Scipedia: Julio García-Espinosa's papers in WoS journals

Thermo-mechanical analysis of laminated composites shells exposed to fire

Julio García-Espinosa — Sat, 13 Jul 2024 10:28:03 +0200

This paper describes the research performed within the scope of H2020 project FIBRESHIP in the development and validation of a thermo-mechanical model to assess the ﬁre performance of composite structures. A one-dimensional thermal model with pyrolisis is used to obtain the temperature prole across the thickness and later introduced in the thermomechanical model with a quadrilateral shell element approach. The composite constitutive model employed is the socalled Serial/Parallel Rule of Mixtures (SPROM) which has been modied to introduce the eﬀect of the thermal deformation. A set of experimental tests are then used to validate the correctness of the numerical method proposed. The experimental data used to validate the thermal model is the classic Henderson experimental test. The thermomechanical coupling is validated against an original vertical furnace test of a FRP ships bulkhead following on the 2010 FTP Code standards. These validations demonstrate the correctness and accuracy of the proposed decoupled thermomechanical formulation.

A Digital Twin for Assessing the Remaining Useful Life of Offshore Wind Turbine Structures

Julio García-Espinosa — Tue, 04 Jun 2024 18:40:02 +0200

This paper delves into the application of digital twin monitoring techniques for enhancing offshore floating wind turbine performance, with a detailed case study that uses open-source digital twin software. We explore the practical implementation of digital twins and their efficacy in optimizing operations and predictive maintenance, focusing on controlling the real-time structural state of composite wind turbine structures and forecasting the remaining useful life by tracking the fatigue state in the structure. Our findings emphasize digital twins’ potential as a valuable tool for renewable energy, driving efficiency and sustainability in offshore floating wind installations. These

aspects, along with the aforementioned simulations, whether in real-time or forecasted, reduce costly and unnecessary inspections and scheduled maintenance.

Methodology and application to assess thermo-mechanical buckling in composite marine structures

Julio García-Espinosa — Tue, 04 Jun 2024 18:28:02 +0200

This paper describes the research performed within the scope of H2020 project FIBRE4YARD in the development of a suitable thermo-mechanical framework to analyse composite structures under fire loads. The thermo-mechanical model uses the adiabatic temperature to obtain the through-thickness distribution of temperature of the triangular shell element, this formulation is able to predict phenomena such as pyrolysis, thermo-mechanical yielding and large displacements (non-linear buckling). An application case of a load-bearing section of a container ship is shown to demonstrate the correctness of the methodology, two type of materials are considered in the analysis, traditional materials such steel and advanced materials like fibre reinforced plastic (FRP) composites.

High Fidelity Hydroelastic Analysis Using Modal Matrix Reduction

Julio García-Espinosa — Tue, 04 Jun 2024 18:16:03 +0200

Structural assessment is a main concern when designing and operating any sort of offshore structure. This assessment is meant to ensure that the structural integrity is preserved along the lifespan of the asset, withstanding the worst sea-states that will be encountered and making sure that the accumulated fatigue damage will not jeopardize its structural integrity neither. The purpose of this paper is to present a fast and reliable hydroelastic model. This model is based on time-domain tight-coupling of a three-dimensional FEM (finite element method) linear structural model and a three-dimensional FEM seakeeping hydrodynamics model. In order to reduce the computational cost of structural dynamic simulations, the high-fidelity structural solution is projected onto the modal basis to obtain the modal matrix system and to extend the response amplitude operators (RAO) to the modal responses (MRAO). From there, the number of structural degrees of freedom can be greatly reduced by retaining only those eigenmodes preserving most of the structural elastic energy. The use MRAOs and/or the large reduction in structural degrees of freedom allows us to: first, quickly analyse the large number of loadcases required on the design stage; and second, to implement a digital twin for structural health monitoring in operational conditions. The paper also presents an application case of the developed methodology.

