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### Shigeki Katsumura (Software Cradle, Assistant Manager, Software Engineering Dept.)Tool for Fast, Cost-Efficient Analysis

Searching for the ideal combination of design variables and objective functions requires high level of engineering knowledge and experience; this is quite a task when there is limited time. Software Cradle’s Extension Option (Optimization) known as EOopti can cut down unnecessary trial and error and identify the most fitting variable and object combinations for each design case, all in a short amount of time. Shigeki Katsumura, Assistant Manager of the Cradle Engineering Department, explains why and how this tool was developed.

Shigeki Katsumura

Assistant Manager
Software Engineering Dept.

Figure 7: Condition wizard

2) Generate the sampling point (design variable values)

Engineers input data for the design variable range, design guidelines for objective functions (whether to target the maximum value or the minimum value) and sampling point. For design variable sampling, EOopti applies Latin hypercube sampling, which can be activated by clicking ‘generate.’ This calculates the design variable values automatically (Figure 7).

Above: Figure 8 Condition wizard
Below: Figure 9 Objective functions inputs using Excel

3) Specify the objective function value based on the design variable value from step 2

In this section, engineers input objective function values into the blank space in condition wizard. They are the values from the LED lamp volume calculated by the design variables at the original sampling point - and the temperature results from the scSTREAM analysis (Figure 8). Values can be both imported and exported in CSV format, allowing users to input the objective functions in Excel or other editing software, and to import the data into EOopti from there (Figure 9).

Figure 10: Condition wizard

This completes setting up the problem. Clicking ‘execute’ activates the optimization, which implements the Kriging method and MOGA (Figure 10).

When optimized, engineers can view the response surface (Figure 1, distribution of contribution, distribution of optimum solutions calculated by MOGA (Figure11), and correlation graph (Figure 12) on the draw window.

​　​Throughout these steps data can be input manually, although this is time consuming especially when generating and inputting sample values for the objective functions. This time consuming process can be streamlined by applying VBA available from Microsoft® and Office products, or Cradle’s VBI for SC/Tetra and scSTREAM. Using these ancillary software products the entire system can be constructed and the entire process automated, from fluid analysis to optimization.

Figure 11: Distribution of optimum solutions calculated by MOGA (click to enlarge)

#### What EOopti Offers

This multi-purpose optimization can generate the distribution of the optimum solutions as shown in Figure 11. While EOopti may not be the best way to identify the single local optimum solution, its greatest advantage is its capability to quickly find several possible optimum solutions. A group of optimum solutions for the objective functions generated for a fixed value, the so-called Pareto front, can be viewed by the curve on the distribution of the optimum solution. By rapidly generating this kind of information, EOopti helps reduce the overall time and cost.

Figure 12: Correlation calculated by MOGA
​(click to enlarge)

One thing to note is that the optimized values will be less reliable if the response surface is not accurate. This is because the response surface model from the Kriging method is only an alternative approximation. To promote certain accuracy, accurate design variable values for the sampling point should be used. This is especially important when fluids are involved. A large number of meshes and adjustments to the setting conditions may be necessary to accurately represent real phenomena. This means use of parallel solvers and sufficient computing horsepower will be helpful to generate accurate results in as short a time as possible.

#### Promising Future of EOopti

EOopti is a new tool, which has only been available from Version 10. It is still at its early phase and will continue to be improved as an even more convenient optimization tool.

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*Contents and specifications of products are as of January 1, 2013 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors.