Unlock precise resistance measurements in naval architecture with Hull Efficiency Calculators.
Discover the critical factors behind resistance to advance and how to optimize your hull design accurately.
Calculadora con inteligencia artificial (IA) Hull Efficiency Calculator for Accurate Resistance to Advance
- Calculate hull efficiency of a 150-meter container ship at 24 knots.
- Estimate resistance to advance for a yacht hull at 12 knots with given hull form coefficients.
- Optimize the hull design of a bulk carrier to reduce resistance based on wave resistance.
- Determine effective power needed considering hull efficiency at 18 knots for a patrol vessel.
Comprehensive Tables of Hull Efficiency and Resistance to Advance Parameters
| Hull Type | Length Overall (m) | Speed (knots) | Hull Efficiency (ηH) | Resistance to Advance (kN) | Froude Number (Fr) |
|---|---|---|---|---|---|
| Container Ship | 150 | 24 | 0.92 | 980 | 0.28 |
| Bulk Carrier | 200 | 16 | 0.88 | 1100 | 0.22 |
| Yacht | 20 | 12 | 0.95 | 85 | 0.40 |
| Patrol Vessel | 40 | 18 | 0.90 | 190 | 0.33 |
| Fishing Trawler | 30 | 10 | 0.87 | 70 | 0.28 |
| Cruise Ship | 250 | 22 | 0.91 | 1450 | 0.27 |
| Ferry | 75 | 20 | 0.89 | 430 | 0.35 |
| Tankers | 180 | 15 | 0.86 | 1050 | 0.20 |
Fundamental Formulas and Variable Definitions for Hull Efficiency and Resistance
Hull efficiency and resistance to advance are essential in quantifying ship performance and optimizing design.
The complex interplay of hydrodynamic forces necessitates precise calculation methods based on fluid mechanics and empirical data.
The Resistance to Advance (RA)
The resistance to advance is the total force opposing the forward motion of a hull through water.
RA = RF + RW + RT
- RF: Frictional resistance
- RW: Wave-making resistance
- RT: Additional resistance (e.g., air resistance, appendages)
Frictional Resistance (RF)
Calculated using ITTC-1957 correlation line as a benchmark, the frictional resistance is computed:
RF = 0.5 × ρ × S × CF × V2
- ρ: Water density (kg/m3)
- S: Wetted surface area (m2)
- CF: Frictional resistance coefficient
- V: Ship speed (m/s)
The frictional resistance coefficient CF is given by the ITTC-1957 formula:
CF = 0.075 / (log10Re – 2)2
- Re: Reynolds number = V × L / ν (ν = kinematic viscosity)
- L: Characteristic length (usually length between perpendiculars, m)
Wave-making Resistance (RW)
Wave-making resistance is complex and depends on hull shape and Froude number:
RW = k × ρ × g × V2 × Sref × (Fr)4
- k: Empirical constant based on hull form
- g: Acceleration due to gravity (9.81 m/s2)
- Sref: Reference area (usually waterplane area, m2)
- Fr: Froude number = V / √(gL)
Hull Efficiency (ηH)
Hull efficiency quantifies the ratio of effective power used for propulsion to the total input power.
ηH = RF / (RF + RW)
Typical values of ηH range between 0.86 and 0.95 depending on hull form optimization and operational conditions.
Effective Power (PE)
The power required to overcome the resistance to advance at speed V:
PE = RA × V
- Expressed in Watts (W) when RA is in Newtons (N) and V in meters per second (m/s)
Variable Descriptions and Common Values
| Variable | Description | Typical Range/Value | Units |
|---|---|---|---|
| ρ | Water density (sea water) | 1025 | kg/m3 |
| S | Wetted surface area | Varies 200 – 15,000 | m2 |
| V | Ship speed | 2 – 30 | m/s (Approx. 4 – 58 knots) |
| CF | Frictional resistance coefficient | 0.002 – 0.005 | Dimensionless |
| L | Length between perpendiculars | 20 – 300 | m |
| Fr | Froude number | 0.1 – 0.4 | Dimensionless |
| g | Gravitational acceleration | 9.81 | m/s2 |
| Sref | Waterplane reference area | Varies with hull type | m2 |
| ηH | Hull efficiency | 0.86 – 0.95 | Dimensionless |
Detailed Real-World Applications of Hull Efficiency Calculations
Case Study 1: Optimizing Resistance in a 150m Container Ship at 24 knots
A container ship with a length overall of 150 meters operates regularly at 24 knots. The naval architect needs to estimate resistance to advance accurately to optimize engine power and fuel efficiency.
Given:
- Length between perpendiculars (L) = 145 m
- Speed (V) = 24 knots = 12.35 m/s
- Wetted surface area (S) = 10,500 m²
- Water density (ρ) = 1025 kg/m³
- Kinematic viscosity ν = 1.14 × 10-6 m²/s
Step 1: Calculate Reynolds number (Re):
Re = V × L / ν = 12.35 × 145 / 1.14 × 10-6 = 1.57 × 109
Step 2: Calculate frictional resistance coefficient (CF):
CF = 0.075 / (log101.57 × 109 – 2)2 ≈ 0.0019
Step 3: Compute frictional resistance (RF):
RF = 0.5 × 1025 × 10,500 × 0.0019 × (12.35)2 ≈ 1,584 kN
Step 4: Calculate Froude number (Fr):
Fr = V / √(gL) = 12.35 / √(9.81 × 145) ≈ 0.33
Step 5: Estimate wave-making resistance assuming k = 0.15 and Sref = 7,000 m²:
RW = 0.15 × 1025 × 9.81 × 12.352 × 7000 × (0.33)4 ≈ 936 kN
Step 6: Total resistance to advance:
RA = RF + RW = 1,584 + 936 = 2,520 kN
Step 7: Calculate hull efficiency ηH:
ηH = RF / (RF + RW) = (Incomplete: max_output_tokens)
