Computational analysis of the dynamic forces in drive train components of an offshore wind turbines

Wind has good potential for contributing to the national energy supply. Offshore sites and deep sea locations can be especially attractive as the wind turbine market grows. In such places larger wind resources are available with reduced turbulence intensity and wind shear. In addition, visual impact along with noise aspects are reduced. Offshore siting requires greater attention to structural stability and endurance. Forces on drive train components, such as the bearing system, are not well understood. This work presents the development a model that calculates dynamical forces in drive train components of off-shore wind turbines. The model of a 5MW off-shore wind turbine was developed based on site conditions for the nearby South Carolina coast. The model accounts for elastic deformation of the tower and distributed loads due to gravity, wind, and waves on the wind turbine elements and tower. A finite element computational model was implemented with external forces estimated from analytical models. The main elements of the turbine were based on actual 5MW wind turbine specifications. The tower was represented as a hollow, tapered steel cylinder with a foundation fixed rigidly to the sea floor. A mono-pile supporting structure was specifically represented, due to its applicability to the relatively shallow coastal waters of South Carolina. The results from time-domain analysis were shown to agree with results generated from other studies. The dynamic response of mean values of loads on drive train components were found to be very similar to those for land-based wind turbines. It was also concluded that magnitude of axial force R_bx in the drive train components depend mostly on thrust force produced on the rotor by the three turbine blades. Its maximum value is determined by peak in thrust force and its periodicity is a result of changing thrust force, when blades rotate. To show the influence of thrust force and ocean wave force on force R_bx, results were presented also in frequency domain. It was shown that force R_bx has the dominant frequency of 0.2 Hz, which is the frequency of the thrust force. Additionally, eigenfrequency analysis was performed to show the lowest natural frequency of the system. It was found to be 1Hz, which corresponds to the fore-aft oscillation of the tower. This value is higher than frequencies of externally applied force that may guarantee that resonance will not occur in the system. Unlike axial forces, vertical forces in drive train components R_bz only determined by weight of components and any change in wind speed, ocean wave height and ocean wave period do not affect the tower deflection in vertical direction

Advanced Fluid–Structure Interaction Techniques in Application to Horizontal and Vertical Axis Wind Turbines

During the last several decades engineers and scientists put significant effort into developing reliable and efficient wind turbines. As a wind power production demands grow, the wind energy research and development need to be enhanced with high-precision methods and tools. These include time-dependent, full-scale, complex-geometry advanced computational simulations at large-scale. Those, computational analysis of wind turbines, including fluid-structure interaction simulations (FSI) at full scale is important for accurate and reliable modeling, as well as blade failure prediction and design optimization. In current dissertation the FSI framework is applied to most challenging class of problems, such as large scale horizontal axis wind turbines and vertical axis wind turbines. The governing equations for aerodynamics and structural mechanics together with coupled formulation are explained in details. The simulations are performed for different wind turbine designs, operational conditions and validated against field-test and wind tunnel experimental data

Using ALE-VMS to compute aerodynamic derivatives of bridge sections

Aeroelastic analysis is a major task in the design of long-span bridges, and recent developments in computer power and technology have made Computational Fluid Dynamics (CFD) an important supplement to wind tunnel experiments. In this paper, we employ the Finite Element Method (FEM) with an effective mesh-moving algorithm to simulate the forced-vibration experiments of bridge sectional models. We have augmented the formulation with weakly-enforced essential boundary conditions, and a numerical example illustrates how weak enforcement of the no-slip boundary condition gives a very accurate representation of the aeroelastic forces in the case of relatively coarse boundary layer mesh resolution. To demonstrate the accuracy of the method for industrial applications, the complete aerodynamic derivatives for lateral, vertical and pitching degrees-of-freedom are computed for two bridge deck sectional models and compared with experimental wind-tunnel results. Although some discrepancies are seen in the high range of reduced velocities, the proposed numerical framework generally reproduces the experiments with good accuracy and proves to be a beneficial tool in simulation of bluff body aerodynamics for bridge design

