Thank you for the tutorial, may i ask why the upper wall boundary condition at 25:39 is not "slip" ? Whats the difference between the upper wall and the back face as you have set the later to "slip" but the upper wall to "outlet".
Thank you for your interest in my tutorial. You are absolutely right: both boundary conditions are possible for the rear wall. I simulated the "wind tunnel" application, hence the boundary condition slip. The boundary condition “outlet” or “open” should in principle also be possible. Please note that I deliberately chose the dimension of the simulation space to be very small in order to save storage space and computing time. If the simulation space had been chosen to be sufficiently large, the difference between these two boundary conditions should be very small.
Thank you for your carefull work. Could you, please, comment on the fact that the corresponding columns 1 and 4 or 2 and 5 or 3 and 6, representing force and pressure components, respectively, are quite close in their values? See at 37:54.
Looking on the header above the columns, you will please find the labels "total_x, [...], pressure_x, [...], viscous_x, [...]. The "total_x" is the sum of "pressure_x" and "viscous_x". Because the share of "viscous_x" is low, the first and the fourth column are nearly equal.
the text you copy and paste at 30:38.... you could simply put it in the description, it requires googling, and a debit or credit card to access online..
Thanks for your question. The tutorial by Mr Oxtoby can be found here: www.opensim.co.za/training.html, the pdf-File is here: github.com/opensimsa/opensim/raw/master/Documentation/CFD/UAV2/CFD%20Tutorial%204%20-%20External%20Aerodynamics%20of%20a%20UAV.pdf The missing text is here: functions { forces_all { type forces; libs ( "libforces.so" ); patches ( wall ); rho rhoInf; rhoInf 1.2; log off; writeControl timeStep; writeInterval 1; CofR ( 0 0.6 0 ); } } I already adapted the Center of rotation (CofR) in the y-axis from 0.0 to 0.6. Currently, a new version for Freecad cfdof is available. In this version, the evaluation of the forces is included. You can find the corresponding posting in the freecad-forum: forum.freecad.org/viewtopic.php?p=592032&sid=94a382e0b80d7b94821582ab076920eb#p592032
Brilliant tutorial. Just a small query, how would I approach this simulation if I had a STL file of the car? I tried converting the stl to mesh and then to solid, and then usung cut expression. But unfortunately, it doesn't work for me
Is there a reason you chose to use a volume refinement vs just a surface refinement? I still use surface refinement at the moment, but was wondering if there is an advantage of one over the other? Let me rephrase my question.. I know that you used both in this excercise but what if i only chose to use surface refinement and only did ONE mesh refinement instead of 2? thanks for great work : )
This seems to be a problem with the part design workbench. As mentioned several times before, youtube is not the right medium for questions like these because a) you do not have the possibility to upload the file and information about your system b) only one (=me) can answer your questions. The right medium is the FreeCad-Forum. In the FreeCad-Forum, many experts can answer your questions. Here is the link to the FreeCad-Forum: forum.freecad.org/index.php
Very good tutorial, many thanks, may give demonstration of wind load on tall building
Thank you for the tutorial, may i ask why the upper wall boundary condition at 25:39 is not "slip" ? Whats the difference between the upper wall and the back face as you have set the later to "slip" but the upper wall to "outlet".
Thank you for your interest in my tutorial. You are absolutely right: both boundary conditions are possible for the rear wall. I simulated the "wind tunnel" application, hence the boundary condition slip. The boundary condition “outlet” or “open” should in principle also be possible. Please note that I deliberately chose the dimension of the simulation space to be very small in order to save storage space and computing time. If the simulation space had been chosen to be sufficiently large, the difference between these two boundary conditions should be very small.
Thank you for your carefull work. Could you, please, comment on the fact that the corresponding columns 1 and 4 or 2 and 5 or 3 and 6, representing force and pressure components, respectively, are quite close in their values? See at 37:54.
Looking on the header above the columns, you will please find the labels "total_x, [...], pressure_x, [...], viscous_x, [...]. The "total_x" is the sum of "pressure_x" and "viscous_x". Because the share of "viscous_x" is low, the first and the fourth column are nearly equal.
the text you copy and paste at 30:38.... you could simply put it in the description, it requires googling, and a debit or credit card to access online..
Thanks for your question. The tutorial by Mr Oxtoby can be found here: www.opensim.co.za/training.html, the pdf-File is here: github.com/opensimsa/opensim/raw/master/Documentation/CFD/UAV2/CFD%20Tutorial%204%20-%20External%20Aerodynamics%20of%20a%20UAV.pdf
The missing text is here:
functions
{
forces_all
{
type forces;
libs ( "libforces.so" );
patches
(
wall
);
rho rhoInf;
rhoInf 1.2;
log off;
writeControl timeStep;
writeInterval 1;
CofR ( 0 0.6 0 );
}
}
I already adapted the Center of rotation (CofR) in the y-axis from 0.0 to 0.6.
Currently, a new version for Freecad cfdof is available. In this version, the evaluation of the forces is included. You can find the corresponding posting in the freecad-forum: forum.freecad.org/viewtopic.php?p=592032&sid=94a382e0b80d7b94821582ab076920eb#p592032
@@techbernd5535 thanks for the prompt reply! and thats a much less painful link than where i found it on Scribd.....
Danke, auch wenn man am Akzent schnell gemerkt hat, dass du Deutscher bist :D
Brilliant tutorial. Just a small query, how would I approach this simulation if I had a STL file of the car? I tried converting the stl to mesh and then to solid, and then usung cut expression. But unfortunately, it doesn't work for me
Your question relates to FreeCad in general. Therefore you should ask this question in the FreeCad forum: forum.freecad.org/viewforum.php?f=37
Really a good tutorial. I have a question, since you modelled half a car, is correct to use a force of 390 N? You don't have to multiply x2?
That is right
Is there a reason you chose to use a volume refinement vs just a surface refinement? I still use surface refinement at the moment, but was wondering if there is an advantage of one over the other?
Let me rephrase my question.. I know that you used both in this excercise but what if i only chose to use surface refinement and only did ONE mesh refinement instead of 2?
thanks for great work : )
Questions like these should be asked in the FreeCad-Forum: forum.freecad.org/viewforum.php?f=37
Thank you for the tutorial. I get an error when using the cut function. The error is "Body: Object not allowed". Could you please assist?
This seems to be a problem with the part design workbench. As mentioned several times before, youtube is not the right medium for questions like these because a) you do not have the possibility to upload the file and information about your system b) only one (=me) can answer your questions. The right medium is the FreeCad-Forum. In the FreeCad-Forum, many experts can answer your questions. Here is the link to the FreeCad-Forum: forum.freecad.org/index.php
@@techbernd5535 Thank you