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Mudde Casper - One of the best experts on this subject based on the ideXlab platform.
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Development and verification of ShorelineS on longshore sediment transport and spit formation: A case study of Lobito, Angola
2019Co-Authors: Mudde CasperAbstract:In the field of coastal engineering computational models are a commonly used tool to gain insight in dynamics of a coastal system, to gain insight in or hindcast the historical development or can be used as engineering tool to assess the efficiency and consequences of a proposed coastal measure. A new coastline model, called ShorelineS, is under development which promises to be applicable for long term simulations on Geometric Complex coastlines or unstable beach regimes where, for example, spit formation may arise. This new model aims to overcome the gap between existing relatively simple coastline models and more advanced coastal area models. In this thesis the applicability of this new model on spit formation was assessed. A study case in Lobito (Angola), were a natural spit has formed, was used for this purpose. Three research objectives are of interest in this thesis: 1) getting insight in the relevant processes regarding spit formation (in general and for the Lobito spit) 2) validate the longshore sediment transport module of ShorelineS and 3) asses (and improve) the spit formation in ShorelineS. An inventory of existing spit formations around the world and a detailed modelling study (XBeach) on the transport rates around a spit showed that especially the bimodality of the wave climate is an important process influencing the final shape of the spit. Regarding the calculation of the longshore sediment transport it was found that for the modelling of the wave transformation a distinction should be made between the static fixed offshore depth contours and the dynamically changing nearshore depth contours for changing coastline orientations. This distinction is essential to consistently and correctly determine the breaking wave parameters which directly influences the longshore sediment transport calculations. This distinction was implemented in ShorelineS using the concept of a so called ‘dynamic boundary’. The spit formation in ShorelineS was assessed by means of hindcasting the historical spit formation of the Lobito spit using the ShorelineS model. Continuing on the previous finding it was found that the coastal orientation for which the longshore transport is maximum, which reflects the direction in which a spit migrates, should be derived on the actual, spatial and temporal variating, transport curves. This in contrast to the theoretical fixed angle as suggested by Ashton et al. which was previously used in ShorelineS. Both the implementation of the dynamic boundary and the routine to find the actual (variable) angle of maximum transport were needed to be able to correctly hindcast the observed spit formation. With the current, underlying, model assumptions it is not possible to correctly model the local decay of longshore sediment transport along the head of the spit. The width and local shape of the spit is therefore controlled by the so called ‘upwind correction’ routine in ShorelineS. This routine was updated to prevent the grid resolution dependency which originally directly controlled (forced) the resulting spit width. With this updated routine the spit width is based on an average (expected) spit width. This new routine should be considered as a proof-of-concept, further research is required to further develop this routine and find ways to include some kind of feedback mechanism in the model between the forcing, shape and the resulting LST over the head of the spit.Coastal Engineerin
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Development and verification of ShorelineS on longshore sediment transport and spit formation: A case study of Lobito, Angola
2019Co-Authors: Mudde CasperAbstract:In the field of coastal engineering computational models are a commonly used tool to gain insight in dynamics of a coastal system, to gain insight in or hindcast the historical development or can be used as engineering tool to assess the efficiency and consequences of a proposed coastal measure. A new coastline model, called ShorelineS, is under development which promises to be applicable for long term simulations on Geometric Complex coastlines or unstable beach regimes where, for example, spit formation may arise. This new model aims to overcome the gap between existing relatively simple coastline models and more advanced coastal area models. In this thesis the applicability of this new model on spit formation was assessed. A study case in Lobito (Angola), were a natural spit has formed, was used for this purpose. Three research objectives are of interest in this thesis: 1) getting insight in the relevant processes regarding spit formation (in general and for the Lobito spit) 2) validate the longshore sediment transport module of ShorelineS and 3) asses (and improve) the spit formation in ShorelineS. An inventory of existing spit formations around the world and a detailed modelling study (XBeach) on the transport rates around a spit showed that especially the bimodality of the wave climate is an important process influencing the final shape of the spit. Regarding the calculation of the longshore sediment transport it was found that for the modelling of the wave transformation a distinction should be made between the static fixed offshore depth contours and the dynamically changing nearshore depth contours for changing coastline orientations. This distinction is essential to consistently and correctly determine the breaking wave parameters which directly influences the longshore sediment transport calculations. This distinction was implemented in ShorelineS using the concept of a so called ‘dynamic boundary’. The spit formation in ShorelineS was assessed by means of hindcasting the historical spit formation of the Lobito spit using the ShorelineS model. Continuing on the previous finding it was found that the coastal orientation for which the longshore transport is maximum, which reflects the direction in which a spit migrates, should be derived on the actual, spatial and temporal variating, transport curves. This in contrast to the theoretical fixed angle as suggested by Ashton et al. which was previously used in ShorelineS. Both the implementation of the dynamic boundary and the routine to find the actual (variable) angle of maximum transport were needed to be able to correctly hindcast the observed spit formation. With the current, underlying, model assumptions it is not possible to correctly model the local decay of longshore sediment transport along the head of the spit. The width and local shape of the spit is therefore controlled by the so called ‘upwind correction’ routine in ShorelineS. This routine was updated to prevent the grid resolution dependency which originally directly controlled (forced) the resulting spit width. With this updated routine the spit width is based on an average (expected) spit width. This new routine should be considered as a proof-of-concept, further research is required to further develop this routine and find ways to include some kind of feedback mechanism in the model between the forcing, shape and the resulting LST over the head of the spit.Civil Engineering | Hydraulic Engineering | Coastal Engineerin
Tobias Klein - One of the best experts on this subject based on the ideXlab platform.
