Master Theses

Behavioral response of benthic invertebrates to high flow and risk of predation in a laboratory flume

Benthic invertebrates are an important component of aquatic ecosystems. They populate macrophyte beds and the interstitial space of the sediment and its surface. Certain benthic organisms can take shelter within grain interstices or actively enter into drift when conditions become unfavorable. Their active behavior and ability to respond to changing conditions by refuge finding is crucial for their survival and important for the modeling of anthropogenic impacts and population dispersion, but poorly understood due to the intricacy of direct observation of living organisms in a flowing environment. Our group has developed a new approach to reveal the behavior of benthic organisms near and within the sediment bed by using high speed imaging in a transparent sediment bed. The aim of this MSc project is to conduct experiments in a hydraulic flume using living macroinvertebrates collected from the field to investigate their response to increasing flow velocities and presence of predators. DownloadRead more (PDF, 390 KB)vertical_align_bottom

Large-eddy simulation of transitional blood flow using the immersed boundary method

Over the last decade, the study of blood flow through computational simulations has gained considerable importance. This approach offers the advantage that it enables the detailed charaterization of the transitional flow regime downstream of an aortic stenosis. Indeed, quantifying the influence of stenosis on blood flow is of crucial importance for diagnostic purposes and for choosing the appropriate treatment for the patient. In this Master thesis, large-eddy simulations (LES) are carried out using the already implemented immersed boundary method (IBM) in OpenFOAM. The work focuses on three parts:

• Adaptation of the forcing term of the IBM such that a rigid wall is modeled.
• Implementations of simulations with one LES model for one realistic geometry of aorta with stenosis.
• Validation of the numerical framework with data from experiments and direct numerical simulations. Read more

Lagrangian model for invertebrate drift in streams

Downstream advection of benthic invertebrates in streams has received much attention, in the context of constant drift, and also in relation to increased flow caused by natural spates and by the release of water from reservoir hydroelectric power stations. However, model studies of the relationships between hydraulic parameters, behavior and drift are unavailable for many taxa. A recent study has shown that certain species of cyclopoid copepods - a widespread taxon and an important component of the meiobenthos - perform active counter-current swimming. They explore the entire water column at low flow velocity, but stay close to and perform frequent incursions into the sediment bed at higher flow velocities. This active behavior supposedly limits their downstream downstream drift, yet the implications for downstream drift and dispersion remain unexplored. The aim of the present study is to explore the drift behavior of invertebrates for varying flow conditions. Read more

Flow patterns in an ascending aortic aneurysm

The goal of this project is to investigate the flow pattern in an in-vitro model for an ascending aortic aneurysm. The results obtained from this project serve as test case for computational fluid dynamics groups. This project will also provide instructive results for the medical community. Read more

Physical disintegration of gross solids in sewers

A better understanding of the process of physical disintegration of gross solids in sewers is critical for increasing the sustainability of these systems and the efficiency in their operation. This process is however poorly understood because it entails a complex interplay between the properties of these solids and hydrodynamics, which can lead to fragmentation and erosion. In this project, we aim at quantifying the disintegration of gross solids, specifically faeces, under realistic hydrodynamic conditions. Based on the experimental data, we will devise a model that will constitute a module in a simulation aiming at assessing the effects of reduction in domestic water consumption and transition to decentralized wastewater treatment systems on the operation of sewer systems. Read more