A havelock source panel method for near-surface submarines

A panel method is described for calculating potential flow around near-surface submarines. The method uses Havelock sources which automatically satisfy the linearized free-surface boundary condition. Outputs from the method include pressure field, pressure drag, wave resistance, vertical force, trim moment and wave pattern. Comparisons are made with model tests for wave resistance of Series 58 and DARPA SUBOFF hulls, as well as with wave resistance, lift force and trim moment of three length-to-diameter variants of the DSTO Joubert submarine hull. It is found that the Havelock source panel method is capable of determining with reasonable accuracy wave resistance, vertical force and trim moment for submarine hulls. Further experimental data are required in order to assess the accuracy of the method for pressure field and wave pattern prediction. The method is implemented in the computer code “HullWave” and offers potential advantages over RANS-CFD codes in terms of speed, simplicity and robustness.     

Port authorities view state coastal management programs

Abstract

An estuarine sanctuary is a store of public values due to the ecological, cultural, recreational, aesthetic, historic, and economic services provided by the preserve. These values may be expected to increase over time because of (1) growth in the population demanding estuarine services, (2) growth in the willingness to pay for such services, and (3) growth in the actual quality and quantity of services which are provided by a protected natural system. Thus an estuarine sanctuary will be more valuable to future generations than to current generations. When weighing the cost and benefits of a preservation or development decision, a preservation decision which seems currently undesirable may in fact be socially beneficial when growth in the value of estuarine services is included.     

The characteristics,uses and potentials of taxicab transportation

Taxicab transportation is a significant segment of urban transportation. Taxicabs, along with other “paratransit” type systems, provide service with characteristics between the automobile and mass transportation. Consequently, they are well suited to a number of special purposes. Taxicabs currently serve a wide range of trip purposes by travellers with varied socio-economic characteristics. Taxicab transportation is most attractive for serving lower density area and off-peak travel particularly where there is only minimal mass transit service. In this regard, taxicabs are a supplement to conventional mass transit. The use of taxicabs for collection and distribution functions for both passengers and freight is gradually being realized. The multiple use of taxicabs offers advantages of increasing taxicab productivity and reducing individual trip costs. Many of the problems related to taxicabs are regulatory and institutional in nature. Unless these constraints are eased or removed, wider application of taxicab transportation, including productivity gains, will be limited.     

The effects of AVL accuracy upon public service bus system performance

Through an examination of the dependence of several key performance parameters of a public bus system upon Automatic Vehicle Location (AVL) estimation accuracy, it becomes possible to place in perspective the value of AVL technology to improved public conveyance performance. Important bus transportation system performance measures dependent upon AVL estimation accuracy are: (1) Headway Control Error; (2) Time-Of-Passage Error, and (3) Required Layover Reserve. An analytical model of the dependence of these bus system performance measures upon AVL estimation error has been constructed. In addition, error models of three basic types of AVL systems, i.e., dead reckoning, proximity, and radio location have been developed and validated by experimental comparisons. By employing both sets of models, i.e. for the bus transport and AVL systems it becomes possible to recommend appropriate AVL technologies that best meet the performance requirements of a public bus service. The accompanying text synopsizes the noted models and provides an example of their use.     

A note on fare policy in personal rapid transit

The choice of fare policy is more flexible in personal rapid transit than in conventional transit and has some unique aspects. The implementation of fare policies as a function of distance are discussed, and, following a discussion of how the fare would be collected in a PRT system, consideration is given to whether the fare should be per person or per vehicle.