The Free-Stream Anemometer: A laser-Doppler system for the reliable assessment of the aerodynamic performance of surface vehicles
B. Tanguay(1), P. Cottin(2), S. Cochard(3)
1: Aerodynamics Laboratory, National Research Council Canada
2: formerly from Institut National d’Optique (INO¶ ), Québec, Canada
3: Aerodynamics, thermodynamics and acoustics dept., Stadler Rheintal AG, Switzerland
DOI:
The Free-Stream Anemometer (FSA) is a dual-channel laser-Doppler system enabling the non-intrusive, real-time measurement of free-stream velocity forward of traveling vehicles. The FSA supports aerodynamic testing in real-life conditions, i.e. in the presence of turbulent terrestrial winds characterizing the atmospheric surface layer. Each of the two non-parallel FSA laser beams is focused in the free-stream zone, illuminating the microscopic natural aerosols traversing the FSA sensing zone as faithful wind tracers. The FSA is able to detect aerosol particles with diameters above 1 μm in concentrations as low as 500 1/L or 2 μg/m3, i.e. well below the concentrations observed in urban and inter-urban environments worldwide. Under yaw-inducing crosswind conditions, the FSA enables the determination of a vehicle’s yaw-dependent aerodynamic drag coefficient, thereby enabling the evaluation of a vehicle’s energy consumption in a variety of wind conditions. This article presents the FSA technology, the several validation tests conducted in the laboratory, in the NRC wind tunnel and on board of ground vehicles. Results obtained from FSA experiments conducted on board of a high-speed train are also presented.
