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max91 July 29, 2008 05:20

Natural convection - Inlet boundary condition
 
Hey everybody,

I read many topic about the natural convection and the boundary conditions for the simulation of this phenomenon.

I'm studying, with CFX 11, the water flow in natural convection throught a square duct which contains heating source. The duct is vertical. So the inlet is at the bottom and the outlet is at the top of the duct. Althought I have a problem : I put static pressure boundary condition for the outlet ( pstatic = 0) but for the inlet : static or total pressure (pstatic = 0 or ptotal = 0) ?? (I read the two answers on the forum).

Could you help me ??

Thanks

max91


Rogerio Fernandes Brito July 29, 2008 20:28

Re: Natural convection - Inlet boundary condition
 
What is your Reynolds number? I think you have a mixed convection (natural and forced convections) and not only a natutal convection. See my Doctorate Thesis for several comparisons with experimental data (it is not mine) and other numerical data: Go, please to my personal home-page: http://rogeriofernandesbrito.googlepages.com. If u wanna compare with CFX, send me your name.cfx file . I will simulate with pleasure for you! MSN: rogeriobrito2007@hotmail.com, Skype: rogeriofbrito

Table 5.2 â€" Comparison of the results for the square geometry of figure 5.5: Gr = 2.0 Ã- 10^4 e Pr = 0.733 .

Reference Nuh Desviation [%] Methd Utilized Ozoe et al. 2.74  Experimental Value Present Work 2.569 - 6.24 Finite Elements (3362 elements) Menon 2.70 - 1.46 Finite Elements (100 elements) Tabarrok et al. 2.695 - 1.64 Finite Elements (200 elements) Wilkes et al. 2.874 - 4.89 Finite Differences (10 x 10) Wilkes et al. 2.516 - 8.18 Finite Differences (20 x 20) Being: Desviation [%] = [( â€" ) / ] 100.

Table 5.3 â€" Comparison of the results for the square geometry: Pr = 0.733.

Ref. Figueredo et al. Present Work Wong e Raithby Present Work Gr

Desviation1 [%]

Desviation2 [%]

34 110 2.884 3.023 4.60 2.972 3.023 1.69

60,000 3.468 3.588 3.34   

100,000 4.160 4.190 0.72   

136,430 4.686 4.602 -1.83 4.51 4.602 2.00

341,070    5.92 6.033 1.87

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