CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

How to map a domain changing in length with time

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 26, 2011, 16:37
Exclamation How to map a domain changing in length with time
  #1
New Member
 
amgotsikmeme
Join Date: Nov 2011
Posts: 6
Rep Power: 5
bababanamzdaalma is on a distinguished road
Hi all;

I have a problem with my CFD project and need help. The problem is I have a 1-D domain which is given by

L=L_0+delta(sin(wt))

and I try to map it into a domain that has one fixed length by using fixed number of grid points at all times. I need to find a mapping function. Thanks for your concern

Last edited by bababanamzdaalma; November 26, 2011 at 17:14.
bababanamzdaalma is offline   Reply With Quote

Old   November 26, 2011, 20:13
Default
  #2
New Member
 
Carlos
Join Date: Nov 2011
Location: The Netherlands
Posts: 17
Rep Power: 5
Caluca is on a distinguished road
If I understand this correctly, you need a 1D domain of fixed length where only the nodes change position in time? So in your simulation you would get that some cell faces are elongating while others or shortening, yet the sum of lengths is constant in time.You could start with a simpler example, by having an uniform motion of nodes:

for i = 0:N
loc_0(i) = L * i/N + L_0
end

for t = 0:T_end
for i = 1:N-1
loc(i,t) = loc_0(i) + L/N*sin(w*t)
end
end

This would get your nodes to move uniformly to the right and back. If this is not want you meant, please post some additional information!
__________________
"Do not worry about your difficulties in Mathematics. I can assure you mine are still greater." - Albert Einstein
Caluca is offline   Reply With Quote

Old   November 26, 2011, 20:32
Default
  #3
New Member
 
amgotsikmeme
Join Date: Nov 2011
Posts: 6
Rep Power: 5
bababanamzdaalma is on a distinguished road
the domain can be considered as 1-D engine piston. I have to figure out an algebraic function that maps the current domain in a constant length one by using constant number of grid points.
bababanamzdaalma is offline   Reply With Quote

Old   November 27, 2011, 06:30
Default
  #4
Senior Member
 
cfdnewbie
Join Date: Mar 2010
Posts: 551
Rep Power: 11
cfdnewbie is on a distinguished road
maybe i misunderstand you, but that should be easy:
you know your domain size (physically) at each time t, so just map that your unit interval as a function of t ....

your domain length is some fct of t: L(t), with a=X(x=0) and b=X(x=L(t))

so your projection is just:

[0,1]-> [a,b(t)] with equidistant nodes....
cfdnewbie is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Full pipe 3D using icoFoam cyberbrain OpenFOAM 4 March 16, 2011 10:20
Domain Imbalance HMR CFX 3 March 6, 2011 21:10
Convergence moving mesh lr103476 OpenFOAM Running, Solving & CFD 30 November 19, 2007 15:09
DPM: Particle Tracking Madhukar FLUENT 1 July 24, 2007 03:51
time averaged heat transfer in oscillating flow Matthieu Ubas Main CFD Forum 2 November 5, 1999 15:20


All times are GMT -4. The time now is 16:31.