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-   -   Coordinate System (http://www.cfd-online.com/Forums/fluent/30544-coordinate-system.html)

Pravesh kumar November 20, 2002 00:43

Coordinate System
 
hi I needed your immediate help.I am having my geometry in Gambit in X-Y plane.I want to know when i am having my Geometry in fourth coordinate whether i should put gravitational acceleration (g) 9.81 or -9.81. Your immediate help is required. With my warm personel Regards pravesh


gavin November 20, 2002 04:28

Re: Coordinate System
 
If I understand your question correctly, you should have 'g' working opposite to the postive y direction, therefore it will be -9.81 m/s^2

Pravesh kumar November 20, 2002 12:29

Re: Coordinate System
 
hi But I having my geometry in fourth coordinate i.e +X,-Y As I have already taken -Y dirn so i am not sure whether to put one more -ve for the downward dirn of gravitational acceleration(g).

Thanks for replying.

Erwin November 20, 2002 13:38

Re: Coordinate System
 
Just check in Fluent in which direction 'the apple should fall'; in the positive y direction or the negative one. If it is the negative y direction, gravity is -9.81 otherwise +9.81.

Pravesh Kumar November 20, 2002 13:49

Re: Coordinate System
 
Dear Erwin As i am having my geometry in fourth coordinate (ie +X and -Y.).As the apple will fall downward ie -Y dirn and i have already taken the -Y dirn in coordinate system so i am not sure whether i should put g as 9.81 or -9.81. Your help is needed. Thanks

Erwin November 21, 2002 05:18

Re: Coordinate System
 
Your gravity is in -Y direction, so fill in -9.81. It doesn't matter in which quadrant you make your grid, +Y still goes up, -Y still goes down.

To see for yourself: read the grid into Fluent. Display the grid. Under Display/Options menu, turn on the 'Display Axis' option. Look at your grid. Decide in which direction gravity acts.

mahdi saniee nezhad November 24, 2002 01:53

Re: Coordinate System
 
Dear sir I have a problem with this title. If it's possible for you please send me your received responses. Very thanks for your attention to my request. With the best regards. Mahdi saniee nezhad


Pravesh Kumar November 26, 2002 10:50

Re: Coordinate System
 
Dear Erwin I can't find 'Display Axis' panel as told by you.I am using fluent6.Plz elaborate. Under Display/Options menu, turn on the 'Display Axis' option.

Thanks


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