CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

How to create a time delay for inlets?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 5, 2015, 12:19
Default How to create a time delay for inlets?
  #1
New Member
 
Danny
Join Date: Jul 2015
Posts: 3
Rep Power: 8
danny21 is on a distinguished road
Hello,
I am having some trouble with a simulation that I am running. I am running a multi element wing for a Formula One style car in a fluid domain with the obvious Inlet, outlet, symmetry planes, and ground plane. However, I also have a small cut in the bottom of the main plane that I want to be an inlet. The thought behind the design is that if you can get air moving faster out of the inlet, you can lower the pressure which creates more downforce.
The problem that I am running into is that I am getting reversed flow even though the air is flowing in the same direction as the fluid domain inlet. I looked towards the streamlines to find some answers. The only idea I saw was that it started flowing before the fluid domain inlet reached it.

Any ideas?

Thanks,
Danny
danny21 is offline   Reply With Quote

Old   July 6, 2015, 02:09
Default
  #2
Member
 
kris
Join Date: May 2014
Posts: 73
Rep Power: 10
kguntur is on a distinguished road
Hi Danny,

Could you be a little more specific? Where is this 2nd inlet? Are you running transient or steady state? How long are you getting the reversed flow?

From your title I assume you want to the inlet velocity to be 0 initially and then at a perticular time or iteration you want to increase the velocity. You can use field function to achive this.

Hope this helps.

-Krishna.
kguntur is offline   Reply With Quote

Old   July 9, 2015, 21:27
Default
  #3
New Member
 
Danny
Join Date: Jul 2015
Posts: 3
Rep Power: 8
danny21 is on a distinguished road
Hi Kirshna,
Thank you for the reply.
I am running a steady state simulation and I am getting flow reversal and the conjugate gradient is unable to converge. The second inlet is on the under side of the wing. I made a cut in the bottom so that the inlet would point tangent to the wing.

I would like the air from the 2nd inlet (under the wing) to be delayed until the air from the front of the fluid domain reaches it so that it simulates the interaction between the two. For example the car driving along at a steady state and the air coming out from under the wing. I've uploaded some pictures that I hope will help.

I have not dealt with field functions and I was wondering if you could either explain how you would go about doing that or point me towards a tutorial that would explain it? I've found a lot that explain how to refine surfaces.

Best Regards,
Danny
Attached Images
File Type: jpg Rear View.jpg (12.3 KB, 11 views)
File Type: jpg Close Up View.jpg (8.6 KB, 10 views)
File Type: jpg Angled View.jpg (18.3 KB, 10 views)
File Type: jpg Simulation.jpg (17.8 KB, 11 views)
danny21 is offline   Reply With Quote

Old   July 14, 2015, 19:02
Default
  #4
New Member
 
Danny
Join Date: Jul 2015
Posts: 3
Rep Power: 8
danny21 is on a distinguished road
Bump for attention
danny21 is offline   Reply With Quote

Old   July 16, 2015, 08:29
Default
  #5
Senior Member
 
Gajendra Gulgulia
Join Date: Apr 2013
Location: Munich
Posts: 144
Rep Power: 11
ggulgulia is on a distinguished road
Hi Danny

I am curious to know the relative locations of the two inlets and the outlet. Is the 2nd inlet opposite to the first one, at the tail of the wing? What exactly is the boundary condition at both the inlets?

Also you should try converting the 2nd inlet as outlet and monitor how much mass flows out of the boundary, the pressure there. The values that need input when using the same as inlet boundary should be more than what you get when you run trial with outlet boundary.

Where exactly are you getting Reversed Flow? (CCM+ output window will give the name of the boundary that has reversed flow)

Thirdly you will have to resort to transient simulation if you want to introduce a delay b/w the inlets of the two boundaries

Hope this was helpful
ggulgulia is offline   Reply With Quote

Reply

Tags
reverse flow, reversed faces, star ccm, wings

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
Transient simulation not converging skabilan OpenFOAM Running, Solving & CFD 14 December 16, 2019 23:12
mixerVesselAMI2D's mass is not balancing sharonyue OpenFOAM Running, Solving & CFD 6 June 10, 2013 09:34
same geometry,structured and unstructured mesh,different behaviour. sharonyue OpenFOAM Running, Solving & CFD 13 January 2, 2013 22:40
Actuator disk model audrich FLUENT 0 September 21, 2009 07:06
Where's the singularity/mesh flaw? audrich FLUENT 3 August 4, 2009 01:07


All times are GMT -4. The time now is 06:02.