POD analysis of a vortex rope with transient boundary conditions

Urban, Ondřej; Rudolf, Pavel

doi:10.1088/1755-1315/405/1/012034

Cited by 4 publications

(2 citation statements)

References 10 publications

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“…For our research of the vortex rope phenomenon, we have designed a new swirl generator capable of changing the swirl intensity smoothly within a wide range while being constructionally simple, without any moving parts. Several studies of the flow in this swirl generator have already been published [12][13][14][15][16]. Its principle resides in mixing flows from two separate inlets -a straight axial inlet and a tangential inlet ended by a spiral case generating rotation.…”

Section: Swirl Generator Apparatusmentioning

confidence: 99%

On the existence of adverse pressure gradient in decelerated swirling flow and its suppression by water jet injection

Urban

Rudolf

2022

IOP Conf. Ser.: Earth Environ. Sci.

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The paper revisits the theory originally published by Hall that explains the presence of adverse pressure gradient at the axis of a diffuser with swirling flow. It presents the fields of the axial pressure derivative obtained by CFD simulations of flow in a swirl generator, which support the theory. The last part brings cautionary results regarding the suppression of the backflow caused by this adverse pressure gradient by water jet injection. On a case with a strong swirl intensity leading to a strong vortex rope, it is shown that the injected jet may be deflected to the outer walls and rotate with the outer swirling flow, eventually leading to stronger pressure pulsations than in the original state. Further investigation shows that high enough diameter of the jet is needed to ensure its stability.

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Section: Swirl Generator Apparatusmentioning

confidence: 99%

On the existence of adverse pressure gradient in decelerated swirling flow and its suppression by water jet injection

Urban

Rudolf

2022

IOP Conf. Ser.: Earth Environ. Sci.

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“…Computational data presented in this paper are part of extensive research aimed on investigation of vortex rope behavior and its control, where visualization is one of partial goals. The reader is referred to Reference [32,33] for details about experiments and CFD simulations.…”

Section: Cfd Simulationmentioning

confidence: 99%

Application of Computer Graphics Flow Visualization Methods in Vortex Rope Investigations

2021

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Computer graphics visualization techniques for application on data from Computational Fluid Dynamics (CFD) simulations of the vortex rope, a phenomenon present in hydraulic turbines operating in off-design conditions, were devised. This included not only objects for visualization (what to visualize) but also methods of the visualization itself (how to do it). By means of advanced methods based particularly on volume rendering of Eulerian fields in combination with Lagrangian objects, various phenomena were captured, such as the motion of the vortex rope or the backflow zone. The data came from simulations using a scale-resolving hybrid turbulence model, the Stress-Blended Eddy Simulation. In such detailed simulations and other applications involving complex three-dimensional structures, proper visualization methods are needed to leverage the content captured in the resultant data.

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Assessment of the distributor layout influence on the vortical flow within the hydraulic turbine

Štefan,

Klement,

Urban

et al. 2024

IOP Conf. Ser.: Earth Environ. Sci.

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The study presents analysis of conditions for the onset of vortices in the simplified geometry of the turbine domain. The simplified geometry, used for this analysis, is based on the physical model of the bladeless swirl generator developed by the research group from Brno University of Technology. This swirl generator was previously used for several studies of the spiral vortex structures generated in the diffuser part. In original geometry there are no guide vanes or other driving geometry features, thus the mixing mechanism is realized randomly, is strongly time-dependent and its behavior is linked to the swirl ratio between the axial and tangential inflows. From previous studies, the appearance of vortical structures with columnar-like shape was identified. Thus, the main aim for the current study is to assess the influence of distributor blade cascade on the onset and behavior of such vortical structures which resembles the ones observed in hydraulic turbines at low load conditions. For selected swirl ratio the distributor blades are designed specifically to influence flow with minimal effect. The distributor layouts with different number of blades are tested. The dynamics of vortices, their spatial shape and extend are examined through several post-processing tools. The results are mainly based on the CFD simulation employing a hybrid RANS+LES turbulence model.

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POD analysis of a vortex rope with transient boundary conditions

Cited by 4 publications

References 10 publications

On the existence of adverse pressure gradient in decelerated swirling flow and its suppression by water jet injection

On the existence of adverse pressure gradient in decelerated swirling flow and its suppression by water jet injection

Application of Computer Graphics Flow Visualization Methods in Vortex Rope Investigations

Assessment of the distributor layout influence on the vortical flow within the hydraulic turbine

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