Fluid behavior as well as ship behavior prediction by means of engineering simulation to maximize proficiency of ship.
Starting in the seventeenth century experimental fluid dynamics appeared in France and England. Subsequently, theoretical fluid dynamics developed. Until about 1960, fluid dynamics were only studied using an experimental or theoretical approach. The rapid development of high-speed digital computers, along with precise numerical algorithms for solving problems using these computers, has introduced an important third dimension in fluid dynamics called Computational Fluid Dynamics, commonly referred to as CFD, and revolutionized the way we study and practice fluid dynamics today.
In the late 1970s supercomputers were used to solve aerodynamic problems. HiMAT (Highly Maneuverable Aircraft Technology) was an experimental NASA aircraft designed to test concepts of high maneuverability for the next generation of fighter planes. Wind tunnel tests of a preliminary design for HiMAT showed that it would have unacceptable drag at speeds around the speed of sound. Redesigning and retesting it would have cost $150,000 and delayed the project unacceptably. The wing was redesigned by a computer at a $6,000 cost.
While the early development of CFD was driven by the needs of the aerospace community it is now used in all disciplines where the flow of a fluid is important. Some examples are the performance improvement of cars and their engines, the examination and better understanding of the real flow behavior of liquid metal during mold filling to help design improved casting techniques, and the calculation of the flow from an air conditioner.
CFD can also be applied to examine the hydrodynamics of high-speed hull forms. While a large number of theoretical and experimental investigations into the hydrodynamics of ships have been carried out there are areas that require further research. The steady free surface flow and related forces prediction by numerical calculations is one example. The prediction of the flow field for high-speed hulls is complicated by the dynamic trim and sinkage which have a remarkable effect on ship generated waves. The existence of a transom stem, used on most high-speed vessels, further complicates the problem as the large low-pressure area behind it generates waves, wave-breaking, and spray.
CFD techniques are especially useful in analyzing flow problems in resistance prediction where complex fluid flow is present. While towing tank tests provide better absolute accuracy, CFD techniques can give results that are comparable to the towing tank results at a smaller cost in money and time. In addition, they have the advantage Numerical simulation of fluid flow around ship models to predict hydrodynamic performance using CFD package STAR-CCM+ of allowing modifications to hull forms to be undertaken so that a comparative study of results can be made in a relatively short time and at relatively small cost.
In brief we can notate our motivation likewise below:
- It is required to predict the power required to design efficient ship to optimize economically and environmentally
- The power required is directly controlled by the resistance ship is facing in seaways
- In order to determine resistance accurately, the features of the flow around the ship hull must be measured accurately in a way that designers can try many hulls without spending too much time, effort and resources.
- Testing a ship model in towing tank is relatively costly and time consuming
- Simulating a ship in a virtual towing tank using computational resources is far more less time consuming and less costly too.
- Testing the accuracy achieved will influence our confidence over computer simulation positively
- Comprehensive data can be extracted from CFD, whereas a physical test case can only provide data from a limited number of locations. In addition, there is no testing apparatus interacting with the flow in case of CFD simulation.
- Greater control over the set-up of the experiment. Conditions which would be difficult or impossible to achieve in a towing tank can be easily created in numerical tank
The benefits of CFD compared to traditional model tests are many, with the major ones being listed below:
- Simulation cost is relatively low compared to physical experiments.
- CFD simulations can be carried out faster than physical experiments. In addition, changes to the original design can be made quickly.
- Comprehensive data can be extracted from CFD, whereas a physical test case can only provide data from a limited number of locations. In addition, there is no testing apparatus interacting with the flow.
- Greater control of the set-up of the experiment. Conditions which would be difficult or impossible to achieve in a towing tank can be easily created in numerical tank.
