Large-scale turbulence phenomena in compound rectangular channels

Meyer, L.; Rehme, K.

doi:10.1016/0894-1777(94)90059-0

Cited by 69 publications

(42 citation statements)

References 20 publications

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“…Lexmond et al, 7 Biemuller et al, 8 and Meyer and Rehme 9 showed that then parallel flow in two rectangular channels connected by a narrow gap presents the same behavior observed by Guellouz and Tavoularis 4 in the region of the narrow gap. The linear stability problem for the laminar flow in this geometry has been analyzed here through a multiblock spectral collocation methodology in Cartesian coordinates.…”

Section: Introductionmentioning

confidence: 62%

Biglobal linear stability analysis for the flow in eccentric annular channels and a related geometry

et al. 2008

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Recently, it has been observed that simple geometry characterized by a low level of symmetry present interesting peculiarities in the process of transition from laminar Poiseuille flow to turbulent flow. Examples of this type of geometry are eccentric channels and, more generally, parallel channels containing a narrow gap. In the present work, a global linear stability analysis for the flow in this class of geometry has been performed. The problem is discretized through spectral collocation and the eigenvalue problem has been solved with the Arnoldi-method based algorithms and the QZ algorithm. Since no numerical studies of this type have yet been performed to address the issue of transition in this geometry, the codes have been validated toward results obtained in simplified geometries ͑e.g., concentric annular channel and square channel͒. The eigenvalue spectra of the Poiseuille flow in eccentric channels and a U-shaped channel have then been computed and analyzed for a wide range of geometric parameters. After comparison with spectra typical of channel flow and pipe flow it is shown that an additional linear mechanism of instability is present, related to the spanwise variation of the laminar velocity profile.

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Section: Introductionmentioning

confidence: 62%

Biglobal linear stability analysis for the flow in eccentric annular channels and a related geometry

et al. 2008

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“…The shape of the structures is constant in the range Q = 0.8 − 0.95. These structures can be related to those observed in geometries that share some similarities with the eccentric annulus by several authors [3,4,28,29]. Their nature is not entirely understood, but it has been experimentally observed to be strongly dependent on the geometric parameters of the problem.…”

Section: Secondary Flows and Streamwise Vorticesmentioning

confidence: 78%

Anisotropic Turbulence and Coherent Structures in Eccentric Annular Channels

Merzari

Ninokata

2008

Flow Turbulence Combust

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Eccentric annular pipe flows represent an ideal model for investigating inhomogeneous turbulent shear flows, where conditions of turbulence production and transport vary significantly within the cross-section. Moreover recent works have proven that in geometries characterized by the presence of a narrow gap, large-scale coherent structures are present. The eccentric annular channel represents, in the opinion of the present authors, the prototype of these geometries. The aim of the present work is to verify the capability of a numerical methodology to fully reproduce the main features of the flow field in this geometry, to verify and characterize the presence of large-scale coherent structures, to examine their behavior at different Reynolds numbers and eccentricities and to analyze the anisotropy associated to these structures. The numerical approach is based upon LES, boundary fitted coordinates and a fractional step algorithm. A dynamic Sub Grid Scale (SGS) model suited for this numerical environment has been implemented and tested. An additional interest of this work is therefore in the approach employed itself, considering it as a step into the development of an effective LES methodology for flows in complex channel geometries. Agreement with previous experimental and DNS results has been found good overall for the streamwise velocity, shear stress and the rms of the velocity components. The instantaneous flow field presented large-scale coherent structures in the streamwise direction at low Reynolds numbers, while these are absent or less dominant at higher Reynolds and low eccentricity. After Reynolds averaging is performed over a long integration time the existence of secondary flows in the cross session is proven. Their shape is found to be constant over the Reynolds range surveyed, and dependent on the geometric parameters. The effect of secondary flows on anisotropy is studied over an extensive Reynolds range through invariant analysis. Additional insight on the mechanics of turbulence in this geometry is obtained.

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“…In very tightly packed rod bundles, a flow instability similar to a Kelvin-Helmholtz instability has been observed (Hooper and Rehme, 1984;Rehme, 1992;Möller, 1991;Meyer and Rehme, 1994). However, the P/D-ratio of 1.28 is too high to observe any such instabilities.…”

Section: Fluid Flow Through Steady Geometrymentioning

confidence: 96%

“…The most well-known example of this is the response of a flexibly mounted cylinder in cross-flow conditions to Von Karman vortices. If the flow direction is aligned with the cylinders in the bundle, Von Karman vortices are not present, but even then, in closely spaced rod bundles, other flow instabilities can occur (Meyer and Rehme, 1994). Additionally, in axial flow conditions vortices shed from supporting structures might trigger vibrations, as happens in grid spaced fuel bundles.…”

Section: Introductionmentioning

confidence: 99%

Predicting modal characteristics of a cluster of cylinders in axial flow: From potential flow solutions to coupled CFD–CSM calculations

Ridder

Degroote

Tichelen

et al. 2017

Journal of Fluids and Structures

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External fluid flow has a number of effects on the dynamics of a submersed structure: e.g., a solitary cylinder exposed to an external flow experiences added mass and damping due to the presence of the surrounding fluid. At high axial flow velocities relative to the stiffness of the cylinder, coupled instabilities such as flutter and divergence occur. Compared to a solitary cylinder, a cluster of cylinders also experiences inter-cylinder coupling: pressure perturbations in the fluid due to the movement or acceleration of one cylinder force another cylinder to move. Consequently, the different cylinders can move in organized patterns.In this contribution, modal characteristics of a 7-rod bundle will be predicted by linear theory as well as by coupled CFD-CSM (Computational Fluid Dynamics -Computational Structure Mechanics) calculations. In the first part, fluid forces which lead to coupling of motion are computed with classical potential flow theory and URANS (Unsteady Reynolds-Averaged Navier-Stokes). Those forces are divided in a contribution in phase with the acceleration and a contribution in phase with the velocity of a cylinder. In the second part, modal characteristics of a 7 cylinder bundle are computed with coupled CFD-CSM simulations. The initial perturbations, which are required for the time-domain simulations come from a simplified structural model, with potential flow coupling between cylinders. The results are compared to linear theory. In the final part, approximations are proposed to predict upper and lower bounds of eigenfrequencies and damping, using calculations with only one cylinder.

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Large-scale turbulence phenomena in compound rectangular channels

Cited by 69 publications

References 20 publications

Biglobal linear stability analysis for the flow in eccentric annular channels and a related geometry

Biglobal linear stability analysis for the flow in eccentric annular channels and a related geometry

Anisotropic Turbulence and Coherent Structures in Eccentric Annular Channels

Predicting modal characteristics of a cluster of cylinders in axial flow: From potential flow solutions to coupled CFD–CSM calculations

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