code: def reynolds(target, u0, b, temperature='pore.temperature'):
      r
      value = u0*sp.exp(b*target[temperature])
      return value
docs: r"""
      Uses exponential model by Reynolds [1] for the temperature dependance of
      shear viscosity
  
      Parameters
      ----------
      target : OpenPNM Object
          The object for which these values are being calculated.  This
          controls the length of the calculated array, and also provides
          access to other necessary thermofluid properties.
  
      u0, b : float, array_like
              Coefficients of the viscosity exponential model (mu = u0*Exp(-b*T)
              where T is the temperature in Kelvin
  
      temperature : string
          The dictionary key containing the temperature values (K).  Can be
          either a pore or throat array.
  
      [1] Reynolds O. (1886). Phil Trans Royal Soc London, v. 177, p.157.