Ship Resistance Calculation (Holtrop-Mennen Method)

This project provides a Python script to estimate ship total resistance using a Holtrop-Mennen style empirical approach.

The current implementation is a command-line calculator in main.py that asks for hull and operating parameters, computes intermediate coefficients, and prints:

• Total Resistance without Bulbous Bow

What the script does

The script computes resistance components and combines them into a total value.

Main computed pieces include:

• Froude number and Reynolds number
• Friction coefficient and frictional resistance
• Form-factor related viscous correction
• Wave-making and wave-breaking resistance terms
• Transom-related additional pressure term (computed, but currently excluded from the final sum)
• Model-ship correlation resistance

Final output in code:

• E60 = E33 * E31 + E37 + E49 + 0 + 0 + E58

This means the present result intentionally excludes:

• Additional pressure resistance of bulbous bow (E52, currently commented out)
• Additional pressure resistance of immersed transom (E55, calculated but not added)

Requirements

• Python 3.8+
• Standard library only (math)

No external package installation is required.

How to run

From the project root:

python3 main.py

Then enter the requested inputs one by one.

Input parameters

The script prompts for 21 numeric inputs (float). Names below follow the variable names in main.py:

1. E2 - LWL (Length on Waterline)
2. E3 - LBP (Length Between Perpendiculars)
3. E4 - Breadth Moulded
4. E5 - Draught Moulded on F.P
5. E6 - Draught Moulded on A.P
6. E7 - Displacement Volume Moulded
7. E8 - Longitudinal Centre of Buoyancy
8. E9 - Transverse Bulb Area
9. E10 - Centre of Bulb Area above keel line
10. E11 - Midship Section Coefficient
11. E12 - Waterplane Area Coefficient
12. E13 - Transom Area
13. E14 - Wetted Area Appendages
14. E15 - Stern Shape Parameter
15. E16 - Propeller Diameter
16. E17 - Number of Propeller Blades
17. E18 - Clearance Propeller with keel line
18. E19 - Ship Speed
19. E20 - Block Coefficient
20. E21 - Immersion of Propeller Shaft
21. E22 - Density in kg/m3

Output

The script prints a single line:

Total Resistance without Bulbous Bow is : <value>

The computed value is in Newtons if your inputs are given in consistent SI units.

Notes and current limitations

• The script is fully interactive; there are no command-line flags or file input support.
• Some inputs are collected but not currently used in the final resistance expression (E3, E6, E8, E16, E17, E18, E21, E22).
• Waterline entrance angle term is fixed as E39 = 1 in the current implementation.
• The script assumes valid numeric input and does not perform input validation.

Suggested next improvements

• Add input validation and unit checks.
• Add non-interactive mode (arguments or JSON/CSV input).
• Include all enabled resistance components in a selectable final sum.
• Return and display a full breakdown table of component resistances.
• Add automated tests using known benchmark hull data.