Drag reduction of semi-trailer aerodynamic devices determined by two different methods

Actual trend in transport is the decreasing of the energy consumption and GHG production. One way how to decrease these two attributes is the reduction of aerodynamic drag using additional aerodynamic devices on semi-trailers. The paper presents the results of their influence measured by using two different methods. The results were obtained by performing coastdown tests and they were compared with outputs obtained by the measurements in the wind tunnel. The driving test consists of the coastdown test on flat straight track protected from the wind impact. The current velocity was measured by the GPS sensor. The vehicle deceleration was used for the acting driving resistances counting-one of them is the air drag-drag coefficient. The results were compared with drag coefficient values examined in a wind tunnel test on a scaled truck model done by authors.