Numerical Study of the Transition Between Reentrant Jet and Twin Vortex Flow Regimes in Ventilated Cavitation

Contrary to natural cavitation, ventilated cavitation is controllable and is not harmful. It is particularly used to reduce the drag of the hydraulic vehicles. The ventilated cavitation is characterized by various gas regimes. The mechanisms of ventilated cavitation are investigated in the present work with CFD based on a 2D solver. The attention is especially focused on the transition between the reentrant jet and twin vortex regimes. The results confirm that the product of ventilated cavitation number and Froude number is lower than 1 (σ_cFr?<?1) in the twin vortex regime, while it is higher than 1 (σ_cFr?>?1) in the reentrant jet regime, as reported in the literature. Further analysis shows that ventilated cavitation is significantly influenced by the natural cavitation number.     

Part I: Externalities and economic policies in road transport

Road transport imposes negative externalities on society. These externalities include environmental and road damage, accidents, congestion, and oil dependence. The cost of these externalities to society is in general not reflected in the current market prices in the road transport sector.An efficient mobility model for the future must take into account the true costs of transport and its regulatory framework will need to create incentives for people to make sustainable transport choices. This paper discusses the use of economic instruments to correct road transport externalities, but gives relatively more weight to the problem of carbon emissions from road transport, as this is particularly challenging, given its global and long-term nature.Economics offers two types of instruments for addressing the problem of transport externalities: command-and-control and incentive-based policies.Command-and-control policies are government regulations which force consumers and producers to change their behaviour. They are the most widely used policy instruments. Examples include vehicle emission and fuel standards in the US as well as driving or parking restrictions in Singapore. The implementation cost of these instruments to the government is small. Although from an economic perspective these policies often fail to achieve an efficient market outcome, the presence of political constraints often make them the preferred option, in terms of feasibility and effectiveness.Economic theory shows how policies, which affect consumption and production incentives, can be used to achieve the optimal outcome in the presence of externalities. Incentive-based policies function within a new or an altered market. We first examine incentive-based policies, which cap the aggregate amount of the externality, such as carbon emissions, by allocating permits or rights to the emitters. The emitters are then free to trade their permits amongst them. The permit allocation mechanism is important-although market efficiency would be satisfied by an auction, political influences usually favour a proportional allocation based on historic emissions. We discuss EU ETS as an example of a cap-and-trade system, however, no such policy for CO₂ emissions in road transport has been implemented anywhere in the world to date.Fiscal instruments are, like command-and-control, widely used in road transport, because they are relatively cheap and simple to implement. They include the use of taxes and charges in order to bridge the gap between private and the social costs and, in principle, can lead to an efficient market solution. Registration, ownership, fuel, emissions, usage taxes, and parking and congestion charges have been implemented in many countries around the world. On the other side of the spectrum, subsidies can be given to those scrapping old cars and buying fuel-efficient vehicles. Some cities, such as London, have implemented congestion charges and many states in the United States have introduced high occupancy lanes. Other interesting possibilities include pay-as-you-drive insurance and other usage charges. However, the size and scope of taxes and subsidies are determined by governments, and because of their imperfect knowledge of the market the outcome is still likely to be inefficient.Governments have many effective economic instruments to create a sustainable road transport model. These instruments can be used separately or together, but their implementation will be necessary in the nearest future.     

Future challenges for transport infrastructure pricing in PPP arrangements

In this paper we report the conclusion of a research project dedicated to pricing regimes in public-private partnership contracts for the provision of transport infrastructure (Macário et al., 2009). Several elements have been brought to the bulk of knowledge that supports the design and implementation of public-private partnership in the transport sector. These developments have been achieved in the following domain:

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Understand difficulties of price setting within the PPP environment, given the potential conflict of interest among the different parties engaged, go beyond the discussion of first best versus second-best price setting mechanisms.

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Understand the role of government and regulators in the performance of a PPP.

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Translate the issue of asymmetries of information between parties into a risk taking language.

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Devise alternative contractual designs that will enable competitive price setting.

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Understand that a structural element is missing to conciliate the views of the different stakeholders over a PPP: a bridge between infrastructure costs and charges.

The objective of this paper is to overview the main challenges ahead of transport infrastructure pricing, considering the current and likely future policies as well as the field constraints. Moreover, a proposal is formulated to overcome some of the current pitfalls associated to transport infrastructure pricing.     

