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boundry conditons

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hi all
Please guide me.As I am new in COMSOL and have some confusions regarding boundry conditions.



1.I am using a chamber of dia 260mm x 150 mm (hight) inside the cavity I have a cylinder of dia 80mm x76mm (hight) at constant isothermal temprature.



2. I have considered 2-D axisymtric case.

3.I have big confusion on the top boundry of the chamber which is infact open boundry.

4.I am using general Heat transfer module with navier stokes





Questions:

1.What should be the boundry condition for the heat transfer module on the opening of the cavity

1. Temprature = ambient temprature?

2. heat flux ?

3.Convective flux?

(I have given the heat flux but bit confused about characteristic length mean its an open cavity if i considered heat flux its mean there is some solid wall or some wall boundry bit confused)



For navier stoke at the opening i Have given the open boundry , boundry condtion,

My model works well but velocity of the air is very very low mean in the range of e-20.



So please guide me whether is it alrite?? or I needed to change somthing.





I will be really thankful to you.

Tassawar






0 Replies Last Post Mar 9, 2012, 11:00 a.m. EST
COMSOL Moderator

Hello Tassawar Hussain

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