CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Acceleration of a point using a UDF

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

LinkBack Thread Tools Display Modes
Old   October 22, 2009, 21:59
Default Acceleration of a point using a UDF
New Member
Join Date: Oct 2009
Posts: 1
Rep Power: 0
fackre2 is on a distinguished road
I am trying to get the acceleration of a point using a UDF. I have called in the velocity of the desired cell using c_v(c,t) and use the simple relation (V2-V1)/dt. When I compare the value of the velocity obtained using the udf to the value I obtained using a point surface and surface monitors, there is a very large discrepency. I have tried setting the surface monitor to both area weighted averages and vertex weighted averages (both give very similar results). My results from the udf are on the order of 1e-11 and the results from the surface monitors are on the order of 1e-2. I have also tried averaging the values over 8 different cells. I also tried creating larger cells to see if it made a difference. It did. By increasing the size of my cells my velocity obtained by C_V(c,t) were also larger. The problem is that they will continue to change as I increase my cell size. What is the relationship between the C_V(c,t) and the cell size? The other problem is that I obtained both positive and negative values. Is there something that relates the velocity obtained with the direction of the face? Are there any other suggestions as to how to determine the acceleration of a point using a udf (I need the acceleration to perform other tasks in my udf)?

Last edited by fackre2; October 23, 2009 at 10:27.
fackre2 is offline   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
cell_t c from point coorfdinates UDF andrea.dicarlo Fluent UDF and Scheme Programming 9 July 4, 2014 12:05
Gmsh and samplesurface touf Open Source Meshers: Gmsh, Netgen, CGNS, ... 2 December 10, 2007 03:27
udf to set vel. = 0 at a grid point or a cell Ralf Schmidt FLUENT 0 September 22, 2006 09:45
UDF to define source term at every grid point Ralf Schmidt FLUENT 0 September 21, 2006 11:32
CFX4.3 -build analysis form Chie Min CFX 5 July 12, 2001 23:19

All times are GMT -4. The time now is 08:54.