Numerical Framework for the Coupled Analysis of Floating Offshore Multi-Wind Turbines

Julio García-Espinosa — Tue, 04 Jun 2024 13:41:04 +0200

Floating Offshore Multi-Wind Turbines (FOMWTs) are an interesting alternative to the up-scaling of wind turbines. Since being new incoming concepts, there are few numerical tools for its coupled dynamic assessment at the present time. In this work, a numerical framework is implemented for the simulation of multi-rotor systems under environmental excitations. It is capable to analyse a platform with leaning towers handling wind turbines with their own features and control systems. This tool is obtained by coupling the seakeeping hydrodynamics solver SeaFEM with the single wind turbine simulation tool OpenFAST. The coupling of SeaFEM provides a higher fidelity hydrodynamic solution allowing the simulation of any structural design since using the Finite Element Method (FEM). Besides, a methodology is proposed for the extension of the single wind solver, allowing the analysis of multi-rotor configurations. To do so, the solutions of the wind turbines are computed independently by several OpenFAST instances, performing its dynamic interaction through the floater. The method is applied to the single turbine Hywind concept and the twin-turbine W2Power floating platform, supporting NREL 5-MW wind turbines. The rigid-body Response Amplitude Operators (RAOs) are computed and compared with other numerical tools. The results showed consistency in the developed framework. Agreement is also obtained in simulations with aerodynamic loads. This resulting tool is a complete time-domain aero-hydro-servo-elastic solver, able to compute the combined response and power generation performance of multi-rotor systems.

Fully 3D ship hydroelasticity: monolithic versus partitioned strategies for tight coupling

Julio García-Espinosa — Wed, 13 Oct 2021 17:28:04 +0200

This paper analyzes the partitioned and monolithic strategies to simulate tightly coupled hidroelastic problems. The seakeeping hydrodynamics solver used is based on a first-order linear time-domain FEM model with forward speed and double-body linearization. The structural dynamics solver is based on a full 3D time-domain FEM with corotational shell elements accounting for the geometric non-linearity. Both solvers are implemented under the same programming framework, which allows to implement the monolithic strategy, and to minimize the communication overheads of the partitioned strategy. Two case studies are used to test and compare the partitioned and monolithic coupling: a flexible catamaran in oblique waves, and a large floating reticulated structure made of fiber reinforced plastic. In both cases, the monolithic strategy is between three and four times faster than the partitioned strategy. This project has been developed under the H2020 project FIBRESHIP aimed at developing the technology to design and build the structure of large-length vessels in fiber reinforced polymers.

A time-domain second-order FEM model for the wave diffraction-radiation problem. Validation with a semisubmersible platform

Julio García-Espinosa — Mon, 04 Nov 2019 20:13:06 +0100

A finite element method for the solution of the up-to-second-order wave diffraction-radiation problem in the time-domain is proposed. The solver has been verified against available analytical solutions, and validated against experimental data available for the HiPRWind semisubmersible platform (designed for floating wind turbines). To perform the validation, the wave diffraction-radiation solver is coupled to a body dynamics and mooring solvers in the time-domain. The HiPRWind movements and mooring forces have been compared for a large number of test cases, including decay tests, monochromatic waves, and bichromatic waves obtaining good agreement for both, body movements and mooring forces.

A Second Order Semi-Lagrangian Particle Finite Element Method for Fluid Flows

Julio García-Espinosa — Wed, 03 Jul 2019 13:04:04 +0200

In this paper, a second order SL-PFEM scheme for solving the incompressible Navier-Stokes equations is presented. This scheme is based on the second order velocity Verlet algorithm, which uses an explicit integration for the particle’s trajectory and an implicit integration for the velocity. The algorithm is completed with a predictor-multicorrector scheme for the integration of the velocity correction using the Finite Element Method. A second order projector based on least squares is used to transfer the intrinsic variables information from the particles onto the background mesh, while a second order interpolation scheme is used to transfer the accelerations from the mesh to the particles. Convergence analyses are carried out to assess the second order convergence.

Seakeeping with the semi-Lagrangian particle finite element method

Julio García-Espinosa — Thu, 11 Apr 2019 19:11:02 +0200

The application of the semi-Lagrangian particle finite element method (SL–PFEM) for the seakeeping simulation of the wave adaptive modular vehicle under spray generating conditions is presented. The time integration of the Lagrangian advection is done using the explicit integration of the velocity and acceleration along the streamlines (X-IVAS). Despite the suitability of the SL–PFEM for the considered seakeeping application, small time steps were needed in the X-IVAS scheme to control the solution accuracy. A preliminary proposal to overcome this limitation of the X-IVAS scheme for seakeeping simulations is presented.

