Inland water transport is an integral part of the Russian economy and performs an important function of cargo and passenger delivery, including to hard-to-reach areas. At the same time, the average age of transport, towing and passenger fleet vessels in operation is more than 40 years, and the average age of decommissioning of vessels is about 50 years.
Therefore, in the coming years, the need for new inland and intermodal vessels to compensate for the retirement of the old fleet may be up to several hundred vessels annually. However, due to the fact that inland water transport business is low-margin, fleet customers are extremely sensitive to project economics.
A bit of theory
The most important characteristic of a ship in terms of economic efficiency is the dynamics of its behavior in the presence of external influences, which is studied in such sections of the theory of the ship as walkability, controllability and rocking. For qualitative solution of tasks related to optimization of these characteristics it is necessary to have information on flow structure around the hull in the early stages of design. These processes can be studied experimentally and numerically.
Traditionally, reliable determination of parameters of ship’s motion, controllability and pitching is made experimentally on the basis of ship model tests in a test basin. However, high enough cost of such researches does not allow using them to the full extent at designing of the majority of inland ships, especially of piece-built ones.
An alternative to experimental pools is numerical research, which is based on the CFD method (Computational Fluid Dynamics), which allows modeling the motion of liquids and gases on the computer. This method has a number of advantages in comparison with the experiment. The most important of which is its low cost, in most cases the cost of the computer time is an order of magnitude lower than the cost of the corresponding experimental research. The importance of this factor increases with increasing scale of research and design variants. Besides, numerical solution gives detailed and complete information, with its help it is possible to estimate values of all available variables (such as velocity, pressure, turbulence intensity, etc.) in the whole solution area, which cannot be measured in any experimental study.
In other words, it is possible to solve the problem of creating new cost-effective inland and intermodal vessels by applying methods of computational hydrodynamics. Understanding of this pushed the specialists of Design Bureau “Proship” to search for tools allowing to solve a wide range of practical tasks in a short time, providing new designs with balanced hull contours, propulsion complex and main power plant for operational modes of vessel operation.
Our choice was based on two software products Simcenter Star-CCM+ and OpenFoam, as these software products have all the necessary tools – from the preparation of the numerical model to the evaluation of the calculation results, and the quality of the results obtained is confirmed by dozens of successful projects carried out by leading enterprises in various industries – Rosatom Group, JSC UEC, FSUE Krylov State Science Center, etc.
Results
First of all, the specialists of Design Bureau Proship performed a series of test calculations of ship hull flowing, for which there are experimental data obtained by the main experimental basins of the world. As a result, the results of numerical modeling turned out to be comparable to the experimental data. As an example, the graph shows the results for the hull of the KCS container ship developed by the Korea Research Institute of Ship and Ocean Engineering (KRISO). The values for drag force are dimensionless using the standard unmeasuring procedure recommended by ITTC87. At Fr = 0.282, the impedance coefficient error was less than 1%.
The experience gained by specialists of Design Bureau “Proship” in the course of comprehensive hull development with known experimental data helped to form a number of ideas allowing to optimize performance characteristics. Thus, for example, on the modes with developed wave formation, insignificant changes of the bow shape can have a noticeable influence on the character of the wave pattern and the value of towing resistance. As a result, the shape of the bow of the workboat was revised. It allowed to reduce the total towing resistance at speeds above 18 km/h by 7.5%. Fuel costs in the structure of operating costs of fishing vessels can reach 30%. Thus, the received result allows to draw a conclusion that outlines made according to the general recommendations and engineering experience have a considerable potential for optimization.
Result
All of the above provides ample evidence that the use of modern engineering analysis tools, such as Simcenter Star-CCM+ and OpenFoam, to optimize seaworthiness early in the design process can significantly improve project economics and balance vessel operating costs.
Alexei Nikitin,
CEO, CB Proship LLC(Russia).