Abstract:The shear webs and laminates of core panels of wind turbine blades must be designed to avoid panel buckling while minimizing blade weight. Typically, buckling resistance is evaluated by consideration of the load-deflection behavior of a blade using finite element analysis (FEA) or full-scale static loading of a blade to failure under a simulated extreme loading condition. This paper examines an alternative means for evaluating blade buckling resistance using non-destructive modal tests or FEA. In addition, pan… Show more
“…Panel modes are localized modes that are active in the blade panels (Griffith and Paquette; Griffith, 2011) occurring in a relatively small region on the blade. the panels are not the major flap-wise blade carrying element of a blade, but they must be designed carefully to avoid buckling while minimizing the blade weight.…”
Section: Discussionmentioning
confidence: 99%
“…Both the numerical and experimental modes indicate the panel modes. The knowledge of the local panel modes can be useful for dynamic characterization, damage detection and structural health monitoring of the blade panels (Griffith, 2011). Figure 10.Localized Panel Modes of Wind Turbine Blade.…”
Section: Discussionmentioning
confidence: 99%
“…Although one surface measurement of the wind turbine blade is enough to characterize the experimental modal character for global beam-type blade modes, especially for low-frequency blade mode shapes. However, as shown in Reference (Griffith and Paquette; Griffith, 2011) via accelerometers measurements placed on both sides of the blade, several high-order blade modes have local panel modes. In some instances, a well perception of these local modes is necessary for blade structural health monitoring and structural damage detection (Griffith, 2011; Griffith et al, 2014; Yin et al, 2017).…”
Section: Introductionmentioning
confidence: 90%
“…However, as shown in Reference (Griffith and Paquette; Griffith, 2011) via accelerometers measurements placed on both sides of the blade, several high-order blade modes have local panel modes. In some instances, a well perception of these local modes is necessary for blade structural health monitoring and structural damage detection (Griffith, 2011; Griffith et al, 2014; Yin et al, 2017).…”
Section: Introductionmentioning
confidence: 90%
“…To directly acquire a large number of experimental degrees of freedom (DOF) from the blade, either optical photogrammetry or Scanning Laser Doppler Vibrometer (SLDV) can be used to measure the mode shape of one surface of the wind turbine blade. Measurements on both sides of the blade with accelerometers were conducted by Griffith et al (Griffith and Paquette; Griffith, 2011). Blade modes including the panel modes can be captured from the modal test, but the measured mode shapes have sparse spatial resolution due to the limited number of accelerometers deployed on the blade.…”
Wind turbine design and operation will benefit from a better understanding of blade dynamics. Usually, only one surface or one side of a 3D structure is measured in Scanning Laser Doppler Vibrometer (SLDV) tests due to test setup and instrumentation limitations. However, in this work, we demonstrate an approach to overcome these limitations while also using an SLDV that provides high spatial resolution measurement. In the case of a wind turbine blade, only one surface is typically measured; however, it is beneficial to investigate both blade global modes and the relative motions of the two blade surfaces by using both numerical models and experimental tests. This work creatively develops both experimental and numerical approaches to investigate the dynamics and the relative motions of both surfaces of the wind turbine blade from global and local perspectives. On the experimental side, experimental modal testing is conducted on both surfaces of the wind turbine blade with a high spatial resolution 3D SLDV. The two surfaces of the wind turbine blade are measured and stitched together to build the blade experimental mode shapes of both surfaces. A total of over 1500 points are scanned from both surfaces of the blade in a non-contact fashion to obtain not only the global bending modes (flap-wise and edge-wise), the global torsional modes, but also the localized panel mode shapes. On the numerical side, a finite element model of the blade is developed to obtain the numerical mode shapes. The experimental mode shapes on either one surface or both surfaces of the blade are used to validate the blade finite element model. The mode shape correspondence between the model and the test is also identified. With the availability of both experimental and numerical mode shapes, localized panel modes of the wind turbine blade are observed and characterized, and as a result the numerical model is validated. This work provides useful case studies for the design and structural analysis of wind turbine blades based on both the experimental observations and the validation of numerical models typical of those used for blade design and blade structural analysis.
