3504. Method for Finding Min and Max Values of Error Range for Calculation of Moment of Inertia

Paper

Abstract

Modern ship design practices require knowledge of a vessel s mass Moment of Inertia (MOI) for various aspects of performance analysis. To find an accurate MOI value of an object, one needs to know the object s actual shape and density to be able to calculate the MOI through integration. Determining the exact MOI for a complete vessel, comprised of thousands of items, is not practical. Instead, engineers simplify the parts of the vessel to point objects or to standard shapes like a box or a cylinder, and calculate an approximation of the MOI. The accuracy of this approximation is dependent on the number of parts the vessel is divided into and how well the shape, orientation and density of each of the simplified items resembles the real objects. The quantification of the inaccuracy involved is seldom addressed. This paper describes a method to find the absolute error range for this simplified MOI calculation by finding the extreme values the MOI approximation can generate, and quantifies the effect that an error in MOI can have on the results of various types of performance analysis.