Global ETD Search
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Showing 1 to 9 of 9 for “"absolute instability"”.
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Hydrodynamic linear stability of the two-dimensional bluff-body wake through modal analysis and initial-value problem formulation
… the base flow. The first order corrections find absolute instability pockets in the first part of the intermediate wake (and not in the near wake, where the recirculating eddies are, as usually seen in literature in contrast with the near-parallelism hypothesis). These regions are present for …
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Ventilation, stratification and flow instability driven by vertically distributed buoyancy sources
… wave modes is a remarkable feature of the instability, distinguishing these `annular wall plumes’ from free plumes/jets for which the helical mode is usually dominant. It is found that higher surface curvature stabilises the temporal axisymmetric mode significantly, but only has moderate …
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Sensitivity analysis of low-density jets and flames
… in the flow or as a mechanism that drives global instability. For the lifted flames, the most sensitive areas lie between the inlet and flame base. In this region the jet is absolutely unstable, but the close proximity of the flame suppresses the global instability seen in the non-reacting case. …
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Numerical studies of the flow around an airfoil at low Reynolds number
… flow field is performed, however no absolute instability is observed that could explain the presence of self sustaining turbulence. A series of simplified DNS are presented that illustrate a three-dimensional in-stability of the two-dimensional vortex shedding that occurs naturally. …
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Stability of fluid-loaded structures
… the 'long time' limit. These include convective instability, absolute instability and negative energy waves which are destabilized by dissipation. However, structures are necessarily of finite length and may have discontinuities. We have undertaken an analytical and computational study to …
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High Order Explicit Semi-Lagrangian Method for the Solution of Lagrangian Transport and Stochastic Differential Equations
… with a spatially growing viscous LSA mode an absolute instability is observed. In that case, a match between DNS and LSA is difficult because of spurious modes introduced by the reflections at the boundaries. In a temporal analysis, it is found that the growth of the temporal mode is greater …
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Three-dimensional effects on flag flapping dynamics ; [and], Study and modeling of incompressible highly variable density turbulence in the bubbly wake of a transom stern
… fluid-structure interaction is the flapping-flag instability. Fluid-mechanical studies of the phenomenon date back to the 19th century, increased in number in recent years with increasingly accurate representations for the coupled fluid-structure interaction. The problem continues to attract …
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On the structure and dynamics of the Asian monsoon anticyclone
… the monsoon anticyclone as a consequence of an absolute instability of the flow field. By performing a comprehensive spatial stability analysis of an idealised representation of the system we were able to develop a theory for the transition between different shedding states. Adapting a simple …
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Forcing of globally unstable jets and flames
… and a reacting jet. Both jets have regions of absolute instability at their base and this causes them to exhibit varicose oscillations at discrete natural frequencies. The forcing is applied around these frequencies, at varying amplitudes, and the response examined over a range of frequencies …