The structure of turbulence in rod bundles and the implications on natural mixing between the subchannels

Rehme, K.

doi:10.1016/0017-9310(92)90291-y

Cited by 138 publications

(23 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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: 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

View full text Add to dashboard Cite

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.

show abstract

Section: Fluid Flow Through Steady Geometrymentioning

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

View full text Add to dashboard Cite

show abstract

“…Predictions for longitudinal flow typically consider the situation as fully-developed flow through a non-circular channel. Rehme [1992] has reviewed the measurements of turbulence structure in longitudinal flow through rod bundles and related approaches to treating mixing between subchannels; he concentrated on conditions for Reynolds numbers of the order of 5 x 10 4 . Rowe, Johnson and Knudsen [1974] measured axial velocity and turbulence intensity and a few data on lateral turbulence intensity in fully-developed flow through rod bundle channels at Reynolds numbers from 5 x 10 4 to 2 x 10 5 .…”

Section: Related Workmentioning

confidence: 99%

Measurements of Fundamental Fluid Physics of SNF Storage Canisters

Condie¹,

Creery²,

McEligot³

2001

View full text Add to dashboard Cite

SummaryWith the University of Idaho, Ohio State University and Clarksean Associates, this research program has the long-term goal to develop reliable predictive techniques for the energy, mass and momentum transfer plus chemical reactions in drying / passivation (surface oxidation) operations in the transfer and storage of spent nuclear fuel (SNF) from wet to dry storage. Such techniques are needed to assist in design of future transfer and storage systems, prediction of the performance of existing and proposed systems and safety (re)evaluation of systems as necessary at later dates.Many fuel element geometries and configurations are accommodated in the storage of spent nuclear fuel. Consequently, there is no one generic fuel element / assembly, storage basket or canister and, therefore, no single generic fuel storage configuration. One can, however, identify generic flow phenomena or processes which may be present during drying or passivation in SNF canisters. The objective of the INEEL tasks was to obtain fundamental measurements of these flow processes in appropriate parameter ranges.With the University of Idaho, an idealization of a combined drying and passivation approach has been defined in order to investigate the generic flow processes. This simulation includes flow phenomena that occur in canisters for high-enrichment and medium-enrichment fuels, where fuel element spacing in the canister is increased as compared with low enrichment fuel. Canister diameter was taken as 46 cm (18 in.) and a single basket of about 1.3 meters (4 ft.) length was considered. A long central tube ("dip tube") served as the inlet as in one earlier concept for a passivation process; while this concept apparently has not yet been selected for application, it provides an excellent example of the coupled, complex phenomena which may be present in canister flows. Suggested design flow rates for this hypothesized application indicate that the Reynolds number in the inlet tube would be expected to be between 2500 and 5000, i.e., relatively low.The local distributions of convective mass transfer characteristics (drying/passivation) are expected to depend on the freestream turbulence in the flow around stored fuel elements. The magnitudes of this turbulence depend on the turbulence distributions on the upstream side of the perforated basket support plate ("inlet plenum") and, in turn, in the impinging jet and in the inlet tube. This information can assist engineers in understanding variations of surface drying and passivation through an array and approaches to modify designs to counter non-uniformities and to improve iii distribution, as well as providing bases for assessment of computational fluid dynamics codes proposed for the purpose.A water-flow experiment with a 3/4-scale model (relative to the idealized canister) has been used for overall flow visualization and velocity measurements, with and without an array of simulated fuel elements. Observations have been made with perforated plates (representing basket support plates) having...

show abstract

“…These secondary 3ows of the second kind maintain the equilibrium between Reynolds stresses and pressure gradients in the flow. Gosman and Rapley observe that although secondary flows may have a velocity magnitude of only 1% to 2% of that of the axial velocity, experiment shows secondary flow can have a significant effect on local values of wall shear stress and turbulence proper- Rehme [29] suggests that the source of the importance of turbulent diffusion anisotropy in rod bundle turbulent transport is the long length scales of turbulent velocity componcnts as compared to the srnall gap Mdths.…”

Section: Contribution Of Secondary Flow To Mixingmentioning

confidence: 99%

“…Large scatter was observed due to the very small change in axial velocity in the azimuthal direction (aU,/d<p). Kim and Park [28] make reference to Rehme's observation that the norrnalized eddy diffusivity in the radial direction is 10 to 100 times smaller than that of the azimuthal component [29].…”

Section: Turbulent Eddy Diffusivity Anisotropymentioning

confidence: 99%

A Numerical Investigation of Turbulent Interchange Mixing of Axial Coolant Flow in Rod Bundle Geometries

Rock

Lightstone

2001

Numerical Heat Transfer, Part A: Applications

View full text Add to dashboard Cite

This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus. some thesis and dissertation copies are in typwriter face, while others may be from any type of cornputer printer.The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct prÏnt, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment c m adversely affect reproduction.In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages. these will be noted. Also, if unauthonzed copyright material had to be rernoved, a note will indicate the deletion.Oversize materials (e-g., maps, drawings, charts) are reproduoed by sedioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is induded in reduced form at the back of the book.Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. As a result, radial diffusion processes (such as pressure drop) were predicted accuratelbut azimuthal diffusion processes (such as turbulent interchange rnixing) were underpredicted. An isotropic eddy viscosity turbulence model, therefore, is not recommended for analysis of turbulent interchange mixing. Acknowledgement sWithout question, this Masters thesis benefited k o m the assistance of a number of people.For technical advice and support, 1 thank

show abstract

The structure of turbulence in rod bundles and the implications on natural mixing between the subchannels

Cited by 138 publications

References 33 publications

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

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

Measurements of Fundamental Fluid Physics of SNF Storage Canisters

A Numerical Investigation of Turbulent Interchange Mixing of Axial Coolant Flow in Rod Bundle Geometries

Contact Info

Product

Resources

About