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- Krank, Benjamin, et al.
(author)
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Evaluating stretched grids and introducing black hole layers as alternative non-reflecting buffer zone
- 2013
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In: 19th AIAA/CEAS Aeroacoustics Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624102134
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Conference paper (peer-reviewed)abstract
- Grid-stretching is often used close to non-reflecting boundaries in order to under-resolve and dissipate outgoing acoustic waves. The resulting buffer zones may be large and computationally expensive, however, since the stretching factor is strongly limited. Two approaches of implementing grid-stretching are considered: Taylor expansion and transformation in curvilinear coordinates. Besides grid-stretching, a new buffer zone technique is introduced, which allows for larger stretching factors and computationally more efficient buffer zones. The speed of sound is varied locally in the buffer zone resulting in spatial under-resolution of outgoing waves similarly to stretched grids. The approach is derived from the concept of acoustic black holes, a method of reducing reflection of bending waves from edges of physical plates, giving the name black hole layer to the new concept. The approach is verified and the performance of stretched grids and black hole layers is evaluated using a linearized Euler equations solver in two space dimensions for several benchmark flows. The most efficient buffer zone is found to be a combination of grid-stretching using Taylor expansion and black hole layer.
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| 2. |
- Krank, Benjamin, et al.
(author)
-
Tuning spot weld models for vehicle body structural dynamics
- 2012
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In: Proceedings Of International Conference On Noise And Vibration Engineering (ISMA2012) / International Conference On Uncertainty In Structural Dynamics (USD2012). - : Katholieke Universiteit Leuven. - 9789073802896 ; , s. 3915-3926
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Conference paper (peer-reviewed)abstract
- Efforts focussing on modelling of spot welds in typical automotive structures have been spent during the last decades resulting in a number of different modelling techniques. One of the crucial aspects common to all these approaches is the difficulties related to the local complexity of the modelling of the actual connections. In order to handle this complexity, spot weld models are often dependent on parameters tuning their characteristics. This paper discusses the tuning of two different spot weld models with respect to certain parameters; the RBE3-Hexa-RBE3 model (also known as the ACM 2) and the Spider2 model available in the pre-processor Ansa. With the current trend towards increasingly refined finite element model meshes, current guide lines need to be updated and elaborated further in order to identify the best performing models. In this paper, model studies are discussed targeting tuning of spot weld parameters together with a new proposal for an exact method for updating the Young's modulus and density of isotropic shell structures analytically using an initial FE calculation.
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