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Lausanne, Switzerland

Gobel F.,University of Federal Defense Munich | Vos J.B.,CFS Engineering | Mundt C.,University of Federal Defense Munich
42nd AIAA Fluid Dynamics Conference and Exhibit 2012 | Year: 2012

The FIRE II flight test is simulated using the CFD code NSMB. Several models for chemical nonequilibrium, the equilibrium constant, thermal nonequilibrium and transport properties are tested and their results in convective wall heat flux are compared to those by former investigators. Using the results of NSMB, a 1D radiative heat transfer analysis is performed using the ESA plasma radiation tool PARADE and the resulting radiative wall heat flux is compared to former simulations as well as to measurements during the real test flight. With a chemical nonequilibrium model by Park combined with an equilibrium constant predicted with Gibb's Free Enthalpy and transport models by Gupta, the best results in terms of convective wall heat flux and flow properties are gained. The convective wall heat flux at the stagnation point predicted by NSMB agrees very well with other investigations. Within PARADE, different accuracies in wavelength integration and different spectroscopic models are tested. With an appropriate number of discretisation points and a certain combination of spectroscopic models for atoms, the predicted radiative wall heat flux between 0.2 μm and 4 μm is a very good approximation of the measured flux during flight. © 2012 by Florian Goebel and Christian Mundt. Source


Berdajs D.A.,University of Lausanne | Mosbahi S.,University of Lausanne | Charbonnier D.,CFS Engineering | Hullin R.,University of Lausanne | Von Segesser L.K.,University of Lausanne
Journal of Surgical Research | Year: 2015

Background The mechanism behind early graft failure after right ventricular outflow tract (RVOT) reconstruction is not fully understood. Our aim was to establish a three-dimensional computational fluid dynamics (CFD) model of RVOT to investigate the hemodynamic conditions that may trigger the development of intimal hyperplasia and arteriosclerosis. Methods Pressure, flow, and diameter at the RVOT, pulmonary artery (PA), bifurcation of the PA, and left and right PAs were measured in 10 normal pigs with a mean weight of 24.8 ± 0.78 kg. Data obtained from the experimental scenario were used for CFD simulation of pressure, flow, and shear stress profile from the RVOT to the left and right PAs. Results Using experimental data, a CFD model was obtained for 2.0 and 2.5-L/min pulsatile inflow profiles. In both velocity profiles, time and space averaged in the low-shear stress profile range from 0-6.0 Pa at the pulmonary trunk, its bifurcation, and at the openings of both PAs. These low-shear stress areas were accompanied to high-pressure regions 14.0-20.0 mm Hg (1866.2-2666 Pa). Flow analysis revealed a turbulent flow at the PA bifurcation and ostia of both PAs. Conclusions Identified local low-shear stress, high pressure, and turbulent flow correspond to a well-defined trigger pattern for the development of intimal hyperplasia and arteriosclerosis. As such, this real-time three-dimensional CFD model may in the future serve as a tool for the planning of RVOT reconstruction, its analysis, and prediction of outcome. © 2015 Elsevier Inc. All rights reserved. Source


Guillaume M.,RUAG Aviation Aerodynamics | Gehri A.,RUAG Aviation Aerodynamics | Stephani P.,RUAG Aviation Aerodynamics | Vos J.B.,CFS Engineering | Mandanis G.,M at M GmbH
Aeronautical Journal | Year: 2011

The Swiss Airforce is operating F/A-18C/D Aircraft since 1997. Since the aircraft's structural design is different from the version operated by the US Navy it was necessary to carry out a structural integrity study (ASIP) which was done by The Boeing Company in St. Louis. To validate this study a full scale fatigue test facility was build at RUAG and operated from 2003 to 2005. When operating this facility difficulties were encountered with the aerodynamic loads data provided by Boeing (insufficient, not well documented, questionable data). As a result RUAG looked for alternative methods to provide the aerodynamic loads, and a large investment was made in the development of a Computational Fluid Dynamics (CFD) tool. The Navier Stokes Multi Block (NSMB) solver, which was developed in an international collaboration, was adopted. In a first phase the code was validated by comparing results of CFD calculations with wind-tunnel results, results from literature and flight test data results. In the second phase, discussed in this paper, a Fluid Structure Interaction (FSI) tool was developed to permit unsteady aero-elastic simulations. Particular attention is- focused on the vertical tail since this component of the F/A-18 fighter is very sensitive to fatigue due to unsteady loads generated by buffeting phenomena. Source


Vos J.B.,CFS Engineering | Vos J.B.,Publet | Sanchi S.,CFS Engineering | Gehri A.,RUAG Aviation
Journal of Aircraft | Year: 2013

CFS Engineering and RUAG Aviation participated in the 4th Drag Prediction Workshop organized by AIAA in June 2009. Calculations were made for the Common Research Model configuration using the Navier-Stokes multiblock solver on the grids generated at CFS Engineering. After the workshop, the polars were computed on the medium multiblock structured grids provided by other workshop participants for the Common Research Model configuration with 0 deg horizontal tail deflection. All these results were processed by a far-field drag extraction tool developed jointly by RUAG Aviation and CFS Engineering. This paper first summarizes the theory behind the drag extraction tool. Theresultsofthe different calculations are presentedandadetailed analysisofthe drag breakdown on the different grids is given. This shows that the spread in drag coefficients obtained on different grids is much lower when using the effective drag computed by the drag extraction tool than when using the near-field drag. © 2013 by Jan B. Vos. Published by the American Institute of Aeronautics and Astronautics, Inc. Source


Barbut G.,CNRS Fluid Dynamics Institute of Toulouse | Braza M.,CNRS Fluid Dynamics Institute of Toulouse | Hoarau Y.,Institute Of Mecanique Des Fluides Et Of Solides Of Strasbourg | Barakos G.,University of Liverpool | And 2 more authors.
Notes on Numerical Fluid Mechanics and Multidisciplinary Design | Year: 2010

The present study presents numerical simulations and turbulence modelling of the flow around a NACA0012 airfoil including a deflected aileron. The results are compared with experiments that have been performed in the N-3 wind tunnel of the Institute of Aviation (IoA), Warsaw. The experiment focused on unsteady flow characteristics and buffet phenomena arising as the result of the transonic shock wave / boundary layer interaction (SWBLI). The transonic buffet is a natural and self-sustaining oscillation of the shock wave and separated flow region, caused by pressure fluctuation. The first objective is to capture the transonic buffet unsteadiness by means of URANS and DES turbulence modelling approaches. Secondly, the periodic flap oscillation has been used to modify the oscillation amplitudes towards an outlook of attenuation of the transonic buffet. © 2010 Springer-Verlag Berlin Heidelberg. Source

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