2d FSI
 

I am trying to do the 2way FSI simulation using system coupling for the simple case of a pipe, whoose wall is subjected to a pressure force in 2d situation. Is it possible to do 2D fsi setup using fluent in ansys workbench, if it is possible then how to define the fluid solid interface in the structural part by selecting only edge for the 2d geometry.

It's not possible. You'd need to use a 3D mesh, 1 element thick.

thanks for your reply.
If i have to do the 1 element thick assumption, Then for the simple case of a pipe with one inlet and outlet, where the wall of the pipe is subjected to fluid-solid interaction. Then how to define the different boundary condition and also which surface I should select for the fluid solid interface.
waiting for the reply

there are step by step instructions for a 2way fsi problem in Ansys Help, under "System Coupling". You can also find the model they used for the tutorial in the CFX examples (if you have CFX licensing that is), or on the online Ansys tut Base

thanks for the reply, but again in those tutorials they have taken the wall boundary condition for both the inlet and outlet, whetehr I can define the same inlet and outlet as velocity inlet or pressure inlet? another thing is that which surface I have to select for the fluid-solid interface.

I'm far from beeing an expert, but the most obvious choice would be to pick the faces responsible for the transfer of forces between the fluid and solid. In your pic, I understand that the "Solid wall" in the pipe wall which will interact with the pressure of the inside fluid, so the logical choice would be to pick the 2 faces that are connecting both domains.

As for the boundary conditions, a velocity or pressure inlets are both viable, as are the outlets (here, I think the pressure outlet would work fine, where you could specify the pressure you want to achieve).