Brian Ray Resor

Handbook on dynamics of jointed structures.

The problem of understanding and modeling the complicated physics underlying the action and response of the interfaces in typical structures under dynamic loading conditions has occupied researchers for many decades. This handbook presents an integrated approach to the goal of dynamic modeling of typical jointed structures, beginning with a mathematical assessment of experimental or simulation data, development of constitutive models to account for load histories to deformation, establishment of kinematic models coupling to the continuum models, and application of finite element analysis leading to dynamic structural simulation. In addition, formulations are discussed to mitigate the very short simulation time steps that appear to be required in numerical simulation for problems such as this. This handbook satisfies the commitment to DOE that Sandia will develop the technical content and write a Joints Handbook. The content will include: (1) Methods for characterizing the nonlinear stiffness and energy dissipation for typical joints used in mechanical systems and components. (2) The methodology will include practical guidance on experiments, and reduced order models that can be used to characterize joint behavior. (3) Examples for typical bolted and screw joints will be provided.

Active Aerodynamic Blade Distributed Flap Control Design Procedure for Load Reduction on the UpWind 5MW Wind Turbine

This paper develops a system identification approach and procedure that is employed for distributed control system design for large wind turbine load reduction applications. The primary goal of the study is to identify the process that can be used with multiple sensor inputs of varying types (such as aerodynamic or structural) that can be used to construct state-space models compatible with MIMO modern control techniques (such as LQR, LQG, H1, robust control, etc.). As an initial step, this study employs LQR applied to multiple flap actuators on each blade as control inputs and local deflection rates at the flap spanwise locations as measured outputs. Future studies will include a variety of other sensor and actuator locations for both design and analysis with respect to varying wind conditions (such as high turbulence and gust) to help reduce structural loads and fatigue damage. The DU SWAMP aeroservoelastic simulation environment is employed to capture the complexity of the control design scenario. The NREL 5MW UpWind reference wind turbine provides the large wind turbine dynamic characteristics used for the study. Numerical simulations are used to demonstrate the feasibility of the overall approach. This study shows that the distributed controller design can provide load reductions for turbulent wind profiles that represent operation in above-rated power conditions.

Numerical Manufacturing And Design Tool (NuMAD v2.0) for Wind Turbine Blades: User's Guide

Sandia National Laboratories has an on-going effort to reduce the cost of energy and improve reliability for wind systems through improved blade design and manufacture. As part of this effort, a software tool named NuMAD (Numerical Manufacturing And Design) has been developed to greatly simplify the process of creating a three-dimensional finite element model for a modern wind turbine blade. NuMAD manages all blade information including databases of airfoils, materials, and material placement to enable efficient creation of models. NuMAD is a stand-alone, user-friendly, graphical pre-processor for the ANSYS ® commercial finite element package. The blade information contained in the NuMAD database is also used to manage capabilities such as output for CFD mesh, computation of blade cross section properties, and aeroelastic instability analysis of the blade. This user’s manual describes the capabilities and usage of NuMAD.

Uncertainties in Prediction of Wind Turbine Blade Flutter.

The blades of a modern wind turbine are critical components central to capturing and transmitting most of the loads experienced by the system. Blades are complex structural items composed of many layers of fiber and resin composite material and typically, one or more shear webs. Simplification of the blade structure into equivalent beams is an important step prior to aeroelastic simulation of the turbine structure. There are a variety of approaches that can be used to reduce the three-dimensional continuum blade structure to a simpler beam representation: two-dimensional cross section analysis, extraction of equivalent properties from three-dimensional blade finite element models and variational asymptotical beam sectional analysis. This investigation provides insight into discrepancies observed in outputs from these three approaches for a real blade geometry. Wind turbine blades of the future will be longer and more flexible as weight is optimized. Innovative large blade designs may present challenges with respect to aeroelastic flutter instabilities. Sensitivity of computed flutter speed with respect to variations in computed beam properties is demonstrated at the end of this paper.

Scaled Wind Farm Technology Facility Overview.

