You and me both if I had only the info I showed you as we see the center of the blue areas at 206 meters behind the tail of the plane are shown at ~8 meters above the wingtips or about 2.5 degrees UP. What I did not mention was that the inlet air hitting the plane comes from a 4.5 degree upward airflow (and the slices are therefore off perpendicular to the freestream by 4.5 degrees) so the blue blobs are really moving down at 2.5 degrees with respect to the free stream velocity which makes the disturbance moving down as expected.
Are you modeling the propeller thrust? If not, it is anticipated that for a viscous simulation the total momentum and energy in the streamwise direction will change with the passage of the aircraft due to drag. This seems like it is accurately captured where the mean flow speed drops from 15 to ~14.91. However, near the outflow boundary condition something funky is indeed happening. There are different ways to specify outflow boundary conditions, and often they are (intentionally) not energy conserving (e.g. sponge layers) in the immediate region of the boundary condition.
Thanks for the feedback. The boundary conditions for the mesh outlet faces (the top+z and the rear+x faces) are set to fixed gage pressue at 0Pa. You can go directly to the outlet conditions at this link: www.simscale.com/workbench/?pid=613334186170559001&mi=spec%3Afe81ef54-8a7a-41d8-ae2b-a54b13f6dfd6%2Cservice%3ASIMULATION%2Cstrategy%3A1057&ps=analysis%2FboundaryConditions%2F3 And no I am not modelling thrust, the props are stationary. I do a lot of gliding :)
That is wild. Curious what code you are running. I have heard that the floats generate enough lift to offset their own weight and so interesting to see the high pressure beneath them.
Hi Winston, there is a link in the description to my SimScale CFD project. Floats are not efficient lift generators so I want them at 0 lift AOA. Until I solve the 'energy from the ether' problem I don't want to quote lift and drag values but I am sure that I have the floats at near 0 lift AOA at this 33.5 mph airspeed. I am sorry for delay in keeping our email chat alive, soon I hope.
Cool to see your other projects too on SimScale. I keep seeing Starry Night when I watch this video. I need to learn more, but even if float lift is not efficient, given that zero lift AOA will not reduce the relatively large parasitic drag of the floats, it seems like a slight AOA to give some lift might be worth the extra drag under the float. No prob on the delay, great to see what you've been working on! Now that I know there is a full 3d model of the eLazair4 I really want to see one in x-plane! While x-plane doesnt have CFD, it is a decent physics engine to run scenarios.@@DaleCKramer
Aren't you be able to load an x-plane model from any 3D CAD? Download .STEP CAD for the eLazair4 file from here: www.simscale.com/workbench/?pid=613334186170559001&mi=geometry%3A1014&mt=GEOMETRY Let me know how it works out....
Awesome! Way more disturbance above the wing, and higher than I would have thought.
You and me both if I had only the info I showed you as we see the center of the blue areas at 206 meters behind the tail of the plane are shown at ~8 meters above the wingtips or about 2.5 degrees UP. What I did not mention was that the inlet air hitting the plane comes from a 4.5 degree upward airflow (and the slices are therefore off perpendicular to the freestream by 4.5 degrees) so the blue blobs are really moving down at 2.5 degrees with respect to the free stream velocity which makes the disturbance moving down as expected.
I just put a better explanation of that in the video description. But still the 'energy from the ether' mystery remains :)
Nice video simulation. Thanks
Are you modeling the propeller thrust? If not, it is anticipated that for a viscous simulation the total momentum and energy in the streamwise direction will change with the passage of the aircraft due to drag. This seems like it is accurately captured where the mean flow speed drops from 15 to ~14.91. However, near the outflow boundary condition something funky is indeed happening. There are different ways to specify outflow boundary conditions, and often they are (intentionally) not energy conserving (e.g. sponge layers) in the immediate region of the boundary condition.
Thanks for the feedback. The boundary conditions for the mesh outlet faces (the top+z and the rear+x faces) are set to fixed gage pressue at 0Pa. You can go directly to the outlet conditions at this link: www.simscale.com/workbench/?pid=613334186170559001&mi=spec%3Afe81ef54-8a7a-41d8-ae2b-a54b13f6dfd6%2Cservice%3ASIMULATION%2Cstrategy%3A1057&ps=analysis%2FboundaryConditions%2F3
And no I am not modelling thrust, the props are stationary. I do a lot of gliding :)
fascinating topic
That is wild. Curious what code you are running. I have heard that the floats generate enough lift to offset their own weight and so interesting to see the high pressure beneath them.
Hi Winston, there is a link in the description to my SimScale CFD project. Floats are not efficient lift generators so I want them at 0 lift AOA. Until I solve the 'energy from the ether' problem I don't want to quote lift and drag values but I am sure that I have the floats at near 0 lift AOA at this 33.5 mph airspeed. I am sorry for delay in keeping our email chat alive, soon I hope.
Cool to see your other projects too on SimScale. I keep seeing Starry Night when I watch this video. I need to learn more, but even if float lift is not efficient, given that zero lift AOA will not reduce the relatively large parasitic drag of the floats, it seems like a slight AOA to give some lift might be worth the extra drag under the float. No prob on the delay, great to see what you've been working on! Now that I know there is a full 3d model of the eLazair4 I really want to see one in x-plane! While x-plane doesnt have CFD, it is a decent physics engine to run scenarios.@@DaleCKramer
Aren't you be able to load an x-plane model from any 3D CAD? Download .STEP CAD for the eLazair4 file from here: www.simscale.com/workbench/?pid=613334186170559001&mi=geometry%3A1014&mt=GEOMETRY Let me know how it works out....
omg dale how long has this cad model been out there?! @@DaleCKramer yes, I see it now. not familiar with simscale so thx for the link.
As long as it can still land on water ...
Well, there it is then....
Is there a way to email you?
You cam PM me at RCgroups.com www.rcgroups.com/forums/member.php?u=36489