CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Reducing drag on a bluff body using dimples

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 19, 2017, 13:30
Default Reducing drag on a bluff body using dimples
  #1
BBA
New Member
 
Grover
Join Date: Apr 2017
Location: New Delhi
Posts: 2
Rep Power: 0
BBA is on a distinguished road
I am performing simulations on an Ahmed body (bluff body) having significant amount of pressure drag and trying to control it using dimples on its surface(Top as well as slant face).

I understand that the problem is one with laminar flow over the surface which transitions to turbulent conditions under the effect of dimples as irregularities and theoretically should result in a reduction of drag value.

But the problem is that we are not able to achieve any drag reduction at all. Drag is always a bit higher than the nominal value, always a bit HIGHER( We have exhausted all the k-e wall treatment options scalable as well as enhanced wall treatment, the low Re number k-w approach with yplus=1 and the 4 eqn transition SST model for our case and still unable to get a reduced drag value).

I would like to know how to tackle the above problem in order to get tangible results.

Just to give you an idea, the dimple dimensions are like 30mm dia with 6mm depth incorporated over a body having a length of 1044mm.

Mesh is about 5.3 million.
Orthogonality is less due to high aspect ratio cells near the wall.
Turbulence intensity at inlet is 1%
Turbulence intensity at Outlet is 5%
Turbulent viscosity ratio is kept at its default value 10 for both inlet and outlet.

Which turbulence modelling to choose (RANS) and with what settings ?
BBA is offline   Reply With Quote

Old   January 27, 2018, 14:37
Default
  #2
Member
 
Join Date: Apr 2017
Posts: 32
Rep Power: 8
Qkarl is on a distinguished road
Hi, can i know do you solve this problem already? I am having this trouble too.
Qkarl is offline   Reply With Quote

Old   January 29, 2018, 09:09
Default
  #3
BBA
New Member
 
Grover
Join Date: Apr 2017
Location: New Delhi
Posts: 2
Rep Power: 0
BBA is on a distinguished road
Hi there !

As far as I know, small scale turbulence effect in dimples which we are trying to capture does not lie in the scope of RANS models.
I would rather go for DNS.

Regards
BBA is offline   Reply With Quote

Old   January 29, 2018, 11:09
Default
  #4
Member
 
Join Date: Apr 2017
Posts: 32
Rep Power: 8
Qkarl is on a distinguished road
Hi,

But mine is just a student project to study how the dimples will affect the drag of the golf ball. I could not run DNS with the limited resources. Is there any way to solve it?
Qkarl is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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
[ANSYS Meshing] Reducing mesh non-orthognality for bluff body with sharp edges Bashar ANSYS Meshing & Geometry 2 November 18, 2016 03:28
Reducing Ship Drag with Air Bubbles tmeysam92 FLUENT 0 September 15, 2016 02:02
Reynolds Stress Models for bluff body flows siw CFX 1 March 4, 2016 06:58
Ahmed body -Drag coefficient not converging!! sam92 FLUENT 9 January 14, 2014 15:00
convergence problem / bluff body / k omega LM4112 OpenFOAM Pre-Processing 3 June 16, 2013 07:28


All times are GMT -4. The time now is 04:45.