The aerodynamic improvement and efficiency of regular goods transportation trucks
have been a topic of current interest; however, the timber transport industry
has not been receiving as much attention. This is due to the small portion of
timber transportation vehicles, compared to regular trucks, not justifying the
cost of investigating these vehicles experimentally. Since these vehicles travel
large parts of their journey at around 80 km/h, their fuel consumption is
heavily affected by the aerodynamic resistance. In Sweden in 2015, there were
around 2000 vehicles in operation transporting 6 billion ton-km with an average
of 0.025 liter Diesel per ton-km. To understand these vehicles’ aerodynamics,
and improve on these in the future, the modelling of the timber stacks is of
utmost importance. Computational Fluid Dynamics (CFD) simulations have been
utilized to conduct this investigation due to recent advancements and the
relatively low cost of these simulations compared to an experimental approach.
By investigating the influence of geometrical modifications of the stacks on the
flow features and accumulated drag, a generic timber stack was created
representative of a real stack for a loaded baseline vehicle. It was found that
the shorter log length and a shuffling of the logs in the stack exhibit
important flow features contributing to drag not present in the other cases.
Based on this, a new baseline loaded truck configuration was created with all
stacks being identical to each other. This generic stack was built with logs
that were 4.25 m long and 0.35 m in diameter, had a smooth surface, and were
stacked with a certain displacement in the lengthwise direction.