Modelling the dispersion and deposition of solid wastes from fish farming with a continuum approach

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dc.contributor.advisorGoosen, Neillen_ZA
dc.contributor.advisorDiedericks, Gerhardus Petrus Jacobusen_ZA
dc.contributor.authorFourie, Samantha-Kerryen_ZA
dc.contributor.otherStellenbosch University. Faculty of Science. Dept. of Mathematical Sciences (Applied Mathematics)en_ZA
dc.date.accessioned2022-03-02T07:56:57Z
dc.date.accessioned2022-04-29T09:33:49Z
dc.date.available2022-03-02T07:56:57Z
dc.date.available2022-04-29T09:33:49Z
dc.date.issued2022-04
dc.descriptionThesis (MSc)--Stellenbosch University, 2022.en_ZA
dc.description.abstractENGLISH ABSTRACT: The sustainability of the environment in coastal ecosystems is of great concern due to aquaculture. There are many unknowns and constraints in the predictive modelling of fish farm waste due to the limitations of obtaining information in the farming area. By understanding the gaps in the information, the necessary research projects can be established, therefore improving the predictive modelling. This project presents an academic case for Delft3D-FLOW to predict the dispersion and deposition of organic mariculture waste using a continuum approach. The continuum approach allows us to model the waste interaction with the seabed as a cohesive sediment, which can be done using Delft3D-FLOW. More information is needed on how the wastes interact with the seabed as it has been observed that the erosion and deposition of the waste is sensitive to the cohesive properties. Delft3D-FLOW was used for the simulation as it includes modules of multi-dimensional hydrodynamic flows and transport phenomena, including the transport of cohesive and non-cohesive sediments. The simulation represents a growth cycle of six months for Atlantic salmon within a simple rectangular grid, using the background currents of a fjord in the Faroe Islands. A six month simulation period was chosen due to time constraints, allowing for a feasible simulation time and time to conduct a sensitivity analysis on the interaction of the waste with the seabed. The growth data of the simulation period was gathered from existing data in order to determine the amount of feed used, therefore representing the growth cycle of the Atlantic salmon. Using the feed cycle and information from literature, the corresponding waste output of the farm was calculated. Observing the output from the simulations, the waste has been completely dispersed from the grid at the end of the cycle, indication a highly dispersive site. These results correlates with the high currents that were calculated within the fjord. Further, an investigation was conducted into the critical deposition and erosion stresses in order to observe the affect the stresses have on the resultant deposition and dispersion of the waste at the seabed. The results of the sensitivity analysis of the shear stresses result in validation that low critical shear stresses were chosenen_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die volhoubaarheid van die natuurskoon in kus-ekosisteme word bedreig as gevolg van akwakultuur boerdery. Met betrekking tot die modellering van vis afval in vis boerdery, vir die doel van voorspelling, is daar vele onbekendes en beperkings wat bestaan. Daar is groot leemtes in die verkryging en versameling van inligting oor vis boerdery. Om al die leemtes te verstaan, kan vele navorsingsprojekte daarvoor bemagtig word, om die skep van voorspellingsmodelle te verbeter. Dié projek stel ’n akademise toetsgeval voor vir die Delft3D-FLOW sagteware om die dispersie en deposisie van organsiese materiaal te voorspel, met behulp van ’n kontinuum benadering. Die kontinuum benadering laat toe dat ons nie net die afval modelleer nie, maar ook die interasie daarvan met die seebodem as ’n kohesiewe sediment. Meer informasie word benodig ten opsigte van die interaksie van die vis afval met die seebodem, aangesien die erosie en ontbinding daarvan sensitief is tot kohesie eienskappe. Ons maak gebruik van Delft3D-FLOW vir die simulasies aangesien dit modules bevat vir die modellering van multi-dimensionele hidrodinamika en transport verskynsels. Die transport verskynsels sluit in die vervoer van kohesiewe en nie-kohesiewe sedimente. Die simulasie bestaan uit ’n ses maande groeisiklus van Atlantiese salm, binne ’n eenvoudige reghoekige area (rooster). Die simulasie maak gebruik van waterstrome in die agtergrond van ’n fjord in die Faroe Eilande. ’n Ses maande simulasie periode word gebruik as gevolg van tyd beperkinge. Die simulasie periode laat nie net toe vir ‘n realistiese simulasie tydperk nie maar ook om sensitiwiteits analise te doen oor die interaksie van die vis afval met die seebodem. Die groei data vir die simulasie was verkry vanaf reeds bestaande data, om die hoeveelheid voer wat gebruik is te bepaal. Dit verteenwoordig die groeisiklus van Altantiese salm. Deur van die groeisiklus gebruik te maak en inligting beskikbaar in literatuur, kon die resultante vis afval gegenereer deur vis boerdery bereken word. Deur na die uitsette van die simulasies te kyk, het ons gesien dat die afval heeltemal versprei het vanaf die reghoekige area teen die einde van die ses maande siklus. Dus, stel dit ‘n hoë verspreidings area voor. Die resultate was gekorreleer met die hoë water spoede in die fjord. Daar was verder ondersoek ingestel na die kritiese deposisie en erosie stresse wat ervaar word deur die vis afval en die impak daarvan op die seebodem. Die resultate van die sensitiwiteits analiese van die stresse, bevestig dat lae kritiese sleurspanning gekies was.af_ZA
dc.description.versionMastersen_ZA
dc.format.extent91 pagesen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/124800
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subjectCohesive sedimentsen_ZA
dc.subjectUCTDen_ZA
dc.subjectFish farmingen_ZA
dc.subjectAquaculture -- Impacten_ZA
dc.subjectSolid waste managementen_ZA
dc.subjectSediment transporten_ZA
dc.titleModelling the dispersion and deposition of solid wastes from fish farming with a continuum approachen_ZA
dc.typeThesisen_ZA
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