
Ido AkkermanDelft University of Technology | TU · Department of Maritime and Transport Technology (M&TT)
Ido Akkerman
PhD Aerospace Eng. TU Delft
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62
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Introduction
Additional affiliations
August 2014 - present
October 2012 - July 2014
February 2009 - September 2012
Publications
Publications (62)
Over the last decades, many diffuse-interface Navier–Stokes Cahn–Hilliard (NSCH) models with non-matching densities have appeared in the literature. These models claim to describe the same physical phenomena, yet they are distinct from one another. The overarching objective of this work is to bring all of these models together by laying down a unif...
In this paper we propose a space-time framework for the computation of periodic flows. We employ the isogeometric analysis framework to achieve higher-order smoothness in both space and time. The discretization is performed using residual-based variational multiscale modelling and weak boundary conditions are adopted to enhance the accuracy near th...
In this work we present a novel monolithic Finite Element Method (FEM) for the hydroelastic analysis of Very Large Floating Structures (VLFS) with arbitrary shapes that is stable, energy conserving and overcomes the need of an iterative algorithm. The new formulation enables a fully monolithic solution of the linear free‐surface flow, described by...
In this work we present a novel monolithic Finite Element Method (FEM) for the hydroelastic analysis of Very Large Floating Structures (VLFS) with arbitrary shapes that is stable, energy conserving and overcomes the need of an iterative algorithm. The new formulation enables a fully monolithic solution of the linear free‐surface flow, described by...
In this work we present a novel monolithic Finite Element Method (FEM) for the hydroelastic analysis of Very Large Floating Structures (VLFS) with arbitrary shapes that is stable, energy conserving and overcomes the need of an iterative algorithm. The new formulation enables a fully monolithic solution of the linear free-surface flow, described by...
Floating offshore structures are of great interest for many applications. A particular type
of floating structures are the so called Very Large Floating Structures (VLFS). One can find several examples of VLFS, such as floating airports, floating solar energy installations,
floating breakwaters, or even futuristic floating modular cities. The stud...
This paper provides an evaluation on the suitability of the Greenheart Project vessel design for the Pacific Islands and proposes adaptations for an improved design that is specifically tailored to an updated set of requirements. The Greenheart Project vessel design was developed by an open-source design process and is part of an initiative to deve...
Over the last decades, many diffuse-interface Navier–Stokes Cahn–Hilliard (NSCH) models with non-matching densities have appeared in the literature. These models claim to describe the same physical phenomena, yet they are distinct from one another. The overarching objective of this work is to bring all of these models together by laying down a unif...
We show that in the variational multiscale framework, the weak enforcement of essential boundary conditions via Nitsche’s method corresponds directly to a particular choice of projection operator. The consistency, symmetry and penalty terms of Nitsche’s method all originate from the fine-scale closure dictated by the corresponding scale decompositi...
Two well-established classes of the interface capturing models are the level-set and phase-field models. Level-set formulations satisfy the maximum principle for the density but are not energy-stable. On the other hand, phase-field models do satisfy the second law of thermodynamics but lack the maximum principle for the density. In this paper we de...
Wind propulsion for commercial ships has been identified as a key component in the energy transition for the maritime industry. The sailing hybrid ship will operate with leeway (drift) angles to produce a lateral force known as sideforce, for steady operation under sail. In this paper, experimental results for the sailing performance of ships fitte...
In this paper we investigate the efficacy of augmenting, or replacing, an active height control system for a submerged hydrofoil with a passive system based on springs and dampers. A state-space model for submerged hydrofoils is formulated and extended to allow for a suspension at the front wing, aft wing or both wings. The model is partially verif...
We show that in the variational multiscale framework, the weak enforcement of essential boundary conditions via Nitsche's method corresponds directly to a particular choice of projection operator. The consistency, symmetry and penalty terms of Nitsche's method all originate from the fine-scale closure dictated by the corresponding scale decompositi...
