## 4 Conclusions  
A numerical modelling of the fire whirl formulated and evolved in an enclosed configuration with different entrainment schemes was performed to evaluate the effect of additional eddy generation to the fire whirl formation and development pathway. The model adopted detailed chemistry, WALES large eddy simulation turbulence and combustion coupling approach to capture the intricate whirling flame flow behaviour. The modelling is conducted in a controlled numerical environment, for example, soot-free alcohol-based fuel injected with fixed inlet velocity and resolved numerically based on a uniformed fully structured discretisation scheme. This approach isolates and constrains the complicated coupling  
Figure 37: Plot of incoming velocity of the Slit 01 and Slit 02 cases, with the marks indicating the representative time instant corresponding to Figure 36.  
effect between the combustion process and the flow dynamics due to theoretically and numerically introduced uncertainties such as radiation feedback from soot particulates, variance in burning rate due to pool-based fuel configuration and numerical variation in spatial resolution due to locally refined mesh that typically implemented in previous studies in the literature. The present numerical simulation of the baseline case consists of a single side flow channelling slit, replicate the experimental setup from the literature. The result yielded from the baseline model compares well with the experimental data, and hence the same numerical methodologies are applied to construct the comparison group with two identical symmetrical entrainment slits, and the results of the two models, from the time of ignition to 50.00 s is presented and compared to reveal the effect of the two eddy generation scheme on the fire whirl formation and development. In conclusion, the following observations can be made:  
* With the existence of the eddy generation sources, i.e., slit(s) on the side of the enclosure, both Slit 01 and Slit 02 case observed the formulation and evolvement of the fire whirl from a buoyancy-driven diffusion flame that flickering randomly into a swirling reacting flow that spanning around the chamber with respect to domain centreline;
* Three-stage of the fire whirl formulation and development pathway can be observed in both cases, namely Stage A as the flame development, Stage B as the fire whirl development and the formation and Stage C as the fire whirl evolution;
* Compared with the baseline model, the Slit 02 case formulated the fire whirl much faster, i.e., 49.58% reduction of the duration in Stage B which transforms from the free-standing buoyant flame into nascent fire whirl;
* The nascent fire whirl formulated in Slit 02 is more intensified and spatially extended compared with baseline case, with the visible height is increased by 84.38%, from 0.32 m to 0.59 m, peak flame temperature increased 9.42%, from 1380 K to 1510 K and relatively consistent vortex core radius compared with that increase of the monitoring flame height;
* Once the nascent fire whirl is formulated, the fire whirl for the baseline model is spinning around the centreline with a relatively small radius of revolution in a semi-steady pattern, for the rest of the simulation duration up to 50 s. On the other hand, the highly centralised fire whirl formulated in the Slit 02 case may gradually diverge via swirling with an increasing radius of revolution. It will eventually achieve an internal balanced semi-stable status that the revolution radius is intensified by the introduction of the additional eddy via the slits and at the same time constrained by the enclosures boundary walls;
* The revolution obit of the fire whirl could be potentially explained based on the theory of circular motion with constant surface drag force to create a radial boundary layer, acting as the centripetal force that balances the velocity field of the vortex and the radius of revolution.