Equation Number | Author [Reference] | Explicit Models | Applicable Range of Re and ε/D | Classification |

2 | Romeo, Royo and Monzon [9] |
| 3 × 10 0 ≤ ε/D ≤ 5 × 10 | Extremely accurate |

3 | Serghides [15] | , , , | Not specified | Extremely accurate |

4 | Chen [11] |
| 4 × 10 10 | Very accurate |

5 | Buzzelli [16] | ; where, | 3 × 10 0 ≤ ε/D ≤ 5 × 10 | Extremely accurate |

6 | Zigrang and Sylvester [14] |
| 4 × 10 4 × 10 | Extremely accurate |

7 | Barr [19] |
| Not specified | Very accurate |

8 | Fang, Xu, Zhou [13] |
| 3 × 10 0 ≤ ε/D ≤ 5 × 10 | Very accurate |

9 | Shacham [20] |
| 4 × 10 | Moderately accurate |

10 | Sonnad and Goudar [21] | ; where | 4 × 10 10 | Moderately accurate |

11 | Manadilli [23] |
| 5.235 × 10 0 ≤ ε/D ≤ 5 × 10 | Less accurate |

12 | Ghanbari, Farshad and Rieke [17] |
| 2.1 × 10 0 ≤ ε/D ≤ 5 × 10 | Less accurate |

13 | Churchill [24] | ; where, | Re > 0 0 ≤ ε/D ≤ 5 × 10 | Less accurate |