|
[Sponsors] |
June 21, 2014, 13:10 |
study of wings (stall)
|
#1 |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
Hi all,
I am currently doing my final degree project to finish my studies in aeroespace engineering. I have to study several wings in ANSYS-FLUENT aerodynamically and to verify the obtained results with experimental results. I am having a lot of problems because in my simulations, the stall appears before that it has to be. For example, the stall appears to 12º angle of attack in the experimental data and it appears to 8º angle of attack in my simulation. any advice about what can be happening?? It is urgent, I have to submit my project in less than a month! Sorry for my English |
|
June 21, 2014, 15:27 |
|
#2 |
New Member
Nick Prendergast
Join Date: Dec 2013
Posts: 28
Rep Power: 12 |
Hi
I might be able to help, but I have a couple questions. 1. what turbulence model and wall treatment settings are you using. 2. what is the Y+ value for your simulations. can you also upload a picture of the mesh you are using Nick |
|
June 21, 2014, 19:27 |
|
#3 | |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
Quote:
I have done an inflation in the wing surfaces with a first layer thickness of 0.005 mm, I have achieved y+<1 in the simulations. I have attached the mesh pictures. Thanks in advance |
||
June 22, 2014, 03:32 |
|
#4 |
New Member
Nick Prendergast
Join Date: Dec 2013
Posts: 28
Rep Power: 12 |
You're already doing what I would have suggested. The only thing I could say is that while you have convergence you might have converged on the wrong answer, your mesh seems fine, so there could be something slightly wrong in your solver settings. Have you tried using a reynold's stress model?
|
|
June 22, 2014, 06:58 |
|
#5 | |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
Quote:
Right now, I am running a case with this model but I am very unexperienced in it, What configuration do you recommend me? I am using the configuration that you can see in the attached image with K or Turbulent Intensity in the Reynolds-Stress Method in inlet and outlet (B.C) In the inlet and outlet boundary conditions, I am using 0.05% turbulent intensity and 0.001m turbulent length scale, Could theses values be correct? Many Thanks!! |
||
June 22, 2014, 11:14 |
|
#6 |
New Member
Nick Prendergast
Join Date: Dec 2013
Posts: 28
Rep Power: 12 |
ye the default settings should be ok, I only suggest this model as a way to check your K-e results have converged on the right answer. The reynolds stress model is the most accurate RANS model available but its also the most computationally expensive, It might be worth running in your case. If you are wondering about any of the settings in it, I recommend checking out the Ansys fluent theory guide. It's a monster but it will explain everything much better than myself
|
|
June 22, 2014, 13:19 |
|
#7 | |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
Quote:
|
||
June 22, 2014, 13:35 |
|
#8 |
New Member
Nick Prendergast
Join Date: Dec 2013
Posts: 28
Rep Power: 12 |
I don't know, try decreasing the turbulent length scale to roughly %5 of your channel height if it isn't already
|
|
June 22, 2014, 13:57 |
|
#9 |
Member
Haris Hameed
Join Date: Oct 2009
Posts: 46
Rep Power: 16 |
hi
your mesh is not fine enough near the wall to capture the stall... you extruded the layers but these layers suddenly meet the coarser unstructured mesh. turbulence model type will effect the results but not that much. your difference is very large, so something is wrong in your computational model. i suggest you refine your mesh near the wall and make it coarse in the farfield.... even SA model will produce good results |
|
June 22, 2014, 14:07 |
|
#10 |
Member
Haris Hameed
Join Date: Oct 2009
Posts: 46
Rep Power: 16 |
here is some model mesh for you
hope this will be helpfull |
|
June 22, 2014, 14:30 |
|
#11 | |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
Quote:
I will try to get that kind of mesh but I don´t know if I will be able to get it, strutured meshes 3D in Ansys Meshing are really difficult to achieve |
||
June 23, 2014, 07:30 |
|
#12 |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
please, can anyone give me any advices to get an suitable mesh in an easy way in Anys Meshing????
|
|
June 23, 2014, 09:02 |
|
#13 |
Member
Haris Hameed
Join Date: Oct 2009
Posts: 46
Rep Power: 16 |
are you using ICEM form meshing???? is it a compulsion??? there are other meshing tools like gridgen, gmabit and pointwise that helps to create hybrid-unstructured mesh of good quality....
|
|
June 23, 2014, 09:48 |
|
#14 |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
No, I am using the meshing tool available in the workbench, What meshing software do you recommend me?
|
|
June 23, 2014, 11:55 |
|
#15 |
Member
Haris Hameed
Join Date: Oct 2009
Posts: 46
Rep Power: 16 |
i have no idea regarding the meshing tool of workbench for CFD.... i dont know how much control it gives to the user....
all the other meshing tools are equally good.... each has its own pros n cons... i use pointwise to create structured and hybrid-unstructured mesh....its T-Rex function is very good for viscous meshing. but i dont know weather it will be easy for you or not. since you have to do this work urgently... |
|
June 24, 2014, 11:12 |
|
#16 |
Senior Member
Gonzalo
Join Date: Mar 2011
Location: Argentina
Posts: 122
Rep Power: 16 |
Hi, have you tried using SST-kw turbulence model? It is a goog model to predict adverse pressure gradient boundary layers and the stall phenomena. But, are you sure thar the result in the paper or experimental results you have are corrected for blockage effects and are for free stream conditions? Regards.
Gonzalo |
|
June 24, 2014, 18:35 |
|
#17 |
Senior Member
Lefteris
Join Date: Oct 2011
Location: UK
Posts: 337
Rep Power: 15 |
Haris and Gonzalo are both right in their comments. However, I find it strange that in your CFD you get the stall earlier rather than later from what the experimental data indicate.
How many points do you have in your boundary layer mesh? Also, the mesh at the trailing edge region doesn't seem to be very good.
__________________
Lefteris |
|
June 25, 2014, 04:27 |
|
#18 | |
New Member
Daniel Ocaña
Join Date: Jun 2014
Posts: 9
Rep Power: 11 |
Quote:
|
||
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Study of wings in Ansys Fluent | danuco | ANSYS | 0 | June 21, 2014 12:41 |
Prediction of stall point | cfdeng | CFX | 1 | February 21, 2013 16:30 |
static stall | atrh | Main CFD Forum | 1 | March 9, 2004 06:07 |
Looking for experiments in dynamic stall | Anton Lyaskin | Main CFD Forum | 0 | February 10, 2003 03:57 |
stall | yin | Main CFD Forum | 1 | May 10, 2000 03:03 |