Aerodynamics

Lift/Drag prediction

CFS Engineering participated in several AIAA drag prediction workshops. After the 4th Drag Prediction Workshop drag polars were computed on the medium multi block structured grids provided by all Workshop participants, and the results were processed by the far field drag extraction tool developed by CFS Engineering and RUAG. These results are presented in a paper published in a paper in the Journal of Aircraft.

Fluid-Structure Interaction

The Swiss Airforce operates the F/A-18 fighter since 1997. The Swiss usage of this aircraft is more severe than the US Navy Design, resulting in a different structural design. To better understand the aerodynamic loads a large investment was made in the development of a CFD capacity to generate these loads for different flight conditions. Procedures were developed for both static and dynamic Fluid Structure Interaction (FSI). Dynamic FSI calculations were made to study vertical tail buffeting using a tightly coupled approach. Papers on studies for the F/A-fighter were given at the AIAA Aviation Conferences in 2017 and 2018. Other papers on FSI were given in 2016 and 2018.

Boundary-layer ingestion (BLI)

Aircraft with an integrated BLI propulsion systems are today seen as enabling technology to reduce fuel burn and thus emissions. This has been confirmed in Wind tunnel tests using a simplified fuselage geometry, and reductions of upto 25% in power savings coefficient (PSC) were obtained. However most studies did not try to answer the question: What is the best aircraft architecture to integrate the BLI technology, and as a result aircraft with integrated BLI technology are today considered at a low Technology Readiness Level (TRL).

Chimera method

Chimera method also called overset grid method is developed to facilitate the mesh generation for complex shapes, using different grids for different parts of a geometry. The grids are used together, with overlapping of several cells and interpolation between these cells in order to have the continuity of the flow through each grids. This technic is also frequently used in the case of moving bodies, where the grid around the moving body overlaps a fixed background grid.

Sliding meshes

The NSMB CFD solver includes a sliding mesh approach that permits to simulate moving configurations, as for example a rotating propellor or a train entering a tunnel.

Transportation

The aerodynamics of high speed trains and the proper ventilation of air therein is of particular interest to ensure passenger safety. Stadler Rail took contact with CFS Engineering to better understand airflow around and in trains, particularly with respect to its new double-decker version.