Coordinate systems

The global coordinate system is located with the z-axis pointing vertical downwards. The x and y axes are horizontal to the side. When wind is specified, the default direction is along the global y-axis. Within the wind system meteorological u,v,w coordinates are used, where u is the mean wind speed direction, v is horizontal and w vertical upwards. When x,y,z notation is used within the wind coordinates, this refers directly to the u,v,w definition. Every substructure and body (normally the same) is equipped with its own coordinate system with origin in node 1 of this structure. The structure can be arbitrarily defined regarding orientation within this coordinate system. Within a body a number of structural elements are present. The orientation of coordinate systems for these elements is chosen automatically by the program. The local z axis is from node 1 to 2 on the element. The coordinate system for the blade structures must be defined with the z axis pointing from the blade root and outwards, x axis in the tangential direction of rotation and y axis from the pressure side towards the suction side of the blade profiles. This is in order to make the linkage between aerodynamics and structure function.

In order to make a quick check of the layout of the structure, the small program “animation.exe” can be used (this requires that an animation file has been written using the command animation in the Simulation block). The view options in this program are handled by keyboard hotkeys:

Animation Hotkeys:

translate: (shift)+{x,y,z}
rotate: arrow keys
rotate about line-of-sight: ctrl+left/right
zoom in: ctrl+up
zoom out: ctrl+down
amplify displacement (only for animation of natural frequencies): +
decrease displacement (only for animation of natural frequencies): -

If the animation does not start, press “s”.

Illustration of coordinate system as result of user input from example in appendix Example of main input file: Example of main input file. There are two coordinate systems in black which are the default coordinate systems of global reference and default wind direction. The blue coordinate systems are main body coordinate systems attached to node 1 of the substructure, the orientation of these are fully determined by the user. The coordinate systems are also defined by the user, but in order to make the linkage between aerodynamic forces and structure work these have to have the z from root to tip, x in chordwise direction and y towards the suction side.