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The flow field driven by a compartment fire usually contains several flow zones with different physical structures. As each type of turbulence model has its own predominant application area, it is logical to apply two or more simple turbulence models to the same fire-induced flow field at different locations according to their predominant features to yield a comparatively simple, accurate, and stable zonal turbulence model. A zonal turbulence model, which is a hybrid of the standard k-ε model and its modification, is developed in this paper. The model is tested and compared with the experimental data. A promising improvement is observed when comparing it with the base turbulence model, i.e., the standard k-ε model, especially in the recirculating region near the corners of the compartment. This approach in having different zones in the plume region will be useful for handling more scenarios at the initial stage of fire hazard assessments. [ABSTRACT FROM AUTHOR]

The rapid rise of the economy all over the world has led to many large-scale new or renovative construction projects with tall building complexes.[1] People change living style in travelling around frequently with mass transport systems through intra-city subway systems, inter-city high-speed railways and intercontinental air passages. FLD requirements for buildings (which includes tall buildings as well) are listed in their respective codes.[17],[21] Passive fire protection Passive fire protection requirements for tall buildings[5],[6],[10] are fire resistance of buildings, refuge floors, means of escape and means of access. Buildings taller than 40 storeys are understood as supertall (or ultra-highrise) buildings in the Hong Kong Special Administrative Region (HKSAR).[7] Different terms were used for very tall buildings, "mega-high-rise buildings"[8] and "super-high-rise buildings".[9] The problems when a very tall building catches fire are long evacuation time for occupants, rescue difficulty for high occupancy, impossible from outside to suppress the fire at high level, etc. Fire safety of tall buildings as an example Numerous tall buildings were built in the past two decades, even residential buildings are up to 80 storeys.[4] A supertall building is taken to be of height over 300 m by the Council on Tall Buildings and Urban Habitat (CTBUH).[5] The term "very tall building"[6] is used by the Society of Fire Protection Engineers. [Extracted from the article]

Compartment fire is an important research area in fire science and fire safety. Owing to its simplicity, the zone model remains attractive in studying compartment fire. Although computer software packages for the two‐layer zone are in popular use, a basic understanding of the physical phenomena involved and the mathematical formulation thereon would benefit users of the zone model in terms of critical judgement of software outputs, which could be unreasonable, and insight of the general trends of important variables. In general, the differential equations based on a two‐layer zone model have no analytical solutions and numerical methods are required. However, stiffness is present in using numerical methods to solve these differential equations, and reliable results are obtained only when very small time steps are used in computation. Nevertheless, in some special cases, analytical solution for the clear height in the zone model exists, as demonstrated in the present study. Predicted values of smoke layer height in the present approach are shown to be in good agreement with experimental results reported in the literature. The present work would provide insight into the tenability condition of a compartment on fire and is an important issue in fire safety management. [ABSTRACT FROM AUTHOR]

Summary: Velocity distribution and motion of a whirling flame in a room fire with vent were studied analytically in this article. Using Rankine vortex model, whirling flame models with and without decay of the rotation velocity were established. The whirling flame model and the cross‐wind velocity boundary conditions were used to study the velocity distribution of the rotating flame under the action of side wind. When there is a linear velocity gradient in the lateral wind, the whirling flame still revolves around the same axis at different heights in the model without attenuation of rotation velocity, but the axis becomes tilted. In the rotation velocity attenuation model, the axis of the whirling flame changes from a straight line to a curve, and the change of the shape of the whirling flame is related to the flame height, the rotation angular velocity, and the maximum wind velocity. Under the assumption of Rankine vortex model with the same rotation angular velocity, the uniform lateral wind and lateral wind with linear velocity gradient can only affect the position and shape of the whirling flame axis but not change the rotation angular velocity. [ABSTRACT FROM AUTHOR]