Sustainability Challenges in the Geoduck Clam Fishery of British Columbia: Policy Perspectives

The geoduck clam fishery, worth approximately CDN $40 million ¹ US $ equivalence: 35 million (Bank of Canada exchange rate on February 1, 2006). in annual landed value, is British Columbia's most valuable invertebrate fishery. This fishery has been co-managed by the Department of Fisheries and Oceans (DFO) and the Underwater Harvesters Association (UHA) since 1989. Earlier input control measures such as effort regulation, seasonal closures, and licenses failed to work effectively for more than ten years, resulting in excess fishing capacity, over harvesting, poor economic returns, and unsafe fishing practices. Output control measures such as the individual vessel quota system (IVQ) have, to some extent, proven successful in improving revenues, controlling excess fishing capacity, gaining compliance with regulations, and involving fishers in the joint decision-making processes. However, there are public concerns about a common property resource at risk of being dominated by a few UHA license holders. Additionally, there are concerns about the job losses resulting from IVQ implementation, as well as distribution and equity issues. This article traces and examines the policy context for fisheries management in the British Columbia (BC) geoduck fishery, discusses the major concerns surrounding the exploitation of long lived Methuselah's clams and concludes with areas for further research in sustaining this lucrative fishery.     

Activity based travel demand models as a tool for evaluating sustainable transportation policies

India is in the course of an economic transition. The economic growth nurtured the life in the cities and cities have become a major livelihood destination for everyone. This migration of people contributed to the increased urbanization of Indian cities. The booming economy fostered the well-being and shaped the lifestyle of people in such a way that the dependency on private vehicle has become an unavoidable affair. Along with population growth, the increased vehicle ownership gave rise to overall spurt in travel demand. But the supply side lagged behind the demand adding to many of the transport related externalities such as accidents, congestion, pollution, inequity etc. The importance of sustainability is understood in the current urban transport scenario leading to the development and promotion of sustainable transport polices. The core agenda of these polices is to target the travel behavior of people and change the way they travel by creating a different travel environment. However, the impacts of many such policies are either unknown or complex. Hence, before adopting and implementing such policies, it is important for the decision makers to be aware of the impacts of them. The role of travel demand models comes here as they predict the future travel demand under different policy scenarios. This paper reviews the ability of travel demand models applied in India in analyzing the sustainable transport policies. The study found that the conventional model system in India, which is trip based four step aggregate methodology, is inadequate in analyzing the sustainable transport policies. A review of alternative approach, known as activity based travel demand modeling found that they are capable of handling such policies better than conventional models and are assistive to the decision makers in arriving at right mix of polices specific to the situations. Since there is no operational activity based travel demand model system developed in India, the study at the end envisaged a conceptual framework of an integrated activity based travel demand model based on the requirements identified from the review. This can potentially replace the existing travel demand models and can be used for planning applications once the modification & validation have been done according to the existing activity-travel behavior of individuals.     

Hydrodynamic performance of multiple-row slotted breakwaters

This study examines the hydrodynamic performance of multiple-row vertical slotted breakwaters. We developed a mathematical model based on an eigenfunction expansion method and a least squares technique for Stokes second-order waves. The numerical results obtained for limiting cases of double-row and triple-row walls are in good agreement with results of previous studies and experimental results. Comparisons with experimental measurements of the reflection, transmission, and dissipation coefficients (C _R , C _T , and C _E ) for double-row walls show that the proposed mathematical model adequately reproduces most of the important features. We found that for double-row walls, the C _R increases with increasing wave number, kd, and with a decreasing permeable wall part, dm. The C _T follows the opposite trend. The C _E slowly increases with an increasing kd for lower kd values, reaches a maximum, and then decreases again. In addition, an increasing porosity of dm would significantly decrease the C _R , while increasing the C _T . At lower values of kd, a decreasing porosity increases the C _E , but for high values of kd, a decreasing porosity reduces the C _E . The numerical results indicate that, for triple-row walls, the effect of the arrangement of the chamber widths on hydrodynamic characteristics is not significant, except when kd<0.5. Double-row slotted breakwaters may exhibit a good wave-absorbing performance at kd>0.5, where by the horizontal wave force may be smaller than that of a single wall. On the other hand, the difference between double-row and triple-row vertical slotted breakwaters is marginal.     

Global logistics city concept: a cluster-led strategy under the belt and road initiative

This paper develops a cluster-led strategic policy framework to assess the strategic positioning of key global logistics cities in Asia, most of which are affected by the ‘Belt and Road (B&R) Initiative.’ One of the key challenges that the B&R Initiative is facing is underdeveloped logistics infrastructure in Asia, not to mention road congestion, dilapidated infrastructure, incessant supply chain disruptions, and capacity constraint, which imposes significant economic costs.

