CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

simpleFoam - validating Drag Coefficient of thin plate

Register Blogs Community New Posts Updated Threads Search

Like Tree1Likes
  • 1 Post By piu58

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 30, 2018, 12:20
Default simpleFoam - validating Drag Coefficient of thin plate
  #1
Member
 
Eduardo Firvida
Join Date: Dec 2010
Posts: 53
Rep Power: 16
efirvida is on a distinguished road
Hi, in the follow image I show my case setup, the main idea is to get the Cd of well documented shapes, starting by the thin plate.



To do this i´m using simpleFoam, I upload my case setup too. The simulation runs without problem but I can´t never reach the Cd=1.9 for Re > 10e4 as the reference value. it always give me Cd > 3. So i´m not sure about what i´m doing wrong.
Attached Images
File Type: jpg Untitled.jpg (68.4 KB, 117 views)
Attached Files
File Type: zip plate.zip (5.8 KB, 13 views)
efirvida is offline   Reply With Quote

Old   March 30, 2018, 13:22
Default
  #2
Senior Member
 
piu58's Avatar
 
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15
piu58 is on a distinguished road
You cannot expect a correct result if you run this high Re numbers with a laminar solver. Even with advanced turbulence modesl it is hard to get an deviation as low as 20%. It is nearly impossible to confirm the drag crisis at even higer Re numbers.
efirvida likes this.
__________________
Uwe Pilz
--
Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)
piu58 is offline   Reply With Quote

Old   April 23, 2018, 14:49
Default
  #3
Member
 
Eduardo Firvida
Join Date: Dec 2010
Posts: 53
Rep Power: 16
efirvida is on a distinguished road
Quote:
Originally Posted by piu58 View Post
You cannot expect a correct result if you run this high Re numbers with a laminar solver. Even with advanced turbulence modesl it is hard to get an deviation as low as 20%. It is nearly impossible to confirm the drag crisis at even higher Re numbers.
Hi. thanks for your reply and, sorry about my late response. I update my case using different turbulence models (k-e,k-w,k-w-sst) and getting good results with that.

Now I have a problem, I have same case, but I change the plate, with a square cylinder, of 1m*1m of size. When I use the case configuration, I get Cd from 1.6 to 1.8 and the reference value must be from 2.1 to 2.3 so the prediction its not good. And I dont understand why, If my case was correct for the previous geometry, rigth now I only change the width of the plate to be equal to the heigth.
But now think as i know if the relation of heigth/width increase the Cd have to decrees, its not a rule but that what I know and what my simulation say. but the books says other thing.

Well... I made another test changing the solver to pimpleFoam to made the case transient, and with this I get the 2.2 average value of the Cd. But if I use pimpleFoam in the thin plate, I get a Cd, over 4. So I dont have a clue of how to set a basic case to this kind of geometries to get the referenced values of the Cd.
efirvida is offline   Reply With Quote

Old   August 7, 2019, 16:55
Default Issue trying to solve the same configuration
  #4
New Member
 
Andrei Cojocea
Join Date: Jul 2019
Posts: 8
Rep Power: 7
avc18 is on a distinguished road
Hi,



I saw your post and I was wondering if you still have the files and you can upload them here. I am trying to solve a 2D incompressible flow past a square cylinder and I cannot get the right solution, after the vorteces start shedding. Maybe I can get some insight with the problem.
avc18 is offline   Reply With Quote

Reply


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Calculation of lift and drag coefficients on airfoil CoolHersheys OpenFOAM Post-Processing 5 September 27, 2021 07:04
Drag coefficient CEL expression sarrazs CFX 2 September 28, 2017 11:21
Problem: calculating drag coefficient RFH_student FLUENT 3 February 8, 2011 09:36
Plot drag coefficient against Y(distance) edwin FLUENT 0 February 4, 2008 10:41
Drag coefficient Oscillating plate Anant Main CFD Forum 0 September 6, 2001 11:31


All times are GMT -4. The time now is 01:06.