Vengatesan Venugopal

• PhD.
• Professor at University of Edinburgh

This paper presents a novel side information assisted Empirical Mode Decomposition (EMD) method for separating wave orbital velocity from a combined wave-tidal current velocity data, measured by three different Acoustic Doppler Current Profilers (ADCPs) deployed in the Pentland Firth, Orkney Waters, UK. The effectiveness of this technique is confir...

This paper describes numerical simulations of an innovative design of close-packed contra-rotating vertical-axis turbines (VATs), which enable assessment of power performance, vorticity distribution, and wake deficit. The design comprises a large diameter rotor without traditional supporting arms, stable in pitch and roll. Close-packing reduces lea...

Montrose Bay’s coastline in Scotland is experiencing the most severe erosions, especially in its southern section, interfacing with the Montrose Tidal Inlet System. This inlet system could induce a distinct ebb tidal jet and eddy when ebbing, influenced by its high-angle half-delta, and the understanding of jet and eddy formation at this type of in...

By 2050 under the predicted climate change high emission scenario, 75% of the soft coastline in Scotland will be susceptible to erosion, including the coastline at Montrose Bay, East Scotland. This paper aims to characterize the prevailing wave and tidal regimes of Montrose Bay and assess their potential role in the coast’s dynamics. The numerical...

Montrose Bay is one of the Scottish Coasts that had been experiencing severe erosions. To explain the bay hydro- and coastal dynamics, modelling study was performed using the software Delft3D-Flexible Mesh. There are a lot of questions regarding coastal processes at Montrose Bay and this makes this study as an important research. This study is infl...

With the combination of climate and energy crises bringing unprecedented challenges, countries are pushing to rapidly decarbonise their energy consumption. As part of this effort, the rapid development of offshore wind in the last decades has led to growing interest from the energy industry which is benefiting from important innovations. One of the...

Floating offshore wind Tension-Leg-Platform (TLP) concepts benefit from a reduced hull tonnage and limit response in vertical modes of motion through the use of pre-tensioned mooring lines to resist aero-hydrodynamic forces. However, this design choice requires an accurate prediction of extreme loadings in the mooring cables such as those generated...

Wave and tidal renewable energy systems have received a great deal of attention in recent years worldwide. A number of Wave Energy Converter (WEC) technologies to harvest wave energy have been proposed, developed, tested and in operation in ocean at different parts of the globe with varying maturity levels. Over the past two decades, a broad range...

The presence of waves exposes tidal stream turbines to large and cyclic hydrodynamic loads which significantly influence the design requirements for tidal turbine blades. Here we describe a loading phenomenon not previously considered in literature caused as blades rotationally sample an oscillating and vertically decaying wave-induced velocity fie...

An array of close-packed contra-rotating cross-flow vertical-axis tidal rotors, a concept developed to maximize the fraction of flow passage swept, has potential advantages for hydrokinetic power generation. To predict the commercial feasibility of such rotors in large-scale application, a numerical model of a vertical-axis turbine (VAT) with a tor...

This paper presents the nature of turbulence parameters produced from 3-dimensional numerical simulations using an ocean scale wave-tidal current model applied to tidal energy sites in the Orkney waters in the United Kingdom. The MIKE 21/3 coupled wave-current model is chosen for this study. The numerical modelling study is conducted in two stages....

Waves induce large loads on tidal turbines, yet the effect of irregular waves, particularly those which oppose the current direction, have received little attention. Here we experimentally assess the loading resulting from 24 irregular combined wave-current cases, statistically presenting the load variability acting on a 1:15 scale tidal turbine. C...

In this paper, a methodology to generate combined wave, tidal current and turbulent flow environment for application to determining hydrodynamic loading on a horizontal axis Tidal Stream Turbine (TST) is proposed. A systematic investigation has been conducted within the framework of OpenFAST software suite. Necessary modifications in OpenFAST tool...

This is a reprint of articles from the Special Issue published online in the open access journal Energies (ISSN 1996-1073) from 2018 to 2019 (available at: https://www.mdpi.com/journal/energies/special issues/marine).

The Sundarbans, a world heritage site in India, is world’s largest inter-tidal delta region containing huge areas of mangrove forests, and lies between India and Bangladesh. The site is intersected by a complex network of tidal waterways, mudflats and small islands of salt-tolerant mangrove forests. The eco-geography of this area is totally depende...

This paper presents a computational fatigue assessment method of mooring chains under tensile loading, it is composed of a mechanical analysis followed by a fatigue analysis. The mechanical analysis is performed in two steps: residual stress prediction and service loading. From this analysis, the shakedown cycle is extracted at the critical points,...

