Rapid prediction of train nose entry pressure gradients

The relative merits of two rapid methods of estimating train nose entry pressure gradients are assessed. The more accurate of the two is analytical and allows for three-dimensional geometry. It has previously been demonstrated to give close correlation with experimental measurements. The other method is numerical and is less accurate because it is based on one-dimensional approximations, but its widespread use for predicting wave amplitudes justifies a careful appraisal of its potential for predicting pressure gradients. Both methods have the important advantage of requiring hugely less calculation time than 3D-CFD methods. It is concluded that the I D method, suitably modified by a predetermined empirical adjustment, is sufficiently accurate for initial design purposes (e.g. feasibility studies), but that the 3D approach should be used for detailed design. Extensive experimental data are used to assess the validity of the two methods and to support the key conclusions.