A. Korobenko

STRUCTURAL MECHANICS MODELING AND FSI SIMULATION OF WIND TURBINES

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 by means of eigenfrequency analysis of the CX-100 blade. For the coupling between the fluid and structural mechanics domains, a nonmatching discretization approach is adopted. The simulations are done at realistic wind conditions and rotor speeds. The rotor-tower interaction that influences the aerodynamic torque is captured. The computed aerodynamic torque generated by the Micon 65/13M wind turbine compares well with that obtained from on-land experimental tests.

Fluid–Structure Interaction Modeling of Vertical-Axis Wind Turbines

Full-scale, 3D, time-dependent aerodynamics and fluid‐structure interaction (FSI) simulations of a Darrieus-type vertical-axis wind turbine (VAWT) are presented. A structural model of the Windspire VAWT (Windspire energy, http://www.windspireenergy.com/ )i s developed, which makes use of the recently proposed rotation-free Kirchhoff‐Love shell and beam/cable formulations. A moving-domain finite-element-based ALE-VMS (arbitrary Lagrangian‐Eulerian-variational-multiscale) formulation is employed for the aerodynamics in combination with the sliding-interface formulation to handle the VAWT mechanical components in relative motion. The sliding-interface formulation is augmented to handle nonstationary cylindrical sliding interfaces, which are needed for the FSI modeling of VAWTs. The computational results presented show good agreement with the field-test data. Additionally, several scenarios are considered to investigate the transient VAWT response and the issues related to self-starting. [DOI: 10.1115/1.4027466]

Aerodynamic Simulation of Vertical-Axis Wind Turbines

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 using a sequence of meshes with increased resolution to assess the computational requirements for this class of problems. The computational results are in good agreement with experimental data. We also perform a computation of two side-by-side counterrotating VAWTs to illustrate how the ALE-VMS technique may be used for the simulation of multiple turbines placed in arrays.

ALE–VMS formulation for stratified turbulent incompressible flows with applications

A numerical formulation for incompressible flows with stable stratification is developed using the framework of variational multiscale methods. In the proposed formulation, both density and temperature stratification are handled in a unified manner. The formulation is augmented with weakly-enforced essential boundary conditions and is suitable for applications involving moving domains, such as fluid–structure interaction. The methodology is tested using three numerical examples ranging from flow-physics benchmarks to a simulation of a full-scale offshore wind-turbine rotor spinning inside an atmospheric boundary layer. Good agreement is achieved with experimental and computational results reported by other researchers. The wind-turbine rotor simulation shows that flow stratification has a strong influence on the dynamic rotor thrust and torque loads.

Fluid–Structure Interaction Modeling for Fatigue-Damage Prediction in Full-Scale Wind-Turbine Blades

This work presents a collection of advanced computational methods, and their coupling, that enable prediction of fatigue-damage evolution in full-scale composite blades of wind turbines operating at realistic wind and rotor speeds. The numerical methodology involves: (1) a recently developed and validated fatigue-damage model for multilayer fiber-reinforced composites; (2) a validated coupled fluid–structure interaction (FSI) framework, wherein the 3D time-dependent aerodynamics based on the Navier–Stokes equations of incompressible flows is computed using a finite-element-based arbitrary Lagrangian–Eulerian–variational multiscale (ALE–VMS) technique, and the blade structures are modeled as rotation-free isogeometric shells; and (3) coupling of the FSI and fatigue-damage models. The coupled FSI and fatigue-damage formulations are deployed on the Micon 13M wind turbine equipped with the Sandia CX-100 blades. Damage initiation, damage progression, and eventual failure of the blades are reported.

Isogeometric Fatigue Damage Prediction in Large-Scale Composite Structures Driven by Dynamic Sensor Data

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Recent Advances in ALE-VMS and ST-VMS Computational Aerodynamic and FSI Analysis of Wind Turbines

We describe the recent advances made by our teams in ALE-VMS and ST-VMS computational aerodynamic and fluid–structure interaction (FSI) analysis of wind turbines. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian–Eulerian method. The VMS components are from the residual-based VMS method. The ST-VMS method is the VMS version of the Deforming-Spatial-Domain/Stabilized Space–Time method. The ALE-VMS and ST-VMS serve as the core methods in the computations. They are complemented by special methods that include the ALE-VMS versions for stratified flows, sliding interfaces and weak enforcement of Dirichlet boundary conditions, ST Slip Interface (ST-SI) method, NURBS-based isogeometric analysis, ST/NURBS Mesh Update Method (STNMUM), Kirchhoff–Love shell modeling of wind-turbine structures, and full FSI coupling. The VMS feature of the ALE-VMS and ST-VMS addresses the computational challenges associated with the multiscale nature of the unsteady flow, and the moving-mesh feature of the ALE and ST frameworks enables high-resolution computation near the rotor surface. The ST framework, in a general context, provides higher-order accuracy. The ALE-VMS version for sliding interfaces and the ST-SI enable moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the sliding interface or the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-SI also enables prescribing the fluid velocity at the turbine rotor surface as weakly-enforced Dirichlet boundary condition. The STNMUM enables exact representation of the mesh rotation. The analysis cases reported include both the horizontal-axis and vertical-axis wind turbines, stratified and unstratified flows, standalone wind turbines, wind turbines with tower or support columns, aerodynamic interaction between two wind turbines, and the FSI between the aerodynamics and structural dynamics of wind turbines. Comparisons with experimental data are also included where applicable. The reported cases demonstrate the effectiveness of the ALE-VMS and ST-VMS computational analysis in wind-turbine aerodynamics and FSI.

Multiscale DDDAS Framework for Damage Prediction in Aerospace Composite Structures with Emphasis on Unmanned Aerial Vehicles

In recent years, there has been a significant increase in the use of Unmanned Aerial Vehicles by the US military. UAVs are expected to fly a large number of long (48 or more hours) missions, and operate without failure. Furthermore, in order to increase the durability of these vehicles and to decrease weight, composite materials are currently experiencing a widespread adoption in applications related both to military and civilian aerospace structures. As a result, in order to decrease costs associated with the operation, maintenance, and, in some cases, loss of these vehicles, it is desirable to have a Dynamically Data-Driven Application System framework that can reliably predict the onset and progressions of structural damage in geometrically and materially complex aerospace composite structures operating in the environments typical of UAVs. In this work we present a multiscale DDDAS framework for damage prediction in aerospace structures with emphasis on self-aware air vehicles

Recent Advances in Fluid–Structure Interaction Simulations of Wind Turbines

In this chapter the numerical challenges of simulating aerodynamics and fluid–structure interaction (FSI) of wind turbines are summarized, and the recently developed computational methods that address these challenges are presented. Several wind-turbine computations at full scale and with full complexity of the geometry and material composition are presented, which illustrate the accuracy, robustness, and general applicability of the methods developed for this problem class.