This study aims to de-risk the development of the Deep Turbine Installation-Floating (DTI-F) concept, a hybrid spar buoy-based floating offshore wind turbine with the novelty of being able to raise up and lower down the tower plus nacelle set. The paper presents the design and construction of a Froude-scaled model based on the DTI-F concept, the ex...

This paper presents the preliminary design of the Deep Turbine Installation-Floating (DTI-F) concept. The DTI-F concept is a hybrid spar buoy-based floating offshore substructure capable of supporting a 7MW wind turbine with the uniqueness of being able to raise and lower the tower and nacelle, which simplifies construction, installation, maintenan...

Floating offshore wind turbine (FOWT) installations are progressing from the R&D stage to commercial installation projects. The prospective sites are situated in increasingly deeper water and further away from the shore. This paper presents the Deep Turbine Installation-Floating (DTI-F) concept, an innovative hybrid spar buoy-based FOWT capable of...

Tidal stream turbines are subject to large hydrodynamic loads, including those induced by extreme waves. Scale model testing in the laboratory plays an important role in ensuring that full scale tidal turbines are designed and operated in a manner that is appropriate for harsh ocean environments where waves and tidal currents coexist. For the first...

Waves interact with currents in tidal channels with the resulting wave–current environment largely determining the loads experienced by tidal stream turbines. Over a tidal cycle, the magnitude and direction of the current velocity changes and hence so does the combined wave–current conditions the turbines must operate within. Here we demonstrate th...

Fast tidal streams are a promising source of clean, predictable power, but the task of arranging tidal turbines for maximum power capture is complicated. Actuator disc models, such as the two-scale actuator disc theory, have proven useful in seeking optimal turbine arrangements, yet these models assume flows that are frictionless and steady, and th...

The offshore renewable energy sector has challenging requirements related to the physical simulation of the ocean environment for the purpose of evaluating energy generating technologies. In this paper the demands of the wave and tidal energy sectors are considered, with measurement and characterisation of the environment explored and replication o...

Experimental data was obtained in order to investigate the effect of waves on the loads and performance of tidal turbines. An instrumented 1:15 scale tidal turbine was installed in the FloWave Ocean Energy Research Facility, and a wide range of regular wave conditions were generated; systematically varying both wave frequency and height. Waves were...

This study presents the variation in turbulence parameters derived from site measurements at a tidal energy test site. Measurements were made towards the southern end of the European Marine Energy Centre’s tidal energy test site at the Fall of Warness (Orkney, Scotland). Four bottom mounted divergent-beam Acoustic Doppler Current Profilers (ADCPs)...

This paper investigates the energy extraction of three types of wave energy converters (WEC) arranged in arrays and subjected to multi-directional seas of different wave spreading. The changes in the wave climate observed in the neighborhood of the arrays by their energy extraction were also reported. The hydrodynamic software, WAMIT, has been used...

Offshore renewable energy includes several forms of energy extraction from oceans and seas, and the most common and successful offshore technologies developed so far are based on wind, wave and tides. In addition to other resources, wind, waves and tides are considered to be abundant, inexhaustible, and harvestable zero-carbon resources which benef...

Tidal turbines are subject to large hydrodynamic loads from combinations of currents and waves, which contribute significantly to fatigue, extreme loading and power flow requirements. Physical model testing enables these loads and power fluctuations to be assessed and understood in a controlled and repeatable environment. In this work, a 1:15 scale...

Renewable energy offers significant opportunities for electricity diversification. South Africa belongs to the group of developing nations and encompasses a lot of potential for renewable energy developments. Currently, the majority of its electricity production originates from fossil fuels; however, incorporation of clean coal technologies will ai...

The study uses a 35-year data set, which can be used to provide a long-term assessment for assessing wave power resources, availability for wave energy converters (WECs), and multithreshold accessibility suitable for numerous vessels and important for offshore maintenance operations. The data set demonstrates that winter months have harsher environ...

At autonomous electricity grids Renewable Energy (RE) contributes significantly to energy production. Offshore resources benefit from higher energy density, smaller visual impacts, and higher availability levels. Offshore locations at the West of Crete obtain wind availability ≈80%, combining this with the installation potential for large scale mod...

To enable accurate prediction of performance, loading and lifetime fatigue, the operating environment of tidal stream turbines must be comprehensively characterised over a range of seasons and tidal cycles. The met-ocean dataset acquired at the European Marine Energy Centre (EMEC), UK as part of the Reliable Data Acquisition Platform for Tidal (ReD...

