DYNAMIST

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DYNAMIST is a dynamic analysis code developed for assessing structural response of Vertical Axis Wind Turbine under dynamic loads.


DYNAMIST will do the dynamic structural response analysis based on a finite-element formulation. In this code, the VAWT is modeled using the lumped mass approach. The rotor blades, struts and the central shaft are divided into simple straight segments and treated as 3-D beam elements. Each 3-D beam element has two nodes with six degrees of freedom at each node. Using the finite element technique, each element can be modeled as a second order differential equation. The formulation includes a mass matrix, a gyroscopic matrix, a stiffness matrix for each element and a second stiffness matrix which results from the spinning of the structure. The gyroscopic matrix has a stabilizing effect while the second stiffness matrix has a destabilizing effect. The force vector contains the aerodynamic loading (load per unit length) acting on the beam elements calculated by the CARDAAV code.


The output is the natural frequency and modes for both spinning and non-spinning rotor, as well as the modal frequency response at required rotational speeds. Output from forced response includes both linear and angular displacements (maximum values at required nodes) at desired rotational speeds. The program can also provide power density spectra. The load per unit length on each element, cross-sectional structural properties of each load element and the rotor operating conditions are required as input. The program was developed last year. The validation is currently underway. The theoretical basis is based on the concept of spinning finite elements.