- •D numerical modelling
- •1 Read the text and mark the statements as ‘true’ or ‘false.’
- •2 Find the English equivalents for the Russian expressions in the text above.
- •3 Complete the sentences according to the text.
- •4 Translate the words in brackets to complete the sentences.
- •5 Write a summary of the text in Russian.
- •6 Put one word in each gap to complete this summary of the text above and compare it to yours.
- •G an auv competition
- •1 What kinds of underwater vehicles do you know? What can they be used for? The words in the box can help you.
- •2 Complete the sentences using the words from the box.
- •3 Match the English expressions with their Russian equivalents.
- •4 The two texts below are about a competition. Look through them and say
D numerical modelling
avoid – избегать computational fluid dynamics – вычислительная гидродинамика considerable – значительный capable – способный equation – уравнение evaluate – оценивать |
finite element analysis (FEA) – анализ конечных элементов liquid – жидкость mesh – решетка polyhedral – многогранный polygonal – многоугольный simplify – упрощать triangular – треугольный |
1 Read the text and mark the statements as ‘true’ or ‘false.’
CAD programs often use models which are more complex than the real objects.
The cells in a mesh are simple geometrical shapes.
The most convenient way to design a ship is to use a new model at each stage.
Modern computers create meshes very quickly.
Numerical simulation allows calculating important hydrodynamic parameters for a given hull form in a short time.
Very powerful calculating facilities are necessary to perform the simulation.
No computer program is capable of manipulating an unlimited amount of data, therefore simplified models are necessary to use different CAD programs. A common tool for creating a computer ship model is the so called finite element analysis (FEA), which allows the designer to construct an approximation of a solid using small tetrahedral or polyhedral cells; a curved surface, such as the surface of a hull, may be represented by triangular or polygonal cells. The resulting mesh is then used by CAD applications for assessing the ship’s various parameters. It is important to have a finite element mesh for the ship structures as early as possible because evaluating structural concepts effectively with FEA allows the designer to avoid problems later.
Mesh generation requires good qualification of the engineer, a very powerful computer and considerable time. High quality meshes often consist of over a million cells. As a result, the processing of a file containing them in a CAD system takes many hours even with modern high-performance CPUs. Moreover, working with such large databases requires powerful video cards and a large amount of memory.
Other recourse hungry applications are those of computational fluid dynamics (CFD). CFD uses complex equations to model the interaction of fluids (liquids and gases) with surfaces. For example, it can allow the designer to calculate wind and water pressure on the hull.
The whole development of a new ship model, that includes the numerical simulation and calculation of the ship’s integral characteristics, must usually be done in less than a month. During this time it is necessary to study the ship’s hydrodynamics at 10-15 different speeds (which means that for each speed the pressure on every part of a ship hull surface must be calculated), and many other parameters. Such tasks are beyond the powers of a personal computer. That is why special supercomputer systems are now created for shipbuilding, which allow the engineers to solve complex problems of numerical modelling. Without modern computers, simulation of this kind would be impossible and testing a new concept would mean experimenting with a physical model in a test tank. However, the new technologies still require considerable resources, both technical and human.