Eva Loukogeorgaki

• PhD
• Professor (Associate) at Aristotle University of Thessaloniki

With the rapid development of offshore renewable energy technologies, open source solvers for hydrodynamic analysis can become beneficial to meet the numerical challenges within the field, particularly when they are both accurate and computationally efficient. Hydrodynamic Analysis of Marine Structures (HAMS), a recently developed open source Bound...

This paper presents a hydrodynamic investigation carried out on the “Wave Attenuator” device, which is a new type of floating breakwater anchored with piles and equipped with a linear Power Take Off (PTO) mechanism, which is typical for wave energy converters. The device is tested in the wave flume, under regular waves, in slightly non-linear condi...

The aim of this paper is to analyse the steel bearing structure of a combined offshore wind and wave energy exploitation system. More specifically, the investigation focuses on the effect of the Wave Energy Converters (WECs) on the bearing capacity of the Offshore Wind Turbine (OWT) to which they are attached by steel arms. Initially, the power abs...

The Lancaster in-house code is a time-domain analysis code, developed especially for the TALOS wave energy converter, a novel wave energy conversion technology. The TALOS wave energy converter is a point absorber-like wave energy converter, but with a unique power take-off (PTO) system. The whole PTO system is fully enclosed within the structure, h...

This paper focuses on the preliminary time-domain analysis of a multi-mode Wave Energy Converter (WEC), the so-called TALOS WEC, by deploying two different computational tools. The device consists of an internal sphere attached to its floater with springs and dampers, and power is captured through the sphere's motions relatively to the floater. The...

In the present paper, a generic numerical tool for the time-domain analysis of a floating Hybrid OffshoreWind and Wave Energy System (HOWiWaES), consisting of a Floating Offshore Wind Turbine(FOWT) and several Wave Energy Converters (WECs) is developed and is preliminary validated. Thefloating platform and the WECs are modeled as one multi-componen...

Ports, coastal and offshore structures play a strategic role in the socioeconomic development of citizens in Europe and worldwide, facilitating the sustainable and secure implementation of various human activities, such as transportation, fishing, leisure, aquaculture, and the protection of coastal areas and the exploitation of energy sources in th...

In the present paper, we introduce a decision-support framework to (a) classify and prioritize the municipalities of a country based on their suitability to host PV energy projects and (b) pinpoint and evaluate suitable technically and economically viable, as well as environmentally and socially sustainable, sites for PV installation in the most su...

The present study investigates the design of an offshore wind turbine in North Aegean. The proposed location, east of Lemnos, is in accordance with the Greek strategic framework of 2015, which has been developed based on sustainability, strategy policy, and buildability axes. A monopile foundation is investigated to support structurally an 5 MW off...

In this paper, an integrated methodology is developed to determine optimum areas for Photovoltaic (PV) installations that minimize the relevant visual disturbance and satisfy spatial constraints associated with land use, as well as environmental and techno-economic siting factors. The visual disturbance due to PV installations is quantified by intr...

Wave Energy Converters (WECs) are expected to significantly contribute to the energy transition; however, this depends on their interactions with the resource. Calculating the power generated by WECs depends heavily on the accurate modelling of wave-structure interactions. The Boundary Element Method (BEM) based on the potential flow theory has yie...

In this paper, we assess numerically the loads applied on PAs of optimally-arranged linear arrays in front of a bottom-mounted vertical wall of finite length under normal operating conditions. The arrays, maximizing the yearly absorbed energy, consist of five, identical, oblate spheroidal heaving PAs and are deployed at three near-shore sites in th...

Offshore solar energy presents a new opportunity for low-carbon energy transition. In this research, we identify and rank suitable Offshore Solar Farm (OSF) sites in the Aegean Sea, Greece, considering various constraints and assessment criteria. The methodology includes two distinct phases. In the first phase, Geographic Information Systems (GIS)...

In the present work, a Boussinesq-type numerical model is developed for the simulation of nonlinear wave-heaving cylinder interaction. The wave model is able to describe the propagation of fully dispersive and weakly nonlinear waves over any finite water depth. The wave-cylinder interaction is taken into account by solving simultaneously an ellipti...

The public acceptance of Offshore Wind Farms (OWFs) is an important issue that is expected to depend highly on their site location. Public involvement in decision-making processes is recommended as it may contribute to the mitigation of opposing, delaying and even blocking OWF projects, as well as increasing future public confidence and support. Th...

