AFRL Improves CFD Analysis Methods

Applications

• Military and Commercial Significance:
• Engineers routinely use CFD to predict the aerodynamic forces and moments of an air or space vehicle at a given flight condition. However, the overall design process requires knowledge of how these forces and moments vary with the vehicle’s motion. While CFD can accurately estimate this information, the process has traditionally required solving complicated nonlinear equations. In addition, its high cost has limited its application to large-scale problems.
• The sensitivity equation method (SEM) is much more efficient at performing these calculations. It finds solutions to complicated CFD nonlinear equations by using linearized equations, which are much easier to solve. The SENSE software package uses the SEM approach to compute flow field sensitivities. The software is compatible with most CFD flow solvers.
• As part of the Small Business Innovation Research program, the AFRL Air Vehicles Directorate worked with Aerosoft, Inc. to improve methods of analyzing CFD solutions. Their efforts led to the development of the SENSE software package, which shows how changing a system parameter affects an existing CFD solution. Engineers can use this capability in a number of ways to gain valuable insight into CFD results. For example, instead of the traditional computation of multiple CFD solutions for each design parameter, SENSE can perform parametric studies from a single CFD solution for less than 10% of the cost of traditional methods.
• SENSE quickly determines the influence and relative importance of all design parameters to find important trends while significantly reducing vehicle design costs and turnaround time. It can also calculate performance measures such as lift curve slope, and stability derivatives such as roll damping. Since any system parameter can be used, SENSE is also capable of solving other engineering problems. It is a powerful tool and should prove to be a valuable asset in the years to come.