CFD analysis of current drag on the Floating Power Plant platform P80

Pedersen, Daniel Rothwell ; Hoffmann, Martin Kirk

4. term

Structural and Civil Engineering, Master

2019

2019-06-07

106

Denne afhandling undersøger, hvordan havstrømme skaber modstandskræfter (drag) på et nyt, halvt neddykket anlæg, der kombinerer en bølgekraftkonverter og en vindmøllegenerator, udviklet af Floating Power Plant. Platformen, P80, kan dreje frit omkring et tårn i fortøjningen (en roterende forankringsenhed), så den kan vende mod indkommende bølger. Da strømme også kan skubbe og dreje platformen, er målet at bestemme deres indflydelse på platformens orientering. Vi bruger computational fluid dynamics (CFD), dvs. computersimuleringer af strømning, i fuld skala ved et Reynolds-tal på omkring 50 millioner. Vi rapporterer modstandskoefficienter (mål for hydrodynamisk modstand) både i og på tværs af strømningsretningen for forskellige angrebsvinkler og estimerer heraf det drejemoment om den lodrette akse (yaw), som strømmen skaber. For at kontrollere simuleringerne udførte vi flumeforsøg (forsøg i en vandkanal) på Aalborg Universitet med småskalaversioner af anlægget. De eksperimentelle resultater bruges til at validere CFD-modellen, som derefter anvendes til at bestemme strøminducerede modstandskræfter. Vi bestemmer også strøminducerede kræfter på en model af anlægget og på ét enkelt ben af konstruktionen; disse CFD-beregninger understøttes af målinger. Alle forsøg er udført af forfatterne og beskrives i detaljer i afhandlingen.

This thesis examines how ocean currents produce drag forces on a new semi-submersible platform that combines a wave energy converter and a wind turbine generator, developed by Floating Power Plant. The platform, called P80, can rotate freely around a mooring turret (a swiveling anchoring system) so it can face incoming waves. Because currents can also push and twist the platform, the study aims to determine how current-induced forces affect its orientation. We use full-scale computational fluid dynamics (CFD)—computer simulations of fluid flow—at a Reynolds number of about 50 million. We report drag coefficients (measures of hydrodynamic resistance) both along and across the current for different angles of attack, and from these estimate the yawing moment (the turning force about the vertical axis) generated by the current. To check the simulations, we carried out flume experiments (tests in a water channel) at Aalborg University with small-scale models of the platform. The experimental results are used to validate the CFD model, which is then applied to determine current-induced drag forces. We also quantify current-induced forces on the model and on a single leg of the structure; these CFD results are supported by measurements. All experiments were conducted by the authors and are presented in detail in the thesis.

[This abstract was generated with the help of AI]

CFD ; Numerisk analyse ; Drag ; Current ; eksperiment

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