curve in airfoil
 

Hi Friends
I have a two-dimensional airfoil got into Gambit.
I wanted to know how to give it a curve?
Wells turbine is the subject of the my Thesis.
Note the curvature of the tip in the image below:


http://www.upload7.ir/imgs/2014-10/9...2347311853.jpg


http://www.upload7.ir/imgs/2014-10/3...0608280524.jpg
Thanks for your help

display what you already have in Gambit

Hi dear friend

Thanks .... note the following:

http://upload7.ir/imgs/2014-10/39760625907744765452.jpg

I would:
- merge edges;
- create the face from merged edges;
- create a volume from sweeping the created face (+z direction);
- copy/rotate the volume aroung the central axis;
- create the central cilinder volume;
- merge all the volumes;
- if you need to "curve" external surfaces, create a cilinder volume and cut the blades;
- create external volume (air volume);
- subtract internal (solid) volume from external (air) volume.

hi dear friend

Thank you.
But as the following:

modelling:

We use the periodic boundary condition

http://www.upload7.ir/imgs/2014-10/7...9032798868.jpg

now,What should I do?

Thanks for your help

Sorry,I have an other question:
Assuming that it is available vertexes of airfoil.

How to put vertexes of airfoil on the Cylinder(Cylinder that must be cut)?

Because the beginning, the points of airfoils are no curvature.

I'm confused!!!!!

--> from here you get your rotor as solid

--> you extract the fluid domain. The height of your external volume must be 12L, and move it to its right place
From here you have a full modell.
If you want to work with periodicity, you can split the model
http://www.upload7.ir/imgs/2014-10/7...9032798868.jpg


I didn't get your point

If u Imagine that I have the vertices coordinates related to airfoil, how can i fit or put the vertices on the rotor hob in order to coincide them.
I don't have any idea about it the software I used is Gambit ver.2.4
Thank you for Your help

As ghost82 mentionned, you can merge all your tiny edges from airfoil, except both designing trailing edge.
Doing that you will still have one vertex (sharp angle from trailing edge)
You are also free to choose another one vertice: you can for example use the split edge tool: https://www.sharcnet.ca/Software/Gam...eom_edge_split

Hi,
here is what I mean:
When you merge the 2 volumes, after sweeping the airfoil, you will have the airfoil edge automatically projected to the cylinder (bottom-left image).
If you need to curve the airfoil create a new cilinder (red dotted) and cut the 3d blade, then delete the more external volume (black dotted).

thank
 

hi my dear friends.

I can almost design Primary model with your guidance s but for merge edge I face a problem.

Edge merge method don't understand.how merge edge?

for this reason,i am doing edge and faces without merge but for Construct blade volume i face a problem and blade volume don't Construct correctly,attention to bellow image:


http://upload7.ir/imgs/2014-10/50916681304851603069.png

According to the following image, For merge,two Later edge don't consider but get following error:

http://upload7.ir/imgs/2014-10/64768975799944540504.jpg

too,total edges consider but again get following error:

http://upload7.ir/imgs/2014-10/22990953390987136913.jpg

vertexes of airfoil figure Before construct volume:

http://upload7.ir/imgs/2014-10/50788530178386686027.jpg

vertexes of symmetrical airfoil:

http://www.upload7.ir/imgs/2014-10/1...8650485083.jpg

edge and faces of symmetrical airfoil:

http://www.upload7.ir/imgs/2014-10/4...5931525284.jpg

http://upload7.ir/imgs/2014-10/80986115583054478951.jpg

Blade figure Before construct volume:

http://www.upload7.ir/imgs/2014-10/0...6905548992.png

figure of modeling:

http://upload7.ir/imgs/2014-10/06065188234221131607.jpg

Thank you for allocating your time.

follow instructions from ghost82: work only with volumes (not surfaces)

Merge edges!
see here:
https://www.sharcnet.ca/Software/Gam...ide/mg0203.htm

Default is split edge, so right click on the split edge button to select merge edges, select 2 edges at a time and merge them.
I suggest to leave 2 vertices to easily mesh geometry (see picture).

PS: I'm automatically updated when somebody reply to this thread so no need to send private messages :P

hi,thanks

In some cases when I do merge some edges by the chance it merges and virtual edge is created instead of the real edge. is there any rule for merging that i don't follow it or these kind of virtual edges don't create any problem in further processing steps?


http://www.upload7.ir/imgs/2014-10/2...7537969885.jpg


http://www.upload7.ir/imgs/2014-10/8...6256172841.jpg


virtual edges:


http://www.upload7.ir/imgs/2014-10/4...5347637087.jpg


thank for your helps.

