docs: def Nu_vertical_cylinder_Carne_Morgan(Pr, Gr, turbulent=None):
      r'''Calculates Nusselt number for natural convection around a vertical
      isothermal cylinder according to the results of [1]_ correlated by [2]_, as
      presented in [3]_ and [4]_.
  
      .. math::
          Nu_H = 1.07 Ra_H^{0.28},\; 2\times 10^{6} < Ra < 2\times 10^{8}
  
          Nu_H = 0.152 Ra_H^{0.38},\; 2\times 10^{8} < Ra < 2\times 10^{11}
  
      Parameters
      ----------
      Pr : float
          Prandtl number [-]
      Gr : float
          Grashof number [-]
      turbulent : bool or None, optional
          Whether or not to force the correlation to return the turbulent
  		 result; will return the laminar regime if False; leave as None for
          automatic selection
  
      Returns
      -------
      Nu : float
          Nusselt number, [-]
  
      Notes
      -----
      Cylinder of diameters 0.475 cm to 7.62 cm, L/D from 8 to 127. Isothermal
      boundary condition was assumed, but not verified. Transition between ranges
      is not smooth. If outside of range, no warning is given. The higher range
      of [1]_ is not shown in [3]_, and the formula for the first is actually for
      the second in [3]_.
  
      Examples
      --------
      >>> Nu_vertical_cylinder_Carne_Morgan(.7, 2E8)
      204.31470629065677
  
      References
      ----------
      .. [1] J. B. Carne. "LIX. Heat Loss by Natural Convection from Vertical
         Cylinders." The London, Edinburgh, and Dublin Philosophical Magazine and
         Journal of Science 24, no. 162 (October 1, 1937): 634-53.
         doi:10.1080/14786443708565140.
      .. [2] Morgan, V.T., The Overall Convective Heat Transfer from Smooth
         Circular Cylinders, in Advances in Heat Transfer, eds. T.F. Irvin and
         J.P. Hartnett, V 11, 199-264, 1975.
      .. [3] Popiel, Czeslaw O. "Free Convection Heat Transfer from Vertical
         Slender Cylinders: A Review." Heat Transfer Engineering 29, no. 6
         (June 1, 2008): 521-36. doi:10.1080/01457630801891557.
      .. [4] Boetcher, Sandra K. S. "Natural Convection Heat Transfer From
         Vertical Cylinders." In Natural Convection from Circular Cylinders,
         23-42. Springer, 2014.
      '''
      Ra = Pr*Gr
      if turbulent or (Ra > 2E8 and turbulent is None):
          return 0.152*Ra**0.38
      else:
          return 1.07*Ra**0.28