|
[Sponsors] |
direction vectors for lift and drag in fluent |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
September 10, 2012, 05:35 |
direction vectors for lift and drag in fluent
|
#1 |
Member
nauman hashmi
Join Date: Jun 2012
Posts: 54
Rep Power: 14 |
hi i have one query regarding direction vectors of drag and lift forces in fluent. in many tutorial the direction vectors at any angle of attack lets say 4 degree is 0.99576 for x axis and 0.06976 for y axis. and for lift the direction vectors are -0.06976 and 0.99576. however the under mention link says that drag direction vector should be negative also.
http://www.engineeringarchives.com/les_fm_draglift.html what is the correct way to calculate lift and drag in fluent need guidance thanks in advance. |
|
September 10, 2012, 09:54 |
|
#2 |
Senior Member
Stuart Buckingham
Join Date: May 2010
Location: United Kingdom
Posts: 267
Rep Power: 26 |
It doesn't matter. You can use the following command to get the force in the positive x-direction
Code:
/report/forces/wall-forces yes 1 0 0 no Code:
/report/forces/wall-forces yes -1 0 0 no |
|
September 10, 2012, 10:02 |
RE
|
#3 |
Member
nauman hashmi
Join Date: Jun 2012
Posts: 54
Rep Power: 14 |
then what is the correct drag force vector direction in fluent. my geometry is in yz plane while flow direction is in y direction and it originates from -162 meters. for a 4 degree aoa what should be the direction vectors i should put in.
regards |
|
September 10, 2012, 10:14 |
|
#4 |
Senior Member
Stuart Buckingham
Join Date: May 2010
Location: United Kingdom
Posts: 267
Rep Power: 26 |
Whatever is parallel to your freestream
|
|
September 10, 2012, 10:17 |
Re
|
#5 |
Member
nauman hashmi
Join Date: Jun 2012
Posts: 54
Rep Power: 14 |
as far as my humble understanding my free stream is flowing from -ve y direction to positive y direction so i should be taking a -ve direction vector of drag. correct me sir if i am wrong.
regards |
|
September 10, 2012, 10:28 |
|
#6 |
Senior Member
Stuart Buckingham
Join Date: May 2010
Location: United Kingdom
Posts: 267
Rep Power: 26 |
You can just take the drag vector in the positive Y direction. Try:
/report/forces/wall-forces yes 0 1 0 no |
|
September 10, 2012, 10:34 |
re
|
#7 |
Member
nauman hashmi
Join Date: Jun 2012
Posts: 54
Rep Power: 14 |
sir my geometry is at an angle of attack not at zero degree. it would be better to use the cosine and sine of aoa as direction of force vectors while owing to -ve direction of flow i can use the -ve sign in force vector. with positive value i am getting higher values then expected. and they stayed the same at different aoa which is not correct.
regards |
|
September 23, 2020, 14:47 |
|
#8 |
New Member
Join Date: Jul 2020
Posts: 1
Rep Power: 0 |
Drag is defined the component of force parallel to the free stream velocity and lift perpendicular to free stream velocity.
Fluent documentation states, "The total force component along the specified force vector () on a wall zone is computed by summing the dot product of the pressure and viscous forces ( and ) on each face with the specified force vector." is free stream velocity. It makes an angle of with x-axis. Direction of drag vector is going to be same as that of free stream velocity Direction of lift vector is perpendicular to direction of free stream velocity Let the angle of force vector is with x-axis, then, Then, ,is the drag. |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Calculating Coefficient of Drag in ANSYS Fluent | osamaghani | FLUENT | 16 | April 21, 2019 10:29 |
drag coefficient in ansys fluent 12.0 | krishna | FLUENT | 19 | April 12, 2018 00:49 |
Force vectors for drag during sweeping motion | aamer | FLUENT | 0 | April 18, 2011 08:17 |
Fluent no longer know their Drag vs. Re curves ? | R. Koeman | FLUENT | 1 | May 3, 2010 12:43 |
Fluent validation test for calculate the drag of a car | ostervi | FLUENT | 0 | June 12, 2009 12:59 |