Hi all. I am trying to simulate the flow around a fluctuating beam. The beam is fixed at one end, and the other end goes up and down. I do not know how to impose the boundary condition for the beam. Should I use Dynamic Mesh? Should I write UDF for the beam motion? I am not familiar with Dynamic Mesh. If someone can help me, that would be great for me.

Thank you...Mehdi

hi Mehdi, I am also trying to compute such problem (simple 2d fsi problem). I can tell you, how I want to handle this calculation, and I am open for any advice-critic about my method First, is you beam fluctuating such as an rigid body (beam's shape doesn't move, but its orientation can --> rotation)? or do you have an deformation of your beam? If you doesn't have any deformation, you can simply use Dynamic Mesh and describe the motion of the beam. If you have deformation, then it is a fluid-structur-interaction problem, which can be handle, with Dynamic Mesh and an UDF (Define Grid Motion) for defining the Node's displacement in your beam. Hope it helps

Dear Max, Thank you so much for your reply. The problem I am solving is a simple beam without deformation. It has only rotation motion. Unfortunately, I am not too familiar with Dynamic Mesh. I generated the a simple, unstructured mesh in Gambit, and do not know if I need to describe any specific type of mesh in gambit or not. If you can help me, I really appreciate it.

in this case it is "easy" to compute such calculation. Is the motion of your beam given, or do you have to compute it ?

the motion of the beam is known. it is Y = AA*sin(OMEGA*t), where Y is the vertical displacement of the beam (assume that beam is oriented parallel to x-axis), AA is the amplitude of displacement which is a linear function of x-coordinate (AA = A*x), OMEGA is the angular velocity and t is time. All the parameters are known. i have shown a schematic of the problem below. the geometry is very simple and the motion is rigid body motion which is known.

/| /| /|_____________________________________

| _____________________________________| /| /| /|

^ |y | |----> x

i am sorry max, i think the figure is not shown properly. please let me know if you do not mind to email you and send you the schematic and primary mesh generated i have done.