CFSE has been involved in several project linked to many disciplines, such as:
- aerodynamics
- hydrodynamics
- hydraulics (pumps)
- biofluid dynamics (cardiac flow)
- natural flow (wind, convection)
Some of theses projects are listed bellow.
Ongoing projects
The Swiss Airforce is operating the F/A-18 C/D aircraft since 1997. The maneuver spectrum for the Swiss usage of this aircraft is about three times more severe than the US Navy design, resulting in a different structural design. As a consequence an Aircraft Structural Integrity Program (ASIP) study was carried out by Boeing, and to validate this study a Full Scale Test Facility was build at RUAG Aviation and operated from 2003 to 2005. To better understand the aerodynamic loads on the aircraft RUAG Aviation looked into methods to generate these loads for different flight conditions.
A large investment was made in further developing the NSMB Navier Stokes Multi Block (NSMB) Computational Fluid Dynamics (CFD) code and in particular its extension for Fluid Structure Interaction (FSI) simulations. Procedures were developed for both static and dynamic Fluid Structure Interaction (FSI). Static FSI was only used to deform the wing of the F/A-18 fighter.
Dynamic FSI simulations were made to study vertical tail buffeting, and employed a linear structural model based on a modal formulation. In this case the CFD solver and the Computational Structural Mechanics (CSM) solver are tightly coupled.
The F/A-18 studies started in 2002 using a grid of around 7 Million points. Since a 2013 CFSE and RUAG use the so called 3rd generation grid that employs the chimera method for easy change of control surface deflections and for adding or removing loads (fuel tanks and weapons). This grid has about 50 Million points for half a configuration.
The need to provide quickly aerodynamic loads for statically deformed wings led to the decision to couple the NSMB CFD solver with the open-source Finite Element Analysis environment B2000++. This has led to the possibility to perform both static and dynamic FSI simulations using either a modal or a FEM approach without the need to interrupt the simulation.
The main objective of the F/A-18 simulations is to generate aerodynamic loads on the different aircraft components.
CFS Engineering collaborates actively with RUAG and Elomatic for a major part of F/A-18 simulations.
Related publications
Swiss/Finnish Collaboration on Aero-elastic Simulations for the F/A-18 Fighter Conference
vol. AIAA-2018-3642, AIAA Aviation 2018 , Atlanta, 2018.
vol. AIAA-2017-4458, AIAA Aviation 2017 , Denver, 2017.
F/A-18 vertical buffeting calculations using unsteady fluid structure interaction Journal Article
In: "The Aeronautical Journal ", vol. 115, no. 1167, 2011.
Fluid Structure Interaction Simulation on the F/A-18 Vertical Tail Conference
vol. AIAA-2010-4613, AIAA Aviation 2010 , Chicago, 2010.
Several studies have been performed since 2012 in collaboration with PD Dr. med. Denis Berdajs regarding flow characteristics within the heart. The blood flow in right ventricule, aortic valve, aortic root, and currently for mitral valve, has been investigated by means of computational fluid dynamics with different levels of geometrical modelling. The movable wall technique has been developed to take into account deformations starting from a sample of simple geometric characteristics, and interpolations between the different steps of the cardiac cycle.
Related publications
Aortic Valve Pathology as a Predictive Factor for Acute Aortic Dissection Journal Article
In: The Annals of thoracic surgery, vol. 104, no. 4, pp. 1340-1348, 2017.
Impact of synthetic elements on aortic root haemodynamics: computed fluid dynamics of aortic root reconstruction and valve reimplantation Journal Article
In: European Journal of Cardio-thoracic Surgery, vol. 51, no. 3, pp. 432-441, 2017.
Aortic root haemodynamics following David procedure: numerical analysis of 3-dimensional haemodynamics Journal Article
In: European Journal of Cardio-thoracic Surgery, vol. 49, no. 6, pp. 1588-1598, 2016.
Numerical analysis of the 3-dimensional aortic root morphology during the cardiac cycle Journal Article
In: European Journal of Cardio-thoracic Surgery, vol. 49, no. 4, pp. 1213-1221, 2016.
Fluid dynamics simulation of right ventricular outflow tract oversizing Journal Article
In: Interactive Cardiovascular and Thoracic Surgery, vol. 21, no. 2, pp. 176-182, 2015.
Analysis of flow dynamics in right ventricular outflow tract Journal Article
In: Journal of Surgical Research, vol. 197, no. 1, pp. 50-57, 2015.
Computational fluid dynamics of the right ventricular outflow tract and of the pulmonary artery: a bench model of flow dynamics Journal Article
In: Interactive Cardiovascular and Thoracic Surgery, vol. 19, no. 4, pp. 611-616, 2014.
Past projects
In the frame of the European Funded H2020 project AGILE (Aircraft 3rd Generation MDO for Innovative Collaboration of Heterogeneous Teams of Experts) aero-elastic simulations were made for a Strut Braced Wing aircraft. The Strut Braced Wing (SBW) aircraft has received much attention over the last 10 years due to its potential to reduce emissions. However the SBW aircraft also poses several challenges, in particular the strong coupling between aerodynamics and structures. The SBW aircraft designed in the AGILE project concerns a 90-seat passenger aircraft. Navier Stokes simulations were carried out for different wing configurations, showing that a wing with a super-critical airfoil and having a 16° sweep angle is the most efficient (compared to the initial configuration having a 0° sweep angle and a NACA009 airfoil). However these high-fidelity simulations did not take into account the deformation of the strut and the wing due to the aerodynamic loads.
An aero-elastic tool chain has been set-up composed of the PROTEUS tool developed at the Delft University of Technology, the AMLoad tool developed by the Netherlands Aerospace Centre (NLR), the FSCON tool developed by SMR and the NSMB CFD solver. FSI calculations were made at different Mach numbers and at different angles of attack.
Internal project about fire and smoke propagation using the FDS software developed by NIST (National Institute of Standards and Technology).
Fire Dynamics Simulator (FDS) is a computational fluid dynamics (CFD) model of fire-driven fluid flow. The software solves numerically a form of the Navier-Stokes equations appropriate for low-speed, thermally-driven flow, with an emphasis on smoke and heat transport from fires.
CFD simulations were made over trains to study :
- the influence of the nose design on the aerodynamic drag
- the influence of the cooling inlets and outlets
- the aerodynamic loads on the train under side winds
- to study the influence of the train on side walls near the track
- to study the influence of a passing train on people waiting on a platform
- to study the entering of the train in a tunnel