anchor.diff:  
   end subroutine porteagel_visualize
   
  +! calculates the onset of far-wake conditions
   subroutine x0_func(rotor_diameter, yaw, Ct, alpha, I, beta, x0)
   
       implicit none
  
positive.code:     
  end subroutine sigmaz_func
  
  subroutine wake_offset_func(rotor_diameter, theta_c_0, x0, yaw, ky, kz, Ct, sigmay, &
                              & sigmaz, wake_offset)
                              
  
negative.code: 	theta_c_0 = 0.3_dp * yaw * (1.0_dp - sqrt(1.0_dp - Ct * cos(yaw))) / cos(yaw)
  
  end subroutine theta_c_0_func
  
  ! calculates the horizontal spread of the wake at a given distance from the onset of far 
  ! wake condition
  subroutine sigmay_func(ky, deltax0, rotor_diameter, yaw, sigmay)
      
      implicit none
  