How to improve the accuracy of the geom in Autogrid?
 

Hi guys,

I imported a .geomTurbo formatted file to the Autogrid. The number of points on hub and shroud curves is less than 20 which covers a range from -600 to 1000. I notice that curves shown in Autogrid is not smooth enough so that I have to try to improve the accuracy to meet the requirement of smoothness.

How can I control the interpolation accuracy of imported geom in Autogrid? Any suggestion is welcome.

Thanks
swm

The hub curve shown in autogrid
 

Attachment 54415

This is the hub curve shown in autogrid

Hi;
Numeca by default uses cubic splines to generate curves out of defined points unless you mention "polyline" somewhere in the geomturbo file. please check it first.
If no polyline is defined in the file, one solution is to import the points to the 3d software you use (NX, Catia, etc.). Then define a spline passing the points. you can define some extra points on the generated curve and exploit its coordiante.
Then add these points to your first batch of points and put them all in your geomturbo file. This will increase the resolution of your curve.

Regards

Yes, you're right. I checked the .geomTurb file and found the word 'ZR' was followed by 'polyline'. You mean I should delete the 'polyline'?

Besides, in the part of coordinates of airfoils, there's no 'polyline' and I'm wondering how the AUTOGRID generates curves of airfoil sections of the blade. Do I need to generate the blade in 3d software first? If it's supposed to use other 3d softwares to guarantee the smoothness of geometry, the Autogrid is not strong enough to generate mesh from .geomTurbo file.

Many thanks.

swm

Hi;
you can remove the polyline from the text.
regarding the quality of model in Autogrid I should say:

- To my experience Autogrid does its best to provide a smooth and precise curve through the defined points using splines and its performance is usually acceptable.
- But if the number of airfoil defining points are low (specially in regions with sudden slope changes e.g. near LE and TE) the quality of the airfoil will not be satisfactory. Therefore even with high performance of Autogrid in surface generation you still need enough points to define airfoil sections. increasiing the density of the points can be done by a 3D modeler as I mentioned before.

Regards

To your experience, how many points per airfoil section can generate a smooth geom by autogrid?

It is not easy to decide upon the number of points. It mainly depends on the type of airfoil and can be determined by try and error for each case.
But generally near the LE and TE points should be more concentrated to better represent the curvatures there. mid parts of the airfoils on both SS and PS can possess lower number of points due to less curvatures.

Regards