Search found 15 matches

by meb15aa
Sun Apr 21, 2019 9:30 pm
Forum: code_saturne usage
Topic: Coarser meshes produces better results?
Replies: 3
Views: 615

Re: Coarser meshes produces better results?

  #6

asda3D

New Member

 

anonymous

Join Date: Apr 2018

Posts: 20

Rep Power: 3

Just an add on the aspect ratio is more than double for the finer meshes compared to the coarser meshes. This may be the reason for the coarser meshes possessing greater accuracy.
by meb15aa
Sun Apr 21, 2019 7:56 pm
Forum: code_saturne usage
Topic: Coarser meshes produces better results?
Replies: 3
Views: 615

Re: Coarser meshes produces better results?

Thank you for the response. I have conducted a mesh independent study where I started off with 42,000 elements and ended up with 19,000 elements, losing around 4% accuracy in my sensitivity study. To put things in perspective the pressure gradient at the end of the calculation for these two meshes w...
by meb15aa
Sun Apr 21, 2019 12:06 pm
Forum: code_saturne usage
Topic: Coarser meshes produces better results?
Replies: 3
Views: 615

Coarser meshes produces better results?

Hi everyone, I am comparing several meshes which utilise coupling CFD and experimental techniques against a fully resolved fine mesh model (19,000 elements using k epsilon model) The coarse meshes are listed below CMesh1-630 elements CMesh2- 960 elements CMesh3- 2400 elements CMesh4- 3600 elements W...
by meb15aa
Thu Apr 04, 2019 1:09 pm
Forum: code_saturne usage
Topic: Y plus for a fuel rod bundle.
Replies: 1
Views: 443

Y plus for a fuel rod bundle.

Hi again everyone, I would just like some clarification on something. I am working on a fuel bundle, and I am unsure if I calculated my y plus value correctly. I used an online Y plus calculator that my peers advised me to use. http://www.pointwise.com/yplus/ https://www.nuclear-power.net/nuclear-en...
by meb15aa
Thu Apr 04, 2019 10:23 am
Forum: code_saturne usage
Topic: Divergence error.
Replies: 8
Views: 1329

Re: Divergence error.

Thank you. This is a nuclear related project and the guideline I have been provided states that I cannot alter the precision (10e-08) or reduce the mesh near the wall for for initial mesh. The meshes I create after for my sensitivity study can be altered and utilised if they match well with the init...
by meb15aa
Mon Apr 01, 2019 11:16 am
Forum: code_saturne usage
Topic: Divergence error.
Replies: 8
Views: 1329

Re: Divergence error.

Hi there again Antech,
I have taken on board what you have said, but still require at least 50,000 iterations for convergence. My model is simulating a segment inside a nuclear reactor core, maybe the extreme conditions it is subjected to mean a a greater number of iterations than predicted.
by meb15aa
Sun Mar 31, 2019 2:47 pm
Forum: code_saturne usage
Topic: faster convergence
Replies: 5
Views: 820

Re: faster convergence

Just a quick update, I have had to decrease the time step to 1-e05 to avoid divergence for my finer mesh models due to a very low y plus (10e-06) at the boundary. As a result i believe several hundred thousands of iterations will be necessary for convergence now. Any suggestions.
by meb15aa
Sun Mar 31, 2019 1:01 pm
Forum: code_saturne usage
Topic: faster convergence
Replies: 5
Views: 820

faster convergence

Hi everyone i have two questions. Firstly my current simulation comprises of 3200 elements but requires convergence of both energy and momentum take 50,000 iterations to converge. Is there any way I can reduce this as I am carrying out a mesh independent study and require analysis of finer mesh with...
by meb15aa
Fri Mar 29, 2019 6:32 pm
Forum: code_saturne usage
Topic: Divergence error.
Replies: 8
Views: 1329

Re: Divergence error.

Thank you Antech :P the solution is showing signs of convergence but I think it will require a lot of iterations. Currently I have run 80,000 iterations with a time step 0.001 and my temperature is very slowly showing signs of leveling off (image attached). I will try a few other techniques that you...
by meb15aa
Wed Mar 27, 2019 4:43 pm
Forum: code_saturne usage
Topic: Divergence error.
Replies: 8
Views: 1329

Divergence error.

Hi there, I am currently experiencing divergence in my temperatures whilst running a steady state simulation. My velocity however seems to converge. I decided to reduce the time step which brings my temperature closer to convergence but my velocity has become negative and possesses a magnitude of or...