PLAT-O #2 is a subsea floating tidal energy generator. A scaled-down physical model of this device was tested at FloWave in steady axial currents of up to 6.2 m/s (full-scale). The platform's motion and mooring tensions were measured to validate a tank-scale numerical model in ProteusDS. In currents above 3.5 m/s (full-scale) the platform with turb...

To date, only a few studies have examined the execution of the actuator disc approximation for a full-size turbine. Small-scale models have fewer constraints than large-scale models because the range of time-scale and length-scale is narrower. Hence, this article presents the methodology in implementing the actuator disc approach via the Reynolds-A...

Theoretical models suggest that in order to maximise their collective power output, tidal turbines should be arranged in a single cross-stream row and optimally spaced to exploit local blockage effects. However, because it is assumed that the turbines within these arrays are identical, such models do not consider the possibility of enhanced power p...

The study focuses around the energetic waters of Scotland that has expressed high interest in the development of wave energy farms. There are only a few long-term suitable studies characterising coastal locations. A detail coastal resource assessment is provided, focusing on wave energy and site characterisation. Mean nearshore energy content in th...

Current standards (as an example, DNV-OS-E301[1] and API-RP-2SK[2]) do not account for mean load in the fatigue assessment of mooring chains. Both standards, provide S-N curves derived from experimental work without specifying the mean load for which they have been obtained or proposing a mean load correction function. This paper reports a fatigue...

Taking an existing spectral wave model of the north Atlantic and adjusting the wind forcing to see how the wave power reaching Scotland changes with the climate to 2100.

Depth-averaged simulations are used to investigate whether the performance of a tidal turbine array can be enhanced by varying either local blockage, local resistance, or both, across the array width. Results suggest that for an initially uniform flow field, the optimal array comprises turbines of equal size, spacing, and tuning.

A number of sites around the UK are being considered for development of tidal stream energy, one of which is Ramsey Sound off the coast of Pembrokeshire, South Wales. The Sound was used to test the prototype of the Delta Stream by Tidal Energy Ltd. After initial testing, a 10 MW tidal array was proposed at St David's Head. To investigate any possib...

Unsteady wave loading on tidal turbines impacts significantly the design, and expected life-time, of turbine blades and other key components. Model-scale testing of tidal turbines in the wave-current environment can provide vital understanding by emulating real-world load cases; however, to reduce uncertainty, it is important to isolate laboratory-...

The oscillating wave surge converter (OWSC) type devices (e.g., an Oyster wave energy converter) generate electric power via rotating motion about the bottom of the device. This type of wave energy converters have a wide power absorption bandwidth which enables the electricity generation at a wide range of wave frequencies. The power produced by th...

This paper reports the results of a study conducted to investigate how residual stresses generated during the manufacturing process and subsequent proof loading may affect the fatigue life of mooring chains. The present paper shows the quantitative predictions of residual stress field obtained from finite element models of the fabrication process,...

The study focuses on a high resolution coastal assessment for the Libyan Sea at the South-West Mediterranean. To date majority of information for the area, are based on large scale oceanic models with coarse resolutions not adequate for nearshore assessments. This dataset and analysis provides an in-depth wave energy resource assessment and detail...

As part of the Terawatt project, two regional-scale hydrodynamic models of the Pentland Firth & Orkney waters were developed using unaltered commercially-available software (MIKE 3 and Delft3D), in order to investigate the suitability of such software for predicting the effects of tidal stream energy development. Realistic scenarios for tidal energ...

Ocean waves have multidirectional components. Most wave measurements are taken at a single point, and so fail to capture information about the relative directions of the wave components directly. Conventional means of directional estimation require a minimum of three concurrent time series of measurements at different spatial locations in order to...

Wave energy is expected to play an important role in the forthcoming years for the de-carbonisation of Scottish and British electricity production. This study underlines the importance of resource assessment and attempts to improve the quantifiable wave power resource, with use of a validated numerical model. While levels of wave flux are high for...

The study enhances the coastal resource knowledge and discusses opportunities for wave energy in the Aegean Sea. A fine-resolution numerical wave model is utilised to provide results for the Greek coastal regions. The model ran for 35 years (1980–2014) estimating wave characteristics, and quantifying the wave energy potential in coastal areas. The...

A cumulative impact assessment of tidal stream developments in the Irish Sea has been conducted on a high-resolution depth-averaged hydrodynamic model, using Telemac2D. Eight sites were investigated, representing the proposed developments at the time of study. These included: Ramsey Sound, Anglesey, Strangford Loch, Mull of Kintyre, Torr Head, Fair...

