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<front>
<journal-meta>
<journal-id journal-id-type="publisher">WESD</journal-id>
<journal-title-group>
<journal-title>Wind Energy Science Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">WESD</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Wind Energ. Sci. Discuss.</abbrev-journal-title>
</journal-title-group>
<publisher><publisher-name></publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/wes-2026-211</article-id>
<title-group>
<article-title>A rigidly-convected, lifting-line vortex model in the optimal control of airborne wind energy systems</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Leuthold</surname>
<given-names>Rachel</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>De Schutter</surname>
<given-names>Jochem</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Crawford</surname>
<given-names>Curran</given-names>
<ext-link>https://orcid.org/0000-0001-6047-728X</ext-link>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Gros</surname>
<given-names>Sébastien</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Diehl</surname>
<given-names>Moritz</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Systems Control and Optimization Laboratory, Department of Microsystems Engineering (IMTEK), Albert-Ludwigs-University, Freiburg, Germany</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>TransnetBW, Wendlingen am Neckar, Baden-Württemberg, Germany</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Institute for Integrated Energy Systems, University of Victoria, Victoria, Canada</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Department of Engineering Cybernetics, Norwegian University of Science and Technology, Gløshaugen, Norway</addr-line>
</aff>
<pub-date pub-type="epub">
<day>12</day>
<month>11</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>67</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Rachel Leuthold et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://wes.copernicus.org/preprints/wes-2026-211/">This article is available from https://wes.copernicus.org/preprints/wes-2026-211/</self-uri>
<self-uri xlink:href="https://wes.copernicus.org/preprints/wes-2026-211/wes-2026-211.pdf">The full text article is available as a PDF file from https://wes.copernicus.org/preprints/wes-2026-211/wes-2026-211.pdf</self-uri>
<abstract>
<p>Solving optimal control problems (OCPs) to estimate the performance of airborne wind energy (AWE) systems can raise the question: &quot;How should one include a vortex-filament model into an OCP on an irregular flight path, specifically where there are also a substantial number of inequality constraints?&quot; Since a rigidly-convected, lifting-line vortex (RLL) model might balance computational expense against sensitivity to geometric assumptions, we construct a solvable problem by judiciously lifting certain algebraic variables into an AWE OCP&amp;rsquo;s decision variables. This RLL model makes predictions that are consistent considering modeling assumptions with independently-published Large Eddy Simulations, during rotationally-steady as well as dynamic situations. Further, demonstrating the importance of including wake-modeling in airborne wind energy applications, solving an AWE OCP including this RLL model finds a substantial difference in power compared to solving an AWE OCP assuming negligible induced velocity; this paper&amp;rsquo;s demonstration problem, with a two-kite (Ampyx-AP2) system and a single- winding trajectory, predicts a 20 %&amp;ndash;30 % loss in harvestable power (depending on initialization and objective). Unfortunately, solving such an RLL AWE OCP is also quite expensive: in the problem instances and solver configurations tested within this work, the required computational memory scales with the total number of vortex elements instantiated in the entire problem, while the processor time scales with more than that number squared. In conclusion, it is possible to include a RLL model into a solvable AWE OCP with an irregular trajectory and many inequality constraints, though the solution is quite expensive and is heavily influenced by the homotopy strategy used for initialization.</p>
</abstract>
<counts><page-count count="67"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>Deutsche Forschungsgemeinschaft</funding-source>
<award-id>504452366 (SPP 2364)</award-id>
<award-id>525018088 (MAWERO)</award-id>
</award-group>
<award-group id="gs2">
<funding-source>Bundesministerium für Wirtschaft und Klimaschutz</funding-source>
<award-id>03EI4057A</award-id>
<award-id>03EN3054B</award-id>
</award-group>
<award-group id="gs3">
<funding-source>European Commission</funding-source>
<award-id>AWESCO 642682</award-id>
<award-id>ELO-X 953348.</award-id>
</award-group>
</funding-group>
</article-meta>
</front>
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<back>
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