Do I need a wider box?

urosgrivc · February 26, 2019, 01:58

Your streamlines look bent. Why is that?
Do you have the option of normal inlet flow direction activated??
You should specify the direction.
If this is maybe the problem

ghorrocks · February 26, 2019, 02:16

Please post your CCL and an image of your setup, including which faces you have applied boundary conditions to.

tyw7 · February 26, 2019, 05:14

What's ccl?

ghorrocks · February 26, 2019, 17:36

CFX command language. This is the text on the top of the output file which describes the setup of the run. For further details look in the CFX documentation.

tyw7 · February 26, 2019, 17:40

Here you go. Had to zip the ccl cause the forum did not recognize it.

ghorrocks · February 26, 2019, 22:59

Do you know what "Normal Speed" means for your boundary condition? You obviously cannot use that option if you are making the 5 faces inlets. Have a look at the other options for inlets and see if something else is more appropriate.

Are you intending running different angles of attack for this model, or just the angle of attack in your solid model?

tyw7 · February 26, 2019, 23:04

For that particular model, no. But for a similiar model, yes. I had a look at the Cartesian uvw coordinate but I'm not quite sure how it'd work. Am I correct to assume that if I put everything as 0 and the velocity at the v axis, it'd be similiar to the wind blowing from the front?

I'm assuming normal mean the wind is blowing normal to the surface? So from the top it'll be straight down?

ghorrocks · February 26, 2019, 23:49

Yes, that is right

urosgrivc · February 27, 2019, 02:03

And check if you need to do some changes to the model, like using the air ideal gas and total energy model to account for compression or some other settings because of the really high velocity you have 250m/s (and will probably be higher locally near the wing) is transonic and some weird stuff begins to happen.

Maybe Glenn knows more about this, as I haven't done any research for transonic and supersonic flows yet, but I have heard that it is not the same as for flows slower than Mach 0.3.

compresible flow
https://www.sharcnet.ca/Software/Ans.../i1298574.html

tyw7 · February 27, 2019, 06:20

How can I know if I need to account for compressibility?

ghorrocks · February 27, 2019, 06:37

The rule of thumb for aircraft flows is that over Mach 0.3 you need to account for compressibility.

February 26, 2019, 02:16		#22
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Please post your CCL and an image of your setup, including which faces you have applied boundary conditions to. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 26, 2019, 17:36		#24
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	CFX command language. This is the text on the top of the output file which describes the setup of the run. For further details look in the CFX documentation. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 26, 2019, 22:59		#26
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Do you know what "Normal Speed" means for your boundary condition? You obviously cannot use that option if you are making the 5 faces inlets. Have a look at the other options for inlets and see if something else is more appropriate. Are you intending running different angles of attack for this model, or just the angle of attack in your solid model? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 26, 2019, 23:49		#28
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Yes, that is right __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 27, 2019, 06:37		#31
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	The rule of thumb for aircraft flows is that over Mach 0.3 you need to account for compressibility. aero_head likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

February 26, 2019, 01:58		#21
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 12	Your streamlines look bent. Why is that? Do you have the option of normal inlet flow direction activated?? You should specify the direction. If this is maybe the problem

February 26, 2019, 05:14		#23
tyw7 Member Thu Win Join Date: Apr 2017 Posts: 70 Rep Power: 9	What's ccl?

February 26, 2019, 23:04		#27
tyw7 Member Thu Win Join Date: Apr 2017 Posts: 70 Rep Power: 9	For that particular model, no. But for a similiar model, yes. I had a look at the Cartesian uvw coordinate but I'm not quite sure how it'd work. Am I correct to assume that if I put everything as 0 and the velocity at the v axis, it'd be similiar to the wind blowing from the front? I'm assuming normal mean the wind is blowing normal to the surface? So from the top it'll be straight down?

February 27, 2019, 02:03		#29
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 12	And check if you need to do some changes to the model, like using the air ideal gas and total energy model to account for compression or some other settings because of the really high velocity you have 250m/s (and will probably be higher locally near the wing) is transonic and some weird stuff begins to happen. Maybe Glenn knows more about this, as I haven't done any research for transonic and supersonic flows yet, but I have heard that it is not the same as for flows slower than Mach 0.3. compresible flow https://www.sharcnet.ca/Software/Ans.../i1298574.html

February 27, 2019, 06:20		#30
tyw7 Member Thu Win Join Date: Apr 2017 Posts: 70 Rep Power: 9	How can I know if I need to account for compressibility?

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