Global logistics cities are evaluated on logistics infrastructure capacity and service responsiveness. This involves selecting the key global logistics cities, identifying key indicators, standardising and indexing, mapping dimensions of global logistics cities, and developing the cluster-led strategic policy framework.

The results indicate the prevalence of a multi-tier system wherein Shanghai and Hong Kong have attained the maturity of a global logistics city, whilst Manila, Jakarta, and Bangalore are making slow but steady progress in that direction. In contrast, Dhaka, Phnom Penh, and Ho Chi Minh City are showing potential but require further enhancement through significant investment in infrastructure and service delivery improvement.

The cluster-led strategic policy framework formulates actions and strategies through which emergent logistics networks can be strategically aligned and functionally integrated with B&R-oriented global trading hubs and transport corridors..     

Analysis of thirty years evolution of urban growth,transport demand and supply,energy consumption,greenhouse and pollutants emissions in Greater Cairo

The objective of the paper is to analyze evolution of urbanization, transport demand and supply in Greater Cairo (GC) over the last three decades of the 20th century. This is in addition to investigating the impact of city growth on energy consumption and emissions from transport. It utilizes results of 1971, 1978, 1987, 1998 and 2001 travel demand surveys, undertaken during the corresponding GC transport studies; each was published a year or two later. No further transport studies have been carried out in GC over the past decade and in view of the current political situation, it is not envisaged that similar studies will be undertaken in the near future. The analysis includes the evolution of daily trips, trip purpose share, modal share and number of cars. More recent trends for 2006/2007 vehicle registration by type and size are given. The evolution of transport supply covers projects until early 2012. In parallel estimates of the evolution of energy consumption and cost, emissions of greenhouse gases (CO₂) and pollutants (CO, HC and NO_x) are given for 1971/2001. The adopted estimation methodology is summarized. Comparative analysis of relevant evolution indexes and trends of growth between 1971 and 2001, taking the former as base year, is given. Land use and transport policies and projects that in some cases helped, directly or indirectly, to reduce traffic congestion, or at least prevented an increase, are addressed, commenting on their outcomes. Thus, transferable experience are useful to sister cities benefiting from successes and avoiding drawbacks. The evolution of the impact of GC metro on energy consumption and cost, and GHG emissions is given for 1987/2001, assuming the scenario “metro did not exist”. More recent impact analysis is given for 2007/2008, as the data allowed estimating traffic volumes that would have been added to the congested metro corridors under the above scenario; and the related fuel consumption and cost and GHGs. The paper ends with conclusions on GC evolution, learned lessons and suggests repeating similar work in other mega cities of the developing countries. Further research is emphasized, e.g., modeling the relationship between land use, transport, energy and emissions; modeling emission factors by vehicle type; and studying fuel-subsidy-reduction scenarios and their socio-economic effects.     

Public transport policy for central-city travel in the light of recent experiences of congestion charging

Excellent public transport which makes the private car a minority mode of central-city travel is a necessary condition for a political process towards the introduction of congestion charges. However, the charging system costs in London and Stockholm have proved to be unexpectedly high. Therefore, before these costs come down to an affordable level, zero-fares for central-city travel and stricter parking policy would be a first-best combination in many cities, always provided that the public transport is really competitive. A bold venture in public transport development is consequently the top priority irrespective of the transport pricing policy direction.     

Elastic local buckling strength of stiffened plate considering plate/stiffener interaction and welding residual stress

An analytical formula for estimating elastic local buckling strength of a continuous stiffened plate subjected to biaxial thrust is derived considering the influence of plate/stiffener interaction and welding residual stresses. Through a comparison of calculated results with those by FEM eigenvalue analysis, high accuracy of the proposed formula is demonstrated. A series of buckling strength analyses is performed on the deck and bottom plating of actual ships. It has been found that:

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Land use/transport models and economic assessment

This paper discusses the economic assessment of policies using land use/transport models. It argues that conventional forms of assessment focussing only on transport changes can underestimate the economic benefits of a policy. The paper argues that the benefits need to be measured by the changes of prices at the end of a trip and not just by the changes in travel costs. Models that do not estimate the changes of prices at the end of a trip cannot properly assess the impact of a policy.The model used in this paper is based on the MEPLAN software and estimates the location of households and employment and the interaction between them. It also estimates the cost of living for households and the production costs for employment. With these costs, it is possible to calculate the wider economic benefits beyond transport.The paper illustrates the assessment of policies for the Cambridge sub-region involving investment in public transport, orbital highway and congestion charging policies. The results forecast by the model are assessed in terms of the conventional cost-benefit using traveller’s surplus as benefits and compared with a wider assessment measure of compensation variation. It demonstrates that the last measure encompasses the wider benefits associated with transport policies which are not taken into account in conventional cost-benefit analysis.     

