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Ghoreyshit M.,University of Liverpool | Vallespin D.,University of Liverpool | Da Ronch A.,University of Liverpool | Badcock K.J.,University of Liverpool | And 2 more authors.
AIAA Atmospheric Flight Mechanics Conference 2010 | Year: 2010

The use of computational fluid dynamics to generate and test aerodynamic data tables for flight dynamics analysis is described in this paper. The test case used is the Ranger 2000 fighter trainer for which flight test data is available. The generation of the tables is done using sampling and reconstruction to allow a large number of table entries to be generated at low computational cost. The testing of the tables is done by replaying, through a time accurate CFD calculation which features the moving control surfaces, manoeuvres and comparing the forces and moments against the tabular values. The manoeuvres are generated using a time optimal prediction code with the feasible solutions based on the tabular aerodynamics. The generated maneouvres are evaluated against flight data to show that they are qualitatively representative. Then the time accurate and tabular aerodynamics are compared, and as expected are in close agreement. © 2010 by K.J.Badcock. Published by the American Institute of Aeronautics and Astronautics, Inc.


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.


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.


Mosbahi S.,University of Lausanne | Mickaily-Huber E.,CFS Engineering | Charbonnier D.,CFS Engineering | Hullin R.,University of Lausanne | And 4 more authors.
Interactive cardiovascular and thoracic surgery | Year: 2014

OBJECTIVES: The reconstruction of the right ventricular outflow tract (RVOT) with valved conduits remains a challenge. The reoperation rate at 5 years can be as high as 25% and depends on age, type of conduit, conduit diameter and principal heart malformation. The aim of this study is to provide a bench model with computer fluid dynamics to analyse the haemodynamics of the RVOT, pulmonary artery, its bifurcation, and left and right pulmonary arteries that in the future may serve as a tool for analysis and prediction of outcome following RVOT reconstruction.METHODS: Pressure, flow and diameter at the RVOT, pulmonary artery, bifurcation of the pulmonary artery, and left and right pulmonary arteries were measured in five normal pigs with a mean weight of 24.6 ± 0.89 kg. Data obtained were used for a 3D computer fluid-dynamics simulation of flow conditions, focusing on the pressure, flow and shear stress profile of the pulmonary trunk to the level of the left and right pulmonary arteries.RESULTS: Three inlet steady flow profiles were obtained at 0.2, 0.29 and 0.36 m/s that correspond to the flow rates of 1.5, 2.0 and 2.5 l/min flow at the RVOT. The flow velocity profile was constant at the RVOT down to the bifurcation and decreased at the left and right pulmonary arteries. In all three inlet velocity profiles, low sheer stress and low-velocity areas were detected along the left wall of the pulmonary artery, at the pulmonary artery bifurcation and at the ostia of both pulmonary arteries.CONCLUSIONS: This computed fluid real-time model provides us with a realistic picture of fluid dynamics in the pulmonary tract area. Deep shear stress areas correspond to a turbulent flow profile that is a predictive factor for the development of vessel wall arteriosclerosis. We believe that this bench model may be a useful tool for further evaluation of RVOT pathology following surgical reconstructions. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.


Berdajs D.,University of Lausanne | Mosbahi S.,University of Lausanne | Vos J.,CFS Engineering | Charbonnier D.,CFS Engineering | And 2 more authors.
Interactive Cardiovascular and Thoracic Surgery | Year: 2015

OBJECTIVES Repair of the right ventricular outflow tract (RVOT) in paediatric cardiac surgery remains challenging due to the high reoperation rate. Intimal hyperplasia and consequent arteriosclerosis is one of the most important limitation factors for graft durability. Since local shear stress and pressure are predictive elements for intimal hyperplasia and wall degeneration, we sought to determine in an oversized 12-mm RVOT model, with computed fluid dynamics simulation, the local haemodynamical factors that may explain intimal hyperplasia. This was done with the aim of identifying the optimal degree of oversizing for a 12-mm native RVOT. METHODS Twenty domestic pigs, with a weight of 24.6 ± 0.89 kg and a native RVOT diameter of 12 ± 1.7 mm, had valve conduits of 12, 16, 18 and 20 mm implanted. Pressure and flow were measured at 75, 100 and 125% of normal flow at RVOT at the pulmonary artery, pulmonary artery bifurcation and at the left and right pulmonary arteries. Three-dimensional computed fluid dynamics (CFD) simulation in all four geometries in all flow modalities was performed. Local shear stress and pressure conditions were investigated. RESULTS Corresponding to 75, 100 and 125% of steady-state flow, three inlet velocity profiles were obtained, 0.2, 0.29 and 0.36 m/s, respectively. At inflow velocity profiles, low shear stress areas, ranged from 0 to 2 Pa, combined with high-pressure areas ranging from 11.5 to 12.1 mmHg that were found at distal anastomosis, at bifurcation and at the ostia of the left and right pulmonary arteries in all geometries. CONCLUSIONS In all three oversized geometries, the local reparation of shear stress and pressure in the 16-mm model showed a similar local profile as in the native 12 mm RVOT. According to these findings, we suggest oversizing the natural 12-mm RVOT by not more than 4 mm. The elements responsible for wall degeneration and intimal hyperplasia remain very similar to the conditions present in native RVOT. © 2015 The Author. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.


