Airfoil paramatrization

[Ms. kristina Pearkes 0]

Hello,

 

I am currently working on the design of the front and rear wings of FSAE electric car. Both the front and rear wings will consist of three elements each. I want to optimize the 12 parameters shown in the picture below as to have maximum lift and minimum drag. The coefficient of lift must be greater than 3.2 and the coefficient of drag needs to be less than 1.3. We do not plan on optimizing the actual airfoils, instead we have a pool of about 12 predefined profiles that we would like to choose from.

 

Is there are way of creating a profile from a set of .dat points? The FBSplineCurve looks promising for this purpose but I can't find a way to import a list of 2D data points. Right now we plan on cadding the airfoils in nx and then bringing them into CAESES.

 

Once the airfoils are in CAESES how would one set up the design variables for the distance between the elements relative to each other (X6 and X7) and the amount of overlap of each element (X4 and X5)?

 

Thank you

Kristina

 

 

[Jörg 29]

Hi Kristina,

 

Please find below a quick solution to the tasks you probably need to do.

 

In the project file, set the profile.txt as input for the "reader" object. The reader then reads in the profile data and creates an interpolation curve. In the second step, a simple transformation is applied to the interpolation curve.

 

Does this give you enough information for your next steps?

 

I am not sure about the distances between the profiles, e.g. a quick optimization could be performed whenever the model changes so as to set the value of such a distance-based design variable. But maybe it is easier and you just need to adjust the design variable directly.

 

Cheers

Joerg

readprofiledata.zip

[Ben Zeitz 1]

Hi Kristina,

 

I guess we will find a solution for your task.

 

1.  It should be possible to import the airfoils by creating a feature. The feature should get the file as an argument, open it, read-in each line and extract the point data from it (that depends on the format the file is written in). With the point data the feature could for instance create FBSplineCurves were the points are set as source.

Please have a look at the feature definition of Features/hull design/connections/neptune/Import SRI Offset File

This feature shows how a file can be read in. Please notice line 20-22 of the feature definition. There are some double values extracted from a read-in line.

Another helpful feature could be Features/curves/nurbs/Planar B-Spline Curve

This feature creates a FBSplineCurve by creating a bunch of F3DPoints and set them as source of the curve.

 

2. The distances X4, X5, X6 and X7 need to be set to some discrete values, right?

You can set-up a number of discrete values for each design variable. E.g. a variable can be 10, 11.5, 13, 17, but nothing else. Now, if you use this design variable in a Sobol it will iterate over the configured possible values only.

Please click onto the three dots symbol (…) in the upper right of the “General” headline when a parameter is selected. This expands the “Possible Values” option. (Hint: Just click on the name “Possible Values” to make the option always visible.)

 

I hope that I have understood your questions correctly. Don't hesitate to post here if you need further assistance.

 

Good luck!

Ben

[Ms. kristina Pearkes 0]

Thank you for your quick reply!

 

I've tried the method Joerg suggested for importing the coordinate file, however I keep on getting an error when I try to set the file as the input for the feature. The consol displays *** ERROR File system : FFile does not exists. Just as an experiment I also tried importing a file using the Import SRI offset file and I got the same error. Does the file need to be located in a specific directory?

 

Once I've got the geometry and parameters set up I plan on connecting with Star CCM and using the optimization tools in CAESES, either the NSGA-II or MOSA. Any recommendations on which of these would be better suited for this task?

 

Thanks

[Jörg 29]

Hi Kristina,

 

Actually, it should be easy, see the screenshot. I downloaded the zip file again, opened the fdb-file and set the profile.txt from the zip file as input. When I look at the 3D view, the data gets imported and visualized. I use version 3.1.1, and you?

 

With regard to the optimization: Is your simulation very expensive? How much time does it take to calculate a single design in STAR-CCM+? Do you know this already?

 

Cheers

Joerg

[Mr. Mattia Brenner 6]

Dear Kristina,

 

I have quickly set up a model using the parameters you described.

 

 

For the moment, I have just used simple NACA 4-digit profiles, but you can replace them with your own profiles using the import described by Joerg.

 

The gaps between the profiles and the the ground clearance are set using internal optimizations without variant creation. These will automatically adjust the vertical position of the profiles to achieve the right gap whenever a parameter is changed.

 

Cheers,

Mattia

frontWingSections.fdb

[Ms. kristina Pearkes 0]

Thank you for the model Mattia, it was very helpful. I was able to fix the problem with the data import, it was just to do with the file permissions on my computer.

 

Thanks,

Kristina