Cylinder Oscillation vertically (Heave)- Assistance

Hello Everyone, I am new to the programming, at the minute I am trying to achieve a cylinder oscillating vertically y= aSin(wt) in water. I am trying to achieve this in Fluent, have generated mesh in a 50*50 mm domain with 0.4m diameter cylinder sitting in the middle of the domain, Fluent can only make the cylinder in one direction either x or y but there is not any options available for oscillation.

I am now trying generate a simple code in C programming to use as User defined function to get the cylinder to oscillate vertically, but not certain how to go about writing a simple code. I will be thankful if anyone here in this communities can provide me with some guidance or a may a an exaple code that can be addopted to my problem.

It would help me to make some forward progress, as I have been trying this for months without any success.

Kind Regards Sritharan