Nortek UK Coastal, Lab and Turbulence Studies 2015

User Presentations

Field measurements at a tidal energy site: challenges and lessons learned  
Brian Sellar, University of Edinburgh

The University of Edinburgh has designed and conducted comprehensive field measurements of the highly energetic environment around a fully operation commercial scale tidal turbine as part of the Reliable Data Acquisition for Tidal (ReDAPT) project. This involved the integration and operation of a variety of acoustic and other sensors on and around the Alstom DEEPGEN IV tidal turbine, installed at the European Marine Energy Centre, Orkney (EMEC).  Target measurements included mean flow, turbulence parameters and waves - requiring a complex instrumentation array.  Challenges around the areas of sensor installation, integration, operation, maintenance and sensor performance will be discussed, and where possible, implemented solutions will be presented. 

Analysis of the onset flow measurements acquired by a multi-sensor array during the ReDAPT project 
Duncan Sutherland, University of Edinburgh

The Reliable Data Acquisition for Tidal (ReDAPT) project has collected an unprecedented amount of tidal flow data from a highly energetic site over three years of deployments.  As part of the University of Edinburgh’s work on the project, field measurements at the European Marine Energy Centre (EMEC) tidal test site would involve deployments of up to 19 acoustic sensors of multiple types on and around a 1MW commercial scale tidal turbine (the Alstom DEEPGEN IV machine).  This presentation will report on the mean flow and turbulence metrics measured at the site and the variation in measurements between difference sensor types.  The advantages of different instrument configurations for different site characterisation requirements will be discussed.

Turbulence measurement in Strangford Narrows
Penny Jeffcoate, Queen's University Belfast

Tidal flow turbulence is a key environmental condition that is generally not well understood, neither are its impacts on tidal stream devices. This presentation will exhibit work undertaken by members of the Marine Research Group at Queen’s University Belfast, and our collaborators, in an effort to gain data capable of enabling turbulence characterisation in high velocity tidal streams. For example, current and turbulence measurements collected using a Nortek Aquadopp and Nortek Vector, upstream of a 1.5m diameter turbine mounted from a moored catamaran platform will be presented. Measurements upstream of a 4m diameter turbine from a moored barge platform will also be presented and compared with collocated MicroRider data (Rockland Scientific). This work will demonstrate the importance, but also the limitations, of characterising turbulence for tidal turbine deployment areas.
 

Measurements of the Schmidt Number in an oscillating grid turbulence tank
Daniel Conley, Plymouth University 

Past work has shown that advection-diffusion modelling of sediment transport under waves can provide highly satisfactory results provided that the temporal resolution is sufficient. However these results are strongly dependent on the magnitude of sediment diffusivity. In order to determine the true nature of sediment diffusivity in relation to eddy viscosity (the Schmidt Number) an oscillating grid turbulence tank has been constructed and utilised. This presentation will discuss our experience using a Vectrino Profiler to characterise the turbulent characteristics of the the oscillating grid tank both in sediment free and sediment laden conditions. Measurements of TKE, turbulent dissipation and other key parameters shall be presented.

Predicting turbulence generation on a sloping boundary in a lake using an Aquadopp HR Profiler
Danielle Wain, University of Bath

A crucial unanswered question in lake and reservoir management is whether the Lake number can be used to predict mixing in a lake. To address this question, three field campaigns with measurements of meteorological conditions, internal wave response by three thermistor chains, and dissipation of turbulent kinetic energy were conducted to study generation of turbulence on the sloping boundary of a small lake for Lake numbers between 0.1 and 1000. We measured the velocities in the bottom boundary layer with an Aquadopp HR (high resolution) Profiler and then computed the dissipation using the structure function method, which uses the spatial correlations of velocity along a beam to estimate the dissipation. During the low Lake number events, the dissipation of turbulent kinetic energy increased by up to four orders of magnitude above the specified background level of 10-10 m2s-3, except during the fall turnover when the wind energy was used in thermocline deepening. To evaluate the Lake number conditions under which turbulence will be generated at the slopes, a power law between the Lake number and turbulence intensity was derived, showing a near linear decrease of turbulence intensity with increasing Lake number.

Hebrides Marine Research Centre: Wave measurements at an ocean energy site
Donald Armstrong, Lews Castle College 

Based on the successful data acquisition with two 1MHz AWACs under the Hebridean Marine Energy Futures project, an enhanced measurement campaign is currently ongoing  using a combination of acoustic sensors, wave buoys and shore based X-band radar.  The previous work has returned long term datasets at a satisfying quality, unprecedented for a high energy near-shore environment, to successfully support wave resource assessment studies.  The detailed analysis of this data has evolved into scientific research questions related to wave mechanics, bottom interaction and wave induced environmental processes.  This talk provides a brief summary of the initial data acquisition experience and outlines the recent field research and data analysis at the Outer Hebrides of Scotland.  A combination of remote and in-situ sensors is used to not only quantify sediment dynamics and wave current interactions, but also to improve the current state of the art of data processing and quality control.

Introduction to activities at the FloWave facility
Thomas Davey, FloWave TT Ltd