Exam Question

### (a) Optimization of Propeller Hull Interface Flow Devices
**1. Introduction**
The propulsive efficiency of a ship is heavily influenced by the interaction between the hull and the propeller. The water flow into the propeller, known as the wake field, is non-uniform due to the hull's boundary layer. Furthermore, the propeller itself imparts a rotational motion (swirl) to the water in its slipstream, which represents a significant energy loss. Propeller-hull interface flow devices, also known as Energy Saving Devices (ESDs), are retrofitted or installed on new builds to manage this flow, thereby improving overall propulsive efficiency and reducing fuel consumption.
**2. Principle of Propulsive Efficiency Improvement**