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Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway.
Thesis (MEng)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2024
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| _version_ | 1867614048569262080 |
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| access_status_str | Open Access |
| author | Tessendorf, Kayle Anthony |
| author2 | Bosman, Adèle |
| author_browse | Bosman, Adèle Tessendorf, Kayle Anthony |
| author_facet | Bosman, Adèle Tessendorf, Kayle Anthony |
| author_sort | Tessendorf, Kayle Anthony |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/130326 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:45:50.231Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/130326 Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. Tessendorf, Kayle Anthony Bosman, Adèle Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Energy dissipation Trajectories (Mechanics) Spillways Streamflow velocity Trajectory buckets Thesis (MEng)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Ski-jump spillways have effectively been used for almost 100 years on high-head dams to dissipate the significant flood discharge energy produced during major flood events. The trajectory bucket installed at the base of the ski-jump spillway deflects high-velocity flow into the air, ensuring the jet impinges the plunge pool at a predetermined impact location that does not compromise the dam’s foundation. Energy dissipation on a ski-jump spillway mainly occurs through jet diffusion within the plunge pool. However, if the jet core remains intact upon impact with the plunge pool, the high erosive power of the solid compact jet may cause significant scour damage to the pool bottom. To limit the potential for scour erosion in the plunge pool, the air entrainment and jet disintegration process during the jet’s travel through the atmosphere can be enhanced by altering the geometry of the trajectory bucket. Various designs have been implemented on ski-jump spillways, with the most notable ones featuring trajectory buckets equipped with splitter teeth or a local insert to break up the jet core at take-off. Such trajectory bucket designs have been refined through model studies, yet a comprehensive design guideline remains a work in progress. A 1:25 scale hydraulic model of a ski-jump spillway was constructed to investigate the effectiveness of different trajectory buckets. Specifically, two trajectory bucket variations, one featuring splitter teeth and the other incorporating a central insert, were compared to a conventional circular-shaped trajectory bucket. The objective was to determine their influence on energy dissipation downstream of a ski-jump spillway. The physical model tests focused on the jet trajectory performance, impact footprint, dynamic impact pressure head, and impact velocity for five different flow conditions. The results of the study indicated that both trajectory bucket variations effectively dissipated the energy, outperforming the conventional circular-shaped trajectory bucket. In addition, the two trajectory buckets ensured an adequate jet trajectory throw distance, safeguarding the integrity and stability of the dam and its foundation. When comparing the splitter teeth design with the central insert design, the former indicated superior performance. The splitter teeth trajectory bucket design used in this study proves to be proficient in effectively dissipating energy, especially when evaluating the jet trajectory and impact parameters under high-flow velocities. However, to comprehensively understand its performance, further research is required to analyse the pressure distribution along the bucket lip to ensure no cavitation occurs on the splitter teeth. Furthermore, a dedicated scour model study is recommended to investigate the influence of this trajectory bucket type in preventing the formation of a scour hole in the plunge pool. AFRIKAANSE OPSOMMING: Ski-sprong oorlope is effektief gebruik vir bykans 100 jaar op hoë damme om energie van hoë vloei wat tydens groot vloedgebeure ontstaan, te verminder. Die trajekvoetstuk wat aan die basis van die ski-sprong oorloop geïnstalleer word, deflekteer die hoësnelheidvloei in die lug om te verseker dat die waterstraal die plonspoel op 'n voorafbepaalde impakligging tref wat nie die dam se fondament benadeel nie. Energie dissipasie op 'n ski-sprong oorloop gebeur hoofsaaklik deur die diffusie van die waterstraal binne die plonspoel. Tog, as die kern van die waterstraal intak bly met impak met die plonspoel, kan die hoë erosiewe krag van die soliede kompakte straal beduidende erosieskade aan die bodem van die poel veroorsaak. Om die potensiaal vir erosie in die plonspoel te beperk, kan belugting en straalontbindingsproses tydens die waterstraal se val deur die lug verhoog word deur die geometrie van die trajekvoetstuk te verander. Verskeie ontwerpe is op ski-sprong oorlope geïmplementeer, met die mees bekendes diè wat ʼn trajekvoetstuk bevat wat toegerus is met verdeeltande of 'n plaaslike invoegsel om die waterstraalkern op te breek wanneer dit die oorloop verlaat. Sulke trajekvoetstuk is verfyn deur modelstudies, maar 'n omvattende ontwerpriglyn moet nog vasgestel word. 'n 1:25 hidrouliese skaal model van 'n ski-sprong oorloop is opgerig om die doeltreffendheid van verskeie trajekvoetstukke te ondersoek. Spesifiek is twee variasies van trajekvoetstukke, een met verdeeltande en die ander met 'n sentrale invoegsel, vergelyk met 'n konvensionele sirkelvormige trajekvoetstuk. Die doel was om hul invloed op energiedissipasie stroomaf van 'n ski-sprong oorloop te bepaal. Die fisiese modeltoetse het gefokus op die waterstraal se trajek, die impak area, die dinamiese drukke met impak met die plonspoel bodem en die impak vloeisnelheid vir vyf verskillende vloedtoestande. Die resultate van die studie het aangedui dat beide variasies van die trajekvoetstukke die energie effektief gedissipeer het, en die konvensionele sirkelvormige trajekvoetstuk oortref het. Daarbenewens het die twee trajekvoetstukke 'n voldoende waterstraal trajekafstand gehandhaaf, wat die integriteit en stabiliteit van die dam en sy fondament beskerm het. Wanneer die ontwerp met die verdeeltande met die sentrale invoegselontwerp vergelyk word, het eerstegenoemde 'n beter prestasie getoon. Die verdeeltand trajekvoetstuk wat in hierdie studie gebruik is, blyk doeltreffend te wees om energie doeltreffend te dissipeer, veral wanneer die waterstraal se trajek en impakparameters onder hoë vloeitoestande geëvalueer word. Tog is verdere navorsing nodig om die drukverspreiding langs die trajekvoetstuklip te ontleed om te verseker dat geen kavitasie op die verdeeltande plaasvind nie. Daarbenewens word 'n toegewyde uitskuringsmodelstudie aanbeveel om die invloed van hierdie tipe trajekvoetstuk op die voorkoming van 'n uitskuringsgat in die plonspoel te ondersoek. Masters 2024-02-20T19:26:28Z 2024-04-26T13:32:17Z 2024-02-20T19:26:28Z 2024-04-26T13:32:17Z 2024-02 Thesis https://scholar.sun.ac.za/handle/10019.1/130326 en_ZA en_ZA Stellenbosch University xxii, 193 pages : illustrations. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Energy dissipation Trajectories (Mechanics) Spillways Streamflow velocity Trajectory buckets Tessendorf, Kayle Anthony Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. |
| title | Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. |
| title_full | Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. |
| title_fullStr | Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. |
| title_full_unstemmed | Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. |
| title_short | Influence of trajectory buckets on energy dissipation downstream of a ski-jump spillway. |
| title_sort | influence of trajectory buckets on energy dissipation downstream of a ski jump spillway |
| topic | Energy dissipation Trajectories (Mechanics) Spillways Streamflow velocity Trajectory buckets |
| url | https://scholar.sun.ac.za/handle/10019.1/130326 |
| work_keys_str_mv | AT tessendorfkayleanthony influenceoftrajectorybucketsonenergydissipationdownstreamofaskijumpspillway |