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Energy dissipation at uncontrolled high dam spillways by flare
Thesis (MEng)--Stellenbosch University, 2020.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2020
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| _version_ | 1867613904644866048 |
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| access_status_str | Open Access |
| author | Saayman, Ruben Lourens |
| author2 | Basson, G. R. |
| author_browse | Basson, G. R. Saayman, Ruben Lourens |
| author_facet | Basson, G. R. Saayman, Ruben Lourens |
| author_sort | Saayman, Ruben Lourens |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2020. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/108302 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:33.723Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/108302 Energy dissipation at uncontrolled high dam spillways by flare UCTD Saayman, Ruben Lourens Basson, G. R. Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Flaring Gate Piers Spillways -- Cavitation erosion Spillways -- Design and construction Thesis (MEng)--Stellenbosch University, 2020. ENGLISH ABSTRACT: Spillways have been used for approximately 3500 years to discharge water from dams. A growing world population has made the construction of dams a matter of critical importance. Several different types of spillways are used on different dams. Ogee spillways attached to stepped spillways are one of the oldest spillway types and with the advancement of new technologies and building techniques, such as Roller Compacted Concrete, the popularity of this spillway type has increased significantly. However, cavitation damage poses a large threat to a spillway and therefore, the safe discharge capacity of spillways has been limited to prevent cavitation damage to the structure itself. It is estimated that future climate change impacts on extreme flood runoff could increase flood peaks by 50% to even 100% by the end of this century in some parts of the world. Dam spillways will therefore have to deal with larger unit discharges. The prevention of cavitation is possible by increasing the air concentration to at least 8% in the flow at the pseudo-bottom of a spillway. Flaring Gate Piers (FGP) were developed in China as an aeration structure. To ensure aeration of the flow, flares are installed on the downstream end of a standard Waterways Experiment Station (WES) spillway. The flares are located upstream of the steps on a smooth ogee. All the flares tested in this study was fitted to a 1:50 model scale of the Dachaoshan dam spillway in China. Research on the effect of the FGP’s has been previously conducted by (Koen, et al., 2019). This research focuses on the removal of the gate piers to determine the effect of cavitation of the flares and the effects of the water jets that form over the flares. The two different types of FGP’s that are investigated are the X-Shape and the Y-Shape FGP. The effect and efficiency of the flares are investigated by taking pressure readings on the flares to identify areas of cavitation for different discharges. The flare type with the least or no areas of cavitation, along with the flare that aerates the flow the most significantly to prevent cavitation, is selected as the best flare type for this study. The water jets caused by the high discharge over the flare were also investigated to determine their effect downstream of the flares. After all 6 flares were tested for cavitation and the water jets were analysed, it was possible to determine which flare type design preformed the best. No pressures severe enough to cause cavitation damage was measured on any of the flares tested in this study. This means that all the flares are save from cavitation damage up to a unit discharge of 200 m2/s. The effects of the water jets were analysed to determine which flare type design preformed the best in this study. Y-shaped flare 3 preformed the best of all the flares tested during this study. This flare design projected the water further and higher than any of the other flare designs. Projecting the water further can lead to the jets being projected into tail waters downstream of the spillway. Deep tail waters can dissipate all the energy of the jets before it causes damage to the riverbed. The higher projected jets collide in the air with one another and dissipate fractions of the energy of the jets. The remaining energy of the jets are further dissipated by the resistance of the air on the water. Further optimization of the flares can be performed by altering the design of the side flares to ensure that the jets from the middle flares do not project over the jets from the side flares. AFRIKAANSE OPSOMMING: Oorlope word al vir ongeveer 3500 jaar gebruik om water uit damme uit te lei. 