Study on the load variation coefficients based on the model test

Abstract

The new method of speed-power trial analysis becomes valid on 1st September, 2015. ISO15016:2015 requires correction of delivered power, revolution speed, and ship speed by the direct power method which differs from the conventional sea trial methods. The direct power method divides the reasons of correction into the resistance increase and the propulsive efficiency decrease in trial. The efficiency decrease in trial can be obtained by the load variation coefficients, quantitatively. However, the guidelines or procedures still have arguments on the detailed analysis of load variation test. Many of the hull form designers are not familiar with the effects of the load variation coefficients used in direct power method. In the present study, a series of load variation tests (LVT) for various hull forms are performed. The procedures on how to measure, perform, and analyze the LVT are presented. The load variation coefficients are calculated from the load variation tests (method 1) and also estimated from the standard propulsion test (method 2). The propeller rotational speed is varied to cover the corresponding added resistance from -10% to +20% of the predicted total resistance in the ideal condition (method 1). The effects of load variation coefficients on the direct power method are investigated through the calculation and the test results.