Computational Wind-Turbine Analysis with the ALE-VMS and ST-VMS Methods

We provide an overview of the aerodynamic and FSI analysis of wind turbines the first three authors’ teams carried out in recent years with the ALE-VMS and ST-VMS methods. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian–Eulerian (ALE) method. The VMS components are from the residual-based VMS (RBVMS) method. The ST-VMS method is the VMS version of the Deforming-Spatial-Domain/Stabilized Space–Time (DSD/SST) method. The techniques complementing these core methods include weak enforcement of the essential boundary conditions, NURBS-based isogeometric analysis, using NURBS basis functions in temporal representation of the rotor motion, mesh motion and also in remeshing, rotation representation with constant angular velocity, Kirchhoff–Love shell modeling of the rotor-blade structure, and full FSI coupling. The analysis cases include the aerodynamics of wind-turbine rotor and tower and the FSI that accounts for the deformation of the rotor blades. The specific wind turbines considered are NREL 5MW, NREL Phase VI and Micon 65/13M, all at full scale, and our analysis for NREL Phase VI and Micon 65/13M includes comparison with the experimental data

Space--Time Computation of Wind-Turbine Aerodynamics With Higher-Order Functions in Time

This thesis is on the space--time variational multiscale (ST-VMS) computation of wind-turbine rotor and tower aerodynamics. The rotor geometry is that of the NREL 5MW offshore baseline wind turbine. We compute with a given wind speed and a specified rotor speed. The computation is challenging because of the large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. The presence of the tower increases the computational challenge because of the fast, rotational relative motion between the rotor and tower. The ST-VMS method is the residual-based VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method, and is also called ``DSD/SST-VMST'' method (i.e., the version with the VMS turbulence model). In calculating the stabilization parameters embedded in the method, we are using a new element length definition for the diffusion-dominated limit. The DSD/SST method, which was introduced as a general-purpose moving-mesh method for computation of flows with moving interfaces, requires a mesh update method. Mesh update typically consists of moving the mesh for as long as possible and remeshing as needed. In the computations reported here, NURBS basis functions are used for the temporal representation of the rotor motion, enabling us to represent the circular paths associated with that motion exactly and specify a constant angular velocity corresponding to the invariant speeds along those paths. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. We name this ``ST/NURBS Mesh Update Method (STNMUM).'' The STNMUM increases computational efficiency in terms of computer time and storage, and computational flexibility in terms of being able to change the time-step size of the computation. We use layers of thin elements near the blade surfaces, which undergo rigid-body motion with the rotor. We compare the results from computations with and without tower, and we also compare using NURBS and linear finite element basis functions in temporal representation of the mesh motion

Computational Wind-Turbine Analysis with the ALE-VMS and ST-VMS Methods

We provide an overview of the aerodynamic and FSI analysis of wind turbines the first three authors’ teams carried out in recent years with the ALE-VMS and ST-VMS methods. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian–Eulerian (ALE) method. The VMS components are from the residual-based VMS (RBVMS) method. The ST-VMS method is the VMS version of the Deforming-Spatial-Domain/Stabilized Space–Time (DSD/SST) method. The techniques complementing these core methods include weak enforcement of the essential boundary conditions, NURBS-based isogeometric analysis, using NURBS basis functions in temporal representation of the rotor motion, mesh motion and also in remeshing, rotation representation with constant angular velocity, Kirchhoff–Love shell modeling of the rotor-blade structure, and full FSI coupling. The analysis cases include the aerodynamics of wind-turbine rotor and tower and the FSI that accounts for the deformation of the rotor blades. The specific wind turbines considered are NREL 5MW, NREL Phase VI and Micon 65/13M, all at full scale, and our analysis for NREL Phase VI and Micon 65/13M includes comparison with the experimental data.This is a chapter from Bazilevs Y., Takizawa K., Tezduyar T.E., Hsu MC., Kostov N., McIntyre S. "Computational Wind-Turbine Analysis with the ALE-VMS and ST-VMS Methods." In: Idelsohn S. (ed.) Numerical Simulations of Coupled Problems in Engineering. Computational Methods in Applied Sciences 33 (2014): 355-386. DOI: 10.1007/978-3-319-06136-8_14. Posted with permission.</p