Development of the simple economic model (SEM) for stormwater management

Includes abstract.Includes bibliographical references.Sustainable urban Drainage Systems (SuDS) are increasingly being implemented around the world. A common barrier to the wider use of SuDS in South Africa is the uncertainty regarding their total cost. The need for reasonable predictions of life cycle cost is vital, both in terms of ensuring the viability of the proposed projects as well as to allow for comparison with more conventional designs that have historically relied on concrete pipes and culverts to transport the stormwater to nearby receiving water bodies as quickly and efficiently as possible

The viability of rainwater and stormwater harvesting in the residential areas of the Liesbeek River Catchment, Cape Town

Includes bibliographical referencesThe sustainable provision of water to South African citizens is a significant challenge facing the country. In order to avert a crisis, municipalities will need to reduce their reliance on traditional water sources. Rainwater harvesting (RWH) and stormwater harvesting (SWH) are two alternative water resources that could supplement traditional urban water supplies. To date, the potential benefits of RWH and SWH within an urban setting have not been adequately considered or investigated in South Africa. The only way to quantify the benefits and potential viability of rainwater and stormwater harvesting was to select and model a representative catchment - the Liesbeek River Catchment, Cape Town South Africa was selected. An Urban Rainwater Stormwater Harvesting Model was developed to model the use of RWH and SWH in the catchment. Additionally, a Storm Water Management Model (SWMM) of the catchment was developed to investigate the stormwater management benefits of RWH and SWH. The study found, inter alia, that: RWH was viable for only a minority of property owners; climate change would have limited impact on the performance of RWH systems; and RWH is an unreliable - even for small storm events - means of attenuating peak flows. On the other hand, SWH has the potential to reduce potable water demand in the Liesbeek River Catchment by up to 20%. However, for SWH to be viable there would need to be a high level of adoption by residents, at least for non-potable uses such as flushing toilets and outdoor irrigation. SWH is also of benefit in the attenuation of peak flows during storm events. Finally, the research found that the implementation RWH and SWH together would be unwise, as both are most cost-effective under conditions of maximum demand. The study concluded that SWH could be a viable alternative water resource for urban residential areas in South Africa - depending on the scale at which it is implemented, the end use for which it is utilised, and the population density that drives the water demand. RHW, on the other hand, has limited potential - depending on climatic conditions; it may, for example, be viable in areas with year-round rainfall

Soldier Boy

https://digitalcommons.library.umaine.edu/mmb-ps/3037/thumbnail.jp

Ditching Investigation of a 1/18-Scale Model of the North American B-45 Airplane

An investigation of a 1/18-scale dynamically similar model of the North American B-45 airplane was made to observe the ditching behavior and determine the proper landing technique to be used in an emergency water landing. Various conditions of damage were simulated to determine the behavior which probably would occur in a full-scale ditching. The behavior of the model was determined from high-speed motion-picture records, time-history acceleration records, and visual observations. It was concluded that the airplane should be ditched at the maximum nose-high attitude with the landing flaps full down for minimum landing speed. During the ditching, the nose-wheel and bomb-bay doors probably will be torn away and the rear of the fuselage flooded. A violent dive will very likely occur. Longitudinal decelerations of approximately 5g and vertical accelerations of approximately -6g (including gravity) will be experienced near the pilots' compartment. Ditching braces installed in the bomb bay will tend to improve the behavior slightly but will be torn away along with the bomb-bay doors. A hydroflap installed ahead of the nose-wheel doors will eliminate the dive and failure of the nose-wheel doors, and substantially reduce the motions and accelerations

A water sensitive urban design framework for South Africa

South Africa (RSA) is a ‘developing country’ still facing the challenge of providing basic water services to a significant proportion of the population. Water security is increasingly a matter of major concern, with most of the surface water resources fully accounted for and poor water quality downstream of urban areas. Whereas service delivery and social upliftment are high on the political agenda, the challenge is to promote economic and social equity, whilst simultaneously ensuring environmental sustainability; this challenge is greatest in the rapidly growing urban areas. Alternative approaches to conventional urban water management, which account for these water-supply and -quality constraints as well as the impacts of extreme weather-related events, are thus required. It is postulated that, from a water-management perspective, this will require strategic planning for the wide-scale implementation of Water Sensitive Urban Design (WSUD) – a systems-based approach that focuses on the interactions between the built form and water-resources management. This article describes a way forward for an integrated management (infrastructure and planning) approach for urban water. It defines what ‘water sensitivity’ might mean in the RSA context, and outlines the process that was followed to develop a framework and guidelines for implementing WSUD in South Africa. The four complementary components of the framework – research, vision, narrative, and implementation – highlight what will be required in order to manage the challenges facing the country’s urban water sector and enable the transition towards water sensitivity

Ditching Tests of a 1/10-Scale Model of the North American XFJ-1 Airplane Ted No. NACA 314

Tests were made of a 1/10-scale dynamically similar model of the North American XFJ-1 airplane to study its behavior when ditched. The model was landed in calm water at the Langley tank no. 2 monorail. Various landing attitudes, speeds, and conditions of damage were simulated. The behavior of the model was determined from visual observations, by recording the accelerations, and by taking motion pictures of the ditchings. Data are presented in tabular form, sequence photographs, and time-history acceleration curves. From the results of the tests it was concluded that the airplane should be ditched at the near-stall, tail-down landing attitude of 12 deg. The flaps should be fully extended to obtain the lowest possible landing speed. The wing-tip tanks should be jettisoned if any appreciable load of fuel remains; if empty, they should be retained for additional buoyancy. In a calm-water ditching the airplane will probably run about 600 feet Maximum longitudinal decelerations of about 2.5g and maximum vertical acceleration of about 2g will be encountered. The nose-intake duct will be clear of the water until practically all forward motion has stopped