CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

help on aximmetric flow needed.

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

LinkBack Thread Tools Display Modes
Old   April 5, 2001, 11:07
Default help on aximmetric flow needed.
Posts: n/a
i am trying to find the flow field around a two stepped cone (axisymmetric case) using McCormak's predictor corrector scheme for shock capturing .Since it is axisymmetric,the problem has become more of a 2d problem and i am solving the eqn:

dE/dx+dF/dy+H=0 where E,F and H are the conventional flux vectors for the strong conservative form.but the problem is that in H i am having a "1/y" factor that becomes undefined at y=0. i have used some limits and have changed the governing equations (continuity,x-mom,y-mom etc ) for y=0 case. here there is another problem. while just at the beginning of the cone,where y=0, i am using this modified eqn in the predictor step . but on the corrector step, since i have already moved a bit up on the cone and y is no longer=0,i am using the above form (ie without applying any limits like y-->0)for the corrector step.will this cause serious errors in the code? also where can i get some material relating to this work.? while pressure on the surface of the first cone should remain constant since it forms a ray, in my case it is steadily decreasing. why is it so ?
  Reply With Quote

Old   April 5, 2001, 18:39
Default Re: help on aximmetric flow needed.
Posts: n/a
From my limited knowledge:

(1) Do a geometric conservation check. Find the solution in a domain containing no solid body. Assign Free stream flow.

(2) At the centerline, only for boundary conditions use L'hopital rule. If your scheme is cell vertex. If cell center you should have no problem representing the boundary conditions.

(3) Check your source term handling method once again.

Hope this helps.

  Reply With Quote

Old   April 5, 2001, 19:06
Default Re: help on aximmetric flow needed.
John C. Chien
Posts: n/a
(1). For axisymmetric 2-D problem, there is a simple method to deal with the centerline singularity. (2). All you need to do is to attach a very thin cylinder to the tip of the cone. You can treat the boundary condition there as symmetric condition. (3). I had used the method many years ago for flow over a cone, and there was no problem as far as I can remember. (4). The method was to solve the Navier-Stokes equations, and it requires artificial viscosity term in the form of higher order pressure derivatives. The method was very popular in 70' and 80's. Look at the publications from NASA/Ames, Air Force research labs and AIAA journals in that period of time.
  Reply With Quote

Old   April 6, 2001, 07:15
Default Re: help on aximmetric flow needed.
Posts: n/a
thank you for your help.i have two more queries.

1)can i use the form of Abett's method we use for boundary correction in the 2D case for correcting boundary condition in the 3d case as well (ie for my axisymmetric case as well)?

2)in the axisymmetric case, is it justified to do boundary corrections both after the predictor and corrector steps instead of applying the boundary condition only once after the predictor-corrector pair.

  Reply With Quote


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
Guessing the static pressure needed to produce flow rate jpo FLUENT 0 June 22, 2009 12:53
radiator flow -help needed. vishwa FLUENT 6 May 15, 2006 01:37
Can 'shock waves' occur in viscous fluid flows? diaw Main CFD Forum 104 February 16, 2006 06:44
Help needed to model gas-solids flow Juliana P FLUENT 3 September 21, 2005 09:42
2D scheme for two-phase flow is needed Oleg Main CFD Forum 3 June 19, 2002 10:31

All times are GMT -4. The time now is 03:48.