Help with CFX

rafaelonos · November 26, 2019, 15:01

Hello! I'm noob with CFX. I want to simulate the air flow inside a bus when the bus is at 30km/h. However, when the simulation is complete, I open the postprocessor and add streamlines of velocity, but looks like the air isn't coming inside the bus, just flowing outside.
This is my geometry
https://ibb.co/Nn6G3vn

This is the streamlines
https://ibb.co/x8jK349

This is my project with the geometry file
https://www.dropbox.com/s/lrtfi1u2s1...OTRAB.zip?dl=0

Thank you!

ghorrocks · November 26, 2019, 16:44

Streamlines are integrated from a seed point. You appear to have put the seed points on your inlet, and not much of your flow from the inlet will get inside the bus. I would recommend putting some seed points inside the bus - as points, lines or volumes which you define inside the bus; then use that object as the streamline seed point.

rafaelonos · November 26, 2019, 17:02

I think I understood hahaha
So if I create domains in all windows and add streamlines starting from the windows? However I don't know how to add domains

rafaelonos · November 26, 2019, 17:40

Well, as I don't know how to see the streamlines starting from the windows (and have no idea of what to search) I'm just clicking every button I see.
Selecting "Default Domain Default" as the starting for the streamlines, I got this:
https://ibb.co/LgVTbT5
Could you explain me what means to select "default domain default" at the "starting from" option? I could say that select the inlet in this option gives me the streamlines starting from the inlet, but I can't understand when I select the "default domain default".

ghorrocks · November 26, 2019, 21:42

If you select a volume for your seed point (such as your domain as you have done) then it will use every node location in the volume as a seed point. But note that by default it then thins them down as there are usually zillions of nodes in a volume.

The easiest way to start a streamline exactly where you want it is to define a point using XYZ coordinates to be inside your bus. Then make a new streamline object using the point object as a seed point.

But the image you show is what I would expect - flow streaming past the bus on the outside and a chaotic flow inside.

rafaelonos · November 28, 2019, 22:08

I really appreciate your help, ghorrocks! I create two plans and with contours I set the plan and the variable velocity to see it! Thats exactly what I want, cause with this plans I can make a relation between velocity of the air and thermal sensation! Thank you!!

November 26, 2019, 15:01	Help with CFX	#1
rafaelonos New Member Rafael Join Date: Nov 2019 Posts: 4 Rep Power: 6	Hello! I'm noob with CFX. I want to simulate the air flow inside a bus when the bus is at 30km/h. However, when the simulation is complete, I open the postprocessor and add streamlines of velocity, but looks like the air isn't coming inside the bus, just flowing outside. This is my geometry https://ibb.co/Nn6G3vn This is the streamlines https://ibb.co/x8jK349 This is my project with the geometry file https://www.dropbox.com/s/lrtfi1u2s1...OTRAB.zip?dl=0 Thank you!

November 26, 2019, 16:44		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	Streamlines are integrated from a seed point. You appear to have put the seed points on your inlet, and not much of your flow from the inlet will get inside the bus. I would recommend putting some seed points inside the bus - as points, lines or volumes which you define inside the bus; then use that object as the streamline seed point. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

November 26, 2019, 21:42		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	If you select a volume for your seed point (such as your domain as you have done) then it will use every node location in the volume as a seed point. But note that by default it then thins them down as there are usually zillions of nodes in a volume. The easiest way to start a streamline exactly where you want it is to define a point using XYZ coordinates to be inside your bus. Then make a new streamline object using the point object as a seed point. But the image you show is what I would expect - flow streaming past the bus on the outside and a chaotic flow inside. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
CFX Treatment of Laminar and Turbulent Flows	Jade M	CFX	18	September 15, 2022 07:08
High Resolution (CFX) vs 2nd Order Upwind (Fluent)	gravis	ANSYS	3	March 24, 2011 02:43
CFX pressure in Simulations problem	nasdak	CFX	1	April 14, 2010 13:22
PhD using CFX	Rui	CFX	9	May 28, 2007 05:59
FSI using CFX and ANSYS	Bi Chang	CFX	2	May 10, 2005 04:47

November 26, 2019, 17:02		#3
rafaelonos New Member Rafael Join Date: Nov 2019 Posts: 4 Rep Power: 6	I think I understood hahaha So if I create domains in all windows and add streamlines starting from the windows? However I don't know how to add domains

November 26, 2019, 17:40		#4
rafaelonos New Member Rafael Join Date: Nov 2019 Posts: 4 Rep Power: 6	Well, as I don't know how to see the streamlines starting from the windows (and have no idea of what to search) I'm just clicking every button I see. Selecting "Default Domain Default" as the starting for the streamlines, I got this: https://ibb.co/LgVTbT5 Could you explain me what means to select "default domain default" at the "starting from" option? I could say that select the inlet in this option gives me the streamlines starting from the inlet, but I can't understand when I select the "default domain default".

November 28, 2019, 22:08		#6
rafaelonos New Member Rafael Join Date: Nov 2019 Posts: 4 Rep Power: 6	I really appreciate your help, ghorrocks! I create two plans and with contours I set the plan and the variable velocity to see it! Thats exactly what I want, cause with this plans I can make a relation between velocity of the air and thermal sensation! Thank you!!