Modeling of fluid flow caused by deformable objects.

I have a stationary object in a stationary fluid at t=0s. At that time, the object (a fixed rectangle) starts moving in a sine wave (eg how flagella or cilia move). Due to this the fluid around it gets moved. I cannot model it, I dont know which model to use and which physics to use to model such a flow.
I have already looked at the example for modelling in fluid structure interaction system. I do not know how to modify the boundary condition do that the rectangle will start moving.