Hi @Jason.Jonkman:

I am getting the below error In TurbSim when I change value of Cohexp to make it greater than 0.35; so for 0.40 I got the error. I would like to use a Cohexp value of 0.85. I believe the error has something to do with my grid size, say. If I use the following model parameters I get no error with a Cohexp of 0.85 .

--------Turbine/Model Specifications-----------------------

31 NumGrid_Z - Vertical grid-point matrix dimension

31 NumGrid_Y - Horizontal grid-point matrix dimension

0.05 TimeStep - Time step [seconds]

3600 AnalysisTime - Length of analysis time series [seconds] (program will add time if necessary: AnalysisTime = MAX(AnalysisTime, UsableTime+GridWidth/MeanHHWS) )

3600 UsableTime - Usable length of output time series [seconds] (program will add GridWidth/MeanHHWS seconds unless UsableTime is “ALL”)

119.0 HubHt - Hub height [m] (should be > 0.5*GridHeight)
210 GridHeight - Grid height [m]
210 GridWidth - Grid width [m] (should be >= 2*(RotorRadius+ShaftLength))

0 VFlowAng - Vertical mean flow (uptilt) angle [degrees]

0 HFlowAng - Horizontal mean flow (skew) angle [degrees]

However, if I use the following model parameters I get the error:

--------Turbine/Model Specifications-----------------------

31 NumGrid_Z - Vertical grid-point matrix dimension

31 NumGrid_Y - Horizontal grid-point matrix dimension

0.05 TimeStep - Time step [seconds]

3600 AnalysisTime - Length of analysis time series [seconds] (program will add time if necessary: AnalysisTime = MAX(AnalysisTime, UsableTime+GridWidth/MeanHHWS) )

3600 UsableTime - Usable length of output time series [seconds] (program will add GridWidth/MeanHHWS seconds unless UsableTime is “ALL”)

150.0 HubHt - Hub height [m] (should be > 0.5*GridHeight)
275 GridHeight - Grid height [m]
750 GridWidth - Grid width [m] (should be >= 2*(RotorRadius+ShaftLength))

0 VFlowAng - Vertical mean flow (uptilt) angle [degrees]

0 HFlowAng - Horizontal mean flow (skew) angle [degrees]

**TurbSim Error**

Reading the input file “150m_88mps_wind_shearJCS1_test.inp”.

Calculating the spectral and transfer function matrices:

u-component matrices (general coherence model)

CalcFourierCoeffs:CalcFourierCoeffs_General:Error in Cholesky factorization: LAPACK_SPPTRF:

Leading minor order 111 of A is not positive definite, so Cholesky factorization could

not be completed.

The error occurred in the u-component coherence matrix at frequency 1 (2.76817E-04 Hz) Check the input file for invalid physical properties or modify the coherence.

I think the error is due to the size of my grid. However, I need a sufficiently large grid width to prevent blades from deflecting outside of the grid and causing an error in OpenFAST.

Please let me know if you have any ideas on how to solve this problem.

Thank you.

Regards,

AOAW