| dc.description.abstract | Denne oppgaven dekker en experimentell studie av et Cabrinha Fusion X1300 foil kit, som benyttes til kiting og surfing. Ettersom det er en eksperimentell oppgave, inneholder den planlegging av eksperiment og testprogram, design av testoppsett, og analyse av resultater.
I prosjektoppgaven som ble utført som forarbeid til masteroppgaven ble det utført et eksperiment i kavitasjonstunnelen hos SINTEF Ocean, hvor foil kitet var fullt neddykket og ble testet for variasjon i angrepsvinkel. Med erfaringer fra dette forsøket ble det bestemt at masteroppgaven skulle dekke et eksperiment i slepetanken på NTNU for å undersøke hvordan overflateeffekter og bølgeinteraksjon påvirker ytelsen til foil kitet.
Løftkoeffisienten viser tydelig påvirkning av overflateeffekt og bølgepåvirkning, da løftkoeffisienten er høyere i kavitasjonstunnelen enn i slepetanken. I følgende sjø finner man den optimale løft/motstand da foilkitet seiler med bølgen.
For store girvinkler ble foilkitet i stor grad påvirket av ventilasjon, hvor ventilasjon oppstod allerede ved lave hastigheter, lenge før foilkitet hadde oppnådd tilstrekkelig løft for en person med utstyr.
Siden eksperimentene kun undersøker stabile kondisjoner er studien noe mangelfull da foil kitet benyttes med dynamiske bevegelser og derfor er påvirket av dynamiske effekter. Til tross for dette gir resultatene en god indikasjon på den generelle ytelsen til foilkitet. | |
| dc.description.abstract | This thesis covers an experimental research on a Cabrinha Fusion X1300 foil kit, and includes planning of test set-up, design of necessary attachments, planning of test programme, data acquistion and analysis of results. Two experiments have been carried out at NTNU and SINTEF Ocean's facilites in Trondheim. The first experiment was carried out in SINTEFs cavitation tunnel during the fall of 2020 as preliminary research for this thesis in a separate project thesis. In the cavitation tunnel the foil kit was fully submerged, and was tested for varying angle of attack and speed. Based on the findings from the cavitation tunnel, it was decided that this master thesis would cover a towing experiment to determine the effect of free-surface effects and wave interaction on the performance of the foil. The towing experiment was carried out at the towing tank at NTNU in June 2021. The towing tank is 260 meters long and 10.5 meters wide. In the towing tank at he foil kit has been tested both fully submerged in a cavitation tunnel, and partly submerged in still water, head sea and following sea. The results from the towing tank has been compared to relevant conditions from the experiment in the cavitation tunnel.
The lift coefficient for the foil kit in still water and head sea is significantly lower than the lift coefficient from the cavitation tunnel, and may be explained by surface effects. The drag coefficient also show a lowered drag in the cavitation tunnel, compared to the runs in the towing tank. However, the total lift/drag relation show that the most efficient conditions occur when riding with a following wave, although this is highly dependent on the position on the wave.
For large yaw angles, the strut appears to ventilate more or less instantly, long before sufficient lift for 1 person has been developed. Consequently, riders should in general be careful with riding with large yaw angles as this appears to provoke ventilation under most circumstances. In addition, the strut generates a large spray pattern where water is pushed up along the mast. When this spray is disturbed by transverse waves, the whole spray may separate which may provoke further flow separation down along the mast.
As this study investigates the hydrodynamic behaviour of the foil kit for steady conditions, it does not consider the dynamic behaviour of the foil when used under actual conditions. Due to this, the test programme is not directly comparable to how the foil kit behaves when in use, but it does give a good indication of the general performance of the foil kit. | |