape and the transition process under different stages.