Large research grant for greener timber trucks

With the aid of a supercomputer, a wind tunnel and a research grant of SEK 5.7 million, the 2,000 timber trucks in Sweden are to achieve lower fuel consumption, becoming in this way a little bit greener.

“The forestry industry is part of the green sector, which has shown considerable interest in our research,” says project manager Matts Karlsson, professor at the Division for Applied Thermodynamics and Fluid Mechanics.

The three-year research project is to show how timber trucks and chip vehicles can be given better aerodynamic properties, achieving in this way lower fuel consumption. This will, in turn, lead to lower carbon dioxide emissions. Several small improvements should be able to give a reduction in fuel consumption of 5-10% within a couple of years.

“Our earlier studies have shown, for example, that rounded corners reduce air resistance and thus fuel consumption. In addition, timber trucks and chip vehicles are driven empty half of the time,” says Matts Karlsson.

The project is being funded within FFI – Strategic Vehicle Research and Innovation, a collaboration between the Swedish Transport Administration, Vinnova, the Swedish Energy Agency, and Swedish commercial vehicle manufacturers such as Scania and Volvo.


The project has been given the catchy name “ETTaero2”, (which is derived from the Swedish words for “one more stack, aerodynamics, second project”), and research is being conducted at LiU together with eight partners: Skogforsk (the Forestry Research Institute of Sweden), Scania, Parator (which constructs trailers for commercial vehicles), ExTe (stakes), Bergs Fegen (superstructure for timber trucks), Maskin och Truck AB (chips containers), the Fröjd haulier company in Kisa, and the forest-owner association Södra.

The first project ETT started a few years ago, with the goal of testing a 30 m, 90 tonne timber truck. Current timber trucks are 25 m long and weigh 60 tonnes. As a subproject on the pathway to larger and heavier vehicles, work within ETTaero2 is concentrated on a truck of normal length that has been modified to a total weight of 74 tonnes.

“We aim to find simple technical solutions that are cheap and practical,” says Matts Karlsson, who is helped by doctoral student Petter Ekman.

From calculations to full-scale tests

The project consists of three parts:
The first involves calculations for design modifications and will be carried out at the National Supercomputer Centre, NSC, at LiU.

The second part will verify and supplement these calculations using experiments at a scale of 1:6 in the wind tunnel.
“The wind tunnel experiments are also useful since it is possible to see the results more directly, and they are easier to explain to others,” says Matts Karlsson.

Different designs will be tested in the wind tunnels for the effects of side winds. These results will subsequently be used as input to the computer simulations, such that these also will take side winds into consideration. SMHI, the Swedish Meteorological and Hydrological Institute, can provide the researchers with data about mean wind speeds and average wind directions for the routes being considered.

The third part of the project will involve full-scale tests to determine how well the measurements and calculations agree with reality.

“The hauliers have been granted special permission to drive the 74-tonne rigs, and we will obtain true operational data from these. These trucks always take the same routes, and the hauliers are familiar with how the drivers drive. The computer power that we have access to at NSC enables us to use advanced fluid mechanics and apply the techniques to practical problems,” concludes Matts Karlsson, who was appointed director of NSC during the summer.

The “ETTaero2” project has just started, and the results will contribute to transport in the forestry industry becoming more environmentally sensitive when they are presented in 2019.

Flow calculations

Beräkningar av timmerbil utan last med 10 graders sidvind

Advanced flow calculations show how a low-pressure region forms just behind the driver’s cabin when the truck is not carrying a load. The figure shows calculations carried out with a side wind at 10 degrees. Petter Ekman

Beräkning av timmerbil med sköld

Air resistance can be reduced by up to 7% by mounting a shield between the front bulkhead and the first pair of stakes. Petter Ekman



Video from the pilot project