Propeller Drag Due To Form Drag Of Propeller With Locked Shaft Calculator

Formula Used:

\[ \text{Vessel Propeller Drag} = 0.5 \times \text{Water Density} \times \text{Propeller Drag Coefficient} \times \text{Expanded or Developed Blade Area of a Propeller} \times \text{Average Current Speed}^2 \times \cos(\text{Angle of the Current}) \] \[ F_{c, prop} = 0.5 \times \rho_{water} \times C_{c, prop} \times A_p \times V_c^2 \times \cos(\theta_c) \]

Water Density (ρ):

kg/m³

Propeller Drag Coefficient (C_{c, prop}):

(dimensionless)

Expanded or Developed Blade Area (A_p):

m²

Average Current Speed (V_c):

m/s

Angle of the Current (θ_c):

radians

Vessel Propeller Drag (F_{c, prop}):

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1. What is Propeller Drag Due To Form Drag Of Propeller With Locked Shaft?

Propeller drag due to form drag refers to the resistance experienced by a ship's propeller when its shaft is locked and unable to rotate. This occurs when water flows past the stationary propeller blades, creating drag forces that affect vessel performance and maneuverability.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ F_{c, prop} = 0.5 \times \rho_{water} \times C_{c, prop} \times A_p \times V_c^2 \times \cos(\theta_c) \]

Where:

\( F_{c, prop} \) — Vessel propeller drag (N)
\( \rho_{water} \) — Water density (kg/m³)
\( C_{c, prop} \) — Propeller drag coefficient (dimensionless)
\( A_p \) — Expanded or developed blade area (m²)
\( V_c \) — Average current speed (m/s)
\( \theta_c \) — Angle of the current (radians)

Explanation: The formula calculates the drag force on a stationary propeller based on water properties, propeller characteristics, and flow conditions.

3. Importance of Propeller Drag Calculation

Details: Accurate propeller drag calculation is crucial for vessel design, performance prediction, and maneuverability analysis, particularly in emergency situations where propellers may become locked.

4. Using the Calculator

Tips: Enter water density in kg/m³, propeller drag coefficient (dimensionless), blade area in m², current speed in m/s, and current angle in radians. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is form drag in propellers?
A: Form drag is the resistance caused by the shape of the propeller blades as water flows around them, particularly when the propeller is stationary.

Q2: Why would a propeller shaft be locked?
A: Propeller shafts may be locked due to mechanical failure, maintenance procedures, or emergency situations where propeller rotation needs to be prevented.

Q3: How does blade area affect propeller drag?
A: Larger blade area increases the surface exposed to water flow, resulting in higher drag forces on the stationary propeller.

Q4: What is typical water density for calculations?
A: Fresh water density is approximately 1000 kg/m³, while seawater density is typically around 1025 kg/m³.

Q5: How does current angle affect propeller drag?
A: The cosine function accounts for the directional component of the current, with maximum drag occurring when current flows perpendicular to the propeller plane.