Wind is the dominant process for wave generation. Detailed evaluation of metocean conditions, strengthen our understanding of issues concerning potential offshore applications. However, the scarcity of buoys and high cost of monitoring systems pose a barrier to properly defining offshore conditions. Through use of numerical wave models, metocean co...

This study reports the practicalities of applying a numerical model to assess the wave energy extraction at proposed development sites in Orkney Waters, Scotland. A state-of-the-art phase averaged spectral wave model, MIKE 21 Spectral Wave, in association with the wave-structure interaction software tool WAMIT, has been employed to study the impact...

This paper presents a detailed parametric analysis on various input parameters of two different numerical models, namely Telemac3D and Delft3D, used for the simulation of tidal current flow at potential tidal energy sites in the Pentland Firth in Scotland. The motivation behind this work is to investigate the influence of the input parameters on th...

• We describe a modelling project to estimate the potential effects of wave & tidal stream renewables on the marine environment. • Realistic generic devices to be used by those without access to the technical details available to developers are described. • Results show largely local sea bed effects at the level of the currently proposed renewables...

The offshore marine environment is home to numerous human activities, such as offshore structures, naval, construction, and maintenance operations. To ensure access and cost-effectiveness requires thorough investigation, in regards to the resource, and accessibility levels. The study presents a comprehensive 35 years resource assessment of the Medi...

Wave data analysis from a short-term deployment of a wave buoy and AWAC in the lee of a Hebridean island in the United Kingdom is discussed in this paper. Significant parameters are calculated and Rayleigh, Weibull and Kernel density probability distributions have been employed to fit the measured data. Results show that while the Atlantic facing s...

The work presented in this study explores the validity of the actuator disc method on the interactions of full size tidal stream devices using the finite element numerical model, Telemac3D. The momentum source in Telemac3D is implemented using the Reynolds-Averaged-Navier-Stokes (RANS) equations to model up to three 20-meter diameter turbines in a...

The implementation of the actuator disc approach for modelling tidal devices has been focused mainly on a very small domain, where the size of essential parameters such as the mesh density is often exaggerated. The work presented in this paper explores the methodology on the implementation of actuator disc approach via Reynolds-Averaged Navier Stok...

A genetic algorithm (GA) optimisation scheme is proposed to seek for the optimal spacing of wave energy convertors (WEC) arranged in arrays. The GA considers three spacing variables that define the arrays' configuration and seek for the optimal spacing by taking the maximum q-factor of the array as the objective function. On the other hand, the q-f...

The oscillating wave surge converter (OWSC) is a type of ocean wave power device typically consisting of a flap, or arm, hinged at the bottom to allow forward and backward movement by surging waves, and is efficient in generating electricity from waves due to its capability in operating at a wide range of wave spectra. The power generated from the...

Actuator disc is one of the simplest model used in simulating the presence of tidal devices. In recent years, three-dimensional RANS models have been employed in simulating the wake effects behind the actuator disc. Nonetheless, majority of these works were conducted on an extremely small scale domain, in which some of the parameters utilised were...

A background knowledge of marine dynamics helps to prepare for the implementation of tidal turbines. The present paper investigates the hydrodynamic conditions within the Pentland Firth and Orkney Waters, which is home to some of the fastest tidal currents in the world. The data obtained from ADCP field measurement surveys are compared with numeric...

Tidal energy is one of the emerging technologies and most promising resources of marine renewable energy. India has a very long coastline with estuarine and gulfs where the tides are strong enough to generate an electrical power. Gulf of Khambhat is located in the state of Gujarat is with a maximum tidal range of more than 11m and current velocity...

Waves are characterised by high energy density content, able to provide significant renewable energy contribution. Identification of wave energy potential locations around Europe can provide significant benefits for application of wave energy converters (WECs’). While the highest resources are placed in the open Atlantic coastlines of Europe that d...

Two-scale actuator disc theory is shown to predict qualitatively the performance of a lateral array of tidal turbines in a depth-averaged channel model. The agreement between the numerical and analytical models is improved by extrapolating the numerical results to zero background roughness. Increasing background roughness is shown to reduce the opt...

This article proceeds with investigations on a 5 MW direct-drive floating wind turbine system (FWTDD) that was developed in a previous study. A fully integrated land-based direct-drive wind turbine system (WTDD) was created using SIMPACK, a multi-body simulation tool, to model the necessary response variables. The comparison of blade pitch control...

Most fatigue loaded structural components are subjected to variable amplitude loads which must be processed into a form that is compatible with design life calculations. Rainflow counting allows individual stress cycles to be identified where they form a closed stress–strain hysteresis loop within a random signal, but inevitably leaves a residue of...

