hi. how to explain a grid orientation in Fluent. There is north and east direction. I thought that i need only 3 points to orientate a grid (for example 1,1,1 tell me that a plane i faced nort, east and under 45deg to horizont isn`t it??). How to explain NORTH 0,0,1 and EAST 1,0,0? please help me with this school problem I don`t want to ask my daughter

The mesh is oriented with respect to the coordinate system. Please explain your question, Cheers

Thanks for reply. lets take an example. We have a brick in Gambit (X,Y,Z) = 1m x 2m x 0.1m (Z coordinate is the high of brick). Now I`d like to establish a calculations in Fluent and I`d like to have this bick orientated: 1 case) direction south angle 30deg, 2 case)parallel to horizont. Hoaw to set up a grid orientation nort and east? Regards Grzesiek

Create the mesh using the default coordinate system, then rotate (using the move command) it the way you like then write the mesh file You can also create the eight vertices of the block in your prefered orientation (using mathematical expressions ..etc) or set up a new coordinate system and ....etc It is up to your imagination and your personal preferences

ok. But what to do whit this grid orientation (i forgot to tell that I need it for solar load model) in Fluent when I have properly (like I want) orientated grid under Gambit? Should I leave a diffoult values under north and east?

It is true that solar radiation depends on the location on planet Earth with respect to the Sun, but believe me, I can not see your logic here, I guess you could explain your problem, geometry and the objectives of such simulation and why you believe CFD is the right tool for your problem..etc, I might be able to help or someone else could get interested, Cheers and Good Luck

my problem to solve is: I want to model a sollar flat plate collector. An efficiency of the collector depend of the angle between collector surface and the ground. In my region it is 30deg. Yes you are right it depend of the location on planet but I set up it in diffrent window. I set up a season of the year, time zone and there is an option to set up a grid orientation. Default parameters are: North x=1, y=0, z=0; East: x=0, y=0, z=1 (or something like that-I don`t remeber it well now). So I don`t have any option only to leave a difult values of grid orientation or to write my own parameters for x,y,z. If I orientated grid in Gambit like I want than what to write in Fluent for grid orientation?.

Another proble for me is to model a desorption process what we can simply describe as an evaporation process but not from the surpface but from whole volume.

1-In fluent there are two thermal BC, Constant temperature and normal heat flux input. To solve your problem, I would alter the heat flux input (Use a UDF) as a function of the orientation of the collector, it is just qn cos (angle).

2- I will think about the other desorption process, meanwhile I hope the change in the title of the query will attract the attention of other readers to this interesting problem.

ok thank you for help. I will let you know what I did and how is it working. I`m a little bit ill so I will check it next week because I must lay at bed. Regards Grzesike

I am not really familiar with the setup in question. I guess you have to activate the mass diffusion equation in your CFD model, but, it would be a good idea if you put a link to a picture of your particular set up or any useful information related to your problem, you have to realize how difficult it is to advice on an unknown geometry

yes you are right. I think I must work a little bit harder to know more aboute Fluent and UDF especially. To set up my simulation (problem) in Fluent I must at first make a new material whichis LiBr-H2O solution. I have already UDF`s for density, viscosity and thermal conductivity an only few left to do. I don`t know how to do a UDF of specific heat. I `ve read in fluent tutorials that it is immposible to do it. WHY? and what to do to set up a specific heat of new solution (material) Do do desorption I need to know and to establish diffusion, mass transferat as you`ve mentionedbut now I need to know more aboute this "stupid" C language for making UDF ) regards Grzesiek