Aerodynamic Development of a New Coach Generation Based on Wind Tunnel Testing, CFD-Simulation and On Road Tests

In order to significantly reduce the vehicle’s fuel consumption, a lot of attention was paid to the new design of the NEOPLAN TOURLINER. During the design phase, each detail was therefore looked at closely in order to determine how to implement the NEOPLAN design criteria, specific vehicle design and detailed design in a way that optimizes the drag value coefficient (c_D). Through optimization loops, we found a target-oriented design using CFD and implemented this meticulously in the area at the front of the bus, the front roof dome, the mirrors, the air-conditioning system cladding, the wheel arch panels, wheel trim, entire rear panel, as well as areas in the underbody. The results were then examined on a scale model in the wind tunnel of Pininfarina. A lot of effort was put to build a model which includes finest details, e.g. the entire underbody-structure and (motorized) rotating wheels. Eventually, the drag value was confirmed through test drives of initial vehicles. These are constant speed tests in which probe data of drive momentum, vehicle speed and wind velocity/direction are used to calculate the c_D value.

The c_D value was reduced by over 20% in comparison to the Tourliner, released in 2002, from 0.46 to 0.36, now. The vehicle therefore achieves overall fuel savings of 10% in comparison to the predecessor bus, reducing fuel consumption to an average of approx. 20 L/100 km.

This represents a high degree of innovation, as the improved consumption is in a standard, entry-level vehicle of the NEOPLAN brand. The standard Tourliner not only has a more attractive acquisition cost – it is also designed to reduce consumption. More for people and the environment!