RESISTANCE AND PROPULSION

Introduction

As with ship powering, Naval Architects are also responsible for calculating a ship’s total resistance, required thrust and required power. The ship-flow interaction problem and some key aspects that can be broken down as follows:

• Resistance: If the ship is pulled by an indefinitely long pulling line, the force in the line is equal to the ship resistance.
• Propulsion: a mechanism or system used to provide thrust required to overcome resistance and achieve specific speed. Power presence of the propulsor behind the hull affects hull’s performance and vice versa.
• Required Power: Installed engine power required to generate sufficient thrust on propulsor to overcome ship resistance.

Ship Resistance

Ship resistance is a function of the following:

• Hull Shape
• Size
• Speed
• Other factors requiring energy to be expended

The flow chart below shows all the components that make up a ship’s Total Hull Resistance.

Ship Propulsion

The power is delivered to the propelling device from a propulsion plant, the size/masses of which is estimated from the required thrust to move the ship in water at its design speed.