“…Panel modes are localized modes that are active in the blade panels (Griffith and Paquette; Griffith, 2011) occurring in a relatively small region on the blade. the panels are not the major flap-wise blade carrying element of a blade, but they must be designed carefully to avoid buckling while minimizing the blade weight.…”
Section: Discussionmentioning
confidence: 99%
“…Both the numerical and experimental modes indicate the panel modes. The knowledge of the local panel modes can be useful for dynamic characterization, damage detection and structural health monitoring of the blade panels (Griffith, 2011). Figure 10.Localized Panel Modes of Wind Turbine Blade.…”
Section: Discussionmentioning
confidence: 99%
“…Although one surface measurement of the wind turbine blade is enough to characterize the experimental modal character for global beam-type blade modes, especially for low-frequency blade mode shapes. However, as shown in Reference (Griffith and Paquette; Griffith, 2011) via accelerometers measurements placed on both sides of the blade, several high-order blade modes have local panel modes. In some instances, a well perception of these local modes is necessary for blade structural health monitoring and structural damage detection (Griffith, 2011; Griffith et al, 2014; Yin et al, 2017).…”
Section: Introductionmentioning
confidence: 90%
“…However, as shown in Reference (Griffith and Paquette; Griffith, 2011) via accelerometers measurements placed on both sides of the blade, several high-order blade modes have local panel modes. In some instances, a well perception of these local modes is necessary for blade structural health monitoring and structural damage detection (Griffith, 2011; Griffith et al, 2014; Yin et al, 2017).…”
Section: Introductionmentioning
confidence: 90%
“…To directly acquire a large number of experimental degrees of freedom (DOF) from the blade, either optical photogrammetry or Scanning Laser Doppler Vibrometer (SLDV) can be used to measure the mode shape of one surface of the wind turbine blade. Measurements on both sides of the blade with accelerometers were conducted by Griffith et al (Griffith and Paquette; Griffith, 2011). Blade modes including the panel modes can be captured from the modal test, but the measured mode shapes have sparse spatial resolution due to the limited number of accelerometers deployed on the blade.…”
Wind turbine design and operation will benefit from a better understanding of blade dynamics. Usually, only one surface or one side of a 3D structure is measured in Scanning Laser Doppler Vibrometer (SLDV) tests due to test setup and instrumentation limitations. However, in this work, we demonstrate an approach to overcome these limitations while also using an SLDV that provides high spatial resolution measurement. In the case of a wind turbine blade, only one surface is typically measured; however, it is beneficial to investigate both blade global modes and the relative motions of the two blade surfaces by using both numerical models and experimental tests. This work creatively develops both experimental and numerical approaches to investigate the dynamics and the relative motions of both surfaces of the wind turbine blade from global and local perspectives. On the experimental side, experimental modal testing is conducted on both surfaces of the wind turbine blade with a high spatial resolution 3D SLDV. The two surfaces of the wind turbine blade are measured and stitched together to build the blade experimental mode shapes of both surfaces. A total of over 1500 points are scanned from both surfaces of the blade in a non-contact fashion to obtain not only the global bending modes (flap-wise and edge-wise), the global torsional modes, but also the localized panel mode shapes. On the numerical side, a finite element model of the blade is developed to obtain the numerical mode shapes. The experimental mode shapes on either one surface or both surfaces of the blade are used to validate the blade finite element model. The mode shape correspondence between the model and the test is also identified. With the availability of both experimental and numerical mode shapes, localized panel modes of the wind turbine blade are observed and characterized, and as a result the numerical model is validated. This work provides useful case studies for the design and structural analysis of wind turbine blades based on both the experimental observations and the validation of numerical models typical of those used for blade design and blade structural analysis.
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