WT_Perf Convergence

Hi,

I’m having a bit of trouble with convergence on a WT_Perf analysis. The results are fine with no yaw but when I add yaw greater than about 3degrees I start having convergence issues at some windspeed/rpm combinations, see below for an example with 5deg yaw (see -999.999 values). Can anyone give me pointers as to what are possible causes are for this?

Thanks in advance,

Mike

Results generated by WT_Perf (v3.10, 16-Dec-2004) for input file “e387_1.wtp”.
Generated on 02-Nov-2010 at 16:59:01.
Input file title:
turbine 5deg yaw


Power (W) for Omega = 975 rpm.

WndSp Pitch (deg)
(mps) 0.000
15.500 2253.399
15.600 2299.333
15.700 2345.705
15.800 2392.585
15.900 2439.960
16.000 2487.803
16.100 2536.143
16.200 2585.015
16.300 2634.379
16.400 2684.210
16.500 2734.560
16.600 -999.999
16.700 2836.776
16.800 2888.583
16.900 2941.035
17.000 2993.832
17.100 3047.137
17.200 3100.921
17.300 3155.150
17.400 3209.941
17.500 3265.413
17.600 3320.961
17.700 3377.582
17.800 3434.351
17.900 -999.999
18.000 3549.396

Hi again,

I’ve done some more investigation and found the higher the yaw angle the worse the problem gets. For example at 10deg yaw WT_Perf freezes.

Mike

Please see this post for an explanation:

[url]http://forums.nrel.gov/t/induced-flow-estimation-in-bem/302/1]

We are working on a more-robust algorithm, but have little time to work on it. You may want to play with the iteration constants to see if it will converge. Please keep in mind that solutions are not guaranteed with BEM theory.