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.


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.


PubMed | University of Lausanne and CFS Engineering
Type: Journal Article | Journal: Interactive cardiovascular and thoracic surgery | Year: 2014

The reconstruction of the right ventricular outflow tract (RVOT) with valved conduits remains a challenge. The reoperation rate at 5 years can be as high as 25% and depends on age, type of conduit, conduit diameter and principal heart malformation. The aim of this study is to provide a bench model with computer fluid dynamics to analyse the haemodynamics of the RVOT, pulmonary artery, its bifurcation, and left and right pulmonary arteries that in the future may serve as a tool for analysis and prediction of outcome following RVOT reconstruction.Pressure, flow and diameter at the RVOT, pulmonary artery, bifurcation of the pulmonary artery, and left and right pulmonary arteries were measured in five normal pigs with a mean weight of 24.6 0.89 kg. Data obtained were used for a 3D computer fluid-dynamics simulation of flow conditions, focusing on the pressure, flow and shear stress profile of the pulmonary trunk to the level of the left and right pulmonary arteries.Three inlet steady flow profiles were obtained at 0.2, 0.29 and 0.36 m/s that correspond to the flow rates of 1.5, 2.0 and 2.5 l/min flow at the RVOT. The flow velocity profile was constant at the RVOT down to the bifurcation and decreased at the left and right pulmonary arteries. In all three inlet velocity profiles, low sheer stress and low-velocity areas were detected along the left wall of the pulmonary artery, at the pulmonary artery bifurcation and at the ostia of both pulmonary arteries.This computed fluid real-time model provides us with a realistic picture of fluid dynamics in the pulmonary tract area. Deep shear stress areas correspond to a turbulent flow profile that is a predictive factor for the development of vessel wall arteriosclerosis. We believe that this bench model may be a useful tool for further evaluation of RVOT pathology following surgical reconstructions.


PubMed | University of Lausanne and CFS Engineering
Type: Journal Article | Journal: Interactive cardiovascular and thoracic surgery | Year: 2015

Repair of the right ventricular outflow tract (RVOT) in paediatric cardiac surgery remains challenging due to the high reoperation rate. Intimal hyperplasia and consequent arteriosclerosis is one of the most important limitation factors for graft durability. Since local shear stress and pressure are predictive elements for intimal hyperplasia and wall degeneration, we sought to determine in an oversized 12-mm RVOT model, with computed fluid dynamics simulation, the local haemodynamical factors that may explain intimal hyperplasia. This was done with the aim of identifying the optimal degree of oversizing for a 12-mm native RVOT.Twenty domestic pigs, with a weight of 24.6 0.89 kg and a native RVOT diameter of 12 1.7 mm, had valve conduits of 12, 16, 18 and 20 mm implanted. Pressure and flow were measured at 75, 100 and 125% of normal flow at RVOT at the pulmonary artery, pulmonary artery bifurcation and at the left and right pulmonary arteries. Three-dimensional computed fluid dynamics (CFD) simulation in all four geometries in all flow modalities was performed. Local shear stress and pressure conditions were investigated.Corresponding to 75, 100 and 125% of steady-state flow, three inlet velocity profiles were obtained, 0.2, 0.29 and 0.36 m/s, respectively. At inflow velocity profiles, low shear stress areas, ranged from 0 to 2 Pa, combined with high-pressure areas ranging from 11.5 to 12.1 mmHg that were found at distal anastomosis, at bifurcation and at the ostia of the left and right pulmonary arteries in all geometries.In all three oversized geometries, the local reparation of shear stress and pressure in the 16-mm model showed a similar local profile as in the native 12 mm RVOT. According to these findings, we suggest oversizing the natural 12-mm RVOT by not more than 4 mm. The elements responsible for wall degeneration and intimal hyperplasia remain very similar to the conditions present in native RVOT.


PubMed | University of Lausanne and CFS Engineering
Type: Journal Article | Journal: The Journal of surgical research | Year: 2015

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.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.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.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.

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