Davi Bernhard - Academia.edu (original) (raw)
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Papers by Davi Bernhard
APS Division of Fluid Dynamics Meeting Abstracts, 2020
Journal of Physics: Conference Series, 2016
Wind tunnels have broad range of applications, and although there are common elements among the d... more Wind tunnels have broad range of applications, and although there are common elements among the different types of tunnels, the layout and configuration of each facility will depend on its particular purpose. The flow conditioners section is a common component for all tunnels, and frequently contains flow straighteners and screens [1]. The role of screens is to minimize non uniformities or turbulence level on the flow field. In this work, the development and characteristics of the vertical velocity profile along an atmospheric wind tunnel length were evaluated. By using such data as initial reference, the effects, on the flow, when screens set is inserted on it were analyzed, in order to identify which changes could be done in the wind tunnel configuration to improve the characteristics of the flow field. Such atmospheric wind tunnel is a facility which belongs to the Brazilian National Metrology Institute INMETRO.
Proceedings of the 25th International Congress of Mechanical Engineering, 2019
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
The jet in crossflow, or a transverse jet, eventually undergoes a linear transition from convecti... more The jet in crossflow, or a transverse jet, eventually undergoes a linear transition from convectively to absolutely/globally unstable as the crossflow to jet velocity ratio increases. This flow field, however, has an extremely complex dynamics. Hence, determining this transition location is not a trivial task. It has long been known that this transition is associated with the upstream shear layer connected to the near field Kelvin-Helmholtz vortex ring, but it was only recently that the most unstable global mode and wave maker were located there as well. These findings led to the realization that an inviscid and planar linear stability analysis of the local velocity profile extracted from the jet in the crossflow upstream shear layer was strongly correlated with its transition to absolute/global instability. It is shown in this paper that such an analysis can be turned into an accurate predictive tool with the use of a viscous (instead of inviscid) and round (instead of planar) mixing layer. In other words, replacing an inviscid analysis of a planar mixing layer with counterflow by a viscous analysis of a round coaxial jet with outer nozzle suction leads to an accurate prediction of the jet in crossflow convective to an absolute instability transition.
APS Division of Fluid Dynamics Meeting Abstracts, 2020
Journal of Physics: Conference Series, 2016
Wind tunnels have broad range of applications, and although there are common elements among the d... more Wind tunnels have broad range of applications, and although there are common elements among the different types of tunnels, the layout and configuration of each facility will depend on its particular purpose. The flow conditioners section is a common component for all tunnels, and frequently contains flow straighteners and screens [1]. The role of screens is to minimize non uniformities or turbulence level on the flow field. In this work, the development and characteristics of the vertical velocity profile along an atmospheric wind tunnel length were evaluated. By using such data as initial reference, the effects, on the flow, when screens set is inserted on it were analyzed, in order to identify which changes could be done in the wind tunnel configuration to improve the characteristics of the flow field. Such atmospheric wind tunnel is a facility which belongs to the Brazilian National Metrology Institute INMETRO.
Proceedings of the 25th International Congress of Mechanical Engineering, 2019
Proceedings of the 23rd ABCM International Congress of Mechanical Engineering, 2015
The jet in crossflow, or a transverse jet, eventually undergoes a linear transition from convecti... more The jet in crossflow, or a transverse jet, eventually undergoes a linear transition from convectively to absolutely/globally unstable as the crossflow to jet velocity ratio increases. This flow field, however, has an extremely complex dynamics. Hence, determining this transition location is not a trivial task. It has long been known that this transition is associated with the upstream shear layer connected to the near field Kelvin-Helmholtz vortex ring, but it was only recently that the most unstable global mode and wave maker were located there as well. These findings led to the realization that an inviscid and planar linear stability analysis of the local velocity profile extracted from the jet in the crossflow upstream shear layer was strongly correlated with its transition to absolute/global instability. It is shown in this paper that such an analysis can be turned into an accurate predictive tool with the use of a viscous (instead of inviscid) and round (instead of planar) mixing layer. In other words, replacing an inviscid analysis of a planar mixing layer with counterflow by a viscous analysis of a round coaxial jet with outer nozzle suction leads to an accurate prediction of the jet in crossflow convective to an absolute instability transition.