Aerodynamic Optimization of Ground Vehicles with the Use of Fluent’s Adjoint Solver
Examensarbete för masterexamen
Automotive engineering (MPAUT), MSc
Like all other areas of the automotive development, environmental issues and fuel efficiency is one of the main driving forces for aerodynamic engineers where the aerodynamic drag force is the dominating resistance force at higher velocities. By improving the shape of a vehicle with respect to aerodynamic performance, the drag force can be reduced hence the fuel consumption can be reduced. The use of Computational Fluid Dynamics is a widely used methodology to carry out simulations that describes the flow in and around a vehicle. With these simulations, aerodynamic engineers can gather information about the aerodynamic performance Of the vehicle and make changes that can improve the performance. However, due to the many variables involved, this can become very computer demanding process and require a high number of design optimization cycles to finally reach valuable stage. Recently, a new procedure used for optimization purposes, named the Adjoint Solver, has been the focus of researchers and engineers. The Fluent Adjoint solver compute derivatives of chosen engineering observation, such as drag, with respect to all inputs and provides a more direct guidance for optimal modifications to improve performance. The Adjoint Solver accomplishes to calculate the derivative data by running only one single computation, very similar to basic CFD computations, and by that providing valuable engineering insight that can both improve and reduce the number for design optimization cycles. The main goal of this master thesis is to state if the Adjoint Solver is ready to be incorporated into Volvo Cars Aerodynamic development process. This project has been carried out as an Master Thesis together with Volvo Cars and Chalmers University of Technology, in a close relationship with Ansys which are the developers of Fluent. Fluent's Adjoint Solver has been tested on its computation abilities, robustness, computer requirements and functionality. The tests are done on four different vehicle models provided by Volvo Cars and simulations are computed in wide variation of different case setups. Based on the results from the simualtions, the conclusion is that Fluent Adjoint Solver is at the moment not at a stage where it is ready to be incorporated as a part of the development process. It is proven that the one can gain valuable engineering insight that surely can improve the development process, however, for external aerodynamics, the Adjoint Solver is not yet ready. Ansys will now continue to develop and improve the Adjoint Solver, with the issues discovered in this project in mind.
Energi , Transport , Grundläggande vetenskaper , Hållbar utveckling , Strömningsmekanik och akustik , Energy , Transport , Basic Sciences , Sustainable Development , Fluid Mechanics and Acoustics