Dear Friends,
First, I would like to thank you for all your help and inform you that I have finally made my intended model.



http://www.upload7.ir/imgs/2014-10/0...1854107784.jpg





In my model, I want to make the upper airfoil cord bigger than the buttom one.

http://www.upload7.ir/imgs/2014-10/1...5700652005.png

I would appreciate it if you could kindly give me your advice. if you could send me a visual, H would be thankful.
Best,
Amir

if you modify the design of your airfoil, you will have to redo everything.
But you can use your previous journal file to "automatically" rebuild your geometry.
https://www.sharcnet.ca/Software/Gam...#menu_file_run

if you only want to extend your domain, the sweep tool should be suitable

hi,

thanks

Yes, but I my problem is making the blade.
Dash line is for previous model.
New model is red lines that I do not know that model.


http://www.upload7.ir/imgs/2014-10/3...9287448245.png


In the meantime I've deleted the journal file and have the file (dbs).
Until now I did not work with journal file.

From First modeling, but how do I create blade?

Such post #10 with pictures to explain me,I would be thankful.

Thank you for allocating your time.

How did you create the blade from your previous model?
:rolleyes:

hi my dear friend

i have created the blade with sweep tool, and so with volume split tool by face.


Procedure is as follows:



http://www.upload7.ir/imgs/2014-10/5...5036733396.jpg


http://www.upload7.ir/imgs/2014-10/3...9574709609.jpg


sweep airfoil(face):


http://www.upload7.ir/imgs/2014-10/4...6873875991.jpg

create new cylinder:

http://upload7.ir/imgs/2014-10/47856518231227698890.png


blade volume subtract volume 6:



http://upload7.ir/imgs/2014-10/18138432192410606333.png




create edges for Faces:



http://www.upload7.ir/imgs/2014-10/1...2672712003.jpg



http://www.upload7.ir/imgs/2014-10/1...0007975334.jpg


http://www.upload7.ir/imgs/2014-10/1...2621827120.jpg


created faces:



http://www.upload7.ir/imgs/2014-10/7...6746482722.jpg


volume split tool by created faces:




http://www.upload7.ir/imgs/2014-10/8...9194383326.jpg

continue.....

deleted volumes:


http://www.upload7.ir/imgs/2014-10/9...1082369121.jpg


http://www.upload7.ir/imgs/2014-10/5...6083214863.jpg


http://www.upload7.ir/imgs/2014-10/5...3427838378.jpg


Thank you for allocating your time.


I really do not know what to do for the new model.Now Here,
I do not think the sweep tool is efficient( in Third picture Previous post).


best,


Amir

if you want to extrude a surface for having a volume, you only have sweep tool, which has more possibility than vector extrusion
https://www.sharcnet.ca/Software/Gam...eom_volm_sweep

I think you'd better to use a cad software to have control of geometries; for example, with autocad you can import and interpolate the airfoil points, create the 2 surfaces and then use the loft command to create side blade surface.
With the sweep command you can only create 2 equal bases.

Hi my dear friends,

I think that have the coordinates of the vertexes from the two airfoils(for blade),I can easily Create New model.

Do not know of a site that would provide the coordinates airfoils with different chord?

The following sites provides coordinates but I think cords are identical:

http://m-selig.ae.illinois.edu/ads/coord_database.html

http://airfoiltools.com/


thanks for your help.

There is no one answerhttps://www.physicsforums.com/styles...foro/clear.png:(

thanks for your help.

You can use that sites for coordinates, then scale the model to have the chord you want.

Hi,

Airfoil coordinates are not perfect .... why?
I created a vertex closer at the interval 0.01 and so I got the face.

In terms of validation does not have problem?


http://www.upload7.ir/imgs/2014-10/1...5973388099.jpg


http://www.upload7.ir/imgs/2014-10/5...5264629418.png

http://www.upload7.ir/imgs/2014-10/4...8534551673.jpg


http://www.upload7.ir/imgs/2014-10/7...1919700994.jpg

thank you for your help.

We don't know why they're not "perfect", maybe the administrator of that site knows :)

However, I'm not an airfoil expert but are you sure that the curved lines end in a point?
Maybe the last 2 points are connected by a vertical edge?

See these for example:
http://s5.photobucket.com/user/kawam...rfoil.jpg.html
https://afinemesh.files.wordpress.co...fig4a-grid.png

However, I think that probably having a vertical edge or not, results will be very similar.

hi dear friends,

Previous modeling is almost done!

Now,a few questions,

Y+, How do I determine for this model?

and y, distance to the nearest wall(i.e. How do I computes the height of the first mesh cell off the wall required to achieve a desired Y+)?

thank you for your help.

best,

Amir

thanks,

but value y+=1 right for this model?

It depends on the turbulence model/wall function you are using.
Try a search in the fluent forum, there are a lot of thread related to yplus values.

hi,

thanks

Matter how I searched but I could not find anything useful.

References and booklet you can introduce yourself for download?

I want to know what y plus is use for models of different solve(K-W,K-e,spallart-Allmaras,....)?.


If Y+=1 be, Results are very wrong? or that more time would be solved?


Actually, I want to recognize turbulence around the blade Correctly, in order to obtain entropy change around the blade.
Which model and what Y plus should we use?

Is it better in other parts of the site, ask my question?

I appreciate your help.

best,

Amir

No one help?,No one can advise?:(

:rolleyes:
I cannot believe you cannot find anything useful on the net.