[356chiru]

Can any one please tell me how to simualte natural convection process in recatangular enclosure in fluent

[dreamz]

First find grashoff number for your flow and decide the nature of your flow whether laminar, turbulent etc. Then specify boussinesq's approximation under the density tab for the material in your cavity e.g. air, water... Vary the value of gravity to get your desired value of natural convection. Then check for convergence.
Hope this helps..

[356chiru]

firstly thank u so much for th e reply!! ya am using bousineeseq itself,its rectangle of 0.0746*0.0376 , i e aspect ration =2, my rayleigh number is 10 power 5.so its laminar only, prandtla number 0.716.what is the limit of grashof number in enclosure that decides turbulent!!

[dreamz]

For grashof number below 10^8 we have laminar natural convection. Based upon the inputs that you have shared, I think you are going fine and you should achieve convergence. Have you got it?

[356chiru]

thanku u once agian/ arrving at convergence ,but the average surface nusselt number was not matching with paper!!
i saw it in cengel textbuk ,vertical rectangular enclosres ,NU =0.22 *((Pr/0.2+pr)*Ra)power 0.29;
solution converged ,i took area avg surface nuselt numebr; but what the text buk i gave i donno!!
boundary conditions :
T HOT =339.5 ; T COLD =323 ; OTHER TWO HOROZONTAL WALLS ARE ADIABATIC:
operating temparature i used avg of hot and cold;
g=-9.81 ; bousnesq with all properties at mean tempearture ;
kindly help me

[dreamz]

Even I got convergence. However you haven't mentioned the unit if temperature for the given values. Is it celcius or kelvin?
After that I will try to verify the nusselt no.

[356chiru]

whats the nuselt number u havae arrived at??

[dreamz]

If the unit if temperature is degree Celsius then the nusselt numbern comes to be around 31