Stabilized methods for high-speed compressible flows: toward hypersonic simulations

A stabilized finite element framework for high-speed compressible flows is presented. The Streamline-Upwind/Petrov–Galerkin formulation augmented with discontinuity-capturing (DC) are the main constituents of the framework that enable accurate, efficient, and stable simulations in this flow regime. Full- and reduced-energy formulations are employed for this class of flow problems and their relative accuracy is assessed. In addition, a recently developed DC formulation is presented and is shown to be particularly well suited for hypersonic flows. Several verification and validation cases, ranging from 1D to 3D flows and supersonic to the hypersonic regimes, show the excellent performance of the proposed framework and set the stage for its deployment on more advanced applications.This is a post-peer-review, pre-copyedit version of an article published in Computational Mechanics. The final authenticated version is available online at DOI: 10.1007/s00466-020-01963-6. Posted with permission.</p

Finite Element Simulation and Validation for Aerospace Applications: Stabilized Methods, Weak Dirichlet Boundary Conditions, and Discontinuity Capturing for Compressible Flows

The objective of this work is to investigate and validate a new stabilized compressible flow finite element framework for the simulation of aerospace applications. The framework is comprised of the streamline upwind/Petrov–Galerkin (SUPG)-based Navier–Stokes equations for compressible flows, the weakly enforced essential boundary conditions that act as a wall function, and the entropy-based discontinuity-capturing equation that act as a shock-capturing operator. The accuracy and robustness of the framework is tested for various Mach numbers ranging from low-subsonic to transonic flow regimes. The aerodynamic simulations are carried out for 2D and 3D validation cases of flow around the NACA 0012 airfoil, RAE 2822 airfoil, ONERA M6 wing, and NASA Common Research Model (CRM) aircraft. The pressure coefficients obtained from the simulations of all cases are compared with experimental data. The computational results show good agreement with the experimental findings and demonstrate the accuracy and effectiveness of the finite element framework presented in this work for the simulation of aircraft aerodynamics.This proceeding is published as Rajanna, Manoj R., Emily L. Johnson, David Codoni, Artem Korobenko, Yuri Bazilevs, Ning Liu, Jim Lua, Nam D. Phan, and Ming-Chen Hsu. "Finite Element Simulation and Validation for Aerospace Applications: Stabilized Methods, Weak Dirichlet Boundary Conditions, and Discontinuity Capturing for Compressible Flows." In AIAA SCITECH 2022 Forum, p. 1077. 2022. DOI: 10.2514/6.2022-1077. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted

Finite element methodology for modeling aircraft aerodynamics: development, simulation, and validation

In this work, we propose and validate a new stabilized compressible flow finite element framework for the simulation of aerospace applications. The framework is comprised of the streamline upwind/Petrov–Galerkin (SUPG)-based Navier–Stokes equations for compressible flows, the weakly enforced essential boundary conditions that act as a wall function, and the entropy-based discontinuity-capturing equation that acts as a shock-capturing operator. The accuracy and robustness of the framework is tested for various Mach numbers ranging from low-subsonic to transonic flow regimes. The aerodynamic simulations are carried out for 2D and 3D validation cases of flow around the NACA 0012 airfoil, RAE 2822 airfoil, ONERA M6 wing, and NASA Common Research Model (CRM) aircraft. The pressure coefficients obtained from the simulations of all cases are compared with experimental data. The computational results show good agreement with the experimental findings and demonstrate the accuracy and effectiveness of the finite element framework presented in this work for the simulation of aircraft aerodynamics.This article is published as Rajanna, Manoj R., Emily L. Johnson, David Codoni, Artem Korobenko, Yuri Bazilevs, Ning Liu, Jim Lua, Nam Phan, and Ming-Chen Hsu. "Finite element methodology for modeling aircraft aerodynamics: development, simulation, and validation." Computational Mechanics 70, no. 3 (2022): 549-563. DOI: 10.1007/s00466-022-02178-7. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted