Aerodynamics

FOI conducts applied and research-driven activities in aerodynamics, focusing on manned and unmanned military aircraft, including weapons and missiles.

The objective is to enhance the capability for evaluating aircraft design concepts, with regard to their fundamental flight performance, stability, weapons integration, weapons separation, and propulsion integration, including the design of air intakes, and so on, to produce aero-data for simulation models and noise analyses.

The research is directed towards simulations of non-steady flow phenomena using CFD (Computational Fluid Dynamics) methods, as well as flow control, aerodynamic design, and shape optimisation.

CFD is a branch of fluid mechanics in which numerical methods are used to analyse flow problems. The principal foundations on which CFD rests are the Navier-Stokes equations. These consist of a system of partial differential equations, which primarily describe the time- and space-dependent velocity field in a fluid. The equations are non-linear and must be solved numerically. FOI is developing its own CFD software, the code M-Edge, to be able to solve the compressible Navier-Stokes equations on computer networks, using a so-called finite volume method.

The aerodynamic studies are normally based on the assumption that the geometry of the aircraft remains unchanged during flight. However, the aircraft’s component materials are not rigid, but elastic, so that the loads acting on the aircraft during flight cause significant deformation of the various structural components, such as the wings. This in turn leads to new loads on the structure and then new deformations, and so on, until equilibrium is established, or severe vibrations occur, in the form of flutter. In working with aeroelasticity, models and computational codes are developed to cope with these problems, which become increasingly important as aircraft become more flexible. The problem of deformation of control surfaces such as rudders in turn creates a connection to the research on flight mechanics and control systems.