CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Post-Processing

Negative drag forces of fanwing airfoil

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

LinkBack Thread Tools Search this Thread Display Modes
Old   March 26, 2017, 07:16
Default Negative drag forces of fanwing airfoil
New Member
Do Quoc Vu
Join Date: Jun 2016
Posts: 2
Rep Power: 0
vkid185 is on a distinguished road
Hi foamers,

I'm trying to extract drag and lift force on a fanwing airfoil. Everythings is ok except when i come to the drag and realize a negative value of the drag.
My cases is as below:
freestream velocity = 10m/s oriented towards X direction
Angular velocity (clockwise) of the fan = 250rad/s
=> negative drag
freestream velocity = 60m/s
Angular velocity of the fan = 250rad/s
=> positive drag

I used functionObject forces to extract the force.
Could anyone explain to me how the drag can be negative in case number 1? Is it because the thrust is bigger than the drag?
Please see the picture of case1 below for better understand my situation

Thanks in advance for any of your help.
vkid185 is offline   Reply With Quote


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
Airfoil lift and drag using k-kl-omega turbulence model hylleman OpenFOAM Running, Solving & CFD 6 June 17, 2016 15:10
Writing drag forces of cylinders in fluent 14.5 vishnum12 FLUENT 1 December 23, 2015 06:19
Negative Pressure Drag Coefficient of main airfoil in Multi-Element rear wing Masoud.A1 FLUENT 4 April 8, 2015 23:17
Negative Drag coefficient naca 0012 airfoil using fluent 15 lucasvfc FLUENT 8 March 13, 2015 14:43
Drag of Plunging Airfoil mahzironrazak FLUENT 0 October 19, 2009 18:41

All times are GMT -4. The time now is 11:15.