This post and its attachments continues a sporadic (and what some might call obsessional) series on the effects of cross winds on trains. It gives links to a downloadable report and a downloadable spreadsheet.
The report (below), which follows on from two papers I wrote in 2010 and 2013, presents a detailed analysis of the effects of unsteady crosswinds on trains using a simple train dynamic system methodology. This begins with the specification of unsteady wind characteristics that are then used to calculate unsteady aerodynamic forces. These are then used as input to the dynamic model to calculate lateral, vertical and rotational displacements and unsteady track forces. Three specific effects are then considered – wheel unloading criteria, track force criteria and vehicle displacement criteria, and a rigorous statistical methodology used to specify values of these under specific unsteady crosswind conditions. A simple methodology for developing wheel unloading cross wind characteristics (CWCs) is then set out and calibrated using the dynamic model. This calibration indicates that the simple model is more than adequate to determine wheel unloadings in design, and that the more complex aspects of the suspension, track roughness of spatial non-correlation of the aerodynamic loads have little effect on the calculated CWCs. Finally possible extensions to the modelling methodology are outlined – in terms of investigating a range of effects on wheel unloading dynamics, the extension of the method to investigate track forces, roof displacements and pantograph / OHL displacements in cross winds.
The spreadsheet gives a simple and straightforward way of calculating the CWCs using the methodology described in the report. It is made available on the basis that the coding has not been verified in any rigorous fashion, and that the user takes full responsibility for the output. That warning being given, I hope some will find it of interest. There are two worksheets. For both the user-defined parameters are highlighted in yellow. The first calculates the CWC from a user-specified value of the characteristic velocity The second calculates the value of characteristic velocity from the vehicle geometric, mass and aerodynamic parameters as in section 11 of the above report. It uses the same values for these parameters as used in the report, but these can be changed as required.