Several times I have been in the situation where I wanted to deform a grid or the elements on a surface in a radial way. I thought of compiling this routine into a GH User Object.. The Twirl GH User object receives as an input an array of 3d points and creates a twirl effect by rotating them by a specific angle from a given point-centre. The field of interaction is parametrically defined and so is the force of the twirl (clockwise + counter-clockwise).
For more info regarding GH user Objects please refer to the previous posts. To download the Twirl GH User Object go here. I will upload a few examples on how to use the GH User Objects in the future since several people have requested..