J. Yan

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]

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.

Graphics processing unit (GPU) accelerated fast multipole BEM with level-skip M2L for 3D elasticity problems

GPU parallel algorithm of the fast multipole BEM with level-skip M2L is presented.A rigid body motion method for the fast multipole BEM is given.Different M2L schemes are compared and discussed in detail.Engineering examples demonstrate the efficiency and accuracy of the algorithm. In order to accelerate fast multipole boundary element method (FMBEM), in terms of the intrinsic parallelism of boundary elements and the FMBEM tree structure, a series of CUDA based GPU parallel algorithms for different parts of FMBEM with level-skip M2L for 3D elasticity are presented. A rigid body motion method (RBMM) for the FMBEM is proposed based on special displacement boundary conditions to deal with strongly singular integration and free term coefficients. The numerical example results show that our parallel algorithms obviously accelerates the FMBEM and can be used in large scale engineering problems with wide applications in the future.

Topology Optimization of Total Femur Structure: Application of Parameterized Level Set Method Under Geometric Constraints

Optimization of the femur prosthesis is a key issue in femur replacement surgeries that provide a viable option for limb salvage rather than amputation. To overcome the drawback of the conventional techniques that do not support topology optimization of the prosthesis design, a parameterized level set method (LSM) topology optimization with arbitrary geometric constraints is presented. A predefined narrow band along the complex profile of the original femur is preserved by applying the contour method to construct the level set function, while the topology optimization is carried out inside the cavity. The Boolean R-function is adopted to combine the free boundary and geometric constraint level set functions to describe the composite level set function of the design domain. Based on the minimum compliance goal, three different designs of 2D femur prostheses subject to the target cavity fill ratios 34%, 54%, and 74%, respectively, are illustrated.

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.