With a change in EU-legislation regarding the dimensions
of heavy trucks  coming up, specifically allowing aerodynamic
devices fitted to the back of trailers, the transportation
industry is set to largely decrease its environmental
impact in the near future. These aerodynamic devices have
been researched for quite some time  but have not yet
gained widespread market acceptance, partly because of
the transportation industry’s complex owner structures and
partly because of size regulations of the past. Though with
this new legislation and other expected new EU-legislation
on CO2 emissions, development of these aerodynamic devices
looks set to become a field of intense study.
The study explores different options regarding the influence
of changing the rear shape of a generalized ground
transportation system (GTS), a simplified model of a truck
geometry. By changing the rear shape the drag force induced
by the oncoming air flow was reduced, and the overall
coefficient of drag (CD) value lowered. There is also an
investigation as to how an added suction slot, and that slots
location, affects the CD.
Computational Fluid Dynamics (CFD) in the form of
the commercial computer software STAR-CCM+ was used
to simulate the flow around the GTS, and the results were
verified with similar studies and experiments  on the
same geometry. RANS equations and Menter k-! SST turbulence
model was used for all simulations.
The results show that CD can be lowered by 21% compared
to a baseline case. Further on the added suction
slots can reduce drag, but depending on slot location also
can add to the drag force experienced by the GTS.
2015. , 86 p.