Curved Blade planform, aerodynamic modelling

Hi all,

Does someone know how you can include the effect of a curved blade planform into a BEM model?
I thought that the classical approach used for swept wing, i.e. projecting the flow perpendicularly to
the LE, could be suitable. Nevertheless, in this way you always reduce the yielded power, because you
reduce the total speed flow (perpendicular to the LE) at the blade elements, and I do not know whether this is realistic or not.
So, is this the correct way to model the effect of a curved planform within BEM or are there any better method?

Marco

Hi Marco,

I saw that Scott Larwood posted his dissertation about swept wind turbine blade analysis on this forum, and he included modifications to FAST to analyze swept blades. Hopefully this will help, here is the thread:

[url]http://forums.nrel.gov/t/swept-wind-turbine-blades-dissertation/163/1]

Danny Sale
University of Washington

Hi Danny,

thanks but I knew this work. In this case the approach I aforementioned (in my first post) is used. The question is whether it is realistic or not? This approach is used for fixed wings, but I do not know if it is suitable to rotating ones.
As I said, in this way you always consider a reduced aerodynamic pressure at the blade sections and this entails a reduction of the yielded power (considering all the other parameters as constant). My question is:

if you curve a blade by translating the sections perpendicularly to the radial direction (without rotating the section), why I cannot consider that the flow is two-dimensional on sections perpendicular to radial direction rather than on sections perpendicular to the blade LE?

From my physical understanding it would seam that the flow could be approximated two-dimensional on sections perpendicular to the LE, even thought the blade is curved. On the other hand, in literature (Larwood or Liebst for example) the other approach is used; so, probably I’am missing something and I would like to understand what it is.

Marco

Hi all

Clarification:
In the last post (the previous one) I wrote LE instead of radial direction, within the last paragraph. So the correct version is:

From my physical understanding it would seam that the flow could be approximated two-dimensional on sections perpendicular to the radial direction, even thought the blade is curved. On the other hand, in literature (Larwood or Liebst for example) the other approach is used; so, probably I’am missing something and I would like to understand what it is.

Marco