What’s so funny about peace, love and transport integration?

The 1998 White Paper proposed integration as the solution to Great Britain’s land transport problems. Most commentators agree that this much vaunted New Deal for Transport has been a failure. Yet some ten years later policy papers from bodies such as the Institution of Civil Engineers and the Centre for Cities are still proposing integration as a possible panacea.There are a number of reasons for the failure of integrated transport over the last decade. The first is the failure to define the concept. The second is the failure to operationalise the concept. The third is the lack of an evidence base on the success of integrated transport policies. Evidence is now emerging in Britain on the benefits (and indeed the costs) of some aspects of integrated transport policies. The fourth, and perhaps the most crucial, is the lack of will in terms of politicians, civil servants and the public at large, to adopt the behavioural changes necessary for an integrated transport policy to be successful. A series of organisational and funding changes are proposed that could advance the prospects for integration.     

Urban transport lending by the World Bank: The last decade

Over the preceding decade, the World Bank committed about US$7.5bn in loans for urban transport projects in its client countries, involving total project costs of nearly US$13bn. Projects are designed by the client city/national governments and the World Bank in an interactive, give-and-take process. As is common in development finance, urban transport projects entail an investment program and a set of policy and institutional initiatives. A majority of Bank-funded operations in this period focused on public transport modes. A clear and overarching strategic thrust is evident, favoring private delivery of services with a strong public role through city-specific regulatory agencies. Depending on the context, projects involved efforts to introduce private operators and competition into an all-public set-up, or tighten up weakly regulated, “informal” public transport markets. A notable feature of many projects in the latter context is the use of investments in bus rapid transit infrastructure to reach multiple goals: improve transport services, maintain affordability for low-income passengers, attract new passengers, reduce negative environmental impacts, and leverage complementary reforms of policies and institutions. The Bank’s program in China, unique in its local context of a dynamic urban society moving away from a near-universal reliance on bicycles, initially did not focus on public transport but on urban roads and traffic management. Towards the end of the last decade, the motorization process and the outlook of decision makers entering a more mature stage, projects in China started to converge towards what the rest of the Bank’s program was doing – searching for a more sustainable path to urban transport development.     

Programming, optimal pricing and partnership contract for infrastructures in PPPs

The development of various forms of public-private partnerships for the financing, building and operating of public infrastructure has not fundamentally altered the economic calculations involved. This chapter examines to what extent it is necessary, however, to change the way that government uses socio-economic and financial evaluations, whether to optimise investment programming or pricing. Ensuring a coherent match between these two types of optimisation can provide a principle for determining the optimal programming price.We begin by showing that when projects are financed by both users (toll revenues) and taxpayers (subsidies), it is socially beneficial to plan these investments on the basis of the net present value (NPV) provided by each unit of public money invested. This NPV/subsidy ratio must obviously be higher than the public-funding scarcity coefficient or else the investment would destroy more wealth than it would produce.One of the ways of improving this ratio is also to optimise the toll level, since increasing it can lower the subsidy but has an adverse impact on the user surplus, it is essential to set the optimal toll.In the case of an approved project considered in isolation, we show that the optimal toll depends upon the public-funding scarcity coefficient. If there is no scarcity, the optimal toll is zero. As public-funding becomes scarcer, the optimal toll draws closer to the toll that optimises revenue.In the case of a programme of several projects subject to budget constraint, we show that the optimal toll no longer depends upon the public-funding scarcity coefficient and that there are several scenarios depending on the relative values of the maximum revenue and the total cost of the project:

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when, whatever the toll, revenue can no longer cover over half of the cost, it is socially beneficial to choose not to levy any toll;

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when there is a toll that covers the total cost, the operator may be left free to set it at the level he sees fit, with the issue of how the profits are to be shared between the franchisee and the franchisor being settled separately;

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when the maximum revenue of the project falls between half and all of the total cost, the value of the toll that maximises the welfare function is lower than the revenue-maximising toll and must therefore be set for the private operator by government.

Thus, the partnership contract must be given a different content in these three cases of optimal pricing.

