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

Stream function

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 12, 2001, 07:06
Default Stream function
  #1
Cauvery G
Guest
 
Posts: n/a
Hi Everybody,

Can someone tell me how to find the streamfunction values from the discrete values of velocity components

thanks
  Reply With Quote

Old   January 12, 2001, 10:58
Default Re: Stream function
  #2
ThoLi
Guest
 
Posts: n/a
Hi G,

because rot ( streamfunction ) = velocity, I started this way:
find the streamfunkton, which minimises ( integral ( rot ( streamfunction ) - velocity ) ^2 )
the usual(?) procedure gives the euler-lagrange-pde:
solve rot ( rot ( streamfunktion ) ) = rot ( velocity )
Note:
rot ( velocity ) is also known as vorticity
rot ( rot (x) ) is similiar to the Laplacian, but be careful when working with other than cartesian coordinates (eg cylinder coordinates)
if you are using finite elements, you can shift one rot-operator to the test function
the rot operator (or rotation or curl) should be found in each book about mathematics for engineers
  Reply With Quote

Old   January 12, 2001, 13:39
Default Re: Stream function
  #3
kalyan
Guest
 
Posts: n/a
Laplacian (stream function) = - vorticity for an incompressible, constant density flow.

Vorticity can be easily computed from the velocity field. Stream function is obtained upon solving the above Poisson equation.
  Reply With Quote

Old   January 13, 2001, 21:10
Default Re: Stream function
  #4
John C. Chien
Guest
 
Posts: n/a
(1). In 2-D flow, it is possible to define the stream function from the velocity field. For example, d(psi)/dy=rho*u, d(psi)/dx=-rho*v, will satisfy the continuity equation automatically. (2). You can then find the stream function, psi distribution from the integration of the definition, given above. (3). To get more accurate stream function distribution, you may have to first curve fit the velocity field and use it in the integration. (4). The other approach is to solve the stream function equation, with the vorticity as the source term (which can be derived from the velocity field through the vorticity definition). This requires programming and will be more involved than the simple integration method.
  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
Compile problem ivanyao OpenFOAM Running, Solving & CFD 1 October 12, 2012 10:31
ParaView for OF-1.6-ext Chrisi1984 OpenFOAM Installation 0 December 31, 2010 07:42
latest OpenFOAM-1.6.x from git failed to compile phsieh2005 OpenFOAM Bugs 25 February 9, 2010 05:37
Error with Wmake skabilan OpenFOAM Installation 3 July 28, 2009 01:35
[blockMesh] Axisymmetrical mesh Rasmus Gjesing (Gjesing) OpenFOAM Meshing & Mesh Conversion 10 April 2, 2007 15:00


All times are GMT -4. The time now is 05:35.