2D gambit and fluent
 

Hello.. I need help here.. Im doing a project which requires me to do turbulence modelling for an airfoil. Im a beginner in this field, just learn gambit and fluent.

As my 1st task, i was ask by my supervisor to compare the best mesh for my airfoil. Use fluent to get the Cl vs alpha and also the required contours. However, after running analysis using fluent for 3 different meshes, i realize that my data is very different from experimental data which i obtained from internet.

Im doing Naca 0012, so from internet, the stall angle for 2x10^6 is around 10-15 deg. However, for my mesh, i run the analysis until 25 deg, but the Cl is still not decreasing.

Can anyone help me and tell me what is wrong with my mesh? Thanx alot..

hi ,,
you have not mentioned your mesh size and type of mesh.Anyhow your problem is simple and the reason for not stalling the airfoil is not dependent upon mesh.you should make sure that your airfoil vortex data was correct in Gambit and proper domain and boundary conditions were given in Fluent.I will suggest a circular domain with "pressure far field" boundary condition.

Will try..
 

hi ,,
you have not mentioned your mesh size and type of mesh.Anyhow your problem is simple and the reason for not stalling the airfoil is not dependent upon mesh.you should make sure that your airfoil vortex data was correct in Gambit and proper domain and boundary conditions were given in Fluent.I will suggest a circular domain with "pressure far field" boundary condition.

Thanks for the comment.. Well, im trying with 3 different meshes, structured, unstructured and also with boundary layer.. I also tried coarse, medium and fine for all the meshes. But for my boundary layer, when i reach 10 deg, my fluent data is not converge, but fluent gives me a repetitive 'mountain shape data. /\../\ something like i show here..
i am using a circular arc to put my airfoil and a rectangular at the back of airfoil.. then boundary condition i used for the arc is velocity inlet. perhaps i will try pressure far field and see whether i get the correct result or not.. Thanks again.. :)

no problem..
 

no need to say thanks,,,
:)
wish you all the best for your project !
by the way you even dont need boundary profile at this stage,,,
simply make an airfoil with circular domain,and tri paved mesh,,
you will find good results..
increase the difficulty gradually...
good luck

Trouble..
 

Im trying to use pressure far field at the arc of my mesh (means the front part, however i still cant get the desired values.. i get a very high value for my cl. I got 4.2 for my angle of attack 5 deg. last time, i used velocity inlet at the arc. Im not that familiar with fluent, but time is kinda limited for me to explore everything.

haha..
 

I set the wrong gauge pressure... hahaha.. :)

Still cant..
 

I still cant get the satisfying results although i used pressure far field.. i dont know wats wrong.. :(

Problem in 2D mesh !
 

Dear Experts,

While making 2D mesh, how to make an inner zone ?

Actually, 5*5 cm box filled with water. Air injection is from bottom INLET 0.1 cm. There is an inner zone that occupies the inlet and the path of bubbly flow. However, bubbles can pass through this zone because this zone is made just for focusing main area.*

Although, it is looking very simple but problem arises when this inner zone should be shown in boundary condition window. ( See Fig. 1)

I made this inner zone, called it INTERIOR and obtained in BC. Because of this inappropriate zone the results are not as actual as it should be. ( see Fig. 2 , 2b). Actual results are shown in Fig. 3.

Any guideline, advise will be highly appreciated. I would be more thankful *If there is guideline by using Gambit software..

Thanks in Advance

M. F. Ali

Problem in 2D mesh !. Available from: https://www.researchgate.net/post/Problem_in_2D_mesh [accessed Jun 20, 2017].

In Gambit you only have to split your domain.
You don't have to set anything with interior.
If your splits are well done, gambit will automatically set the zones as fluid.
Then in Gambit you have to differentiate your fluid domains for being able to patch them separately for any BC.
Check Specify Continuum Types:
https://www.sharcnet.ca/Software/Gam...zone_cont_type