The present paper aims at determining optimum layouts for a cluster of identical semi-immersed oblate spheroidal heaving Point Absorbers (PAs) in front of a bottom-mounted wall-type structure under the action of regular waves. Optimum layouts correspond to those that for a given incident wave frequency and direction maximize the power absorbed by t...

Wave Energy Converters (WEC) have seen a wide variety of innovations capable to harness the vast untapped energy source of the seas. This wide range of WECs often has varied applicability and power production capabilities, making the selection of a device overwhelming. These uncertainties are increased when considering the interactions and suitabil...

The present paper focuses on the determination of optimum layouts for linear arrays of heaving Wave Energy Converters (WECs) in front of a vertical wall. Optimum layouts maximize the annual averaged absorbed energy at a given marine site and satisfy spatial constraints. For achieving this goal, we developed an efficient optimization numerical frame...

In this paper, we determine optimum layouts of a cluster of oblate spheroidal heaving point absorbers in front of a wall, that maximize the annual averaged power absorbed by the cluster, while satisfying specific spatial constraints. An iterative optimization process is developed by coupling a hydrodynamic model with a genetic algorithms solver. Op...

In this paper, linear frequency-domain hydroelastic analysis is performed to investigate the behavior of the spar-type supporting platform of a floating offshore wind turbine, considering the platform’s flexibility. A “dry” mode superposition approach is used, wherein the flexible mode shapes are determined through the application of a finite eleme...

In this work, an innovative sustainable spatial energy planning framework is developed on national scale for identifying and prioritizing appropriate, technically and economically feasible, environmentally sustainable as well as socially acceptable sites for the siting of large-scale onshore Wind Farms (WFs) and Photovoltaic Farms (PVFs) in Israel....

In this paper, we investigate, in the frequency domain, the performance (hydrodynamic behavior and power absorption) of a circular array of four semi-immersed heaving Wave Energy Converters (WECs) around a hybrid wind–wave monopile (circular cylinder). The diffraction/radiation problem is solved by deploying the conventional boundary integral equat...

The main objective of this study is to develop a semi-analytical formulation for the hydrodynamic diffraction and radiation problems of a fully submerged spheroid. The term “spheroid” refers here to the oblate geometry of arbitrary eccentricity and to the axisymmetric configuration, i.e. the spheroid’s axis of symmetry is oriented perpendicular to...

The main objective of this study is to develop a semi-analytical formulation for the radiation problem of a fully immersed spheroid in a liquid field of infinite depth. The term “spheroid” refers herein to the oblate geometry of arbitrary eccentricity and to the axisymmetric case, where the axis of symmetry is normal to the free surface. The propos...

This study focuses on the determination of optimum layout configurations for a linear array of identical mutually interacting truncated cylinders. Optimum configurations correspond to those that maximize either the total heave exciting force acting on all cylinders of the array or the heave exciting force applied on pairs of cylinders within the ar...

In the present paper, a nesw Floating Wave Energy Converter System (FloWECS), consisting of a floating platform and multiple rotating flaps, is proposed and is preliminary investigated. The numerical analysis is implemented in the frequency domain under the action of regular head and oblique incident waves and it is based on a “dry” mode superposit...

In the present article, a new methodological framework for the efficient and sustainable exploitation of offshore wind potential was developed. The proposed integrated strategic plan was implemented for the first time at national spatial planning scale in Greece. The methodological approach is performed through geographical information systems (GIS...

This study exploits the Touvia Miloh oblate spheroid theorem with a special focus on hydrodynamical applications. The theorem provides explicit relations that express the oblate spheroidal harmonics, given in terms of the fundamental solutions of the Laplace equation. Here, the theorem is employed to transform the underlying Green’s function into t...

In this paper, we investigate the performance of a linear array of five semi-immersed, oblate spheroidal heaving Wave Energy Converters (WECs) in front of a bottom-mounted, finite-length, vertical wall under perpendicular to the wall regular waves. The diffraction and radiation problems are solved in the frequency domain by utilizing the convention...

In the present paper, the hydrodynamic performance of a linear array of truncated circular cylinders in front of a bottom–mounted vertical wall is analysed in the frequency domain in order to investigate the effect of the wave reflections combined with the disturbances induced by the bodies themselves. Infinite and finite-length wall cases are exam...