In the past decade wind energy installations have increased exponentially driven by reducing cost from technology innovation and favorable governmental policy. Modern wind turbines are highly efficient, capturing close to the theoretical limit of energy available in the rotor diameter. Therefore, to continue to reduce the cost of wind energy through technology innovation a broadening of scope from individual wind turbines to the complex interaction within a wind farm is needed. Some estimates show that 10 40% of wind energy is lost within a wind farm due to underperformance and turbine-turbine interaction. The US Department of Energy has recently announced an initiative to reshape the national research focus around this priority. DOE, in recognizing a testing facility gap, has commissioned Sandia National Laboratories with the design, construction and operation of a facility to perform research in turbine-turbine interaction and wind plant underperformance. Completed in 2013, the DOE/SNL Scaled Wind Farm Technology Facility has been constructed to perform early-stage high-risk cost-efficient testing and development in the areas of turbine-turbine interaction, wind plant underperformance, wind plant control, advanced rotors, and fundamental studies in aero-elasticity, aero-acoustics and aerodynamics. This paper will cover unique aspects of the construction of the facility to support these objectives, testing performed to create a validated model, and an overview of research projects that will use the facility.

Design, Fabrication, Assembly and Initial Testing of a SMART Rotor 1

Sandia National Laboratories has designed and built a full set of three 9m blades (based on the Sandia CX-100 blade design) equipped with active aerodynamic blade load control surfaces on the outboard trailing edges. The design and fabrication of the blades and active aerodynamic control hardware and the instrumentation are discussed and the plans for control development are presented. , Albuquerque, NM 87185-1124

Impact of Higher Fidelity Models on Simulation of Active Aerodynamic Load Control For Fatigue Damage Reduction

Active aerodynamic load control of wind turbine blades is being investigated by the wind energy research community and shows great promise, especially for reduction of turbine fatigue damage in blades and nearby components. For much of this work, full system aeroelastic codes have been used to simulate the operation of the activel y controlled rotors. Research activities in this area continually push the limits of the models and assumptions within the codes. This paper demonstrates capabilities of a full system aeroelastic code recently developed by researchers at the Delft Universi ty Wind Energy Research Institute with the intent to provide a capability to serve the active aerodynamic control research effort, The code, called DU_SWAMP, includes higher fidelity structural models and unsteady aerodynamics effects which represent improvement over capabilities used previously by researchers at Sandia National Laboratories. The work represented by this paper includes model verification comparisons between a standard wind industry code, FAST, and DU_SWAMP. Finally, two different types of a ctive aerodynamic control approaches are implemented in order to demonstrate the fidelity simulation capability of the new code.

An evaluation of wind turbine blade cross section analysis techniques.

The blades of a modern wind turbine are critical components central to capturing and transmitting most of the load experienced by the system. They are complex structural items composed of many layers of fiber and resin composite material and typically, one or more shear webs. Large turbine blades being developed today are beyond the point of effective trial-and-error design of the past and design for reliability is always extremely important. Section analysis tools are used to reduce the three-dimensional continuum blade structure to a simpler beam representation for use in system response calculations to support full system design and certification. One model simplification approach is to analyze the two- dimensional blade cross sections to determine the properties for the beam. Another technique is to determine beam properties using static deflections of a full three-dimensional finite element model of a blade. This paper provides insight into discrepancies observed in outputs from each approach. Simple two-dimensional geometries and three-dimensional blade models are analyzed in this investigation. Finally, a subset of computational and experimental section properties for a full turbine blade are compared.

Decades of Wind Turbine Load Simulation.

A high-performance computer was used to simulate ninety-six years of operation of a five megawatt wind turbine. Over five million aero-elastic simulations were performed, wit h each simulation consisting of wind turbine operation for a ten minute period in turbulent wind conditions. These simulations have produced a large database of wind turbine loads, including ten minute extreme loads as well as fatigue cycles on various turbine components. In this paper, the extreme load probability distributions are presented. The long total simulation time has enabled good estimation of the tails of the distributions down to probabilities associated with twenty-year (and longer) return events. The database can serve in the future as a truth model against which design-oriented load extrapolation techniques can be tested. The simulations also allow for detailed examination of the simulations leading to the largest loads, as demonstrated for two representative cases.

Mapping of 1D Beam Loads to the 3D Wind Blade for Buckling Analysis.

This paper discusses the development of a consisten t methodology for mapping onedimensional distributed beam loads to a three-dimensional shell structure. The resultant force distribution is a linear approximation to the actual aerodynamic pressure distribution but is sufficient to obtain accurate strain and dis placement results. The purpose of the mapping technique is to apply more realistic wind l oads to the shell model of a wind turbine blade without the need to set up and run expensive computational fluid dynamics or fluid structure interaction problems. Subsequent buckling and stress analysis reveal how this approach compares to other simplified methods of defining the loads.