MFEM is an open-source, lightweight, flexible and scalable C++ library for modular finite element methods that features arbitrary high-order finite element meshes and spaces, support for a wide variety of discretization approaches and emphasis on usability, portability, and high-performance computing efficiency. MFEM’s goal is to provide applicatio...
Two well-established classes of the interface capturing models are the level-set and phase-field models. Level-set formulations
satisfy the maximum principle for the density but are not energy-stable. On the other hand, phase-field models do satisfy the
second law of thermodynamics but lack the maximum principle for the density. In this paper we de...
This paper presents a novel variational formulation to simulate linear free-surface flow. The variational formulation is suitable for higher-order finite elements and higher-order and higher-continuity shape functions as employed in Isogeometric Analysis (IGA).
The novel formulation combines the interior and free-surface problems in one monolithic...
ARTICLE INFO Keywords Numerical error RANS Computational fluid dynamics Sailing vessels Emission control areas Green shipping ABSTRACT A Reynolds-averaged Navier Stokes computational fluid dynamics (RANS-CFD) package will be one of the primary tools used during the development of a performance prediction program for wind-assisted commercial ships....
This paper presents the notion of a variation entropy. This concept is an entropy framework for the gradient of the solution of a conservation law instead of on the solution itself. It appears that all semi-norms are admissible variation entropies. This provides insight into the total variation diminishing property and justifies it from entropy pri...
In this paper we show that the variational multiscale method together with the variation entropy concept form the underlying theoretical framework of discontinuity capturing. The variation entropy [M.F.P. ten Eikelder and I. Akkerman, Comput. Methods Appl. Mech. Engrg. 355 (2019) 261-283] is the recently introduced concept that equips total variati...
Wind-assisted ship propulsion is an effective short-to mid-term mitigation option for the maritime shipping industry's essential course for rapid decarbonisation. Wind propulsion devices such as the Flettner rotor develop an aerodynamic thrust that can replace main engine thrust, promising large reductions for the fuel consumption of ships. This st...
Computational fluid dynamics (CFD) and fluid-structure interaction (FSI) are growing disciplines in the aeroelastic analysis and design of long-span bridges, which, with their bluff body characteristics, offer major challenges to efficient simulation. In this paper, we employ isogeometric analysis (IGA) based on nonuniform rational B-splines (NURBS...
This paper presents a new monolithic free-surface formulation that exhibits correct kinetic and potential energy behavior. We focus in particular on the temporal energy behavior of two-fluids flow with varying densities. Correct energy behavior here means that the actual energy evolution of the numerical solution matches the evolution as predicted...
This paper presents a novel variational formulation to simulate linear free-surface flow. The variational formulation is suitable for higher-order finite elements and higher-order and higher-continuity shape functions as employed in Isogeometric Analysis (IGA). The novel formulation combines the interior and free-surface problems in one monolithic...
This paper presents the notion of a variation entropy. This concept is an entropy framework for the system of equations that results when taking the gradient of a nonlinear conservation law. It appears that all semi-norms are admissible variation entropies. This provides insight into the total variation diminishing property and justifies it from en...
An efficient methodology of Roll load prediction of 2D bodies in non-linear flows circumventing the traditional approach of solving two boundary value problems: one for velocity potential and the other for its temporal derivative. We invoke the fundamental principle of conservation of fluid momentum to estimate the loads.
This paper presents the construction of a correct-energy stabilized finite element method for the incompressible Navier–Stokes equations. The framework of the methodology and the correct-energy concept have been developed in the convective–diffusive context in the preceding paper [M.F.P. ten Eikelder, I. Akkerman, Correct energy evolution of stabil...
This paper presents a new monolithic free-surface formulation that exhibits correct kinetic and potential energy behavior. Correct energy behavior means here that the energy evolution of the discretized and continuous two-fluid equations match. We adopt the level-set method to describe the two-fluid surface. To ensure the correct energy behavior we...
This paper presents the construction of novel stabilized finite element methods in the convective-diffusive context that exhibit correct-energy behavior. Classical stabilized formulations can create unwanted artificial energy. Our contribution corrects this undesired property by employing the concepts of dynamic as well as orthogonal small-scales w...
