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Old   June 23, 2008, 04:33
Default Flow direction in Buoyant flow
  #1
Nav
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Hi

i am dealing with a problem in Natural Convection with air at 25deg as fluid medium. took buoyant condition and defined gravity direction.i took airvolume around the heat sink as cuboid and defined all the boundary conditions as 'OPENING' .

But finally the flow direction has been reversed, ie reversal to the direction of gravitational force. Could you help me what might me the reasons for flow reversal.

thanks in advance

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Old   June 23, 2008, 07:40
Default Re: Flow direction in Buoyant flow
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Johnny
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If your gravity vector is in say the negative y direction, any fluid you heat up should flow in the positive y direction. It sounds from your description that this is what is happening, which is physically correct.
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Old   June 23, 2008, 08:33
Default Re: Flow direction in Buoyant flow
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Nav
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hi Thanks for the response --but, i am not getting the flow motion as you said, i have given the gravity in negative Z dirn so that model will be vertical,,and the flow was also flowing in negative Z dirn. i have given all the boundary conditions to be 'Opening',if they lead to the situation of reverse flow,and the velocities obtained through the plot are also high,ie around o.9m/sec to 1.5m/sec. i would like to ask if these velocities are possible in Natural convection problem?

Thanks in advance
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Old   June 24, 2008, 06:30
Default Re: Flow direction in Buoyant flow
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Andy
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Hi Nav,

from my point of view, it seems that these velocities of 0.9 m/sec to 1.5m/s is a bit to fast in case of natural convection.

What are the dimensions of your model?
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Old   June 30, 2008, 01:50
Default Re: Flow direction in Buoyant flow
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Nav
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Hi

i had asked earlier regarding the high velocities , my air domain was having an air volume of .3048*.2032*.4064 ie l*b*h.

gravity direction was given along the height. here there was another problem i am faced-- that was flow reversal.....ie flow was in along the gravity direction

plz could anyone respond...
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