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Fix Bug in FAST.Farm Causing Wake Bounce-Back #839

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merged 2 commits into from
Sep 27, 2021

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jjonkman
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This pull request is ready to be merged.

All tests are expected to pass.

Feature or improvement description
For wake planes that are skewed relative to domain boundaries (e.g., due to nacelle-yaw), the weighting used in the spatial averaging to calculate the meandering velocity of wake planes when Mod_Meander = 3 could end up being negative as wake planes were leaving the domain. But the code always assumed that the weighting was positive. This bug fixes that.

Related issue, if one exists
This solves the issue reported on our forum dated July 06, 2021: https://wind.nrel.gov/forum/wind/viewtopic.php?f=13&t=2117&start=225.

Impacted areas of the software
The Ambient Wind and Wake Effects (AWAE) module of FAST.Farm.

For wake planes that are skewed relative to domain boundaries (e.g., due to nacelle-yaw), the weighting used in the spatial averaging to calculate the meandering velocity of the plane when Mod_Meander = 3 could end up being negative as wake planes were leaving the domain.  But the code always assumed that the weighting was positive.  This bug fixes that.  This solves the issue reported by on our forum dated July 06, 2021: https://wind.nrel.gov/forum/wind/viewtopic.php?f=13&t=2117&start=225.
@rafmudaf
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@jjonkman Is this situation covered in the existing FAST Farm related tests?

@jjonkman
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@rafmudaf -- Not really. The FAST.Farm r-test only tracks the OpenFAST output. The bug was most easily seen in the visualization output, although the OpenFAST output could be effected for the wake bounce back was significant. The bug would only manifest itself if the wake planes where skewed relative to the boundary of the low-resolution domain and would only be seen in the OpenFAST output if the domain boundary was close to a wind turbine rotor.

@jjonkman
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@rafmudaf -- Here is an image showing the visualization result after the bug fix. The wake has clearly no longer bounced back.
image

@rafmudaf
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Yes, that looks like a good fix compared to the plot shown in the forum. Thanks for the additional information.

@rafmudaf rafmudaf merged commit f59488a into OpenFAST:dev Sep 27, 2021
@rafmudaf rafmudaf mentioned this pull request Mar 2, 2022
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3 participants