Model Preparation
 

Hello together,

just a short question: If I want to investigate the gap losses of a rotor blade, what should I prepare relating to my model? Do I have to create three models, the blade, the hub and the tip curve or should I create one model where all this is included?

Thanks a lot.
Greetings

I assume you are going to use AutoGrid for this task? If so, it is necessary for Autogrid that your blade geometry must be extended over the hub and shroud curve, even if you are going to model a tip gap.
In AutoGrid you create an initial, in most cases very good mesh with the RowWizard. During this process you can define the tip gap at leading and trailing edge. AutoGrid automatically cuts the blade at the desired location and creates a fluid block at the top of the blade, which is the tip gap.

If you have further questions, please feel free to ask.

Hello Holger,

thanks for your helpful answer.
So now I got the Hub & tip curve and the blade ready in CAD.
What are the next steps to import the model in Numeca (Numeca just know certain formats I guess)?

Thanks a lot.
Greetings

Dear dha_90,

at first you can import the CAD geomtry (for example iges, parasolid and catia files) with the "import and link CAD" button. Please load the geometry with File -> Open and select a part (blade, hub curveor shroud curve) and link it with the right mouse button. If it appears that the flow direction of your CAD model does not match the flow direction in AutoGrid you can change it Edit -> Geomtry Axis.

Secondly you should request an user account to NUMECA's customer area to have access to the manuals and tutorials. The license administrator of your company/university is able to create an account for you.

If you have further questions please feel free to ask.

I tried to link my model to blade, but there occurs a fault message: "No Blade Selected in Configuration View":(

I already have an user account to NUMECA's customer area, but in the tutorials there are always geom.files which I have to import and mesh. There is no description for the procedure in case of external geometry isn't it?

Yes this is tricky. You need to select row 1 in the top left panel in the Autogrid GUI. Then the linking works. You are right, in the tutorials always geomturbo files are provided. But maybe you find some useful information in the online documentation?

You said, that the blade has to intersect the hub und shroud curve. Is this the only way to make a simulation?

I made some tutorials from the online documentation. And I saw that I can define the gap between blade and shroud after the geometry check. But I have the problem, that my gap is not linear. The gap is bigger on the leading egde, becomes smaller downstream and becomes bigger again on the trailing edge (sounds strange but I want to cut the upper edges of the blade).

Is this possible in Numeca?

Greetings

Dear dha90,

yes, it is mandatory that the blade intersects hub and shroud during import. For simple cases it is often sufficient to define the gap width at leading and trailing edge, AutoGrid interpolates between these two values.

In your case you should define the shape of the gap by an external geometry file (.dat format). This is possible in the Gap Properties box. In the online documentation you find it in this chapter:

AutoMesh™ > AutoGrid5™ > User Guide > Meridional Control > Mesh Control > Hub/Shroud Gaps Control

I hope this helps you to proceed.
Kind regards,
Holger

Thank you very much for your help. I saw you are german, so we could switch in german (but I think english is one of the rules in this forum:D)

Anyway I hope that I can handle the simulation with my strange blade.
Before cutting my blade I wanted to try test simulation with the original one. But during the geometry check I got some error messages (see attached). Do you have any ideas to solve this?
(my blade looks a bit strange cause I had to extend the upper and lower surface sp that the hub & shroud curve intersect my blade.

Greetings

Hi,
I would prefer english so non-german speaking readers can participate, too. The problem might be a poorly defined cad geometry, are there any open gaps in the surface of the blade?

Secondly you should do what AutoGrid suggests. Are the units of your project are correct? In the meridional view you can use the distance tool to measure the channel height. If not correct, I'm the left bar under 'units' you can adjust it.

Another option is to manually increase the sewing tolerance to merge possible gaps. The geometry properties box is on the third level of the tree-structure on the top left panel (Row 1, Blade, Geometry). But if there are any gaps in the blade surface I suggest to spend some time repairing the cad model first.

Very strange. I am sure there are no gaps in the CAD model. I can send it to you if you want (I created it in solidworks) to see that the model should be all right.:confused:
I can understand if you don't want, cause I have to do the work;)
Then I have to check again and again to hopefully find the mistakes.

Greetings

The CAD model seems to be ok. Maybe I should describe the linking process in detail.

Please switch to surface-selection by Strg-S, then please select both suction and pressure side. Right-click "link to blade". In a next step please define leading edge and trailing edge. Please keep in mind that both curves must have the same orientation. Finally you link the hub and the shroud curve.

In the contrary only for blades with blunt leading edge and blunt trailing edge it is necessary to link pressure side and suction side explicitly and separately.