In this paper, linear frequency-domain hydroelastic analysis is performed for investigating the behavior of a spar-type supporting platform of a floating offshore wind turbine considering the platform's flexibility. A "dry" mode superposition approach is utilized, where the flexible mode shapes are determined through the application of a FEM based...

The deployment of suitable configurations of mutually interacting floating bodies for efficiently controlling their hydrodynamic interactions towards the reduction of the wave drift forces and, thus, of the mooring lines’ loads, has, nowadays, gained a great scientific interest. In this paper, the hydrodynamic behaviour of a floating cylinder and a...

This paper presents a methodological framework for evaluating marine areas in Greece for the purpose of identifying the most adequate sites for Hybrid Offshore Wind and Wave Energy Systems (HOWiWaES), with special focus on the HOWiWaES’ environmental impact assessment evaluation. Nine evaluation criteria that reflect various environmental, economic...

In the present paper, a computational tool (FloaTWEC tool) is developed for the time-domain analysis of a floating oscillating-body Wave Energy Converter (WEC). Assuming a floating body with six rigid-body modes, the WEC's response is calculated based on the well-known Cummins equation, where fluid memory effects are captured through appropriate co...

In this paper, linear and frequency-domain hydroelastic analysis is performed for investigating the behavior of a free floating, annular and flexible plate. A “dry” mode superposition approach is utilized, where the flexible mode shapes are determined through the derivation of analytical expressions. The diffraction/radiation problem is solved usin...

The present paper focuses on the numerical investigation and the assessment of finite water depth effects on the performance (hydrodynamic behavior and energy absorption) of a wave farm. The farm consists of nine, free floating, mutually interacting, heaving Wave Energy Converters (WECs), arranged in a 3x3 rectilinear grid. The WECs’ Power Taking O...

In this paper, the effect of an Offshore Wind Farm (OWF) on the surrounding wave field is numerically investigated in the frequency domain through the use of a Boundary Element Method (BEM) numerical model based on the potential flow theory. The analysis is performed for regular waves of various periods and incident wave directions and for irregula...

In this paper, the hydrodynamic interaction effects and the performance (hydrodynamic behavior and power absorption) of an offshore wave farm, consisting of nine, free floating heaving WECs, under the action of head and oblique regular and irregular waves are numerically investigated. Focus is given on the effect of: (a) the incident wave direction...

The deployment of Hybrid Offshore Wind and Wave Energy Systems (HOWiWaES) towards the simultaneous exploitation of the corresponding offshore renewable energy sources, may efficiently address the common challenge of the offshore wind and the wave energy sector to reduce their costs, with multiple additional benefits. A prerequisite at an early stag...

In this paper, 3D experiments are conducted aiming at the combined investigation of the hydroelastic and the structural (connectors' internal forces) response of a pontoon-type modular Floating Breakwater (FB), consisting of flexibly connected, moored with chains modules, under the action of perpendicular and oblique regular waves. Regarding the FB...

In this paper, the condition and the behavior of an installed and operating Modular Floating Structure (MFS) is investigated and assessed by harnessing field monitoring data and using collectively multiple Correlation Coefficients (CCs) between measured quantities. The examined MFS consists of five pairs of interconnected floating concrete modules...

This paper presents the results of an experimental campaign regarding the hydrodynamic loading on a three-legged jacket support structure of offshore wind turbines. The campaign aims to the assessment of the violent hydrodynamic impact on the structure due to impulsive loading, which occurs in a sudden liquid-structure collision. The experiments we...

In this paper, the effect of climate change on the design of horizontal composite breakwaters is investigated. A methodological framework is developed that integrates analytical solutions with numerical models towards the efficient design of the rubble-mound multilayered part of the examined structures under the effect of climate change impacts (me...

In this paper, the effect of an Offshore Wind Farm (OWF) on the surrounding wave field is numerically investigated in frequency domain, using a BEM numerical model based on the potential flow theory. The analysis is performed for regular waves of various periods and incident wave directions and for irregular waves with variable peak period and sign...

In the present paper, three-dimensional finite element analyses of tripod skirted foundations for offshore wind turbines are presented. Combined (vertical – horizontal – moment) loading under undrained conditions is considered and the undrained bearing capacity of the foundations is calculated. Emphasis is given on the investigation of the effect o...

