Numerical Analysis of Freight Train-Tunnel Overpressure Through Steady-State CFD Simulations

Train–tunnel overpressure has been mainly studied for high-speed trains, while limited attention has been given to freight trains. This is mainly due to pressure variations scaling with the square of train velocity, and freight trains generally operating at lower speeds. However, freight trains may still produce significant pressure levels, which during crossings with passenger trains can lead to passenger discomfort and potential infrastructure damage. This work extends the current understanding of freight train–tunnel overpressure by analysing the effects of wagon geometry, train length, and inter-vehicle gaps using a simplified steady-state CFD approach. Results show that wagon geometry affects the pressure signature, both in terms of local pressure peaks and boundary layer development. The effect of inter-vehicle gaps depends on the balance between pressure growth at wagon leading edges and pressure recovery upstream of trailing wagons. For homogeneous trains with a well-developed boundary layer, larger gaps increase pressure peaks by up to 29%, whereas for configurations with large spacing and thicker boundary layers, increasing gaps reduce peak pressures by up to 34%. Train length effects are assessed using a container train with three different lengths, showing an approximately linear pressure increase with convoy length.