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A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part I: numerical validation
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. (Hydraulic Engineering)
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
2016 (English)In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 54, no 6, 663-677 p.Article in journal (Refereed) Published
Abstract [en]

Analyses of turbulent flows through the downstream slopes of embankment dams are important for dam safety assessments, especially considering high-risk scenarios such as a sudden release of water due to internal erosion. Flow prediction is difficult in such situations due to coarseness of construction materials and high Reynolds numbers. The present study addresses this issue through comprehensive numerical modelling. The novelty of the proposed approach lies in a combination of large-scale experiments and three-dimensional numerical simulations, leading to a fully calibrated and validated model that is applicable to flows through cobble-sized materials (100–160 mm in diameter) at high Reynolds numbers (>104). Comparing the results of the standard turbulence models to data from the large-sale experiments, the renormalization group theory-based model yielded the smallest relative errors based on the hydraulic gradients. Considering the flow field, the turbulent shear stress increased by a factor of 17, and the time-averaged vorticities intensified by factors of 2, 6 and 10 for vorticities in the x-, y- and z-directions, respectively, due to the presence of cobbles.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016. Vol. 54, no 6, 663-677 p.
Keyword [en]
CFD validation, high Reynolds number turbulence, laboratory studies, numerical turbulence models, porous media flow
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-193718DOI: 10.1080/00221686.2016.1211184ISI: 000386438300005Scopus ID: 2-s2.0-84982292500OAI: oai:DiVA.org:kth-193718DiVA: diva2:1033915
Note

QC 20161121

Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2017-11-29Bibliographically approved
In thesis
1. Internal Erosion Phenomena in Embankment Dams: Throughflow and internal erosion mechanisms
Open this publication in new window or tab >>Internal Erosion Phenomena in Embankment Dams: Throughflow and internal erosion mechanisms
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 In this study, two major internal erosion initiation processes, suffusion and concentrated leak mechanisms, which lead to both defect formation in a dam’s body and its foundation and high throughflow in dams subjected to internal erosion were studied. This understanding has the potential to facilitate numerical modelling and expedite dam safety assessment studies. 

The throughflow properties of coarse rockfill material were studied by; analysing filed pump test data, performing extensive laboratory experiments with a large-scale apparatus and numerically simulating the three-dimensional flow through coarse rock materials, replicating the material used in the laboratory experiments.

Results from the tests demonstrate that the parameters of the nonlinear momentum equation of the flow depend on the Reynolds number for pore Reynolds numbers lower than 60000. 

Numerical studies were also carried out to conduct numerical experiments. By applying a Lagrangian particle tracking method, a model for estimating the lengths of the flow channels in the porous media was developed.  The shear forces exerted on the coarse particles in the porous media were found to be significantly dependent on the inertial forces of the flow.

Suffusion and concentrated leak mechanisms were also studied by means of laboratory experiments to develop a theoretical framework for continuum-based numerical modelling. An erosion apparatus was designed and constructed with the capability of applying hydraulic and mechanical loading. Results were then used to develop constitutive laws of the soil erosion as a function of the applied hydromechanical load for both suffusion and concentrated leak mechanisms. Both the initiation and mass removal rate of were found to be dependent on the soil in-situ stresses.

A three-dimensional electrical-resistivity-based tomography method was also adopted for the internal erosion apparatus and was found to be successful in visualising the porosity evolution due to suffusion.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 74 p.
Series
TRITA-HYD, 2016:4
Series
ISSN, ISSN 1650-8602
Keyword
Internal erosion modelling in porous material; Constitutive law of erosion for closure of continuum-mechanics-based balance equations for numerical modelling; High Reynolds-number turbulent flow; Flow laws; Coarse rockfill material throughflow; Computational Fluid Dynamics.
National Category
Geotechnical Engineering Water Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-193627 (URN)978-91-7729-130-5 (ISBN)
Public defence
2016-11-04, Kollegiesalen, Brinellvägen 8, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20161006

Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-11Bibliographically approved

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Publisher's full textScopushttp://dx.doi.org/10.1080/00221686.2016.1211184

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