The effect of different modeling techniques of the local joint flexibility on the local dynamics of a jacket support structure for an offshore wind turbine is investigated. Two numerical models of a jacket supporting a generic turbine are analyzed in the aero-hydro-servo-elastic tool ADCoS-Offshore. The first model is set up with Euler-Bernoulli be...

in offshore structures. Therefore, the investigation of the effect of corrosion in their life-time structural reliability is considered of great importance for the optimization of the maintenance schemes. In this paper an approach is proposed for the estimation of the long term process of corrosion in offshore structures based on a contemporary lon...

The effect of different modeling techniques of the local joint flexibility on the local dynamics of a jacket support structure for an offshore wind turbine is investigated. Two numerical models of a jacket supporting a generic turbine are analyzed in the aero-hydro-servo-elastic tool ADCoSOffshore. The first model is setup with Euler-Bernoulli beam...

In this paper, a 3D experimental and numerical investigation of the performance of a Pontoon-type Floating Structure (PFS) is implemented focusing on: (a) the validation of the applied numerical modeling and (b) the analysis of the wave characteristics’ effect on mooring lines’ tension and PFS’ hydroelastic response. 3D experiments are conducted fo...

The objective of the present paper is the implementation of 3D experiments in order to investigate and assess the structural response (connectors' internal forces and mooring lines' tensions) of a Floating Breakwater (FB) along with its wave attenuation effectiveness under the action of perpendicular and oblique regular and irregular waves. The exa...

In this paper, 3D linear “Dry” and “Wet” Mode Superposition Approaches (DMSA and WMSA) for the frequency domain hydroelastic analysis of Floating Structures (FSs) are compared and assessed. The Present WMSA (PWMSA) enables the consideration of “wet” natural frequencies and “wet” mode shapes through the appropriate solution of a nonlinear (due to fr...

In practice, in some cases, tandemly applied pile-mounted horizontal or inclined thin plates emerge as functional coastal structures in terms of diminishing wave height in front of Rubble Mound Breakwaters (RMBs) and consequently, reduce the required armor unit size and RMB's overall weight. In this study, the hydrodynamic performance of an Incline...

In the present paper, the effect of tendons' material on the dynamic behavior of a Tension Leg Platform (TLP) is investigated in both frequency and time domain. Specifically, uncoupled frequency domain and uncoupled and coupled time domain analyses are preformed. Three different types of material with different modulus of elasticity are taken into...

In this paper, the dynamic behavior of a single free span pipeline is analyzed and the effect of various factors/parameters (different design conditions, wave and current characteristics, soil characteristics, length of the free span and boundary conditions at the ends of the pipeline) on its dynamic behavior and its structural integrity is investi...

During their operation life-cycle, tension leg platforms (TLPs) may experience, under wave and wind loading, response amplitudes that affect their operational and structural reliability. Uncertainties related to the excitation characteristics (for example significant wave height or zero up-crossing period) or to the TLP-model properties (for exampl...

In the present paper a recently installed Sensor Network for Monitoring the Response (SNMR) of a Floating Structure (FS) is presented. SNMR is deployed on a pontoon-type FS operating as a floating breakwater, located 300m from the coast in the port of Neos Marmaras in Greece. The developed SNMR consists of: (i) sensors for real time measurement of...

A simulation-based framework is discussed in this paper for quantification/evaluation of risk and development of automated risk assessment tools, focusing on applications to offshore wind turbines under extreme environmental conditions. The framework is founded on a probabilistic characterization of the uncertainty in the models for the excitation,...

In this paper, 3D experiments are conducted focusing on the structural response (connectors’ and mooring lines’ loads) assessment of a Floating Breakwater (FB) under the action of normal and oblique regular waves. The FB consists of floating modules connected with flexible connectors and moored with chains. The effect of the incident wave character...

In practice, in some cases, tandemly applied pile-mounted horizontal or inclined thin plates emerge as functional coastal structures in terms of diminishing wave height in front of Rubble Mound Breakwaters (RMBs) and consequently, reduce the required armor unit size and RMB’s overall weight. In this study, the hydrodynamic performance of an Incline...

Motivation: Risk assessment has been performed in a fragmented way creating problems with interfaces and quantification. A consistent methodology for risk quantification is required. Main Results: The new IRIS Risk Paradigm provides a conceptual framework for consistent harmonized risk assessment and quantification.

