Simulation of the interception of plastic fluxes in rivers

One of the preferred features of plastic is its high durability. This merit is its main disadvantage in the natural environment. When poorly disposed of, plastic waste can enter rivers from surface waters and subsequently end up in the ocean. Here, plastic spreads out over the entire ocean and ultimately ends in ocean gyres....

Flow reconstruction using Bayesian inference with model reduction techniques

RANS equations are nowadays widely used in industry because of their affordability in terms of computational costs. They reached a high level of complexity, as they involve systems of non-linear partial differential equations. However they still lack of generality as they are based on closure coefficients determined from fundamental real flow...

Simulations of steady and oscillating flow in diffusers

In this thesis diffuser performance will be simulated with computational fluid dynamics, which will be done with the program Ansys Fluent. The expanding geometry creates an adverse pressure gradient and under certain conditions there will also be separation.<br/><br/>At first a relative simple simulation will be done of a one-directional...

Development of the Generalised Hybrid Turbulence Model for RANS simulations

Turbulence plays an important role in a broad range of engineering applications. In the industry RANS simulations are a common method for predicting turbulent flow. A broad range of RANS turbulence models have been developed over the past decades. For the assessment of complex three-dimensional flow fields Reynolds Stress Transport Models are a...

Turbulence modelling in environmental flows: Improving the numerical accuracy of the k-epsilon model by a mathematical transformation

Numerical modelling for environmental flow applications, such as for rivers, lakes, estuaries and coastal flows, faces a trade-off between the numerical accuracy and the required computation time. This trade-off results in grids which typically contain 10 to 100 layers in the vertical direction. Such a grid resolution poses severe limitations to...

Accurate vertical profiles of turbulent flow in z-layer models

Three-dimensional hydrodynamic z-layer models, which are used for simulating the flow in rivers, estuaries, and oceans, suffer from an inaccurate and often discontinuous bottom shear stress representation, due to the staircase bottom. We analyze the governing equations and clearly show the cause of the inaccuracies. Based on the analysis, we...