Symmetry Boundary Condition for a fluid domain

Zaqie · August 31, 2009, 04:19

Hi

I am doing a fluent analysis on a water turbine blade. The bondaries I have used are as follows.

1. Velocity Inlet - at inlet
2. Mass flow outlet - at exit
3. Wall - at turbine blade
4. symmetry - at outer domain

I am fine with the first three, but I am not quite sure about the fourth one i.e is the symmetry condition. As far as I know symmetry condtion is like a wall but without a shear. But in practicality wont there be some outflow.

Please advice if I have some other option.

Regards

Zaqie

-mAx- · August 31, 2009, 05:34

Switch massflow outlet to pressure outlet.
Indeed you have already defined a massflow at inlet
To your symmetry... it depends on your geometry (and also your BC), but "turbine blade" sounds like periodicity.
Check the help for understanding the difference

Zaqie · September 4, 2009, 11:05

Hi again

Please find attached a jpg image of 2d cross-sectional view of the turbine and its domain. I get the idea of the periodic boundary that can be used. But I am not sure of the boundary that is to be selected at the domain extends (rectangular box enclosed in the image). Any advice on that?.

Regards

Zaqie

P.S: I tried pressure far field condition and then found out that it can only be used for ideal gas equations, rendering it not suitable for my case.

delfel · September 4, 2009, 17:57

Hello,

My vote is for a slip wall or a pressure outlet. I'd also put it as far from the foil as you can.

Cheers,
-sean

August 31, 2009, 04:19	Symmetry Boundary Condition for a fluid domain	#1
Zaqie New Member Zaqie Join Date: Jul 2009 Posts: 22 Rep Power: 16	Hi I am doing a fluent analysis on a water turbine blade. The bondaries I have used are as follows. 1. Velocity Inlet - at inlet 2. Mass flow outlet - at exit 3. Wall - at turbine blade 4. symmetry - at outer domain I am fine with the first three, but I am not quite sure about the fourth one i.e is the symmetry condition. As far as I know symmetry condtion is like a wall but without a shear. But in practicality wont there be some outflow. Please advice if I have some other option. Regards Zaqie

August 31, 2009, 05:34		#2
-mAx- Super Moderator Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41	Switch massflow outlet to pressure outlet. Indeed you have already defined a massflow at inlet To your symmetry... it depends on your geometry (and also your BC), but "turbine blade" sounds like periodicity. Check the help for understanding the difference __________________ In memory of my friend Hervé: CFD engineer & freerider

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September 4, 2009, 17:57		#4
delfel New Member Sean Delfel Join Date: Aug 2009 Posts: 27 Rep Power: 16	Hello, My vote is for a slip wall or a pressure outlet. I'd also put it as far from the foil as you can. Cheers, -sean