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Universiteit Utrecht

1. Vellinga, A.J. Morphodynamics of bedforms in a supercritical-flow regime: a depth-resolved numerical modelling approach.

Degree: 2014, Universiteit Utrecht

URL: http://dspace.library.uu.nl:8080/handle/1874/301315 

Both open-channel flows and density currents are able to create supercritical-flow bedforms. The morphodynamics of these supercritical-flow bedforms are, however, still poorly understood. This is mainly due to a lack of measurements of flow processes occurring within these types of flows. Cyclic steps have successfully been simulated in open-channel flow using a depth-resolved numerical model. The equilibrium conditions at which certain supercritical-flow bedforms are stable are investigated. The temporal variation in Froude number is indicative of at which conditions cyclic steps are in a macroscopic equilibrium at a variability of grain sizes, discharges and sediment concentrations. The depth-resolved model provides insight into the dynamic interaction between velocity structure, shear stresses, and sediment concentrations within the flows and resulting erosion and deposition patterns, which, in their turn affect the flow-properties again. The velocity structure downstream of a hydraulic jump displays highest flow velocities near the bed, whilst lowest or even negative velocities are located at the top of the flow, causing the flow to remain exerting shear stresses on the bed even after the hydraulic jump. The sediment concentrations within the flow only decrease after a 30 second, or half a meter lag, causing most of the deposition to take place at the last two-thirds of subcritical region of the flow. The resulting depositional pattern consists of upstream-dipping backset laminations deposited on the stoss-side of the bedform, cross-cut by the erosive surface of the lee-side of the cyclic step, this interplay between erosion and deposition also causes an upstream migration of the cyclic steps. Advisors/Committee Members: Eggenhuisen, J.T., Cartigny, M.J.B..

Subjects/Keywords: morphodynamic; supercritical; flow; bedform; bedforms; cyclic step; cyclic steps; RANS; depth-resolved; numerical; model

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Vellinga, A. J. (2014). Morphodynamics of bedforms in a supercritical-flow regime: a depth-resolved numerical modelling approach. (Masters Thesis). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/301315

Chicago Manual of Style (16th Edition):

Vellinga, A J. “Morphodynamics of bedforms in a supercritical-flow regime: a depth-resolved numerical modelling approach.” 2014. Masters Thesis, Universiteit Utrecht. Accessed February 28, 2021. http://dspace.library.uu.nl:8080/handle/1874/301315.

MLA Handbook (7th Edition):

Vellinga, A J. “Morphodynamics of bedforms in a supercritical-flow regime: a depth-resolved numerical modelling approach.” 2014. Web. 28 Feb 2021.

Vancouver:

Vellinga AJ. Morphodynamics of bedforms in a supercritical-flow regime: a depth-resolved numerical modelling approach. [Internet] [Masters thesis]. Universiteit Utrecht; 2014. [cited 2021 Feb 28]. Available from: http://dspace.library.uu.nl:8080/handle/1874/301315.

Council of Science Editors:

Vellinga AJ. Morphodynamics of bedforms in a supercritical-flow regime: a depth-resolved numerical modelling approach. [Masters Thesis]. Universiteit Utrecht; 2014. Available from: http://dspace.library.uu.nl:8080/handle/1874/301315


Universiteit Utrecht

2. Poos, W.J.R. Stability Diagram of upper flow regime bedforms. An experimental study.

Degree: 2011, Universiteit Utrecht

URL: http://dspace.library.uu.nl:8080/handle/1874/217191 

Water flowing over a bed made of silici-clastic material forms bedforms. A stability diagram for these bedforms is available for the lower flow regime where the Froude number < 0.8. No such diagram is available for the upper flow regime (Fr > 0.8). Experiments in a tiltable flume show that the bedforms for the upper flow regime can be characterized as: upper plane bed, antidunes, chute and pools and cyclic steps. These bedforms are plotted in a stability showing the relation between the dimensionless grain size and the ratio of minimum and maximum Froude number (before and after the hydraulic jump if present) showing proof of concept for such a stability diagram. Advisors/Committee Members: Postma, G..

Subjects/Keywords: Geowetenschappen; upper, flow, regime, supercritical, cyclic, step, antidunes, chute, pools, experimental

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Poos, W. J. R. (2011). Stability Diagram of upper flow regime bedforms. An experimental study. (Masters Thesis). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/217191

Chicago Manual of Style (16th Edition):

Poos, W J R. “Stability Diagram of upper flow regime bedforms. An experimental study.” 2011. Masters Thesis, Universiteit Utrecht. Accessed February 28, 2021. http://dspace.library.uu.nl:8080/handle/1874/217191.

MLA Handbook (7th Edition):

Poos, W J R. “Stability Diagram of upper flow regime bedforms. An experimental study.” 2011. Web. 28 Feb 2021.

Vancouver:

Poos WJR. Stability Diagram of upper flow regime bedforms. An experimental study. [Internet] [Masters thesis]. Universiteit Utrecht; 2011. [cited 2021 Feb 28]. Available from: http://dspace.library.uu.nl:8080/handle/1874/217191.

Council of Science Editors:

Poos WJR. Stability Diagram of upper flow regime bedforms. An experimental study. [Masters Thesis]. Universiteit Utrecht; 2011. Available from: http://dspace.library.uu.nl:8080/handle/1874/217191

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