How do i achieve circular Gerstner waves?

Hi,

Thanks for the reply, I do however have a working Gerstner wave for my displacement using just equation 9 (i believe the equations afterwards are to calculate normals)

What im particularly interested in is how it provides the equation for circular waves slighty above equation 9 and instructs to replace “Di” with this new equation which is what i have done but am not achiving the desired result