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MAP++ linear spring approach improvement #1752

Merged
merged 1 commit into from
Sep 8, 2023
Merged

MAP++ linear spring approach improvement #1752

merged 1 commit into from
Sep 8, 2023

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RBergua
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@RBergua RBergua commented Aug 30, 2023

Small modification for the linear spring approach in MAP++. This modification allows to study conventional catenary systems as well as lines that have the anchor point above the fairlead connection.

Feature or improvement description
The default MAP++ version can only apply vertical forces in the downward direction. This is the force that we would expect in a conventional mooring line system. However, there are some conditions when the force should be applied in the upward direction (e.g., when then anchor location is above the fairlead connection).

The proposed modifications allows MAP++ to apply positive or negative forces in the vertical direction when using the linear spring approach.

For reference MAP++ can solve a mathematical problem by means of a catenary formulation or a linear spring formulation. The modifications presented here, only impact the linear spring formulation.

Related issue, if one exists
This modification solves the problems for the linear spring approach in MAP++ reported here: #1750

Impacted areas of the software
The modifications only affect MAP++ when the linear_spring flag is selected in the line properties section.

Additional supporting information
Sometimes, when performing scale tests of floating offshore wind turbines in a wave tank, horizontal mooring lines are used. Usually monofilament fishing lines connected in series to a spring are used to reproduce a similar elastic restoring force as the corresponding catenary line. See for reference section 2.4 of the paper: https://doi.org/10.3390/machines11090865. For this kind of applications, the linear spring approach from MAP++ is a convenient approach to simulate the system.

Test results, if applicable
Several tests cases have been performed with satisfactory results. The outputs from the modified code (MAP++) has been also compared against MoorDyn v2. See for reference: #1750

Small modification for the linear spring approach in MAP++. This modification allows to study conventional catenary systems as well as lines that have the anchor point above the fairlead connection. This modification solves the problems reported here for the linear spring approach: #1750
@ebranlard ebranlard self-requested a review August 30, 2023 01:04
@ebranlard ebranlard self-assigned this Aug 30, 2023
@andrew-platt andrew-platt added this to the v3.5.1 milestone Sep 5, 2023
@andrew-platt andrew-platt changed the base branch from dev to rc-3.5.1 September 5, 2023 16:09
@RBergua
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RBergua commented Sep 5, 2023 via email

@andrew-platt
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Thanks @RBergua!

@andrew-platt andrew-platt merged commit 900d12b into OpenFAST:rc-3.5.1 Sep 8, 2023
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@andrew-platt andrew-platt mentioned this pull request Oct 19, 2023
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3 participants