Shiphandling Simulation: Application to Waterway Design (1992)

The design of waterways affects the nation's economy, the safety of ships and their crews, the inhabitants near waterways, and the natural environment of waterways. Over the past two decades, the use of shiphandling simulation to achieve refinements in waterway design not verifiable with other design tools has significantly increased. However, use of simulation in this way has been incorporated in only a small portion of the total number of waterway projects.

Shiphandling simulation has been used effectively as a design tool by planners and engineers to aid substantially in waterway design. The committee found the following:

• Simulation can be and is used during early and later stages of the design process to answer critical design questions, including those raised during permitting. Early use of simulation is especially important in cases where it can be used on a recurring basis throughout the design process.

• Pilot acceptance of simulations during validation and study trial phases indicates reasonable success in re-creating a realistic piloting experience.

• Simulation offers a systematic means for capturing the complexity

of a waterway layout, the physical environment, and operational factors of a waterway design in an integrated and visible fashion.

• Simulation enhances communication between design participants. It brings together various constituencies with interests in waterway design, thereby providing a unique, common forum and framework for discussion and decision making.

Although cost, significant gaps in knowledge and capabilities, and lack of confidence inhibit wider use of simulation, the efficacy of applying shiphandling simulators as a design aid has been proven in practice. In spite of all the uncertainties that exist in terms of modeling and interpreting simulation results, the demonstrated benefits of simulation for a wide variety of projects more than adequately justifies its use as a standard practice in waterway design.

Simulation should be used in the following situations:

• When vessel operational risk is a significant design issue. Representation of human pilot skills and reactions in the prediction of vessel behavior in a proposed waterway is unique to shiphandling simulation. Differences in risk under various critical environmental conditions can be identified. Requirements for aids to navigation to further reduce risk can also be assessed.

• When cost and design optimization is an issue. The effect on risk resulting from variations in many design factors that define a waterway can be evaluated. This capability is important for assessing the components of life cycle costs. Simulation is particularly useful for assessing operational differences between design alternatives.

• When competing interests among technical and nontechnical participants in the waterway design process are an issue. Simulation provides a unique way to bring critical and contentious aspects of the design into sharp focus. The consequences of what participating parties are interested in can be acquired and displayed in formats that do not require technical expertise to assimilate and understand.

Because elements of these three issues are frequently associated with most waterway designs, shiphandling simulation should be developed as a

standard tool for use in the waterway design process. The level of sophistication of simulations needed for this process depends on the particular design. However, guidelines for what level is appropriate for a given situation are not available within the current state of practice.

Simulation is not used more often by designers for three principal reasons: costs and schedule of simulation, lack of confidence in the results, and lack of awareness of simulation as a design tool.

Costs of conducting simulation studies presently inhibit the use of simulators in the design effort. The cost of the simulator itself, because of advances in computer technology, is no longer the limitation it was just a few years ago.

The state of practice of shiphandling simulation for waterway design varies widely. No agreement exists among practitioners on the minimum requirements for simulator fidelity for a given application. From examination of previous applications to waterway design, it is evident that a significant level of confidence in the application of shiphandling simulation to waterway design is not uniformly shared by all waterway design participants.

This lack of confidence revolves about questions of overall fidelity and validation. The components where fidelity is questioned are mathematical models of ship dynamics, waterway data bases, and visual displays. The behavior of ships with small under-keel clearances is especially not well understood nor well represented in existing models. Increasing the level of user confidence and acceptance will require development and validation of more robust mathematical models. Other factors that inhibit simulation include:

• the lack of a formal, objective method to validate the model and

• the lack of an accepted scientific framework for interpreting simulator results for waterway design. No consistent means exist for extrapolating results from the small sample of real-time runs to a prediction of the performance of the design over the life of the waterway.

To make simulation a more attractive design option, basic research should be conducted to resolve confidence issues and provide the capability

for more effective simulation. A single, cohesive research program, focused on identified research needs, should be defined and managed as a coordinated effort that draws on the best technical expertise available within the waterway design and simulation community. Multi-disciplinary involvement in improving simulation capabilities would help increase confidence by the port and maritime transportation communities in simulation as a design and evaluation tool for waterways. Multi-disciplinary participation can be improved immediately by establishing formal validation processes that include essential operational and technical expertise in carefully composed interdisciplinary validation teams.

RECOMMENDATION: A systematic program of research designed to put simulation on a firmer scientific footing and to develop means for guiding its use and interpretation should be undertaken as a joint government-industry initiative. It should be coordinated by the U.S. Army Corps of Engineers and should include participation by pertinent federal agencies and the port and marine transportation communities. The research needs identified in Chapter 8 should be the central elements of the research program designed to

• assess the need for fidelity in mathematical models and simulator hardware,

• develop accurate means to identify the elements in the mathematical model, and

• develop means to interpret the results of simulation.

The research program should improve the design tools needed to develop safe and cost-effective waterways. The program would be expensive and would require long-term funding. The size and scope of the research program is beyond the budget allocations from government agencies with responsibilities for waterway design and operation. Such a program would also have a cost and time frame that would be beyond incremental improvements of current programs. Implementation will require recognition of these research needs by Congress and the Departments of the Army and Transportation as a national priority to assure competitiveness with national research needs in other fields.

The U.S. Army Corps of Engineers, in view of its designated responsibility for waterway design, should take the lead in coordinating the research program. Such a research program should be carried out on a cooperative basis by all interested parties and beneficiaries. Program participants should include the U.S. Coast Guard, the U.S. Maritime Administration, and other

organizations within the marine transportation and port communities. Funding support should be provided by the federal government because of national interests in ports and waterways and by beneficiaries in the port and marine transportation communities. Development and execution of the research program should take advantage of available expertise and capabilities of the existing research and simulation facilities across the country.