A real-time decision support system for the adjustment of sailboat rigging

Julio García-Espinosa — Thu, 11 Apr 2019 19:08:02 +0200

The operational complexity and performance requirements of modern racing yachts demand the use of advanced applications, such as a decision support system (DSS) able to assist crew members during navigation. In this article, the authors describe a near-time computational solver as the main piece of a DSS which analyses and monitors the behaviour of sails and rigging. The solver is made up of two different interconnected tools: an iterative FluidStructure Interaction algorithm and an advanced Wireless Sensor Network to monitor rigging. The real-time DSS quantifies crew manoeuvres in physical terms, which are reproduced by a simulation program. It can be used in the design phase of sailing yachts and as an aid for realtime boat performance optimisation and accident prevention. This novel DSS is a useful tool for navigation, especially in races.

Tool development based on FAST for performing design optimization of offshore wind turbines: FASTLognoter

Julio García-Espinosa — Thu, 11 Apr 2019 19:06:02 +0200

The new engineering FASTLognoter software is presented. This code is essentially the result of the integration of two tools, along with some additional features. Theﬁrst basis tool is FAST (developed by NREL), a comprehensive aeroelastic simulator code for wind turbines. The second basis tool is Lognoter (developed by CompassIS), a general-purpose commercial software for managing and creating engineering forms. The integration of FAST and Lognoter gives a useful, comprehensive and versatile toolkit, which is veriﬁed in this work by means of bibliographic documented cases. An important advantage of the tool presented is the parametric design capability, allowing the user of FAST/AeroDyn/HydroDyn codes to analyze a massive group of cases; therefore, optimal design can be carried out.

On the interpolation of normal vectors for triangle meshes

Julio García-Espinosa — Thu, 11 Apr 2019 18:59:02 +0200

This paper analyzes the problem arising from the need to assign information about the normal vectors to the surface at the nodes of a mesh of triangles. Meshes of triangles do not have normals uniquely defined at the nodes. A widely used technique to compute the normal direction at any given node is to compute the weighted average of the normals of each surrounding triangle. The present study proposes new weighting factors to compute the normal directions at the nodes of the mesh of triangles of a general surface. Previous weights found in the literature used the geometric dimensions of the triangles themselves to design the weighting factors. The new factors are proposed using the triangles’ circumscribed circles dimensions. The new weights provide superior results than the ones obtained by previous best practices for a wide range of surfaces. An advanced framework based on the approachability of smooth surfaces by quadrics is presented and used. This framework helps to understand the improved performance of the presented factors with respect to other factors found in the literature. A comprehensive numerical comparison analysis is performed, and the most precise of all factors is clearly identified.

Simulation of Water Circulation over a Model of a Submarine Canyon by Using FIC-FEM Numerical Model

Julio García-Espinosa — Thu, 11 Apr 2019 18:56:02 +0200

A set of numerical model experiments has been conducted to simulate the circulation driven by oscillatory forcing over a theoretical continental slope configuration used previously in laboratory experiments. The test case considered was the numerical simulation of the flow over a model of a submarine canyon, and the numerical model used in the analysis was a coastal ocean model version based on an adaptation of the finite-calculus–finite-element method (FIC-FEM) approach implemented in the commercial package Tdyn. Two cases were analyzed involving changes in fluid density. Structured and unstructured finite-element spatial discretizations were generated for the same study domain to compare the resulting velocity field with outputs from the laboratory experiments and to assess which mesh provided a better representation of the complex geometry of the channel model and the water circulation process. The comparison between the laboratory results from the reference article and the output of the numerical model showed good agreement in the structure and magnitude of the phaseaveraged and residual velocity fields.

Analysis of a consistency recovery method for the 1D convection–diffusion equation using linear finite elements

Julio García-Espinosa — Thu, 11 Apr 2019 18:46:02 +0200

For residual-based stabilization methods such as streamline-upwind Petrov–Galerkin (SUPG) and ﬁnite calculus (FIC), the higher-order derivatives of the residual that appear in the stabilization term vanish when simplicial elements are used. The sub-grid scale method using orthogonal sub-scales (OSS) attempts to recover the lost consistency by using a ﬁne-scale projected residual in the stabilization term. The FIC method may also be cast into an OSS form with very little manipulation using an auxiliary convective projection equation. This paper discusses the gain/loss by recovering the consistency of the discrete residual in the stabilization terms via the form that includes the convective projection (as in the OSS method). We present the von Neumann analysis of the FIC method with recovered consistency (FIC RC) for the 1D convection–diffusion problem and we compare it with the standard Bubnov–Galerkin linear ﬁnite element method and FIC/SUPG methods. The transient analysis is done by examining the discrete dispersion relation of the stabilization methods. The spectral results for the semi-discrete and fully discrete problem are presented with time integration done by the trapezoidal and second-order backward differencing formula schemes. The effect of lumping the effective mass matrix T is considered relative to using a consistent form. The effect of reﬁnement in space and time is also discussed. Finally, an optimal expression for the stabilization parameter for the FIC RC method on a uniform grid and for the steady state is given and its performance in the transient mode is discussed.