This paper presents the comparison of results from two open source 3D numerical models, namely Telemac3D and Delft3D, which are applied to the Pentland Firth and Orkney Waters in the United Kingdom. An extended description of the model setup is presented, with an elaboration on the physical and numerical parameters utilised in the models developmen...

In a previous theoretical paper submitted to EWTEC, the authors showed that the wave energy converter (WEC) wave field can be accurately and analytically represented by cylindrical linear waves with the appropriate coefficients. In that paper, the coefficients were found computationally using the boundary-element method software, WAMIT. For the pre...

A free surface semicircular breakwater (SCB) with rectangular perforations has been developed to serve as a wave defence structure. Hydrodynamic performance of the breakwaters of various perforations has been thoroughly investigated through wave measurements in a wave flume under random waves. The SCBs were experimentally confirmed to be good anti-...

The paper analyses the changes in wave conditions during wave propagation between intermediate and shallow water depths at a potential wave energy deployment location. The Outer Hebrides of Scotland in the United Kingdom are home to the world’s largest fully consented wave power project and hence a detailed understanding of the local resource is im...

This paper reports the methodology established in the application of a numerical wave model for hindcasting of wave conditions around the United Kingdom, in particular for Scottish waters, for the purpose of wave energy resource assessment at potential device development sites. The phase averaged MIKE 21 Spectral wave model has been adopted for thi...

Current circumstances globally, require a diverse mixture of energy sources; each country has to take advantage of its available resources. Renewable energy plays a significant role in the decarbonisation in future markets. One emerging technology that can be utilized by most Mediterranean countries is wave energy. Although estimated resources are...

Wave resource identification affects the decision making process for the deployment of offshore infrastructure and future marine energy projects. Investigating and identifying trends in the sea state for a location of interest is somewhat difficult, the interaction between shallow and deep waters influences, significantly the viability of future in...

Wave energy sites around Scotland, are considered one of the most energetic waters, as they are exposed to the Atlantic Ocean. The amount of energy reaching the shoreline provides an opportunity for wave energy deployments. Currently, considerations on wave devices expect them to be installed at nearshore locations. That means that the potential wa...

A frequency domain hydrodynamic assessment was carried out using WAMIT on buoy type wave energy converters (WECs), constrained to move in heave only. Control of the power take-off (PTO) system has been established through real control (damping resistance only) for an isolated WEC. This fixed value has then been applied to all WECs in an array of te...

Some preliminary results obtained from a coupled wave and 3D tidal flow numerical model, applied to the Orkney and Pentland waters in the Scottish region of the United Kingdom, are reported in this paper. The coupled wave and flow model was applied to the Orkney Islands comprising a domain of 1.25oW - 5oW and 58.25o N - 59.75oN. The model was run b...

A new concept floating breakwater was developed and tested to evaluate its hydrodynamic performance in this paper. This innovative floating breakwater has a rocking body shape which could also be used as a wave power device. A scale model was tested in a wave flume under regular and irregular wave conditions for various combinations of wave frequen...

This work forms the first of a two-part investigation aimed at identifying the challenges and opportunities of implementing a direct-drive generator for a spar-buoy type floating wind turbine. Preliminary specifications are presented for a fully coupled aero-hydro-servo-elastic model of a floating wind turbine with a 5MW direct-drive generator. The...

Any investigation of the interaction between marine renewables and their physical environment requires detailed information about the baseline wave resource. Hebridean Marine Energy Futures (HebMarine) have been conducting a high resolution spectral wave model of the Outer Hebrides of Scotland, site of several planned wave energy deployments. The s...

In this work, the suitability of a direct-drive radial flux permanent magnet generator is examined as a probable drive-train candidate for a stepped-spar floating wind turbine system that supports a 2 MW downwind turbine. The suitability of the generator is assessed based on the structural integrity of its design (i.e., the stability of the air-gap...

Knowledge of the wave field modification by a wave energy converter (WEC) is important to device and wave farm design. Cylindrical solutions to the linear wave field have long been used to analytically compute wave forces on circular-cylindrical geometries and have been the means of an important multi-body interaction theory. The cylindrical soluti...

Knowledge of the wave field modification by a wave energy converter (WEC) is important to device and wave farm design. Cylindrical solutions to the linear wave field have long been used to analytically compute wave forces on circular-cylindrical geometries and have been the means of an important multi-body interaction theory. The cylindrical soluti...

A semicircular breakwater model with rectangular perforations and with truncated wave screen(s) of different porosities has been developed in this study which could act as an anti-reflection wave barrier, providing wave protection to coastal and marine infrastructures. The hydrodynamic performance of the breakwater model is evaluated through wave m...