Heavy/Commercial Vehicles and PowerFLOW

Truck Aerodynamics

The benefits of PowerFLOW for passenger vehicle development apply equally well for commercial vehicles.  The design process for heavy highway trucks is significantly influenced by aerodynamic drag performance within the constraints of cooling flow requirements.  Bumper, fascia, fender, hood, cab, roof fairing, and side fairings are designed to meet fuel economy targets for the truck.  PowerFLOW provides a digital process for vehicle development to design the truck.  Simulations provide diagnosis of pressure distributions that contribute to drag – flat forward-facing areas produce high pressure that increase drag, but curved forward edges can produce low-pressure peaks that reduce drag.  Other regions such as the hood and roof require optimization of panel angles, radii and curvature profiles in order to direct the flow appropriately with minimum pressure drag.  Separations off of rear-facing edges can be optimized to minimize low pressure associated with vortices and wakes.  Deflection of flow around components under the vehicle, especially the wheels and axles, is critical for minimizing drag.  Finally, the impact of flow circulation in the large wake behind the truck on the base-pressure drag of the vehicle can be assessed.

External aerodynamic simulation of heavy truck. Image courtesy of Freightliner.

Diagnosis of the aerodynamic shape leads to ideas for design changes.  Some design changes are related to the proportions of different regions and panels.  Others are described by parametric angles and radii, while others are presented as alternative styling designs.  All of these design changes can be accomplished using Exa’s PowerCLAY as the primary design test tool.  PowerCLAY allows rapid modification of vehicle geometry to support design process timelines.  Pin-point analysis of pressure distributions from one change to the next provides immediate feedback about design changes, and PowerCLAY provides the tool to modify the geometry in the direction of drag improvement.

Thermal Management

For heavy trucks, the aerodynamic performance requirements are significant but are secondary to cooling performance.  A large grille opening, heat exchangers and cooling fan are the prominent features of the truck front-end, and are optimized for maximum cooling flow into the underhood.  Cooling flow is also managed to control temperatures of underhood components which are heated by the engine, exhaust and hot flow through the heat exchangers. 

For low-speed or stationary commercial vehicles, the thermal management requirements are met by design of the cooling flow path, heat exchangers and cooling fans, and placement of hot components and heat shields.

The applications of PowerFLOW for automobile thermal management apply equally well to heavy trucks and other commercial vehicles, and provide support of the complete design process for managing thermal requirements.

Complex geometry is no problem for Exa PowerFLOW. Aerodynamic results on simplified parts may result in insufficient or incorrect data. Image courtesy of Freightliner.