Presented at the STAR Global Conference 2012.
Cutting CO2 emissions and improving fuel economy is a primary focus for the entire global product line-up at the Ford Motor Company. Optimizing the aerodynamics of the vehicle is a key contributor to achieving those fuel economy targets. To this end, the Ford Ranger provides a unique set of challenges for the aerodynamicists and designers as they balance the constraints of class leading design with the clear functional needs of a Global Compact Pick-Up. Adopting a systems engineering approach that integrates aerodynamics in an interdisciplinary and collaborative design and development process with other fuel-economy technologies has resulted in a vehicle with best-in-class aerodynamic drag characteristics and outstanding fuel efficiency.
Typically, the aerodynamic characteristics of a vehicle are optimized through an interactive computational and wind tunnel testing regime. As vehicle development cycle times are compressed, timing and cost constraints associated with developing physical test properties have shifted Ford's engineering focus from physical validation towards analytical 'sign-off'. Throughout the Ranger vehicle programme, the computational fluid dynamics (CFD) codes STAR-CD and more recently STAR-CCM+ have proved indispensable as tools to assess multiple design configurations, in order to reduce drag without the need for extensive physical testing.
The success of the CFD process at Ford APA is demonstrated by the fact that a vehicle programme with more than 100 vehicle configurations, to be sold in 180 countries, was aerodynamically optimized with one physical test buck. Good agreement between the physical and computational test data ensured that the analytical model could be deployed to gain an improved understanding of the flow phenomena around the vehicle and the subtle interactions between components on the vehicle. Notably, no additional modifications to the aerodynamic configuration of the vehicle were required beyond the analytical phase of the vehicle programme.
In order to achieve the aerodynamic gains and balance the conflicting requirements of the varying attributes within a vehicle programme it is essential to have a robust and efficient computational tool set. The aerodynamic process within the Ford Motor Company APA initially utilised STAR-CD in conjunction with third party mesh generation and post-processing tools. Advances in the robustness of mesh generation improved modelling physics and post-processing functionality of STAR-CCM+ and led to a migration of the aerodynamic process to a single process within STAR-CCM+. The development of a simple spreadsheet based interface between STAR-CCM+ and the user enables the engineer to focus on shifting from that of a specialised CFD modeller to a pure aerodynamicist. In addition, the modular nature of the process has permitted extension of the aerodynamics tool, with minimal modification, to include analysis for powertrain (intake/exhaust), engine cooling, heating ventilation and air-conditioning (HVAC) and noise, vibration and harshness (NVH).
This presentation will demonstrate that successfully deploying STAR-CD and STAR-CCM+ on the Ford Ranger vehicle programme has enabled the delivery of a class leading product that will compete globally. The advances in code functionality within STAR-CCM+ and the potential to extend the aerodynamics processes to provide a CFD solution for other attributes will be discussed.