Unsteady aerodynamic forces on long lorry platoons

In an earlier paper the authors describe experimental investigation to measure forces on 1/20th scale vehicles in long platoons, together with flow field around using University of Birmingham moving model TRAIN rig facility, that can accommodate 8-vehicle platoons and provide a realistic ground simulation. This analyses results further look at unsteady flows. Using conventional Fourier spectral analysis wavelet analysis, it is found there are two modes – one low frequency affects multiple platoon any time, has wavelength several vehicle lengths; high much shorter localised specific vehicles. These flows very intermittent unsteady, switching between both spatially temporally. Associated DDES calculations only capture mode. Scaling up measured values full-scale situation gives standard deviation side force individual lorry 260 ?N, major oscillation 1.0 ?Hz.