PSI - Issue 73

Ivan Kolos et al. / Procedia Structural Integrity 73 (2025) 58–65 Author name / Structural Integrity Procedia 00 (2025) 000 – 000

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Fig. 2. Zones in the computational domain.

Preliminary simulations have shown that modelling rotating wheels entering the fluid and spraying it is too computationally demanding and not very efficient with respect to the size of the entire domain. Therefore, a simplified model is considered, where particles are injected from the sidewalls of the tyres. The particle size and flow rate were selected based on the results of studies published in (Lottes & Bojanowski, 2013). The results show that particles with a diameter of 2.5e-5 m travel the furthest from the injection point, so we chose this diameter for our simulations to increase the probability of particle capture in the most distant sampling planes. When selecting the flow rate, i.e. the amount of liquid sprayed from the truck wheel, we chose a value of 4.5 kg/s, which is the result of an analysis carried out in the work (Paschkewitz, 2006). For calculation purposes, these are inert particles of constant diameter 2.5e-5 m, total flow rate 4.5 kg/s, and initial particle velocity magnitude of 25 m/s. The speed of the particles corresponds to the speed of the vehicles. We have used the maximum speed allowed on this highway, which is 90 km/h (25 m/s). The particle material is simplified to liquid water with a density of 998.2 kg/m 3 . The total modelled vehicle travel time is 14.76 s, with the non-stationary calculation performed at a constant time step of 0.01 s. First, the air flows through an empty domain without trucks. At the moment when the turbulent flow in the domain can be considered fully developed, the first vehicle enters the preparation zone. After 6.12 s, the first vehicle enters the analytic zone, followed by the second vehicle, which enters the zone 2.64 s later. The second truck leaves the exit zone after 6 seconds. The particles are evenly sprayed from the moment each vehicle reaches a distance of 120 m from the front of the analytic zone, and the spraying continues throughout the entire run. In the model, two directions of the wind are simulated. The wind directions are shown schematically in Fig. 3. The angle is measured in the XZ plane relative to the X axis. The directional vector of the wind is horizontal, i.e. it lies in the XZ plane.

2.2. Boundary conditions

The bottom faces of the domain and the walls of the trucks have the wall boundary condition. The top face of the domain is the zero-shear wall. The front, back, left, and right sides of the domain are velocity inlets or pressure outlets depending on the direction of the wind flow, according to Fig. 3. There are also interfaces between the moving subdomain and the surrounding domain, allowing smooth fluid and particle transport. The magnitude of the inlet wind velocity is 20 m/s. Vehicles move at a constant speed of 25 m/s.

Fig. 3. Wind flow directions.