Unit 6. Response amplitude operator

I. Words to be remembered:

floating structure – наплавное сооружение

to determine – определять, устанавливать

ship motion – движение корабля

wave heading – головная волна

to require – требовать

shifting – перемещение, смещение

robust – крепкий, прочный

capsizing – опрокидывание

to dimension – измерять

criteria – критерии

emphasis – предыскажение

naval warship – морской военный корабль

II. Read and translate the following text:

In the field of ship design and design of other floating structures, a response amplitude operator (RAO) is an engineering statistic, or set of such statistics, that are used to determine the likely behavior of a ship when operating at sea. Known by the acronym of RAO, response amplitude operators are usually obtained from models of proposed ship designs tested in a model basin, or from running specialized CFD computer programs. RAOs are usually calculated for all ship motions and for all wave headings.

RAOs are effectively transfer functions used to determine the effect that a sea state will have upon the motion of a ship through the water, and therefore, for example, whether or not (in the case of cargo vessels) the addition of cargo to the vessel will require measures to be taken to improve stability and prevent the cargo from shifting within the vessel. Generation of extensive RAOs at the design phase allows shipbuilders to determine the modifications to a design that may be required for safety reasons (i.e., to make the design robust and resistant to capsizing or sinking in highly adverse sea conditions) or to improve performance (e.g., improve top speed, fuel consumption, stability in rough seas). RAOs are computed in tandem with the generation of a hydrodynamic database, which is a model of the effects of water upon the ship’s hull under a wide variety of flow conditions. Together, the RAOs and hydrodynamic database provide certain assurances about the behavior of a proposed ship design. They also allow the designer to dimension the ship or structure so it will hold up to the most extreme sea states it will likely be subjected to.

Different modeling and design criteria will affect the nature of the “ideal” RAO curves being sought for a particular ship: for example, an ocean cruise liner will have a considerable emphasis placed upon minimizing accelerations to ensure the comfort of the passengers, while the stability concerns for a naval warship will be concentrated upon making the ship an effective weapons platform.

III. Answer the following questions:

1. What is a response amplitude operator?

2. How is RAO obtained?

3. Where is RAO used?

4. What is a hydrodynamic database?

5. What affects the nature of the “ideal” RAO?

6. Are RAOs usually obtained from models of proposed ship designs?

7. Generation of extensive RAOs at the design phase allows shipbuilders to determine the modifications to a design, doesn’t it?

IV. Insert the missing words, using the text:

1. Known by the acronym of RAO, … … … are usually obtained from models of proposed ship designs tested in a … basin.

2. Generation of extensive RAOs at … phase allows shipbuilders to make the design … and … to capsizing or sinking in highly adverse sea conditions.

3. Together, the RAOs and … … provide certain assurances about the behavior of a … ship design.

4. An ocean cruise liner will have a … … placed upon minimizing accelerations to ensure the comfort of the passengers.

5. RAOs are usually obtained from running … … computer programs.