Numerical modelling of wind-blown rain on railway station platforms and mitigation through canopy design

Abstract eng:
Rainfall on station railway platforms is potentially hazardous to passengers because it increases the risk of slips and trips. Canopies provide shelter for passengers and also prevent rain from soaking the platforms. However not all modern canopy designs have proved effective with some canopies showing poor performance at sheltering platforms during showers and storms. Validated numerical simulations were conducted to determine which style of canopy design keeps a platform the driest in the presence of wind-driven rain (WDR), while also complying with design criteria specified by Network Rail Standards. Steady Reynolds-averaged Navier-Stokes simulations were conducted to model the WDR and assess the performance of a variety of canopy designs currently in use on the UK rail network. The numerical simulations were validated against experiments that measured the wind and rainfall rate at two positions on platform two at Rugby station in the UK. It was found that the penetration of rainfall onto platforms could be best mitigated through reducing canopy height and that at the wind angle investigated, there was a large sensitivity to canopy geometry. Introduction In the day-to-day use of railway station platforms, high volumes of passengers walk along them and it is the responsibility of the network operator to ensure that stations are a safe environment. Rainfall is common on platforms and canopies are often provided to shelter waiting passengers but also to reduce the amount of water gathering on the platforms. High volumes of water falling on station platforms can be ‘walked’ around stations and cause slip hazards for passengers. Anecdotally there are reports that modern canopy designs do not provide adequate shelter for passengers in the event of winddriven rain (WDR) and in some cases rainfall penetration onto the platforms has been significant. In cases such as storms, where wind speeds are excessive (> 15 m/s) WDR on station platforms is unavoidable, regardless of the canopy design. However for lower-speed winds, canopy designs can seriously influence the penetration of rain beneath the canopies. The University of Birmingham conducted work on behalf of Network Rail, UK to assess the performance of a variety of station canopies in conditions with wind speeds of less than 3 m/s. The work used validation experiments and steady-state computational fluid dynamics (CFD) simulations to develop models of the WDR around Rugby station for different canopy designs within the criteria set by the Operational Property Design and Construction Handbook (OPDCH) [1] and the Railway Group Standard (RGS) GI/RT7016 [2].

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