Q9
(a) Describe the effect of cavitations on the propeller blades.
(6)
(b) A propeller 4.6m diameter has a pitch of 4.3m and boss diameter of 0.75m. The real slip is 28% at 95 rev/min. Calculate the speed of advance, thrust and thrust power.
(10)
Reference Answer
### Part (a): Effect of Cavitation on Propeller Blades Cavitation is a complex hydro-dynamic phenomenon involving the formation and subsequent collapse of vapor-filled cavities (bubbles) in a liquid. It occurs when the local static pressure drops below the liquid's vapor pressure. On a propeller, this is most common on the low-pressure suction side (back) of the blades, particularly near the leading edge and blade tips where water velocity is highest. **Mechanism of Cavitation:** 1. **Bubble Formation:** As a propeller blade rotates at high speed, the water flowing over the curved suction face accelerates. In accordance with Bernoulli's principle, this increase in velocity leads to a significant drop in local pressure.
Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.
