Research

Tidal Basin Hydrodynamics

The group is conducting research to understand how much tidal power can be extracted from a variety of coastal basins and what effect power extraction will have on the natural hydrodynamics within these basins. The group is using both analytical and numerical modelling to investigate this, both for idealised geometries and for possible sites for tidal energy extraction around the United Kingdom.

Axial Flow Devices

Axial Flow DeviceThe effect of realistic conditions of the underwater environment on the performance of generic axial flow tidal energy converters is being thoroughly investigated. Components of ocean flow such as surface waves, velocity profile, large and small scale turbulence and yawed flow are modelled, and their influences on both bare and ducted turbines are examined.

Cross-Flow Turbine Hydrodynamics

CFD_IIIThe group conducts research to investigate the hydrodynamic performance of tidal turbines; both generic devices as well as a specific proprietary device being developed at Oxford. This project is part of a consortium of research activities at Oxford that are collectively investigating the feasibility of a Transverse Horizontal Axis Water Turbine (THAWT) to extract energy from tidal streams. This project’s contribution to the THAWT project is centred on an extensive CFD investigation aimed at furthering the understanding of flows through generic cross-flow turbines and at improving THAWT's hydrodynamic performance.

Advanced Turbine Concepts

pressureSimulation of flows through ducted and open-centre horizontal axis turbines form another part of the research conducted within the group. This research project extends the range of turbine concepts under investigation to include further novel advanced concepts currently proposed by the industry. The goal of this project is to determine, through theoretical modelling, numerical simulation and small-scale experiment, the fluid mechanics behaviour and performance of ducted and open-centre turbines. Furthermore, the project will seek to optimise such novel turbine concepts through the improved understanding of the flow and the theoretical flow models developed during the project.

Transverse Horizontal Axis Water Turbine

The Transverse Horizontal Axis Water Turbine was conceived by Prof. Guy Houlsby, Prof. Martin Oldfield and Dr. Malcolm McCulloch in the Department of Engineering Science at Oxford. The patent pending design uses turbine blades as structural members so that the device can be stretched laterally across a channel and use blockage effects to extract more power than rival designs.

High Order Computational Fluid Dynamics

Esteban_sumThe group is developing a high order discontinuous Galerkin finite element code, DG@Tidal with a moving mesh capability for simulation of flow problems in which flux conservation is problematic. Of particular interest are flows through tidal turbines in which sliding domain interfaces are present. The method allows for accurate preservation of interface fluxes as well as being able to predict the effects of freestream turbulence and wake development in turbine efficiency.

Other low speed fluid mechanics projects

Bluff Body Flows

For all but the lowest flow speeds the flow past a bluff body, such as a circular cylinder, results in the periodic shedding of vortices into the cylinder’s wake, producing oscillatory lift and drag forces. The group conducts Direct Numerical Simulations of bluff body flows to investigate bluff body wake dynamics as well as their link to the unsteady forces experienced by bluff bodies.

Much attention has been paid in the literature to the wake dynamics of cylinders in cross-flow, i.e. where the cylinder axis is perpendicular to the incident flow direction. Of particular interest to the group are the wake dynamics of bodies whose axes are yawed, i.e. not perpendicular, to the incident flow direction and the validity of the so-called independence principle.

Vortex-Induced Vibrations

VIV_summaryThe vortex shedding that occurs in the wake of a bluff body can result in unsteady periodic loading that can, if the body is compliant or elastically supported, cause it to experience Vortex-Induced Vibrations (VIV). Such vibrations can contribute significantly to the fatigue damage of engineering structures exposed to environmental flows, such as the long flexible riser pipes used for offshore oil recovery.
The group’s work in this area is two-fold; investigation of the fundamental structural and fluid dynamics, including vortex shedding modes, that occur during VIV, and more applied research in to the dynamics of offshore riser pipes, including the contributions of high mode super-harmonic responses on riser pipe fatigue damage.