'n Toenemende wêreldbevolking maak die bou van damme 'n saak van groot belang. Verskeie soorte oorlope word op verskillende damme gebruik. Ogee-oorlope geheg aan trap oorlope is een van die oudste soorte oorlope, en met die bevordering van nuwe tegnologieë en boutegnieke, soos rolbeton, het die gewildheid van hierdie oorlooptipe aansienlik toegeneem. Kavitasiebeskadiging hou egter 'n groot bedreiging in vir die oorlope en daarom is die veilige afvoervermoë van oorlope beperk om kavitasiebeskadiging aan die struktuur self te voorkom. Daar word beraam dat toekomstige uitwerking van klimaatsverandering op die uiterste die pieke van vloede in sommige wêrelddele met 50% tot selfs 100% kan verhoog. Damoorlope sal dus groter eenheidsdeurstromings moet hanteer. Die voorkoming van kavitasie op ʼn damoorloop is moontlik deur die lugkonsentrasie te verhoog tot ten minste 8% in die vloei op die pseudobodem. “Flaring Gate Piers” (FGP’s) is in China ontwikkel as 'n belugtingstruktuur. Om die deurstroming van die vloei te verseker, word flares op die stroomaf deel van 'n standaard WES oorloop geïnstalleer. Die flares is stroomop geleë van die trappe op 'n gladde ogee oorloop. Die oorloop is volgens die skaal 1:50 gemodelleer vanaf die Dachaoshandam in China. Navorsing oor die invloed van die FGP's is voorheen deur Koen (2019) gedoen. Hierdie navorsing fokus op die verwydering van die sluispylers om die invloed van slegs die flares op die belugting van die vloei te bepaal. Die verskillende soorte FGP's wat ondersoek word, is die X-vorm en die Y-vorm FGP. Die invloed en doeltreffendheid van die “flares” word ondersoek deur druklesings op die “flares” te neem om areas of sones van moontlike kavitasie vir verskillende deurstromings te identifiseer. Die “flare” met die minste of geen sones van kavitasie nie, tesame met die “flare” wat die vloei die beste belug, word gekies as die beste “flare” tipe vir hierdie studie. Die waterstrale wat veroorsaak word deur die hoë eenheidsdeurstroming oor die “flares”, is ook ondersoek om die invloed daarvan stroomaf van die “flares” te bepaal. Nadat al 6 “flares” vir kavitasie getoets is en die waterstrale geanaliseer is, kon daar bepaal word watter “flare” ontwerp die beste prestreer. Geen druk wat ernstig genoeg is om kavitasie skade te veroorsaak, is gemeet op enige van die “flares” wat in hierdie studie getoets is nie. Dit beteken dat al die “flares” veilig is van kavitasieskade tot 'n eenheidsdeurstroming van 200m2/s. Die effekte van die waterstrale is geanaliseer om te bepaal watter “flare” ontwerp die beste in hierdie studie geprestreer het. Y-vormige “flare” 3 het die beste prestreer van al die “flares” wat tydens hierdie studie getoets is. Hierdie “flare” ontwerp het die water verder en hoër geprojekteer as enige van die ander “Flare” ontwerpe. Deur die water verder te projekteer, kan daartoe lei dat die straalwater in die stertwater stroomaf van die damwal af projekteer. Diep stertwater kan al die energie van die strale versprei voordat dit die rivierbedding beskadig. Die hoër geprojekteerde waterstrale bots in die lug met mekaar en versprei dele van die energie van die waterstrale. Die oorblywende energie van die waterstrale word verder versprei deur die weerstand van die lug op die water.Verdere verbetering aan die “flares” kan gedoen word deur die ontwerp van die “flares” aan die kante te verander om te verseker dat die water wat oor die middelste “flares” geprojekteur word nie hoër is as die van die “flares” aan die kante nie. Masters 2020-02-26T14:35:50Z 2020-04-28T12:31:07Z 2020-02-26T14:35:50Z 2020-04-28T12:31:07Z 2020-03 Thesis http://hdl.handle.net/10019.1/108302 en Stellenbosch University xx, 172 leaves : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Flaring Gate Piers Spillways -- Cavitation erosion Spillways -- Design and construction Saayman, Ruben Lourens Energy dissipation at uncontrolled high dam spillways by flare |
| title | Energy dissipation at uncontrolled high dam spillways by flare |
| title_full | Energy dissipation at uncontrolled high dam spillways by flare |
| title_fullStr | Energy dissipation at uncontrolled high dam spillways by flare |
| title_full_unstemmed | Energy dissipation at uncontrolled high dam spillways by flare |
| title_short | Energy dissipation at uncontrolled high dam spillways by flare |
| title_sort | energy dissipation at uncontrolled high dam spillways by flare |
| topic | Flaring Gate Piers Spillways -- Cavitation erosion Spillways -- Design and construction |
| url | http://hdl.handle.net/10019.1/108302 |
| work_keys_str_mv | AT saaymanrubenlourens energydissipationatuncontrolledhighdamspillwaysbyflare AT saaymanrubenlourens uctd |