IN-PLANE AND SINGLE BLADE LOADS MEASUREMENT SETUPS FOR PROPELLER PERFORMANCE ASSESSMENT DURING FREE RUNNING AND CAPTIVE MODEL TESTS.

Over actual operative condition, the inflow to the propeller of a ship is considerably different from the one adopted during design phase. In fact, small adjustments of the route, tight manoeuvres at high speed, heavy sea or emergency stops are some of the conditions that could occur in seaway and which alter the wake and inflow to the propeller. This time-varying and strongly non-uniform flow gives rise to a complex system of loads developed by the propeller, which is directly transmitted to the propulsive system and mechanical structures, with subsequent occurrence of failures and damages. Moreover these loads, especially the in-plane propeller forces, have a direct impact on the manoeuvring ability of the ship, because tend to stabilize the navigation. The assessment of those loads is of paramount importance in order to understand and characterize the cause-effect relation between ship dynamics, wake and propeller and quantify their magnitude with the purpose of understanding, evaluating and mitigating their effects. The present paper describes two experimental setups, implemented on two scaled models of twin screw propellers ships, with the aim of measure, on the first one, the in-plane loads (i.e. bearing loads) developed by the propeller and, on the second one, the complete set of loads (three forces and three moments) acting on one of the blades, that, beside the higher detail of the provided investigation, they are also useful to derive the loads developed by the whole propeller.