Curved tunnels are more likely to have an accident and a fire source due to their physical characteristics. Using a 3D computational fluid dynamics tool with body-fitted grids, three different fire locations were investigated numerically in a series of curved tunnels with a turning radius of 50–1000 m and a heat release rate of 5–15 MW. Results showed that the critical velocity increased with increasing tunnel turning radius, and the straight tunnel had the highest critical velocity in all scenarios. For a tunnel with a 10 MW heat release rate, the critical velocity increased by 19 % from R = 50 to 1000 m. Furthermore, it was shown that the critical velocity was proportional to one-third power of the heat release rate. A gradual increase in critical velocity was also observed as the fire source was displaced from the tunnel's center to the walls. Furthermore, this increment increased as the fire source approached the internal curvature. During the displacement of the fire to the inner and outer walls of a tunnel with R = 100 m and a 10 MW heat release rate, the critical velocity increased by 7.7 % and 5.6 %, respectively. Therefore, the worst fire scenario occurs when a fire is close to a tunnel's internal curvature and has the largest turning radius and the maximum heat release rate. Tunnel curvature and fire location are not considered in normal dimensionless analysis (commonly used for tunnels). Thus, the numerical results were unified in a non-dimensional form, and a modified formula was developed to calculate critical velocities in curved tunnels. The proposed formula includes tunnel curvature, heat release rate, and fire location with a coefficient of determination of 0.98. Numerical simulations confirmed the predictions of the proposed formula. Compared to other models in straight and curved tunnels, the predicted correlation developed in the present study can accurately predict critical ventilation velocity in curved tunnels.

弯曲的隧道由于其物理特性更容易发生事故和火源。使用带有贴身网格的 3D 计算流体动力学工具，在一系列转弯半径为 50-1000 米、热释放率为 5-15 MW 的弯曲隧道中对三个不同的火灾位置进行了数值研究。结果表明，临界速度随着隧道转弯半径的增加而增加，直隧道在所有情况下的临界速度最高。对于热释放率为 10 MW 的隧道，临界速度从 R = 50 增加到 1000 m，增加了 19%。此外，还表明临界速度与放热率的三分之一次方成正比。随着火源从隧道中移开，临界速度也逐渐增加。以墙壁为中心。此外，随着火源接近内部曲率，该增量增加。在 R = 100 m 和 10 MW 热释放率的隧道的内壁和外壁发生火灾位移时，临界速度分别增加了 7.7 % 和 5.6 %。因此，最严重的火灾场景发生在靠近隧道内曲率、转弯半径最大和热释放率最大的地方。正常无量纲分析（通常用于隧道）不考虑隧道曲率和火灾位置。因此，数值结果统一为无量纲形式，并开发了一个修正的公式来计算弯曲隧道中的临界速度。拟议的公式包括隧道曲率、放热率、确定系数为 0.98 的火灾位置。数值模拟证实了所提出公式的预测。与直线和弯曲隧道中的其他模型相比，本研究开发的预测相关性可以准确预测弯曲隧道中的临界通风速度。