Evaluation of the optimal geometry of the hump slab in desert railways with the solid-gas two-phase simulation approach

One of the inevitable necessities for the development of the rail transport network is to pass through desert and sandy areas. At the same time, desert railways increase maintenance and repair costs, reduce speed and block the line during operation, and even cause the train to derail. So far, various solutions have been proposed to deal with quicksand in desert railways. One of the newly developed methods is the hump slab track, which seeks to control and pass the amount of incoming sand from the railway track. In this system, the ballast material is removed and the height of rails is raised by means of concrete supports known as humps. As a result, channels for the passage of sands under the rails are created. The geometry of the hump should be such that, in addition to favorable aerodynamic conditions, it provides maximum free space for sand to pass through. In this research, with the aim of optimizing the geometry of the hump, different sections for the hump have been investigated and then two main sections including oval and rectangle-semicircle with two different heights have been evaluated. Simulations have been carried out in the platform of computational fluid dynamics and in Ansys Fluent software. Two-phase solid-gas flow including a sand flood and wind flow has been passed through the models and the amount of sand volume fraction has been compared. The results show that the rectangular-semi-circular geometric section (height of 20 cm) shows more favorable results against the influx of quicksand.