**5. Conclusions**

This paper used a series of LES methods to conduct a simulation. The heat exhaust coefficient associated with tunnel fire lateral smoke exhaust has been investigated. A correlation for predicting the heat exhaust coefficient has been proposed. The main conclusions are:

(1) There will be an increase in the amount of hot smoke in the exhaust mass flow if the transverse distance between the exhaust vent and the fire source increases, increasing the heat exhaust coefficient in tunnel fires.

(2) The more expansive the tunnel, the weaker the anti-buoyancy wall jet, and its vertical length decreases significantly. In addition, as the tunnel width grows, the smoke layer thickness becomes gradually thinner.

(3) A calculation model was developed to compute the heat exhaust coefficient (Figure 10, Equation (17)) taking into account the lateral position of the fire source and the width of the tunnel.

**Author Contributions:** Methodology, Z.X.; software, W.X.; validation, H.T.; formal analysis, Q.L.; investigation, Q.L.; resources, H.Y.; data curation, J.Z.; writing—original draft preparation, Q.L.; writing—review and editing, S.M.S.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** The Fundamental Research Funds for the Central Universities of Central South University (No. 2021zzts235) provided funding for this project.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We acknowledge the High Performance Computing Center of Central South University for its support. This work was supported by the Natural Science Foundation of Hunan Province of China (Grant No. 2020JJ3046) and the Fundamental Research Funds for the Central Universities of Central South University (Grant No. 2021zzts235).

**Conflicts of Interest:** The authors declare no conflict of interest.
