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HD: Bug fix for potential-flow wave excitation with multiple bodies and large yaw offset#2408

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andrew-platt merged 1 commit intoOpenFAST:devfrom
luwang00:b/HD_NBody_LrgYaw
Sep 9, 2024
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HD: Bug fix for potential-flow wave excitation with multiple bodies and large yaw offset#2408
andrew-platt merged 1 commit intoOpenFAST:devfrom
luwang00:b/HD_NBody_LrgYaw

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@luwang00 luwang00 commented Sep 7, 2024

Feature or improvement description
Two bugs were identified that led to incorrect potential-flow wave excitation when multiple bodies are present with large yaw offset (PtfmRefY!=0 or PtfmYMod=1):

  • When NBodyMod=1 and NBody>1, only the wave excitation on the first body is transformed back to the inertial frame. This PR adds the transformation of the subsequent bodies.

  • When PtfmRefxt!=0 or PtfmRefyt!=0, there is effectively a displacement of each potential-flow body due to platform yaw offset when precomputing the wave excitation. In other words, the effect of this baseline displacement is already baked into the precomputed wave excitation, so it needs to be subtracted from the total body displacement when interpolating the wave excitation if ExctnDisp>0. This correction is implemented in this PR.

Impacted areas of the software
HydroDyn

Test results, if applicable
Existing tests are not impacted by the bugs identified, so no change to the test results.

…nd large yaw offset

Two bugs are identified that lead to incorrect potential-flow wave excitation when multiple bodies are present with large yaw offset (PtfmRefY!=0):
* When NBodyMod=1 and NBody>1, only the wave excitation on the first body is transformed back to the inertial frame in WAMIT_Init.
* When PtfmRefY!=0 with PtfmRefxt or PtfmRefyt being nonzero, there is effectively a displacement of each potential-flow body due to platform yaw offset when precomputing the wave excitation each body. In other words, the effect of this baseline displacement is already baked into the precomputed wave excitation, so it needs to be subtracted from the total body displacement when interpolating the wave excitation in WAMIT_CalcOutput if ExctnDisp>0.
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I don't know all the details in your transform, but this looks correct.

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Related to #2203

@andrew-platt andrew-platt merged commit 2246bef into OpenFAST:dev Sep 9, 2024
@luwang00 luwang00 deleted the b/HD_NBody_LrgYaw branch September 9, 2024 18:37
@andrew-platt andrew-platt mentioned this pull request Dec 24, 2024
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