|
[Sponsors] |
![]() |
![]() |
#1 |
Guest
Posts: n/a
|
When i plot force magnitude on a wall surface, i get a range of force value from 0 to some positive number and there is no negative number plotted. Is it not possible to plot negative value of forces or is it because Star-cd can't extract negative value of aerodynamic force? I think a force pushing on the surface should be positive value and a force lifting the surface should be negative value and negative value of force should exist to represent effect of suction due to low pressure in high velocity regions.
|
|
![]() |
![]() |
![]() |
#2 |
Guest
Posts: n/a
|
Negative values of force are possible. You may have extracted the wrong forces, there are quite a number of options and it can be confusing.
|
|
![]() |
![]() |
![]() |
#3 |
Guest
Posts: n/a
|
Isn't force MAGNITUDE = sqrt(Fx^2+Fy^2+Fz^2). If so, then you should look at the individual components.
|
|
![]() |
![]() |
![]() |
#4 |
Guest
Posts: n/a
|
yes, magnitude should be that (all positive) but i need to plot force magnitude in normal direction of the surface, not simply Fx or Fz or Fz but a combination of all .. somehow, a force component in the normal direction of surface? Is it possible?
|
|
![]() |
![]() |
![]() |
#5 |
Guest
Posts: n/a
|
Hi,
The force normal to the surface is caused by the pressure. If you want to have a negative value, you should plot the total pressure. Force = pressure * area the area is the cell area on which the pressure is being ploted. you should be able to load this value manually in the post register in addition to the pressure value. eg. pressure in register 4 and area in register 5. put the new value in register 6 then plot it. you should get a negative value. cheers |
|
![]() |
![]() |
![]() |
#6 |
Guest
Posts: n/a
|
should the area typed in be the area for each range of pressure in the legend or the area of the entire surface?
|
|
![]() |
![]() |
![]() |
#7 |
Guest
Posts: n/a
|
The area should be the surface on which the pressure is being plotted. You can maipulate this with in the post register.
Klick on OPERATE then....FUNCTION Choose LOAD CELL DATA...then AREA...then choose the register you want to put the data into. Cheers! |
|
![]() |
![]() |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Vorticity magnitude | CFD-junior | Main CFD Forum | 10 | October 8, 2021 03:42 |
y+ and velocity magnitude | Simone | Main CFD Forum | 3 | December 12, 2008 06:44 |
MRFZonesC questions what is the mesh_V and why only Coriolis force no centrifugal force | waynezw0618 | OpenFOAM Running, Solving & CFD | 49 | April 8, 2008 04:23 |
Plotting ribbons with mapped velocity magnitude | Ulf | Siemens | 1 | July 30, 2004 08:00 |
Vorticity magnitude | Hernani | Siemens | 2 | August 20, 2001 09:48 |