Traffic-based methodology to develop peak Heat Release Rate probability distributions for sizing road tunnels ventilation systems when using a probabilistic approach

Sonia Fernandez — 2025-04-02

Road tunnels are a crucial part of today’s transport infrastructures worldwide. Among the installed systems, the tunnel ventilation is key, as in the case of fire, it establishes and keeps appropriate conditions for self-evacuation and emergency services operations. Recent works propose using a probabilistic approach to assess road tunnels ventilation systems’ capacity for fire scenarios. Under this approach, key design variables are defined based on probability distributions. From these distributions, the analysis uses the different possible values of the variables, including lower and upper limits as well as mean and characteristic values. The results obtained with this proposed probabilistic approach allow not only designers, but also tunnel operators and administrations, to quantify the reliability of the capacity of the ventilation system, assess its probability of failure, and define safety levels. This paper illustrates a methodology to define the design fire as a probability distribution for sizing road tunnels ventilation systems when applying the above-mentioned probabilistic approach. The methodology uses traffic information (crucial in road tunnels) and correlates it to peak Heat Release Rate (HRR) values from published reports by PIARC to obtain the design fire variable in terms of peak HRR probability distributions. The methodology is applied to two case study tunnels with different characteristics. The obtained results for the two tunnels are then compared and analyzed to peak HRR values normally recommended and used when sizing road tunnels ventilation systems to understand the uncertainty and sensitivity of the results.

Effect of inverse-square heat absorption on MHD natural convection flow in a vertical concentric annulus with radial and induced magnetic fields

Muhammad Yusuf Muhammad — 2025-04-03

This study investigates the impact of inverse-square heat absorption on steady, fully developed laminar MHD natural convection flow within an infinite vertical concentric annulus under the influence of applied radial and induced magnetic fields. The governing transport equations in the model were transformed into a non-dimensional form, allowing for the derivation of unified analytical solutions for the velocity, temperature, magnetic field, and induced current density distributions for both isothermal and iso-flux on the inner cylinder of concentric annuli. The influence of key physical parameters in the model is illustrated through a comprehensive analysis of graphs and tables. The findings reveal that increasing the heat absorption parameter intensifies thermal gradients near the inner cylinder, while stronger magnetic fields suppress fluid motion, reducing mass flux and enhancing flow resistance. Mass flux and induced current density decrease as Hartmann number and heat absorption parameter increase, demonstrating the combined influence of thermal and electromagnetic forces. The magnetic field distributions and associated current densities exhibit pronounced attenuation near the inner cylinder under a higher Hartmann number. These findings highlight the intricate interaction between thermal and electromagnetic forces, offering valuable insights for applications in nuclear reactors, MHD power generation, and advanced cooling technologies. This study contributes to refining MHD-driven thermal management approaches for Advanced engineering systems.

Mechanical Engineering Advances

Traffic-based methodology to develop peak Heat Release Rate probability distributions for sizing road tunnels ventilation systems when using a probabilistic approach

Effect of inverse-square heat absorption on MHD natural convection flow in a vertical concentric annulus with radial and induced magnetic fields