Experimental and Numerical Investigation on Wave Interaction with Submerged Breakwater
Md. Ataur Rahman,
Silwati Al Womera
Issue:
Volume 2, Issue 6, December 2013
Pages:
155-164
Received:
7 October 2013
Published:
10 November 2013
Abstract: Experimental studies are carried out in a two-dimensional wave flume (21.3 m long, 0.76 m wide and 0.74 m deep) to investigate the performance of rectangular type submerged breakwater. A set of experiments are carried out at 50 cm still water depth with fixed submerged breakwaters of three different heights (30 cm, 35 cm and 40 cm) for five different wave periods (1.5 sec, 1.6 sec, 1.7 sec, 1.8 sec and 2.0 sec) in the same wave flume. For fifteen run conditions, water surface elevations are collected at six different locations both in front of and behind the breakwater. Also the type of wave breaking and position of wave breaking are simultaneously recorded with a digital video camera. Effects of breakwater height and length along the wave direction on wave height reduction are analyzed. It is found that both the relative structure height (hs/h) and relative breakwater width (B/L) have strong influence in reducing transmitted wave height. Experimental analysis prevails that the reduction of transmitted wave height are 50%, 58% and 68% for relative structure height (hs/h) of 0.6, 0.7 and 0.8 respectively, for a particular value of relative breakwater width (B/L =0.35). Also, the reduction of transmitted wave height is 32% and 50% for relative breakwater width (B/L) of 0.25 and 0.4 respectively, for a particular value of relative structure height (hs/h =0.6). A two-dimensional numerical model based on the SOLA-VOF method has been developed in this study to investigate the wave interaction with fixed submerged breakwater. The developed model can simulate time series water surface profiles, water particle velocity field, VOF function F, pressure around a breakwater. The water surface profiles and wave breaking positions in various wave conditions simulated by the developed numerical model show good agreement with the experimentally measured values. The numerical model developed in this study is expected to serve as tool to analyze wave deformation due to submerged breakwater and will be important for designing submerged breakwater as a coastal protection measure.
Abstract: Experimental studies are carried out in a two-dimensional wave flume (21.3 m long, 0.76 m wide and 0.74 m deep) to investigate the performance of rectangular type submerged breakwater. A set of experiments are carried out at 50 cm still water depth with fixed submerged breakwaters of three different heights (30 cm, 35 cm and 40 cm) for five differe...
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Gonadal State and Condition Factor of Oreochromis Niloticus (Linnaeus 1758)in a Hypereutrophic Lake
Beaven Utete,
Edmore Happison Chikova
Issue:
Volume 2, Issue 6, December 2013
Pages:
165-169
Received:
18 September 2013
Published:
10 November 2013
Abstract: Condition factor, sexual maturity and length-weight relationship of 1132 Oreochromis niloticusinhabiting the hypereutrophic Lake Chivero in Zimbabwe were studied. Fish samples were collected through gill netting and from selected commercialfisheries around the lake from February - November 2011. Comparative analysis of age and size at maturity revealed that the O. niloticus reached maturity at 30±2.5 mm males and 50±3.6 mm females in total length. There was a significant difference in sexual maturity in both sexes with the inactive (I) stage more frequent. Both sexes of fish indicated a negative allometric increase in weight.August and November were determined as the most intensive and sensitive breeding periods for O. niloticus in Lake Chivero.Fishing activities in the lake need to be regulated in tandem with the breeding cycles of the O. niloticus.
Abstract: Condition factor, sexual maturity and length-weight relationship of 1132 Oreochromis niloticusinhabiting the hypereutrophic Lake Chivero in Zimbabwe were studied. Fish samples were collected through gill netting and from selected commercialfisheries around the lake from February - November 2011. Comparative analysis of age and size at maturity reve...
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The Potential of Rainwater Harvesting: A Case of the City of Windhoek, Namibia
Festus Panduleni Nashima,
Martin Hipondoka,
Inekela Iiyambo,
Johannes Hambia
Issue:
Volume 2, Issue 6, December 2013
Pages:
170-174
Received:
20 November 2013
Published:
10 December 2013
Abstract: Windhoek, Namibia’s capital has experience for more than 25 years of novel approaches in integrated water management largely driven by the scarcity of water in the area. Notably absent in their approaches however, is the rooftop rainwater harvesting which is regarded as one of the viable alternative sources of water for domestic use. This paper assesses the potential economic benefits for rooftop rainwater harvesting for the City of Windhoek. The rooftop areas from four representative formal suburbs of Okuryangava (low income) in the north, Academia (middle income) in the south-central, Pioneers Park (middle income) in the south-west and Ludwigsdorf (high income) in the east, were estimated from high resolution satellite images captured from Google Earth. These estimates were used to extrapolate for the potential amount of rainwater that can be harvested in an average rainy season (i.e. December to April) in the study area. The estimated harvestable amount for each residential area was developed using a simple model that incorporates total rooftop area and estimated rainwater. The derived figure was then expressed in terms of cost per unit prices charged by the City of Windhoek. Pioneers Park attests to have the highest (134 m3) potential harvestable rainwater per household, while Okuryangava is estimated to harvest the least amount of 36 m3 per raining period. Given the high density of erven, however, Okuryangava has a potential to harvest approximately 920484 m3 of water per hectare, ranking this suburb second after Academia, which stands at 1120716 m3. This is a significant amount of water effectively taken from rainwater rooftop that could also provide justifiable saving to residents if used instead of tap water. It is therefore recommended that the City of Windhoek actively promotes rooftop rainwater harvesting for the benefit of residents and also as a measure to reduce storm-water runoff due to urban development.
Abstract: Windhoek, Namibia’s capital has experience for more than 25 years of novel approaches in integrated water management largely driven by the scarcity of water in the area. Notably absent in their approaches however, is the rooftop rainwater harvesting which is regarded as one of the viable alternative sources of water for domestic use. This paper ass...
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