Lal C. Wadhwa

CFD modelling pond dynamic processes

The parametric pond simulation methodology AUTOPOND was developed as a tool to evaluate the effect of aerators on the sediment quality in an aquaculture pond. The methodology is capable of simulating any combination of paddlewheels and propeller-aspirators in a single pond. Pond bathymetry is modelled with a smooth bottom and a piece-wise series of inclined banks, to generally represent any convoluted shoreline. Simulations predict that a paddlewheel imparts more circulation into a pond than a propeller-aspirator of the same motor horsepower. The propeller-aspirator concentrates an intensive effect in a localized scourhole, surrounded by relatively weak bottom stress. In contrast, paddlewheel simulations predicted a wide swath of high stress, followed by an equally extensive region of moderate stress. A simulation of the combined effect of two paddlewheels and four propeller-aspirators was produced to represent a ‘real world’ earthen mariculture pond stocked with P. monodon. Water currents and sediment conditions reported in the real pond were comparable with the results of the simulation. Given sufficient computational resources, it is now possible to investigate the interactions of pond geometry and aerator operation with a computer. Portions of pond bottoms found to experience high shear stress are now identified for reinforcement to prevent the sedimentation of sludge in otherwise productive zones. This would result in improved feed conversion and reduced ammonia levels. Ponds and aerators can now be objectively coordinated to achieve more productive culturing conditions.

Arrangement of aerators in an intensive shrimp growout pond having a rectangular shape

Simulations have been conducted to suggest general principles for the arrangement of aerators within a rectangular pond used for the growout of marine shrimp such as Penaeus monodon and Penaeus japonicus. Computational fluid dynamic models were produced for three schemes that were identified in a survey of Australian Prawn Farming Association members. These arrangements are ‘in-line’ (series), ‘parallel’ (side by side), and ‘diagonal’ (diverting apart). Model results were assessed on the basis of benthic shear stress by classifying regions of pond bottom as ‘red zone’ (excessive stress), ‘green zone’ (desirable), and ‘dead spots’ (sediment traps). A comparison of results indicates that conventional aerators should be arranged diagonally or in parallel. It is also apparent that low-speed operation would be advantageous. These recommendations are consistent with the long-established practice of establishing pond-wide circulation.

Relative safety of alternative intersection designs

Accidents at intersections in Queensland accounted for 45% of total accidents and 19% of fatal accidents on the State roads in 2002. The number of accidents at intersections is purported to be primarily correlated to the number of conflict points but geometric characteristics also influence intersection safety. Queensland Transpot database of reported accidents over the past ten years has been used in this study to investigate the contribution of intersection design and characteristics on the relative safety of intersections. Queensland Transports road crash database, WebCrash2, has been used to analyse the accident records at intersections in the Townsville region. The detailed analysis has included road user, vehicle type, collision type, BAC, use of seat belt and intersection type. Considering the common variations in the number of approaches, entry and exit lanes, type of control, phase design for signalisation, the road environment and other features like flaring, channelisation and signage, each intersection is peculiar and unique in some way. However, research has been focussed on three main types of intersections. These include T junctions, cross intersections and roundabouts. Three levels of control are also considered. The objective is to relate the intersection safety to the number of conflict points, conflict types, and intersection geometry. The results show that roundabouts are the safest types of intersection while uncontrolled cross intersections are least safe. The level of safety decreases with the increase in the number of approaches and the number of conflict points.

Financing of the Transport Infrastructure in Australia

Australia has an extensive multi-modal transport infrastructure comprising of well-developed road, rail, air and coastal networks. It has a relatively low road density of 0.10 km/sq.km. as well as the lowest number of persons per kilometer or road length in the world, which is indicative of the extensive road network per captia. Australia’s transport infrastructure is financed by all three tiers of government - Commonwealth, State and Local governments. A number of financing regimes have been adopted by the Australian Government since 1981, which are indicative of government priorities and distribution of responsibilities for provision and maintenance of transport infrastructure with the State and Local Government. Recently the Commonwealth Government has developed a planning and financing strategy in the form of AusLink. It is the Australian government’s latest approach to land transport infrastructure to achieve better national and land transport planning, funding, and investment decision-making. The salient features of AusLink approach that make it distinct from previous approaches include an integrated corridor approach to planning, integrated land use and transport planning, increasing private sector involvement, focus on sustainable development and shared responsibility and funding with States and Territories. The methodology for identification and appraisal of specific projects to achieve the AusLink objectives are discussed.

TRUE COST OF ROAD TRAVEL

A key strategy in achieving sustainable transportation is the full cost charging regime for the motorists. However, the development of rational and fair charging policies must be based on the recognition of true externalities that are currently not paid for by the motorists. This research has revealed that contrary to common belief, the external components of the highly publicized community cost of accidents and congestion are insignificant. However, the environmental impacts of transportation are significant and very little of this cost is recovered from the motorists. This finding is useful for developing full cost charging system.

Global Perspectives In Sustainable Urban Environments

Arguably, sustainability is the most commonly used word in the literature today. Every project, plan, action, policy or strategy formulated by government agencies and large organisations must address the issue of sustainability, even if inconsequentially. City councils are at the forefront of urban sustainability movement. Some of their activities have significant and far-reaching effects while others appear good for public relations/propaganda only. The projects usually focus on one or more of the four elements of sustainability: resource conservation, transportation, protection of the environment and public health, or land-use planning and economic development. In this paper, a review is made of a large number of sustainable city projects/plans from around the world. The aspects of sustainability covered by the various projects are discussed.

Industrial engineering in banana packaging in Australia

Summary form only given. An industrial engineering approach has been used to study the current practices and technologies employed in the banana packaging industry in North Queensland in Australia. The objectives of this study include the following: understanding of the variations in practices and technologies in banana packaging in North Queensland; analysis of the relationship between level of technology, workforce, and output; scientific determination of the time required to complete various elements of the banana packaging activity; establishing the standard production level for various levels of technology and workforce; and designing a well-balanced and efficient packaging system.