| 1. |
- Hoffman, Johan, et al.
(author)
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Computation of slat noise sources using adaptive FEM and lighthill's analogy
- 2013
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In: 19th AIAA/CEAS Aeroacoustics Conference.
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Conference paper (peer-reviewed)abstract
- This is a summary of preliminary results from simulations with the 30P30N high-lift device. We used the General Galerkin finite element method (G2), where no explicit subgrid model is used, and where the computational mesh is adaptively refined with respect to a posteriori error estimates for a quantity of interest. The mesh is fully unstructured and the solutions are time-resolved, which are key ingredients for solving challenging industrial applications in the field of aeroacoustics. We present preliminary results containing time-averaged quantities and snapshots of unsteady quantities, all reasonably agreeing with previous computational efforts. One important finding is that the use of adaptively generated meshes seems to be a more effcient way of computing aeroacoustic sources than by using "handmade" meshes.
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| 2. |
- Hoffman, Johan, et al.
(author)
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Time-resolved adaptive FEM simulation of the DLR-F11 aircraft model at high Reynolds number
- 2014
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In: 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Conference paper (other academic/artistic)abstract
- We present a time-resolved, adaptive finite element method for aerodynamics, together with the results from the HiLiftPW-2 workshop, where this method is used to compute the flow past a DLR-F11 aircraft model at realistic Reynolds number. The mesh is automatically constructed by the method as part of the computation, and no explicit turbulence model is needed. The effect of unresolved turbulent boundary layers is modeled by a simple parametrization of the wall shear stress in terms of the skin friction. In the extreme case of very high Reynolds numbers we approximate the small skin friction by zero skin friction, corresponding to a free slip boundary condition, which results in a computational model without any model parameter that needs tuning. Thus, the simulation methodology by- passes the main challenges posed by high Reynolds number CFD: the design of an optimal computational mesh, turbulence (or subgrid) modeling, and the cost of boundary layer res- olution. The results from HiLiftPW-2 presented in this report show good agreement with experimental data for a range of different angles of attack, while using orders of magnitude fewer degrees of freedom than what is needed in state of the art methods such as RANS.
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| 3. |
- Jansson, Johan, et al.
(author)
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Adaptive stabilized finite element framework for simulation of vocal fold turbulent fluid-structure interaction
- 2013
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In: Proceedings of Meetings on Acoustics. - : Acoustical Society of America (ASA). ; , s. 1-9
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Conference paper (peer-reviewed)abstract
- As a step toward building a more complete model of voice production mechanics, we assess the feasibility of a fluid-structure simulation of the vocal fold mechanics in the Unicorn incompressible Unified Continuum framework. The Unicorn framework consists of conservation equations for mass and momentum, a phase function selecting solid or fluid constitutive laws, a convection equation for the phase function and moving mesh methods for tracking the interface, and discretization through an adaptive stabilized finite element method. The framework has been validated for turbulent flow for both low and high Reynolds numbers and has the following features: implicit turbulence modeling (turbulent dissipation only occurs through numerical stabilization), goal-oriented mesh adaptivity, strong, implicit fluid-structure coupling and good scaling on massively parallel computers. We have applied the framework for turbulent fluid-structure interaction simulation of vocal folds, and present initial results. Acoustic quantities have been extracted from the framework in the setting of an investigation of a configuration approximating an exhaust system with turbulent flow around a flexible triangular steel plate in a circular duct. We present some results of the investigation as well as results of the framework applied to other problems.
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| 4. |
- Jansson, Johan, 1978-, et al.
(author)
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Gestural 3D Interaction with a Beating Heart : Simulation Visualization and Interaction
- 2011
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In: Proceedings of SIGRAD 2011. - : Linköping University Electronic Press. - 9789173930086
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Conference paper (peer-reviewed)abstract
- The KTH School of Computer Science and Communication (CSC) established a strategic platform in Simulation-Visualization-Interaction (SimVisInt) in 2009, focused on the high potential in bringing together CSC core com-petences in simulation technology, visualization and interaction. The main part of the platform takes the form aset of new trans-disciplinary projects across established CSC research groups, within the theme of ComputationalHuman Modeling and Visualization: (i) interactive virtual biomedicine (HEART), (ii) simulation of human mo-tion (MOTION), and (iii) virtual prototyping of human hand prostheses (HAND). In this paper, we present recentresults from the HEART project that focused on gestural and haptic interaction with a heart simulation.