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augmented fauna and glass mutations a dialogue between material and technique in glassblowing and 3d printing
International Conference on Computer Graphics and Interactive Techniques, 2018Co-Authors: Tobias KleinAbstract:3D printing allows unprecedented freedom in the design and manufacturing of even the most Geometric Complex forms—seemingly through a simple click of a button. In comparison, the making of glass is an analogue craftsmanship, coordinating an intricate interplay of individual tools and personal skills, giving shape to a material during the short time of its temperature-based plasticity. The two artworks discussed in this article, Augmented Fauna and Glass Mutations, were created during the artist’s residence at the Pilchuck Glass School and articulate a synthesis between digital workflows and traditional craft processes to establish a digital craftsmanship.
Ramona Hölker - One of the best experts on this subject based on the ideXlab platform.
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New Concepts for Cooling of Extrusion Dies Manufactured by Rapid Tooling
2016Co-Authors: Ramona Hölker, Nooman Ben Khalifa, Andreas Jäger, Erman Tekkaya A. DAbstract:Abstract. To prevent local overheating of the workpiece material in hot aluminum extrusion the influence of die cooling was investigated. Numerical simulations of extrusion revealed an advantage of the die bearing cooling, which can be accomplished by locating the cooling channels close to the die/bearing surface. Since the fabrication of especially Geometric Complex cooling channels located near the die surface is not possible by conventional manufacturing technologies, the technology of rapid tooling was introduced into hot aluminum extrusion and experimentally tested. Cooling channels near to the bearings show promising results allowing extensions of extrusion limits, especially the extrusion speed and therefore productivity. Cooling of extrusion dies- state of the art In hot metal extrusion of homogeneously preheated billets, the exit temperature of the extrudate increases immediately after starting the process due to heat generated in the forming zone. Heat is also generated as the ram displacement increases because of friction and shear in the peripheral zone of the billet [1]. Surface extrusion defects like hot cracks can occur [2]. In typical wrought aluminum alloys these type of defects are caused by local melting of particular low temperature microstructure phases, e.g. along the grain boundaries, where temperatures exceed the solidu
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new concepts for cooling of extrusion dies manufactured by rapid tooling
Key Engineering Materials, 2011Co-Authors: Ramona Hölker, Nooman Ben Khalifa, Andreas Jäger, Erman A TekkayaAbstract:To prevent local overheating of the workpiece material in hot aluminum extrusion the influence of die cooling was investigated. Numerical simulations of extrusion revealed an advantage of the die bearing cooling, which can be accomplished by locating the cooling channels close to the die/bearing surface. Since the fabrication of especially Geometric Complex cooling channels located near the die surface is not possible by conventional manufacturing technologies, the technology of rapid tooling was introduced into hot aluminum extrusion and experimentally tested. Cooling channels near to the bearings show promising results allowing extensions of extrusion limits, especially the extrusion speed and therefore productivity.
Erman Tekkaya A. D - One of the best experts on this subject based on the ideXlab platform.
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New Concepts for Cooling of Extrusion Dies Manufactured by Rapid Tooling
2016Co-Authors: Ramona Hölker, Nooman Ben Khalifa, Andreas Jäger, Erman Tekkaya A. DAbstract:Abstract. To prevent local overheating of the workpiece material in hot aluminum extrusion the influence of die cooling was investigated. Numerical simulations of extrusion revealed an advantage of the die bearing cooling, which can be accomplished by locating the cooling channels close to the die/bearing surface. Since the fabrication of especially Geometric Complex cooling channels located near the die surface is not possible by conventional manufacturing technologies, the technology of rapid tooling was introduced into hot aluminum extrusion and experimentally tested. Cooling channels near to the bearings show promising results allowing extensions of extrusion limits, especially the extrusion speed and therefore productivity. Cooling of extrusion dies- state of the art In hot metal extrusion of homogeneously preheated billets, the exit temperature of the extrudate increases immediately after starting the process due to heat generated in the forming zone. Heat is also generated as the ram displacement increases because of friction and shear in the peripheral zone of the billet [1]. Surface extrusion defects like hot cracks can occur [2]. In typical wrought aluminum alloys these type of defects are caused by local melting of particular low temperature microstructure phases, e.g. along the grain boundaries, where temperatures exceed the solidu
Erman A Tekkaya - One of the best experts on this subject based on the ideXlab platform.
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new concepts for cooling of extrusion dies manufactured by rapid tooling
Key Engineering Materials, 2011Co-Authors: Ramona Hölker, Nooman Ben Khalifa, Andreas Jäger, Erman A TekkayaAbstract:To prevent local overheating of the workpiece material in hot aluminum extrusion the influence of die cooling was investigated. Numerical simulations of extrusion revealed an advantage of the die bearing cooling, which can be accomplished by locating the cooling channels close to the die/bearing surface. Since the fabrication of especially Geometric Complex cooling channels located near the die surface is not possible by conventional manufacturing technologies, the technology of rapid tooling was introduced into hot aluminum extrusion and experimentally tested. Cooling channels near to the bearings show promising results allowing extensions of extrusion limits, especially the extrusion speed and therefore productivity.