Hi, I would like to simulate the natural convection adjacent to a horizontal flat plate. I have created a square, the top wall be the plate and how can I define the left and right side boundary condition and the bottom boundary condition? Suppose I want to cool the plate, should I use one side pressure inlet BC and other side pressure outlet BC and the bottom symmetry? If ok then why I should use this kind of BC, could anybody explan me? Thank you very much in advance.....

For natural convection over a horizontal flat plate, you can use symmetry around the flat plate. So in the rectangular domain (2D), the plate will be bottom edge (wall at desired temperature), one of the vertical edge will have symmetry BC and other two can have pressure inlet/outlet BC with P = atomosperic pressure (most obviously).

For cooling problem, you have to set the air flowing and BCs will depend upon what cooling scheme you are looking for cooling the plate. This is a conjugate heat transfer problem and you will have to have 2D model representing wall cross section also.

- Prasad

Thanks Prasad, I want to make the plate infinitely long on both sides. So the symmetry condition is not appropriate as the flow can not move freely over that boundary. I want to cool the top boundary of the rectangle (plate) by giving the temp 280K and the ambient temperature will be 300K. The presure inlet or outlet conditions are not good as well for the temperature. However, the flow can move freely. We have to set up the tempearure of the backflow here. We should make dT/dx=0 here. I wrote a UDF to make the temperature gradient zero but I could not hook that. I dont know where I should hook it.

Thanks Suvash