code: def design(self):
          
          floc_dict = {'channel_n': self.channel_n,
                       'channel_L': self.channel_L,
                       'channel_W': self.channel_W,
                       'baffle_S': self.baffle_S,
                       'obstacle_n': self.obstacle_n,
                       'G': self.vel_grad_avg,
                       't': self.retention_time,
                       'expansion_max_H': self.expansion_max_H,
                       'drain_ND': self.drain_ND}
          return floc_dict
docs: Returns the designed values.
          :returns: list of designed values (G, t, channel_W, obstacle_n)
          :rtype: int