This paper presents the construction of a correct-energy stabilized finite element method for the incompressible Navier-Stokes equations. The framework of the methodology and the correct-energy concept have been developed in the convective-diffusive context in the preceding paper [M.F.P. ten Eikelder, I. Akkerman, Correct energy evolution of stabil...
This paper presents the construction of novel stabilized finite element methods in the convective-diffusive context that exhibit correct-energy behavior. Classical stabilized formulations can create unwanted artificial energy. Our contribution corrects this undesired property by employing the concepts of dynamic as well as orthogonal small-scales w...
The physical level of interaction between fluid and structure can be either one-way or two-way depending on the direction of information exchange at the interface of fluid and solid. The former can be solved by a partitioned approach and weak coupling. In problems involving two-way fluid-structure interaction, using a partitioned approach and stron...
In this paper we present approaches that address two issues that can occur when the level-set method is used to Simulate two-fluid flows in engineering practice. The first issue concerns regularizing the Heaviside function on arbitrary meshes. We show that the regularized Heaviside function can be non-smooth on non-Uniform meshes. Alternative regul...
A validation study using the National Renewable Energy Laboratory (NREL) Phase VI wind turbine is presented. The aerodynamics simulations are performed using the finite element arbitrary Lagrangian–Eulerian–variational multiscale formulation augmented with weakly enforced essential boundary conditions. In all cases, the rotor is assumed to be rigid...
Full-scale, 3D, time-dependent aerodynamics modeling and simulation of a Darrieus-type vertical-axis wind turbine (VAWT) is presented. The simulations are performed using a moving-domain finite-element-based ALE-VMS technique augmented with a sliding-interface formulation to handle the rotor-stator interactions present. We simulate a single VAWT us...
Isogeometric analysis of Lagrangian shock hydrodynamics is proposed. The Euler equations of compressible hydrodynamics in the weak form are discretized using Non-Uniform Rational B-Splines (NURBS) in space. The discretization has all the advantages of a higher-order method, with the additional benefits of exact symmetry preservation and better per-...
A fluid–structure interaction (FSI) validation study of the Micon 65/13M wind turbine with Sandia CX-100 composite blades is presented. A rotation-free isogeometric shell formulation is used to model the blade structure, while the aerodynamics formulation makes use of the FEM-based ALE-VMS method. The structural mechanics formulation is validated b...
We present our free-surface flow and fluid-object interaction computational framework. The framework is an instantiation of the Mixed Interface-Tracking/Interface-Capturing Technique (MITICT) (Akin et al. in Comput. Fluids 36:2–11, 2007; Cruchaga et al. in Int. J. Numer. Methods Fluids 54:1021–1031, 2007; Tezduyar in Arch. Comput. Methods Eng. 8:83...
In this book chapter we give an overview of our recent work in computational methods for geometry modeling, fluid mechanics, structural mechanics, and fluid–structure interaction that enable high-fidelity simulations of offshore wind turbines. Computational examples involving free-surface flow and full-scale wind turbine simulations are presented t...
In this paper we focus on a class of applications involving surface vessels moving at high speeds, or “planing”. We introduce a Fridsma planing hull benchmark problem, and simulate it using the finite-element-based ALE-VMS (Bazilevs et al. in Math Models Methods Appl Sci 2012; Takizawa et al. in Arch Comput Methods Eng 19: 171–225, 2012) approach....
In this article we present a validation study involving the full-scale NREL Phase VI two-bladed wind turbine rotor. The ALE–VMS formulation of aerodynamics, based on the Navier–Stokes equations of incompressible flows, is employed in conjunction with weakly enforced essential boundary conditions. We find that the ALE–VMS formulation using linear te...
We develop a residual-based variational multiscale (RBVMS) method based on isogeo-metric analysis for large-eddy simulation (LES) of wind-driven shear flow with Langmuir circulation (LC). Isogeometric analysis refers to our use of NURBS (Non-Uniform Rational B-splines) basis functions which have been proven to be highly accurate in LES of turbulent...
