# CFdesign and Natural Convection

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 November 10, 2009, 14:56 CFdesign and Natural Convection #1 New Member   J Join Date: Nov 2009 Posts: 2 Rep Power: 0 Hello to everyone: Since August 2009 I have been involved in a project related to natural convection problems. I am working with cfdesign (V9) because it has an amazing integration module with CAd softwares. My problems are focused on the convergence monitor: I am not an expert on this field but according to the guideline, all the lines (P,T,Vx,Vy,Vz,Ek...) that are drawn in this monitor must tend to be horizontal. In addition to that, CFdesign gives the oportunity to choose 4 diffferent turbulent models: K-epsilon, low Re, mixed lenght, Eddy viscosity. There are other parameters quite important such as turb/lam ratio and so on. The maximum iteration number i have been working with has been 1000. But even with that amount of iterations i can not get the convergence of the different variables. That is why i would be very appreciative if anyone can brief me on the different parameters are suitable to set in CFdesign v9 in order to get the convergence. I will also thank any experience on natural convection case studies. Because to be honest, I find myself very discouraged about this project. Thanks for your time

 November 17, 2009, 13:59 reply: Radiation units WRONG DEFINED IN CFDESIGN 9 #2 New Member   J Join Date: Nov 2009 Posts: 2 Rep Power: 0 Hi everyone: According to the experience let me response myself in order to encourage people to send me some replies. I can get the convergence making use of Mixing lenght turbulence model. By the way; i have been calculating the results that i get from CFdesign (making use of mathematics functions) andi would like to confirm something: I got the following table: Radiation Heat Loads by Part ID ID Radiation (Watts) Area (m^2) ___Surface Temp (K) Emissivity 1 __24.485_________0.4308____________285.09_______0.99 2 ___-24.485________0.4308____________ 309.8________0.99 3 ______0 ___________11.629____________285.03 0 Totals -1.6611e-007_12.491 285.88 Can anyone confirm me that the column RADIATION units are not Watts (total watts emitted by a body), but Watt/m2 (Total watts emitted by a body/body surface)??? looking to your reply. regards.