Hi Steve, thank you very much for your reply, and yes I will describe more details about my model.
My model is about 2-way FSI. The model is a hollow cylinder, and there is a plate (with a very small orifice) in the middle which separate the hollow cylinder into two parts, like figure 1 and figure 2 shown below. The hollow cylinder is fixed, and the rim of the plate is fixed, but the other parts of the plate are free. For example, the center of the plate can move up and down.

At beginning, the upper part contains water & air, and the lower part contains air, and mixed water & air near the orifice, like figure 3 shown below (in figure 3, the red is water and blue is air, it is a contour of Volume of Fraction of water). If the plate keep static, because of surface tension, the water will not flow into the air through a very small orifice, like the figure 3 shown below.

When the plate starts to vibrate (the rim of the plate is fixed, but the plate center can move), especially the plate moves up, the water is going to be 'filtered' by the orifice to form a droplet and flows into the air. For this process, I need VOF method and Patch in Fluent.
For the plate vibration, if I apply force or displacement on the plate, there is no problem because I can use 'Transient Structural Analysis' to do this, and then couple 'Transient Structural' with 'Fluent' to do this 2-way FSI, like figure 4 shown below. In figure 4, the plate moves up, and more water is filtered by the orifice. (there is no droplet formation because of the unsuitable Boundary Conditions, but at least I can use Transient Structural and Fluent to couple).

However, currently, this plate is vibrating in a Harmonic Response Way, which means I can only simulate the vibration of this plate in 'Harmonic Response Analysis'. Therefore, the result is, I find that I can't couple the 'Harmonic Response' with 'Fluent', so I have no idea about how to do this 2-way FSI simulation.
In this way, could you please tell me if you have some recommendations? Thanks in advance.