Hi Jorge and Mauricio,
About the normal drag force per unit length on the cylinder, from my understanding, the current implementation uses a formulation

with a constant C_D. This is appropriate for a Reynolds number in the range 100-10^5.
For Alexandre's problem, to provide damping at low velocity or even in zero-flow conditions, it'd be nice to have a drag coefficient that varies with the Reynolds number R_e in this way

where the Reynolds number is defined as R_e=d*|U_rel|/nu, with U_rel being the instantaneous relative velocity between the cylinder element and the flow.
The advantage of this formulation is that at low R_e, it enforces a drag force that is linear with the relative velocity, hence creating damping.
There should be a warning in the code if R_e exceeds 2*10^5 in which case the drag coefficient relation breaks down as it does not account for the drag crisis.

Reference for the drag formulation.
https://ascelibrary.org/doi/10.1061/%28ASCE%29HY.1943-7900.0000722