Preamble

Most of the theoretical studies devoted to optimising public investment programming and infrastructure pricing have, since the work of Jules Dupuit (1844), focused on the salient issues of the transport sector, even though this work was relevant to all sorts of public infrastructure. The analysis presented in this paper deals with transport economics, but in line with this tradition, is also applicable to any field in which public-funding is combined with commercial revenue. For example, the question of determining how the financing of an opera should be shared between taxpayers and opera-goers raises the same type of issues as the optimal combination of tolls and subsidies for financing a motorway project. This report will be focused on these issues. We shall see that certain precautions are called for in investment programming together with some new thinking on pricing principles.     

Designing Coastal Management Strategies for Populations with Distinct Needs: The Case of Learning Disabilities

The Disability Discrimination Act (1995, amended 2005), Equality Act (2010 Equality Act. 2010. Equality Act. http://www.legislation.gov.uk/ukpga/2010/15/contents#openingWholeMod (accessed May 17, 2012) [Google Scholar]), EU Disability Action Plan (2003 –2010), and EU Disability Strategy (2010–2020) were designed to make equal opportunities a “reality.” As 16% of the EU population, is statutorily disabled there are considerable implications for beach management. Research examples of beach users include swimmers, anglers, etc. - but rarely people with learning disabilities (LD). This paper considered beach users with LD and their appreciation of three different coastal classifications in South Wales. Because of their disabilities, the research applied a participatory photo interpretation methodology (photovoice). A comparison of the LD ranking of beach issues was made with rankings provided by the general public at the same beaches. Results demonstrated some similarities between LD and general public coastal needs, but identified the need for specific considerations to be made by beach managers for LD users, including informed self-advocacy, use/application of signage, instructive access and a requirement for baseline information gathering. The research proposes an integrated coastal access model from which coastal management/gatekeepers can consider LD needs within coastal strategies. Finally, findings highlight the use of photovoice in coastal research projects and the need for innovative methodological considerations when researching certain groups.     

Fatigue crack growth behaviour of A5083 series aluminium alloys and their welded joints

We investigated the difference in fatigue behaviour between the aluminium alloys A5083-O and A5083-H321, which are used as structural components in ships and high speed craft. We obtained S–N curves for the base materials and the welded joints made of A5083-O. The relationships between the fatigue crack propagation rates and the stress intensity factor ranges ΔK, ΔK _eff and ΔK _RPG (Toyosada et al. in Int J Fatigue 26(9):983–992, 2004) were determined. Additionally, the evolution of fatigue crack growth for the base materials and the welded joints made of A5083-O was measured. We also carried out numerical simulations of fatigue crack growth for both base metals and their welded joints made of A5083-O. The difference in fatigue crack growth behaviour for each alloy and the validity of the numerical simulations of fatigue crack growth based on the RPG stress criterion (Toyosada et al. 2004) in the base materials and their welded joints was investigated.     

Total oil spill costs and compensations

Although counteracting environmental programmes and policies have been strengthened, large oil spills still occur at irregular intervals. The total oil spill costs and their compensations have attracted much interest from various parties, such as local stakeholders, and state and federal governments. This paper addresses five major cost categories whose aggregations are expected to cover the overall direct and indirect costs after the release of an oil spill. Among them, research costs should not be neglected, since they tend to be high if public attention has been drawn to the case. Through an examination of the relationship between the total oil spill costs and their admissible claims, we found that:

1. admissible claims do not cover the overall costs of the oil spill, and

2. admissible claims cannot be compensated in full in the case of large spills.

Clearly, a sound oil spill contingency management aims to minimize both the environmental impacts of areas most at risk and the total oil spill costs. In this paper an economic model for measuring environmental damages following an oil spill is addressed and applied to the Prestige case which happened to be the worst oil pollution in the history of Spain. The model indicates how an ideally a priori economic evaluation may intuitively help managers to make informed as well as fast decisions in contingency cases.     

Cities on the move – Ten years after

The World Bank urban transport strategy review, “Cities on the Move” analyzed urban transport problems in developing and transitional economies and articulated a proposed strategy framework for national and city governments. This paper describes how the urban transport problems of the developing world have changed in the last decade and assesses the extent to which the strategies recommended in 2002 have been successfully implemented. It shows that progress has been widespread in some areas – particularly in mass transit analysis and investment and some environmental policies – and that there have developed some good planning and public transport practices in a smaller number of model cities. But more strategic institutional and policy issues, including the mobilization and regulation of private sector initiative in meeting infrastructure and public transport supply deficiencies, have tended to be poorly developed. Above all, the growth of medium sized cities with weak institutions and finance highlights the need for the international development institutions to put greater emphasis on helping those cities by dissemination of best practice in strategic transport planning and traffic management.