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

DEFINE_CG_MOTION for flapping wing UDF

Register Blogs Community New Posts Updated Threads Search

Like Tree1Likes

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 15, 2016, 09:53
Default
  #21
New Member
 
Giorgio
Join Date: Jun 2016
Posts: 12
Rep Power: 10
Faggio11 is on a distinguished road
Quote:
Originally Posted by xyzch001 View Post
The problem is that when you derive theta to find the angular velocity you lose the constant, so when Fluent integrates the velocity (DEFINE_CG_MOTION requires the angular velocity, not the angle(t)) it loses the constant "-15", giving the symmetrical function 25*sin(2*pi*frequency*t+arcsin(3/5)). But unfortunately I want an asymmetrical function ranging from +10deg to -40deg.
What is the integration scheme used by Fluent to get the angle theta knowing the angular velocity???

I am experiencing some problems because I imply a constant angular velocity in steps but the angle changes after each cycle because of rounding off errors!!!
Faggio11 is offline   Reply With Quote

Old   February 7, 2022, 08:47
Default UDF for asymmetric motion
  #22
New Member
 
radzee
Join Date: Jul 2020
Posts: 8
Rep Power: 6
rdhkpatel is on a distinguished road
Quote:
Originally Posted by xyzch001 View Post
Hi pdp.aero!
Finally I found the solution: this is the function that gives me the desired flapping angles: theta[t] = 0.8409*sin(w*t - 0.2563) + 0.6643*cos(w*t + 0.7741) - 0.000001868*Sin(0.7629*w*t + 0.1884) +0.3773*cos(-0.000002463*w*t + 2.338)
It has no constants so that, when I derive it to find the omega[t] and then Fluent integrates it,Fluent gets back the original theta[t]. I used Matlab "Curve fitting toolbox" to find this function by interpolation of many points.
Anyway thank you for your help!
Hye, please help me!!

I am learning how to write a UDF for a flapping door, angle is from +50 to -10 degrees, please give me some hints.
rdhkpatel is offline   Reply With Quote

Reply

Tags
ansys fluent, define_cg_motion, flapping wing, udf


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
DEFINE_CG_MOTION for flapping wing UDF xyzch001 Fluent UDF and Scheme Programming 0 December 14, 2011 09:39
flapping wing udf a serious doubt doctsh Fluent UDF and Scheme Programming 0 February 17, 2011 13:05
UDF for sweeping wing aamer Main CFD Forum 0 December 16, 2010 08:35
ask help about flapping wing UDF aeropeng Fluent UDF and Scheme Programming 0 December 24, 2009 23:09
udf for 3d wing giorgio FLUENT 0 October 8, 2004 10:13


All times are GMT -4. The time now is 06:57.