Modelling and modal characteristics of NPS-100 9.2m wind turbine

This paper presents a methodology for modeling and modal characteristics of wind turbine blade. Structures with different cross section airfoils, different chord lengths and manufactured with composite materials are difficult to model. Moreover, modeling should be such that it can address requirements from aerodynamic as well structural perspective. Complexity is further added when failure analyses are also required. Ideal modeling tool is therefore should be capable of addressing all above requirements along with ease of modeling in less time. NuMAD (Numerical Manufacturing And Design) developed by Sandia National Laboratories offers all such capabilities. In the present work, NPS-100 wind turbine blade has been used as test case to demonstrate and share the capabilities of the package. NuMAD generated input files for ANSYS which is then used to perform modal analysis in wind off and wind on conditions with cantilevered boundary condition. In wind off condition, modes were extracted without the application of any force and in un-deformed state. Results were in good agreement with those of published data. In wind on condition, axial load was applied with pre-stress option on, followed by nonlinear modal analysis. Results indicated a progressive increase in frequencies with the increase of axial load. This is because of stress stiffening effect. Similarly bucking analysis and other FEM based analyses may be performed with the modeling procedures adopted in this work for the current geometry or for any other geometry of interest.