In this paper, a numerical tool (MicroSAS-OWT) for the integrated analysis of Offshore Wind Turbines (OWTs) with fixed-bottom support structure of arbitrary shape is presented. MicroSAS-OWT is developed through the coupling of FAST with MicroSAS. FAST is used for modeling the rotor nacelle assembly, while the tower and the support structure are mod...

A comprehensive, versatile framework is discussed for analysis and design of offshore energy (waves and/or wind) conversion devices in presence of modeling uncertainties. The framework is founded on a probabilistic characterization of the uncertainty in the models for the excitation, the system (wave energy conversion device) and its performance. S...

A comprehensive, versatile framework is discussed for analysis and design of offshore energy (waves and/or wind) conversion devices in presence of modeling uncertainties. The framework is founded on a probabilistic characterization of the uncertainty in the models for the excitation, the system (wave energy conversion device) and its performance. S...

In the present paper hydroelastic analysis of a flexible Floating Structure (FS) is performed under the action of oblique regular waves in order to investigate and evaluate: (a) the FS's hydroelastic response and (b) the FS's axial and shear forces. The FS consists of a grid of floating modules connected to each other with flexible connectors in bo...

In this paper, the significance of the inclusion of the wave frequency dependent added mass, additionally, to the hydrostatic-gravitational stiffness in the hydroelastic analysis of flexible Floating Structures (FSs) is demonstrated and investigated. The numerical approach includes the application of a 3D structural model (eigenvalue analysis), a 3...

In this paper, linear hydroelastic analysis is performed in order to investigate the dynamic response and the effectiveness of a new type of Floating Breakwaters (FBs) that consists of a grid of flexible floating modules connected with flexible connectors in longitudinal and transverse directions. This analysis is performed with a 3D structural mod...

In this paper a numerical model is developed for the status identification and optimum adjustment of the performance of a moored floating breakwater (MFB) during its operation. The optimum adjustment is achieved through the appropriate modification of the current total unstretched length of the mooring lines, Lcurtot. The model consists of 2 module...

The performance of free and moored twin-pontoon floating breakwaters, under the action of normal incident waves, is investigated in frequency domain. For moored twin-pontoon floating breakwaters, the 3D hydrodynamic analysis of the floating body is coupled with the static and dynamic analysis of the mooring lines. Regarding free twin-pontoon floati...

In this paper a numerical model capable of optimizing the performance of a Moored Floating Breakwater (MFB) through the appropriate modification of the current total unstretched length of the mooring lines, L totcur, is developed. The model consists of two modules. The first one includes the identification of the current status of the MFB, which is...

In the present paper a Multi-Layer Perceptron (MLP) model capable of identifying the current status (expressed with the total unstretched length of the mooring lines) of a Moored Floating Breakwater (MFB), for a given wave frequency and for given amplitudes of the accelerations of the MFB's degrees of freedom is developed. Each status of the MFB is...

The aim of this paper is to assess the application of four Case Studies of Special Coastal and Inland Water Floating Structures (SCIWFS) in northern Greece, in terms of functionality and environmental protection. For each Case Study the selection criteria that advocate the application of SCIWFS, their technical characteristics and their functional...

In this paper the performance of moored floating breakwaters under the action of normal incident waves is investigated in frequency domain. A 3-dimensional hydrodynamic model is coupled with a static and dynamic model of the mooring lines, using an iterative procedure. The models are validated through comparison with numerical and experimental resu...

In the present paper, the performance of a moored floating breakwater under the action of normal incident waves is investigated in the frequency domain. A three-dimensional hydrodynamic model of the floating body is coupled with a static and dynamic model of the mooring lines, using an iterative procedure. The stiffness coefficients of the mooring...

A new strategic vision of the extensively debated European higher education is proposed with focus on civil engineering. Civil engineering education for the future is considered with relevance to potential world-wide trends and anticipated societal requirements and, therefore, required employee qualifications of the construction-related providers t...

In the present paper the effect of mooring lines' stiffness and damping on the performance of moored floating breakwaters under the action of normal incident waves is investigated in frequency domain. A three dimensional hydrodynamic model is coupled with a static and dynamic model of the mooring lines, using an iterative procedure. An extensive pa...