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| 5. |
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| 6. |
- Vilela De Abreu, Rodrigo, et al.
(author)
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Towards the development of adaptive finite element methods for internal flow aeroacoustics
- 2013
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In: 19th AIAA/CEAS Aeroacoustics Conference. - 9781624102134
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Conference paper (peer-reviewed)abstract
- We report the latest results obtained in the development of an adaptive finite element method for computational aeroacoustics (CAA). The new methodology is based on the General Galerkin (G2) method, which has been successfully used for the computation of incompressible, turbulent flow. Here, we simulate the flow past an in-duct mixer plate and compare the results with available experimental data. The comparisons include mean velocity profiles and frequency content of the turbulent signal. No direct simulation of sound or sound wave propagation has been performed; instead, simple analogy arguments have been used to extract acoustic results from incompressible simulations by assuming a direct correlation between the computed pressure drop signal and the sound at the far field. We were able to reproduce the sound signal from experiments with our incompressible simulation and our results compared well with both the level and the broadband frequency peak of the measured sound. We suggest that the methodology presented here is mainly suitable for the prediction of sound in low Mach number pipe flows.
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| 7. |
- Abreu, Rodrigo, et al.
(author)
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Adaptive computation of aeroacoustic sources for a rudimentary landing gear using lighthill's analogy
- 2011
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In: 17th AIAA/CEAS AeroacousticsConference 2011.
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Conference paper (peer-reviewed)abstract
- We present our simulation results for the benchmark problem of the ow past a Rudimentary Landing Gear (RLG) using a General Galerkin (G2) nite element method, also referred to as Adaptive DNS/LES. In G2 no explicit subgrid model is used, instead the compuational mesh is adaptively re ned with respect to an a posteriori error es-timate of a quantity of interest in the computation, in this case the drag force on the RLG. Turbulent boundary layers are modeled using a simple wall layer model with the shear stress at walls proportional to the skin friction, which here is assumed to be small and, therefore, can be approximated by zero skin friction. We compare our results with experimental data and other state of the art computations, where we nd good agreement in sound pressure levels, surface velocities and ow separation. We also compare with detailed surface pressure experimental data where we nd largely good agreement, apart from some local dierences for which we discuss possible explanations.
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| 8. |
- Albrektsson, Joakim, et al.
(author)
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Assessment of fire exposed concrete structures
- 2012
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In: fib Symposium 2012: Concrete Structures for Sustainable Community. - 9789198009811 ; , s. 619-622, s. 619-622
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Conference paper (peer-reviewed)abstract
- Annually, several concrete structures, such as buildings, bridges, parking garages and tunnels are exposed to fires. An assessment is then necessary to decide whether the structure can be repaired or needs to be replaced. In a recent research project, recommendations for assessments of fire exposed concrete structures have been developed. The recommendations are based on a literature survey, results from an experimental study, where ultrasonic measurements, microscopy, Digital Image Correlation (DIC) measurement on loaded core samples were used and practical experience of real post-fire structural assessments. A refined assessment of the fire damage is obtained by combining these test methods.
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| 9. |
- Anderson, Johan, et al.
(author)
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Façade fire tests : Measurements and modeling
- 2013
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In: 1st International Seminar for Fire Safety of Facades, FSF 2013. - : EDP Sciences. - 9782759811007
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Conference paper (peer-reviewed)abstract
- In two recent papers [1, 2] the fire dynamics in a test rig for façade constructions according to the test method SP Brand 105 [3, 4] was investigated both experimentally and numerically. The experimental setup simulates a three-story apartment building (height 6.7m, width 4m and depth 1.6m), with external wall-cladding and a "room fire" at the base. The numerical model was developed in the CFD program Fire Dynamics Simulator (FDS) [5] with analogous geometry and instrumentation. The general features of the fire test were well reproduced in the numerical model however temperatures close to the fire source could not be properly accounted for in the model. In this paper the bi-directional probe measurements are elaborated on and the test used in Ref. [1] is revisited using different heat release rates in the numerical model. The velocity of the hot gases along the façade was well reproduced by the simulations although some deviations were found.
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| 10. |
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