## 4 Results and Analysis
### Analysis of the Pedestrian Evucuation Strategy with the Thermal Radiation Field of the EV Fire
#### 4.2.2 Analysis of the Influence of the Direction of the Pedestrians Fleeing the EV Fire
Figure 16: (**a**) Declining curve of the accumulated thermal radiation received by the pedestrians at different speeds in the x\({}^{\prime}\) direction; (**b**) Declining curve of the Accumulated thermal radiation received by the pedestrians at different speeds in the y\({}^{\prime}\) direction. According to the component of the pedestrian evacuation speed \(v\) in the x\({}^{\prime}\) direction, the dwell time of the pedestrian in each grid was calculated to determine the accumulated thermal radiation received by the pedestrian along the evacuation path. Taking the unit speed as an example, the results are shown in Figure 19. It can be seen that the minimum cumulative thermal radiation received by a pedestrian during the evacuation was 68.78 kJ. According to the numerical calculation, the destination point of the evacuation was approximately (3.2, 2.87) and the angle between the evacuation direction and the x\({}^{\prime}\)-axis was 41.85\({}^{\circ}\). Figure 17: Grid diagram of the thermal radiation flux distribution at a height of 1.1 m in the pedestrian evacuation area. Figure 18: Dividing line \(f\) (4.5) with the thermal radiation flux of 4.5 kW/m\({}^{2}\) in the pedestrian evacuation area. It was assumed that the flame shape remained unchanged and it was easy to obtain from Equation (10) that the total combustion release related to the PHRR was directly proportional to the incident thermal radiation received by the pedestrian. We analyzed the impact of a pedestrian's evacuation speed on the evacuation decisions. The cumulative thermal radiation values for a pedestrian at different speeds were obtained, as shown in Figure 20. With an increasing speed, pedestrians had more choices for avoidance strategies. In other words, the pedestrian had more evacuation destination points to choose within the safety threshold of the pedestrian's cumulative thermal radiation. (2) Scenario with airflow  
According to the analysis in Section 3.4, the flame of the EV fire was affected by the airflow and the geometry of the SFM tilted in the air-flow direction. Considering the most adverse condition, the airflows towards the pedestrian evacuation area caused the rectangular flame model to tilt in the positive direction of the x\({}^{\prime}\)-axis and the included angle with the z-axis was \(\varphi\). As the tilted flame occupied the pedestrian evacuation area,  
Figure 19: Cumulative thermal radiation of the pedestrian fleeing to the safety threshold line \(f\) (4.5). Figure 15:0 Relationship between the minimum value of the accumulated thermal radiation and the evacuation speed when the pedestrian flees to the safety threshold boundary \(f\) (4.5). the distance \(L_{0}\) from the initial position O\({}^{\prime}\) of the pedestrian fleeing the flame surface is as follows:  
\[L_{0}=\left\{ \begin{array}{cc}0.2&\text{$\varphi<\arctan\left(\frac{0.2}{H_{ \text{G}}}\right)$}\\ H_{\text{G}}\times\tan(\text{$\varphi$})&\text{$\varphi>\arctan\left(\frac{0.2}{H_ {\text{G}}}\right)$}\end{array} \right\} \tag{11}\]  
where \(H_{\text{G}}\) is the height of flame surface #2 and \(\varphi\) is the tilt angle of the flame surface. The thermal radiation accumulation of the pedestrians under the flames with different tilt angles \(\varphi\) was analyzed for \(\varphi=\{5^{\circ},\ 10^{\circ},\ 15^{\circ},\ 20^{\circ},\ 18^{\circ},\ 25^{\circ},\ 30^{ \circ},\ 35^{\circ},\ 40^{\circ},\ 45^{\circ},\ 50^{\circ},\ 55^{\circ}\}\). A thermal radiation flux curve of \(4.5\) kW/m\({}^{2}\) at the plane z = 1.15 is shown in Figure 21. In the y\({}^{\prime}\) direction, with an increase in the flame tilt angle, the #3 and #4 flame surfaces were closer to the pedestrian area, which increased the view factors between the flames and the pedestrian. Therefor, as the thermal radiation flux increased, the threshold curve departed from the initial point O\({}^{\prime}\) in the y\({}^{\prime}\) direction.