This paper presents our approach for the computation of free-surface/rigid-body interaction phenomena with emphasis on ship hydrodynamics. We adopt the level set approach to capture the free-surface. The rigid body is described using six-degree-of-freedom equations of motion. An interface-tracking method is used to handle the interface between the...
In this article we present a high-performance computing framework for advanced flow simulation and its application to wind energy based on the residual-based variational multiscale (RBVMS) method and isogeometric analysis. The RBVMS formulation and its suitability and accuracy for turbulent flow in a moving domain are presented. Particular emphasis...
This paper presents a formulation for free-surface computations capable of handling complex phenomena, such as wave breaking, without excessive mass loss or smearing of the interface. The formulation is suitable for discretizations using finite elements of any topology and order, or other approaches such as isogeometric and finite volume methods. F...
This paper presents the first application of isogeometric analysis, a new computational technology built on higher-order and higher-continuity basis functions employed in Computer-Aided Design and computer graphics, to the computation of free-surface phenomena described using the level set approach. The method is based on the variational framework...
We develop duality-based a-posteriori error estimates for functional outputs of so-lutions of fluid–structure-interaction problems. The crucial complication in obtain-ing these estimates pertains to the derivation of the coupled dual (exact linearized-adjoint) problem owing to the free-boundary character of fluid–structure interaction. We present t...
In this two-part paper we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The...
One of the dominant failure modes of levees during flood and storm surge
events is erosion-based breach formation due to high velocity flow over
the back (land-side) slope. Modeling the breaching process numerically
is challenging due to both physical and geometric complexity that
develops and evolves during the overtopping event. The surface water...
In this chapter the recently introduced Variational Germano procedure is revisited. The procedure is explained using commutativity
diagrams. A general Germano identity for all types of discretizations is derived. This relation is similar to the Variational
Germano identity, but is not restricted to variational numerical methods. Based on the genera...
We present an application of the residual-based variational multiscale turbulence modeling (RBVMS) methodology to the computation of turbulent Taylor–Couette flow at high Reynolds number. We show that the RBVMS formulation globally conserves angular momentum, a feature that is felt to be important for flows dominated by rotation, and that is not sh...
In this paper the recently introduced Variational Germano procedure is revisited. The procedure is explained using commutativity diagrams. A general Germano identity for all types of discretizations is derived. This relation is similar to the Variational Germano identity, but is not restricted to variational numerical methods. Based on the general...
Two-phase Navier-Stokes models are becoming increasingly popular for investigating free-surface flows and hydrodynamic processes. They hold particular appeal for problems where full vertical resolution is required in velocity and pressure, (e.g., short-wave phenomena, flow around coastal structures and levees, and extreme erosion processes). Level-...
This paper examines the role of continuity of the basis in the computation of turbulent flows. We compare standard finite elements and non-uniform rational B-splines (NURBS) discretizations that are employed in Isogeometric Analysis (Hughes et al. in Comput Methods Appl Mech Eng, 194:4135–4195, 2005). We make use of quadratic discretizations that a...
A class of multiscale overlap coupling methods is proposed for hybrid computations which supplement partially-resolved simulations using low-frequency solutions. In this class of methods, the largest resolved scales of the partially-resolved simulation are forced to resemble low-frequency solutions in overlapping near-boundary regions. Simultaneous...
It is well known that standard Galerkin methods often need to be augmented with stabilizing terms. In the realm of fluid problems, this necessity can usually be traced back to either the mixed nature of these problems or dominating convection. Both issues have already been resolved in the 80s resulting in a.o. [1][2]. Physical justification of thes...
A Residual-Based Large-Eddy Simulation (RB-LES) method is developed. This is done by discretizing the Navier-Stokes equations directly. A priori filtering is omitted. Analytical approximation of the subgrid scales results in a unusually-stabilized finite-element method with additional terms arising due to the nonlinearity. This RB-LES method is use...