Computation of turbulent flows using a finite calculus–finite element formulation

Julio García-Espinosa — Thu, 11 Apr 2019 18:41:02 +0200

We present a formulation for analysis of turbulent incompressible flows using a stabilized finite element method (FEM) based on the finite calculus (FIC) procedure. The stabilization terms introduced by the FIC approach allow to solve a wide range of fluid flow problems at different Reynolds numbers, including turbulent flows, without the need of a turbulence model. Examples of application of the FIC/FEM formulation to the analysis of 2D and 3D incompressible flows at large Reynolds numbers exhibiting turbulence features are presented.

Modeling incompressible flows at low and high Reynolds numbers via a finite calculus–finite element approach

Julio García-Espinosa — Thu, 11 Apr 2019 18:33:03 +0200

We present a formulation for incompressible ﬂows analysis using the ﬁnite element method (FEM). The necessary stabilization for dealing with convective eﬀects and the incompressibility condition is modeled via the ﬁnite calculus (FIC) method. The stabilization terms introduced by the FIC formulation allow to solve a wide range of ﬂuid ﬂow problems for low and high Reynolds numbers ﬂows without the need for a turbulence model. Examples of application of the FIC/FEM formulation to the analysis of 2D and 3D incompressible ﬂows with moderate and large Reynolds numbers are presented.

Finite calculus formulations for finite element analysis of incompressible flows. Eulerian, ALE and Lagrangian approaches

Julio García-Espinosa — Thu, 11 Apr 2019 18:30:02 +0200

We present a general formulation for incompressible ﬂuid ﬂow analysis using the ﬁnite element method (FEM). The standard Eulerian formulation is described ﬁrst. The necessary stabilization for dealing with convective eﬀects and the incompressibility condition are introduced via the ﬁnite calculus (FIC) method. A simple extension of the ﬂuid ﬂow equations to an arbitrary Lagrangian–Eulerian (ALE) frame adequate for treating ﬂuid–structure interaction problems is brieﬂy presented. A fully Lagrangian formulation called the particle ﬁnite element method (PFEM) is also described. The PFEM is particularly attractive for ﬂuid–structure interaction problems involving large motions of the free surface and breaking waves. Examples of application of the Eulerian, the ALE and the fully lagrangian PFEM formulations are presented.

An unstructured finite element solver for ship hydrodynamics problems

Julio García-Espinosa — Wed, 10 Apr 2019 22:07:03 +0200

A stabilized semi-implicit fractional step algorithm based on the ﬁnite element method for solving ship wave problems using unstructured meshes is presented. The stabilized gov-erning equations for the viscous incompressible ﬂuid and the free surface are derived at a differential level via a ﬁnite calculus procedure. This allows us to obtain a stabilized numerical solution scheme. Some particular aspects of the problem solution, such as the mesh updating procedure and the transom stern treatment, are presented. Examples of the efﬁciency of the semi-implicit algorithm for the analysis of ship hydrodynamics problems are presented.

A finite element method for fluid-structure interaction with surface waves using a finite calculus formulation

Julio García-Espinosa — Wed, 10 Apr 2019 21:26:41 +0200

A stabilized semi-implicit fractional step finite element method (FEM) for solving coupled fluid-structure interaction problems involving free surface waves is presented. The stabilized governing equations for the viscous incompressible fluid and the free surface are derived at a differential level via a finite calculus (FIC) procedure. A mesh updating technique based on solving a fictitious elastic problem on the moving mesh is described. Examples of the efficiency of the stabilized semi-implicit algorithm for the analysis of fluid-structure interaction problems in totally or partially submerged bodies is presented.

Computation of the stabilization parameter for the finite element solution of advective–diffusive problems

Eugenio Oñate — Fri, 11 Jan 2019 12:14:02 +0100

In a previous paper a general procedure for deriving stabilized finite element schemes for advective type problems based on invoking higher order balance laws over finite size domains was presented. This provides an expression for the element stabilization parameter in terms of the solution residual and its first derivatives in a kind of iterative or adaptative manner. Details of the application of this procedure to 1D and 2D advective- diffusive problems are given. Some examples of applications showing the potential of the new approach are presented.