docs: def Nu_vertical_cylinder_Eigenson_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]_,
      presented in [3]_ and in more detail in [4]_.
  
      .. math::
          Nu_H = 0.48 Ra_H^{0.25},\; 10^{9} < Ra
  
          Nu_H = 51.5 + 0.0000726 Ra_H^{0.63},\; 10^{9} < Ra < 1.69 \times 10^{10}
  
          Nu_H = 0.148 Ra_H^{1/3} - 127.6 ,\; 1.69 \times 10^{10} < Ra
  
      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
      -----
      Author presents results as appropriate for both flat plates and cylinders.
      Height of 2.5 m with diameters of 2.4, 7.55, 15, 35, and 50 mm. Another
      experiment of diameter 58 mm and length of 6.5 m was considered.
      Cylinder of diameters 0.475 cm to 7.62 cm, L/D from 8 to 127.Transition
      between ranges is not smooth. If outside of range, no warning is given.
      Formulas are presented similarly in [3]_ and [4]_, but only [4]_ shows
      the transition formula.
  
      Examples
      --------
      >>> Nu_vertical_cylinder_Eigenson_Morgan(0.7, 2E10)
      230.55946525499715
  
      References
      ----------
      .. [1] Eigenson L (1940). Les lois gouvernant la transmission de la chaleur
         aux gaz biatomiques par les parois des cylindres verticaux dans le cas
         de convection naturelle. Dokl Akad Nauk SSSR 26:440-444
      .. [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 > 1.69E10 and turbulent is None):
          return 0.148*Ra**(1/3.) - 127.6
      elif 1E9 < Ra < 1.69E10 and turbulent is not False:
          return 51.5 + 0.0000726*Ra**0.63
      else:
          return 0.48*Ra**0.25