Fluid Mechanics and Turbulence

Fluid Mechanics and Turbulence

The governing equations for fluid mechanics are those for conservation of mass and momentum. Since these cannot be solved for high Reynolds numbers, approximations should be found that account for the effects of turbulence. Particularly when the flow domain is large and gives rise to three-dimensional effects such as river bends, the flow over weirs, through gates, in flood plains and other spatially varying bathymetries, the inclusion of the effects of turbulence can be quite problematic. It is therefore important to understand such flows and identify the dominant interactions that govern the flow directions and local shear stresses. The latter are important when it comes to sediment transport, stability of river banks and armour layers as well as vegetation interaction.

Examples of recent and current research are:
•    Stability of armour layers on breakwaters and transport through open filters
•    Scour around mono-piles of wind turbines, and other hydraulic structures
•    Interaction of waves and currents with (flexible) vegetation

Through laboratory experiments information can be obtained on the flow details under controlled conditions. Flow velocities, turbulence properties and forces on objects can be determined and used for the interpretation of observed phenomena, e.g. scour, and data can be used for model validation.  In the Waterlab of our faculty we have the opportunity to perform such experiments for various conditions of currents, waves, bathymetries and composition of bed and bank material.  At the larger scale field data are obtained.By developing advanced numerical modelling technique many details of the flow can be captured.

Current development in the group comprise:
•    3D modelling of free-surface flows using finite element  and finite volume techniques
•    Particle-based and hybrid methods for free surface flows interacting with granular structures
•    Turbulence modelling using Large Eddy Simulation for small domains

Detailed numerical modelling in three dimensions requires powerful computing facilities such as the 240 core computer cluster  that is at the disposal of the group.

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