# problem in runing linearization with aerodyn

**URL:** <https://forums.nlr.gov/t/problem-in-runing-linearization-with-aerodyn/2088>\
**Category:** Structural Analysis\
**Created:** [July 11, 2019, 7:37am UTC](https://forums.nlr.gov/t/problem-in-runing-linearization-with-aerodyn/2088 "2019-07-11T07:37:43Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Shijing.Xu](https://avatars.discourse-cdn.com/v4/letter/s/9de053/32.png) [@Shijing.Xu](https://forums.nlr.gov/u/Shijing.Xu)\
**Post date:** [July 11, 2019, 7:37am UTC](https://forums.nlr.gov/t/problem-in-runing-linearization-with-aerodyn/2088/1 "2019-07-11T07:37:43Z")

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Dear all,  
I am trying to use OpenFast to linearize with the ElastoDyn, AeroDyn enable. However I encountered the following error:

OpenFAST-v2.0.0-dirty  
Compile Info:

- Architecture: 32 bit
- Precision: single
- Date: Dec 05 2018
- Time: 14:55:05  
Execution Info:
- Date: 07/11/2019
- Time: 15:17:55+0800

OpenFAST input file heading:

Running ElastoDyn.  
Running AeroDyn.  
Running AirfoilInfo.  
Running BEM.  
Running InflowWind.

FAST\_InitializeAll:InitModuleMappings:ED\_2\_AD\_TowerMotion:MeshMapCreate:CreateMotionMap\_L2\_to\_L2:CreateMapping\_ProjectToLine2:Found close value for node 94. (4.99752E-03 m)

Performing linearization at simulation time 0 s. (RotSpeed=9.92 rpm, BldPitch1=18.44 deg)

FAST\_Linearize\_T:FAST\_Linearize\_OP:AD\_JacobianPInput:CheckLinearizationInput:Blade1, node 1:  
residual is discontinuous or undefined because z%phi = 0.  
FAST\_Linearize\_OP:AD\_JacobianPConstrState:CheckLinearizationInput:Blade1, node 1:  
residual is discontinuous or undefined because z%phi = 0.

FAST encountered an error at simulation time 0 of 1 seconds.  
Simulation error level: FATAL ERROR

Aborting OpenFAST.

I wonder if anyone can help me? ❓

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<div class="post-metadata">

**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\
**Post date:** [July 15, 2019, 3:30am UTC](https://forums.nlr.gov/t/problem-in-runing-linearization-with-aerodyn/2088/2 "2019-07-15T03:30:34Z")

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Dear Shijing.Xu,

We are aware of an issue in AeroDyn that prevents linearization when the local inflow angle (phi) equals zero, which usually occurs due to some unfortunate combination of tilt and precone angles, rotor speed, and wind speed. Until we fix this issue, usually linearizing at a slightly different time allows OpenFAST to linearize without error.

I hope that helps.

Best regards,