On the extrapolation of CFD results for smoke and heat control in reduced-scale set-ups to full scale: Atrium configuration

Abstract

It is common practice to use reduced-scale experiments to develop formulae for the design of smoke and heat exhaust ventilation systems. Implicitly, up-scaling of results is assumed justified. A similar approach can be adopted with numerical simulations, i.e. a reduced-scale setup can be up-scaled to compare results to full-scale observations. However, both in numerical simulations and in experiments, scaling must be done in a proper way. The classical method for up-scaling results obtained in fire related experiments is based on preservation of the Froude number only. The present paper, focusing on the up-scaling of results by means of a series of CFD simulations of fire-induced flows in an atrium configuration, confirms this to be justified as long as the flows in both the reduced-scale and full-scale configurations are sufficiently turbulent. If this is not the case, it is illustrated that other dimensionless numbers must also be preserved in scaling, in addition to the Froude number.2

Numerical investigation of the temperature characteristics beneath the ceiling driven by a strong plume in a longitudinal ventilated tunnel

“…21 The applicability of FDS for tunnel fire research has been effectively verified. 22,23 24 It can be found that scholars have mainly studied the temperature characteristics of tunnel fires in the conditions of weak plumes. Therefore, a simulation of a small-scale tunnel is established based on FDS to carry out a numerical simulation study of tunnel fire with strong fire plume conditions.…”

“…Tilley achieved the retention of the Reynolds number and Froude number by changing the ambient air viscosity coefficient and gravity in FDS, and obtained good similarity results in the reduced‐scale model. At the same time, they also pointed out that if the Reynolds number is insufficient, the retention of the Froude number only would cause great experimental error 24 …”

Verification of Similarity of Scaling Laws in Tunnel Fires with Natural Ventilation

“…Vauquelin et al [29] discussed some scaling laws and concluded that when the Boussinesq approximation cannot be assumed, a density distortion between full scale and reduced scale is not compatible with full similitude. Tilley [30] studied the application of scaling laws in an atrium configuration and the results showed that preserving the Froude number alone is not sufficient when the flow becomes weakly turbulent.…”

“…It is noted that even the flows for fires with heat release rates of 5.6 kW and 11.2 kW were in a turbulent region, which satisfied the requirements of Froude scaling laws, significant errors in the temperature rises, smoke concentrations, as well as velocities were observed. Tilley [30] pointed out that preserving the Froude number alone is not sufficient when the flow becomes weakly turbulent. For natural ventilation in tunnels, the velocities of the upper zone and lower zone are large enough for fully turbulent flow.…”

大型工业建筑中高温含尘气流的流动规律及控制方法

“…此外, 模型 实验中气流在高于临界雷诺数的条件下流动(即雷诺 数处于自模区), 气流流动与雷诺数无关, 因此, 不 必保证模型和原型的雷诺数相同. 最终, 阿基米德数 成为描述气流流型的关键参数 [12] .…”