Subaqueous dunes using detailed hydrodynamics
Reason of the research
It is observed in open channels that the bed is often made up of statistically periodic irregularities called dunes. Dunes exert considerable influence on sediment transport and flow resistance. By growing the dunes, the resistance increases and the maximum flood intensity occurs at the maximum dune dimensions. These floods can lead to very significant population displacement and loss of infrastructure and agricultural land. Thus it is important to predict the flooding by predicting the dunes dimension growth.
Recent years have seen spectacular progress in our knowledge of dune dynamics that has often been linked to significant advances in our ability to monitor flow and dune morphology in the laboratory and field, and the increasing sophistication of numerical modeling to capture not only the characteristics of the mean flow field but realistically simulate the origins and motions of coherent flow structures above dune beds. Only a few years ago models of turbulent flow over dunes were thought not to be as ‘‘impressive as one might desire’’, recent models have begun to produce more detailed simulations of the instantaneous structure of flow over dune topography. These advances in laboratory, field and numerical modeling now leave us, as never before, in a position to make radical progress in quantifying, modeling and understanding the dynamics and kinematics of alluvial dunes.
Nowadays models are not able to simulate the detailed instantaneous three dimensional dunes topology. Developing a model which can describes the detailed information of bed-form migration and sediment transport, can be very important for developing the physical knowledge of subaqueous dunes.
Project plan
The aim of the present project is developing a numerical model to simulate the generated ripples and dunes in the rivers in its details. Three cases are necessary to have a good estimation for this problem, a model for turbulent flow, model for the sediment transport and a morphology model for the bed-form migration. The results of the model will be compared with experimental data.
Project results
The model can be solved for a part of the river to have a better understanding of the physical phenomena of dunes generation. A good understanding of the physical phenomena gives the ability to generalize the model and extract characterized relations for the general case of the rivers. By this way it is also possible to extract and develop empirical relations for the bed-form topology.
The present project is supervised by Prof. Huib de Vriend, dr. Erik Mosselman and dr. Kees Sloff, and started under DC2.
Promoter
Prof. de Vriend
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