I have a question about directional wave spreading in HydroDyn. As far as I understand, HydroDyn can include directional wave spreading function using cos-2s model. A small s which is the directional wave spreading parameter is a function of frequency. However, I found that the input of s in HydroDyn is defined as a constant value. So, I would like to ask about how to define s? Could you please explain me?