Using approximate similitude to design dynamic similar models

Abstract

Abstract This research deals with the analysis of approximate similitude between the dynamic similar models and the full-scale prototype of an aircraft. Due to physical and technical constraints, a full dynamic similarity is not practically possible and previous works have all neglected one or two similarity criteria like Mach or Reynolds numbers for the sake of Froude number similarity. In this work, it is shown that Mach number has an important effect on aerodynamic characteristics and dynamic response of an aircraft and that neglecting it makes the generalization of the scale-model test data invalid for the full-scale prototype. In order to address this problem, a measurable quantity named approximate similitude parameter is proposed, which takes into account both dynamic similarity criteria and the scale model test objectives. The effectiveness of this parameter is shown by a case study to find out optimal weight, moments of inertia and velocity for the scale model to achieve optimal dynamic similarity.