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Application Examples

FLUID TECHNO Co., Ltd.
Enhancing Ship Design through Combinational Use of CFD (Computational Fluid Dynamics) and Extensive Data

[Vol.2] Fluid Techno has cultivated advanced technologies for designing ships, providing ship-related manufacturing and training services, and developing ship-specific energy saving devices. Faced with the need to improve energy efficiency, they use Software Cradle SC/Tetra CFD software to develop more capable products in a shorter period of time.

CFD as an Essential Tool

The ship design process starts by determining a conceptual hull shape based on the specifications given by the order. Specifications include cargo weight, velocity of the ship, and the amount of carbon dioxide in the exhaust. Based on these, outlines of the ship geometry and thereby performances are determined. Simple simulations are conducted to assess design feasibility. This is followed by the construction of an accurate digital representation of the geometry using 3D CAD. This 3D model is then passed to CFD for evaluating towing condition, self-propulsion condition, surface flow of the ship, and resistance created by waves. Fluid Techno considers this CFD evaluation process critical. If no problems are detected during this phase, the process moves to designing the propeller, calculating other performance parameters, and conducting experiments. The experiments are usually done only for one model. If problems are detected in this phase, re-designing is performed, but that usually leads to a loss of another half a year which also requires additional cost for physical testing. The completion of all possible preliminary performance evaluations is essential to prevent this. “The time has put CFD at the forefront of today’s alternative means of evaluation,” says Mr. Tamashima. To further promote CFD applications, Fluid Techno collaborated with Software Cradle to introduce SC/Tetra to in-house engineers.

To reduce fuel usage, the hull shape must be constructed to minimize resistance caused by the water. The hull shape must also be adequate for loading cargo. The best shape is determined by balancing all the requirements. To help determine the best design, fluid dynamics technologies are needed. “Major shipbuilders have technical departments specialized for this, but small firms don’t even have such divisions. It takes years of experience to gain proficiency in this field. This is where we can offer our expertise,” says Mr. Tamashima. Fluid Techno conducts CFD evaluations to determine the best shape, which can then be used for the large scale tank test.

Figure 3: Analysis results of evaluating the condition shown in Figure 2 using SC/Tetra
Force acting on rudder is verified by changing the size of rudder valve and visualizing the flow.
(Click to enlarge)

CFD for Above Water and Inside Ship

In addition to using simulation to optimize fuel efficiency while satisfying the other ship design requirements, Fluid Techno has keen interests in investigating other issues using SC/Tetra. One of them is worsened maneuverability with increasing ship speed. Conventional CFD tools can be used to analyze resistance caused by water, but they cannot analyze maneuverability thoroughly. SC/Tetra is a candidate tool to verify it (Figure 3).


While Fluid Techno mainly analyzes the section of the ship that is underwater, they also intend to investigate wind pressure resistance above the water surface, which their clients have been requesting. They will evaluate how to reduce wind pressure resistance by altering structure shape.

Figure 4 Analysis of sea chest
(Click to enlarge)

The ship-related flows include not only external flows around the ship but also internal flows within the ship. For example, the engine cooling system takes in sea water from sea chests located at the bottom of the ship. Fluid Techno is proceeding with verification of SC/Tetra for simulating the ingestion of sea water (Figure 4).

The use of energy saving devices is another key approach for further improving fuel efficiency. Fuel efficiency could be improved even further by installing these devices in addition to the improved hull shape. Fluid Techno expects to undertake all these evaluations with SC/Tetra.

 

Fluid Techno is currently calibrating their simulation inputs. “Using experimental data, we are now establishing methods of mesh generation, number of mesh elements generated, and numerical value for tuning. Hopefully this will encourage applications of CFD,” says Mr. Tamada.

The goal of using CFD is to evaluate flow phenomena related to ships across the board. This includes external and internal flows for both water and air. “We are aiming to figure out these types of flows early in the design phase. Our ultimate objective is to come up with the best design in shortest amount of time possible. We expect that CFD will be of great use for achieving this. Through providing our experimental data and improving CFD applications with Software Cradle, the simulation environment will advance drastically,” says Mr. Tamashima.

 

Easy-to-use Tool with High Quality Postprocessor Capability

Mr. Tamada says: “We found Software Cradle products easy to use. Support engineers of Software Cradle certainly stand ready in doing everything possible to support us. The user reference is well documented for us to understand.”

Fluid Techno finds that mesh generation using SC/Tetra is easy and robust compared to other tools, which, often times, produced errors. They are now working to determine the ideal settings in SC/Tetra for generating mesh elements and mesh refinement. They still want higher calculation speed out of the software although they are facilitating more powerful hardware for that purpose at the same time.

Setting up the SC/Tetra postprocessor to view simulation results is very simple. Results can be easily visualized in many different ways. “SC/Tetra is well-developed software from the aspect of visualization capability,” says Mr. Tamada. He recommends enhancing the report output function to make it even more useful. The future challenge is to analyze vessel performance on waves.
 

Easier Verification Process

So far, Fluid Techno has completed thorough verification of only rudder capability. “Verification was easy as I imagined.” Mr. Tamashima says, noting that relative differences were clearly identified. “The verification process became much easier and effectively faster.” says Mr. Tamashima. Performing analyses helped them plan better for experiments. “If we didn’t have CFD, we would have to run five experiment cases. But with CFD, we would be able to reduce the number of test cases. It would be possible to allocate experiments of other topics for the place of the eliminated cases instead. Without a doubt, if CFD is incorporated into the ship hull design process, the overall work flow will be much more efficient,” says Mr. Tamashima.

In their continual pursuit of better design, Fluid Techno is always looking to implement new approaches. While they have been designing and performing analyses in three dimensions, viewing models and analysis results has been limited to two dimensions using graphics monitors and paper. As an alternative, Fluid Techno is planning on extending the application of 3D printers. “Some details are difficult to grasp in two dimensional plans, but these can be intuitively evaluated when converted to three dimensional models. The shape of the ship stern is especially important. We are planning to use a three dimensional models for its evaluations,” says Mr. Tamashima. Fluid Techno expect to improve the certainty of the model ship experiments by adding an evaluation process using 3D printers between the CFD analysis phase and model ship experiments.

Fluid Techno has actively implemented 3D applications to elevate their competitiveness. Software Cradle will continue to support their design development.
*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of February 29, 2016 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors in this brochure.

Company Details




 

FLUID TECHNO Co., Ltd
Founded 2001
Business Provides ship design and development support including model ship designs for experiments, test services for ship experiments, and software programs for calculating ship performance. Provides design and implementation services for ship energy saving devices.
Head Office 6F Gibraltar Seimei Bldg., Tokiwa-cho, Sasebo, Nagasaki Japan
Representative Masahiro Tamashima, President
URL http://www.fluidtechno.com/

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