Q5
With respect to Energy efficient running of ships.
(a) Sketch and explain the optimization of propeller hull interface flow devices and improvement of propulsion efficiency.
(8)
(b) sketch and explain the optimization of Auxiliary machinery using VFDs.
(8)
Reference Answer
### Part (a): Optimization of Propeller Hull Interface Flow Devices #### 1. Concept of Propulsive Efficiency Improvement The primary goal of propeller-hull interface devices is to improve the overall propulsive efficiency of the vessel. This is achieved by managing the water flow into and out of the propeller. The hull's passage through water creates a non-uniform wake field. A conventional propeller operating in this field experiences fluctuating loads, cavitation, and energy losses. Additionally, the propeller itself generates rotational flow (swirl) and a hub vortex in its slipstream, which do not contribute to forward thrust and represent wasted energy. Energy Saving Devices (ESDs) are designed to mitigate these effects. #### 2. Types of Propeller Hull Interface Flow Devices
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