The figure below represents the Bourdet derivative with varying skin from -3 to +10. Note that the infinite acting radial flow period (zero slope) on the Bourdet derivative remains constant regardless of the skin value. However, as skin becomes more positive, the separation between the derivative and the normalized pressure increases.
Once radial flow is reached, it basically has no impact on the position of the derivative. It also does not affect the time at which PSS is reached on the derivative.
