code: def W_min_HS_ratio(self):
          
          return ((self.HS_RATIO_MIN * self.Q / self.downstream_H) *
                 (self.BAFFLE_K /
                  (2 * self.downstream_H * pc.viscosity_kinematic(self.temp) * self.vel_grad_avg ** 2)) ** (1/3)
                 ).to(u.cm)
docs: Calculate the minimum flocculator channel width, given the minimum
          ratio between expansion height (H) and baffle spacing (S).
          :returns: Minimum channel width given H_e/S
          :rtype: float * centimeter