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

Quick question - Can I use rotating wall for a spinning rugby ball (with seams)??

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 1, 2017, 07:54
Default Quick question - Can I use rotating wall for a spinning rugby ball (with seams)??
  #1
New Member
 
Jake McPherson
Join Date: Jan 2017
Posts: 6
Rep Power: 6
Rake32 is on a distinguished road
Hi,

I'm simulating a rotating Rugby ball to look at spin effects. I'll be spinning it along it's longitudinal axis. I have seen that the rotating wall can only be used for symmetrical geometries, does this rule the ball out?

I've added a picture so you can see the seams.
Attached Images
File Type: jpg ball with seams.jpg (99.3 KB, 28 views)
Rake32 is offline   Reply With Quote

Old   March 1, 2017, 14:22
Default
  #2
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,569
Rep Power: 53
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
By itself you can do a spinning ball (i.e. there's no wind). The problem is when you want it to spin and translate. It's doable in some cases depending on your boundary conditions. The question is whether or not the seams actually move, if the mesh needs to move or not.
LuckyTran is offline   Reply With Quote

Old   March 1, 2017, 14:29
Default
  #3
New Member
 
Jake McPherson
Join Date: Jan 2017
Posts: 6
Rep Power: 6
Rake32 is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
By itself you can do a spinning ball (i.e. there's no wind). The problem is when you want it to spin and translate.
I'm not sure what you mean. I planned on making a fluid domain with a velocity inlet, then have the ball spin in there. The wall motion, rotating boundary condition works for spheres etc but will it work with a seemed ball?

I've put another pic in showing where it'll be rotating. If I can't use the moving wall I'm really stuck on how to model it
Attached Images
File Type: jpg showing axis.jpg (98.6 KB, 13 views)
Rake32 is offline   Reply With Quote

Old   March 1, 2017, 14:53
Default
  #4
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,569
Rep Power: 53
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
The problem is that your mesh is fixed in space, unless you do a dynamic mesh (which is the general solution).

If the velocity is coming along the axis of the ball then it can work. If you go into a rotating reference frame, then it's possible to solve it using a static mesh as long as you can specify the correct boundary conditions. If there's an angle of attack, then it doesn't work.

This is also a hint. Nothing happens if the ball is spinning on its longitudinal axis and moving in the same direction. If there's an angle of attack, you get the magnus effect because a fixed point on the ball sees a time-varying velocity.
LuckyTran is offline   Reply With Quote

Old   March 1, 2017, 15:17
Default
  #5
New Member
 
Jake McPherson
Join Date: Jan 2017
Posts: 6
Rep Power: 6
Rake32 is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
The problem is that your mesh is fixed in space, unless you do a dynamic mesh (which is the general solution).

If the velocity is coming along the axis of the ball then it can work. If you go into a rotating reference frame, then it's possible to solve it using a static mesh as long as you can specify the correct boundary conditions. If there's an angle of attack, then it doesn't work.

This is also a hint. Nothing happens if the ball is spinning on its longitudinal axis and moving in the same direction. If there's an angle of attack, you get the magnus effect because a fixed point on the ball sees a time-varying velocity.
I'm trying to avoid the dynamic mesh at the minute. The model I showed was just going to be my comparison to current work, to show I'm in the right range for drag.

I was going to create 6 different models, each with a different angle of attack (0-90 degrees), then set the spin axis accordingly.

So i.e at 15 deg, rotational origin =(0,0,0)

Then use trig to find xy coordinates the would relate to 15 deg.

The entire scope of my project really is looking at magnus effects on the ball.

P.s thanks for the replies
Rake32 is offline   Reply With Quote

Old   March 1, 2017, 15:24
Default
  #6
New Member
 
Jake McPherson
Join Date: Jan 2017
Posts: 6
Rep Power: 6
Rake32 is on a distinguished road
I've just figured it out for 15 as an example.

If I assume the vector has a length of 1 and an angle of 15 deg, y=1sin(15) and x=1cos(15)

This gives rotation axis direction (0.9659,0.25882,0). Would that work?
Rake32 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
Divergence in AMG solver! marina FLUENT 20 August 1, 2020 12:30
heat transfer through rotating metal wall groonm CFX 0 September 12, 2016 11:20
Car external aerodynamic with wheel spinning issue hokhay FloEFD, FloWorks & FloTHERM 2 August 18, 2016 05:23
Question about bcdefw.f for wall temperature bc. Jimmy Siemens 10 March 18, 2008 16:28
Quick Question - Wall Function D.Tandra Main CFD Forum 2 March 16, 2004 05:29


All times are GMT -4. The time now is 18:25.